Band 39, Heft 1

The dissolution characteristics and electrochemical reduction mechanism of oxides of refractory metals ZrO 2 , HfO 2 and MoO 3 in NaCl-KCl-NaF melts are studied. The results shows that there are no chemical reaction of ZrO 2 and HfO 2 in NaCl-KCl-NaF melts, the dissolution of MoO 3 is chemically dissolved, and MoO 3 reactwith melts to form Na 2 Mo 2 O 7 . The reduction process of zirconium in the NaCl-KCl-NaF-ZrO 2 melts is a reversible process of one-step electron transfer controlled by diffusion. The electrochemical reduction process of ruthenium is a one-step reversible process and the product is insoluble; Electrochemical reduction of metallic molybdenum in melts is controlled by the diffusion and electron transfer process of active ion Mo 2 O 2 7 − . The electrochemical reduction process of the metal molybdenum in the melts is carried out in two steps.

The change regulations of the smelting parameters in a gas-injection blast furnace are investigated using theoretical calculations. The results show that when the volume of gas injected, the oxygen enrichment rate and the theoretical combustion temperature of tuyere are 600 m 3 /tHM, 10% and 1950~2200 ∘ C, respectively, the conditions meet the smelting requirements of a blast furnace. With the increase of the oxygen enrichment rate, the required air volume decreases, the contents of CO and H 2 in the top gas increase, and the content of CO 2 first increases and then decreases.With an increase of the volume of gas injected, the coke rate decreases. In addition, when the oxygen enrichment rate and the volume of gas injected are 10% and 600 m 3 /tHM, respectively, the CO content of the top gas constantly increases with the increase of the coke rate, while the H 2 and CO 2 contents both decrease. With the increase of the H 2 content in the gas, the direct reduction degree of iron gradually decreases and the volume shrinkage burden increases. Apparently, injecting gas into the blast furnace can prevent the theoretical combustion temperature from being too high and solve the contradiction between the upper cooling and lower heating of the blast furnace.

Porous Ti-Si-Mo intermetallic compounds were fabricated by reactive synthesis using C 7 H 10 N 2 O 2 S as a foaming agent. The effects of Mo content on the microstructure, phase composition and oxidation behavior were investigated. The results show that the porosity and the fractal dimension decreases and then increases as the Mo content increases. It is found that the pore size is mainly distributed in less than 1μm. The phase compositions mainly consist of TiSi, Ti 5 Si 4 , Mo 5 Si 3 and TiO, and the Ti 5 Si 3 phase is detected at Mo content of 16 wt.% in particular. In addition, the mass gain of the oxidized samples gradually decreases as the Mo content increases. It is concluded that the oxidation resistance at high-temperature generally decreases as the fractal dimension increases. It is suggested that porous Ti-Si-Mo intermetallic compounds have potential applications in sound absorption and heat dissipation at high-temperature.

The microstructural characteristics and mechanical properties of the simulated coarse grained heat affected zone (CGHAZ) in high N V-alloyed steel have been conducted under different welding heat input, characterized by the cooling time taken from 800°C to 500°C (t 8/5 ). The experimental results show that the microstructure is dominantly composed of lath bainite (LB) and granular bainite (GB) at t 8/5 30 s– 90 s. The content of LB decreases with t 8/5 increasing, and that of GB increases. When t 8/5 further increases to 120 s and 180 s, the microstructure mainly consists of intragranular polygonal ferrite (IPF) and acicular ferrite (IAF). The higher t 8/5 leads to the increased content of intragranular ferrite (IGF). Meanwhile, the prior austenite grain size (PAGS) progressively increases from 56 ± 6.0 μm to 148 ± 9.9 μm as t 8/5 increases from 30 s to 180 s. Besides, EBSD analysis indicates that the fraction of high angle grain boundaries (HAGBs) is 0.570, 0.427 and 0.624, respectively, corresponding to t 8/5 30, 90 and 180 s. Moreover, the impact toughness decreases as t 8/5 increases from 30 s to 90 s caused by the increased PAGS and GB content, and then sharply increases with t 8/5 exceeding 90 s due to the increased formation of IGF, especially IAF. Furthermore, the high nitrogen content accelerates V(C,N) precipitation, which not only inhibits the coarsening of prior austenite grains, but promotes the formation of IGF, resulting in the increased number of HAGBs and raising impact toughness.

With the concern of the environment, green dry cutting technology is getting more and more attention and self-lubricating tool technology plays an important role in dry cutting. Due to the demand for high temperature performance of tools during dry cutting process, cemented carbide with Ni 3 Al as the binder phase has received extensive attention due to its excellent high temperature strength and high temperature oxidation resistance. In this paper, WC-TiC-Ni 3 Al-CaF 2 graded self-lubricating material and tools were prepared by microwave heating method, and its microstructure, mechanical properties and cutting performance were studied. Results show that gradient self-lubricating material can be quickly prepared by microwave heating technology, and the strength is equivalent to that of conventional heating technology. CaF 2 not only plays a role in self-lubrication, but also refines the grain of the material. A reasonable gradient design can improve the mechanical properties of the material. When the gradient distribution exponent is n 1 = 2, the material has high mechanical properties. Cutting experiments show that the WC-TiC-Ni 3 Al-CaF 2 functional gradient self-lubricating tool has better cutting performance than the homogeneous WC-TiC-Ni 3 Al hard alloys.

The multimode resonant cavity is the most common cavity. The material often shows on selective heating performance during the heating process due to the effect of microwave heating having a closely relationship with the electromagnetism parameters. This paper is based on finite difference time domain method (FDTD) to establish the electromagnetic-thermal model. The electromagnetic sensitivity property parameters of sodium chloride including relative dielectric constant, loss angle tangent and water content of sodium chloride is studied during the heating and drying process. The heating rate and the electric field distribution of sodium chloride, at the different water content, were simulated with the electromagnetic characteristic parameters changing. The results show that with the electromagnetic sensitivity property parameters varying, the electric field strength, heating rate and steady-state temperature of the heating material will all have a variety in the cavity. Some measures are proposed to improve the heating efficiency and ensure the stability of the microwave heating system in the industrial application.

According to the downhole temperature filed, the mechanical behavior of TWIP steel for expansion tube was studied in the temperature range from 25°C to 300°C. Meanwhile, the phase and microstructure changes before and after deformation were investigated by X-ray diffractometer (XRD), optical microscope (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that yield strength, tensile strength and elongation decrease with temperature increasing. The TWIP steel is single-phase of austenite before and after deformation. Analysis on the microstructure shows that the deformation twins gradually decrease with increasing temperature. The deformation process cannot benefit from the deformation twins, which is responsible for the decreased ductility. In addition, due to the increased temperature, the stacking fault energy becomes high enough to restrain twinning, thus dislocation glide becomes the main deformation mechanism.

In order to improve the recycling efficiency of stainless-steel slag resources, the effect of different cooling rates on the crystallization behavior of CaO-SiO 2 -MgO-Cr 2 O 3 based system was studied by using FactSage 7.1, XRD, SEM and IPP 6.0. The results indicated that the spinel is a high-temperature precipitated phase and the cooling rate had less effect on the final grain size of spinel crystals, but had greater influences on the nucleation of spinel crystals and the crystallization of silicates such as α -C2S.When the cooling rate was 12 ∘ C/min, the spinel crystals was the unique precipitation. However, the spinel crystals and α -C2S could produce during the slag cooling process as the cooling rate was1 ∘ C/min. Chromium in silicate phase is inclinable to leaching with the dissolution of silicate phase, so the formation of silicate phase should be controlled. According to the influence of the cooling rate on the formation of spinel crystals and the erosion of spinel crystals by α -C2S, it is suggested that the cooling rate of the stainless-steel slag in industrial treatment should not be lower than 12 ∘ C/min.

Microscopic morphologies of reticular cracks in Nb-bearing pipeline surfaces are shown in this work. A decarburization layer, oxidized round spots, and the distributions of residual elements are each detected to better understand the mechanisms of reticular crack formations. The results show that reticular cracks are discontinuously distributed and filled with iron oxide. The oxidized round spots near the crack sides are larger and more intensive than steel matrix, with primary chemical compositions of Fe, Mn, and Si oxides. There is no obvious enrichment of Cu, Cr, or Sn near the crack zones. The formation of reticular cracks occurs prior to both decarburization and the formation of oxidized round spots. The ferrite potential (FP) of the examined pipeline steel is 1.05, which leads to a higher relative crack susceptibility. It is concluded that reticular cracks are generated during the continuous casting solidification process due to the extension of intergranular microcracks along grain boundaries under the abnormal conditions of the continuous casting process.

The B 2 O 3 -SiO 2 -Al 2 O 3 -CaO brazing fluxes and slags were investigated by using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The microstructure of the fluxes and slags and its transformation mechanism during the brazing process were investigated, especially the effect of ratio of B 2 O 3 to SiO 2 (B 2 O 3 /SiO 2 ) on the microstructural transformation was analyzed. The results show that the structure units of the fluxes and slags are [BO 4 ], [BO 3 ], [SiO 4 ], [AlO 4 ] and [AlO 6 ], and the network structure is a silicon-boron network structure. The O in the slags consist of bridged oxygen, non-bridged oxygen and free oxygen. During the brazing process, part of the [BO 4 ] in slag combined with silica-oxygen network to form Si-O-B structure, which contribute to the network structure of slag, and another part of the [BO 4 ] was transformed to [BO 3 ]. The increase of (B 2 O 3 /SiO 2 ) contribute to the transformation of [BO 4 ] to [BO 3 ], and more B 2 O 3 take part in the interface reaction with the increase of (B 2 O 3 /SiO 2 ). Therefore, the increase of (B 2 O 3 /SiO 2 ) leads to the decrease in the viscosity of the slag, which is beneficial to the spreading behavior during the brazing process.

The gas-injection blast furnace (BF) is a new iron-making technology with an injecting gas instead of traditional pulverized coal injection (PCI) and recycling of the BF top gas through a gasifier. In contrast to traditional all-coke and PCI BFs, the coke rate will depend mostly on the heat consumption in a gas-injection BF with abundant injected gas, which results in a large coke-saving potential. Based on energy conservation, carbon recycling, CO 2 abatement and fuel cost, the degree of direct reduction should be between 0.2 and 0.3. In addition, in terms of the effects of the gas injected and the rich oxygen rate in the tuyere region, the optimum injection parameters were obtained, which can reduce the coke rate to 273.36 kg/tHM, carbon recycling to 100.72 kg/tHM and abate carbon dioxide emissions by 94.00 Nm 3 /tHM. Theoretically, the minimum total carbon consumption value is 399.73 kg/tHM. These results illustrate the great potential for carbon recycling and coke saving in gas-injection BFs without increasing total carbon consumption.

The reaction mechanism models of dechlorination and [Zn] reclaiming in the roasting steelmaking zincrich dust process are studied. The dust collected from a steelwork contains 63.8% zinc and 3.18% chlorine (mass percent), of which, almost all zinc elements exist in ZnO and ZnCl 2 forms, and all the chlorine elements are stored in ZnCl 2 . When the dust is roasted at above 732 ∘ C in an air atmosphere, the ZnCl 2 in the steelmaking zinc-rich dust is volatilized into steam and then oxidized into ZnO. Finding the position where the chemical reaction occurs is the key to determining the reaction mechanisms of dechlorination and [Zn] reclaiming. In this study, two groups of thermal experiments are designed and executed for roasting in different atmosphere environments and at different roasting temperatures. Based on the experiment results, the mechanism model is discussed and built, and the reaction of dechlorination and [Zn] reclaiming is shown to be a multi-step process. Because O 2 from the air cannot transmit into the dust particle interior or dust bed effectively, the chemical reaction of [Zn] reclaiming occurs in the external gas environment outside of the dust, where the [Zn] recalcining reaction should be limited by the dynamics of new nucleation of ZnO solids.

Selective laser melting (SLM) is considered as an important additive manufacturing (AM) technology which can fabricate parts with complex geometry. However, it is difficult to predict the optimal SLM-parameters of metallic materials. In this study, orthogonal experiments were designed to study the influence of SLM-process parameters on the density and fabricated quality of Hastelloy X superalloy. Moreover, the relationship between microstructure evolution and performance of deposited microstructure was studied after heat treatment. The laser power, scanning speed and energy density have a significant effect on the density of the fabricated parts. The optimal parameters for determining Hastelloy X are 250 W laser power, 500 mm/s scanning speed, 100 μm hatch space, and 30 μmlayer thickness. The deposited microstructure is a lamellar microstructure in the horizontal direction and a columnar crystal in the longitudinal direction, and the microstructure is mainly martensite. After solid-solution and aging treatment, grain grows up. Martensite decomposes and the carbide M 6 C was precipitated during the aging process. The strength of the microstructure decreases slightly due to the growth of grain size.

The parallel flow drop solvothermal method was utilized to synthesize the crystal of MOF-5 by taking the molar ratio of the metal ions to the organic ligands of 2:1 at 140 ∘ C, and the reaction time at 12 hours. Meanwhile, the structure and properties of MOF-5 were characterized by the X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TGA) and fourier transform infrared spectroscopy (FTIR). SEM analysis shown that the crystal morphology of MOF-5 changed from sheet to cubic with increasing reaction temperature and molar ratio of the metal ions to the organic ligands, and its thermal stability was also gradually increased. TGA analysis shown that its thermal stability could live up to 489.36 ∘ C. FTIR analysis shown that the terephthalic acid is completely protonated, and the Zn 2+ and the carboxyl group are formed by the coordination of the multi-tooth bridge in the crystal of MOF-5. Then the structure activity relationship of the crystal MOF-5 synthesis, microstructural, thermal stability and N 2 adsorption property were further studied.

Al-Li alloy 2198 exhibits good combination of toughness and strength but its application is strongly limited by the poor weldability due to the formation of porosities during fusion-welding. This is the first study proposing and verifying a new approach to produce defect-free laser welds of poorly fusion-weldable Al-Li alloy 2198 with applied external pressure, i.e ., feasibility of laser pressure welding to Al-Li alloy 2198 was examined. The microstructures associated with tensile shear behavior of laser pressure welded Al-Li alloy 2198 obtained at various welding parameters were analyzed. The results showed that formation of the welding defect in the weld could be successfully suppressed by applying laser pressure welding, even without shielding gas. Three microstructural zones, including the chill zone, the columnar zone and the equiaxed zone were observed in the fusion zone. Size of fusion zone and area fraction of porosities generally increased with increasing roller pressure and welding heat-input, and they dominantly affected the tensile shear behavior, including the peak load and the failure mode, of the weld.

Microstructural evolution in the TiC-reinforced Mo–Si–B-based alloy during tensile creep deformation at 1,500°C and 137 MPa was investigated via scanning electron microscope-backscattered electron diffraction (SEM-EBSD) observations. The creep curve of this alloy displayed no clear steady state but was dominated by the tertiary creep regime. The grain size of the Mo ss phase increased in the primary creep regime. However, the grain size of the Mo ss phase was found to remarkably decrease to <10 µm with increasing creep strain in the tertiary creep regime. The EBSD observations revealed that the refinement of the Mo ss phase occurred by continuous dynamic recrystallization including the transformation of low-angle grain boundaries to high-angle grain boundaries. Accordingly, the deformation of this alloy is most likely to be governed by the grain boundary sliding and the rearrangement of Mo ss grains such as superplasticity in the tertiary creep regime. In addition, the refinement of the Mo ss grains surrounding large plate-like T 2 grains caused the rotation of their surfaces parallel to the loading axis and consequently the cavitation preferentially occurred at the interphases between the end of the rotated T 2 grains and the Mo ss grains.

This study was aimed at examining the effects of different deoxidization methods on the physical properties of metallic melts by measuring the changes in the kinematic viscosity, electrical resistivity, surface tension, and density of the metallurgical melts during the heating and cooling processes. Our results indicate that high-temperature physical properties are consistently affected by specific elements and compounds.

The liquidus surface projection and isothermal section at 1,800°C in the Mo–Ti–C ternary system are examined using arc-melted alloys. A ternary transition peritectic reaction (L + Mo 2 C → Mo + TiC) takes place during solidification, which is apparently different from the ternary eutectic reaction (L → Mo + TiC + Mo 2 C) observed in a previous report. Since the composition of the eutectic reaction (L → Mo + TiC) shifts toward the Mo–Ti binary line with increasing Ti concentration, the volume fraction of the Mo phase and the interlamellar spacing of the Mo and TiC phases increase in the eutectic microstructure. At 1,800°C, the TiC phase in equilibrium with the Mo phase can contain more than 28 at% Mo and a Mo/TiC/Mo 2 C three-phase region exists at around Mo–15Ti–10C.

P92 steel is used as a piping material in ultra super critical power plants that can be operated at steam temperatures up to 650°C. The changes in the martensitic microstructure of P92 steel must be evaluated thoroughly before it is put into actual service. In this study, indigenously developed P92 steel was used. The steel was subjected to normalizing and tempering heat treatments in the range of 1,040–1,060°C and 740–780°C. The changes in the microstructure were evaluated and creep-rupture properties were studied at test temperatures of 600 and 650°C. Although normalizing temperatures influenced the microstructure and creep strength marginally, the change in tempering temperatures led to significant changes. The creep rupture strength at 600°C was influenced largely by the changes in the dislocation substructure, while the precipitation of Laves phases was a significant observation made for 650°C test temperature. Proposed mechanisms for the microstructural evolution and its consequences on the rupture life are discussed in this study.

In this paper, the temperature-dependent matrix multicracking evolution of carbon-fiber-reinforced silicon carbide ceramic-matrix composites (C/SiC CMCs) is investigated. The temperature-dependent composite microstress field is obtained by combining the shear-lag model and temperature-dependent material properties and damage models. The critical matrix strain energy criterion assumes that the strain energy in the matrix has a critical value. With increasing applied stress, when the matrix strain energy is higher than the critical value, more matrix cracks and interface debonding occur to dissipate the additional energy. Based on the composite damage state, the temperature-dependent matrix strain energy and its critical value are obtained. The relationships among applied stress, matrix cracking state, interface damage state, and environmental temperature are established. The effects of interfacial properties, material properties, and environmental temperature on temperature-dependent matrix multiple fracture evolution of C/SiC composites are analyzed. The experimental evolution of matrix multiple fracture and fraction of the interface debonding of C/SiC composites at elevated temperatures are predicted. When the interface shear stress increases, the debonding resistance at the interface increases, leading to the decrease of the debonding fraction at the interface, and the stress transfer capacity between the fiber and the matrix increases, leading to the higher first matrix cracking stress, saturation matrix cracking stress, and saturation matrix cracking density.

Few studies of cryogenic treatment were focused on nonferrous alloys, such as magnesium alloy. In this work, the effect of cryogenic treatment (77 K) before extrusion on microstructure and mechanical properties of ZK60 alloy was investigated. The results showed that many fine G.P. zones were formed during the cryogenic treatment and then grew to short fine β1′{\beta }_{1}^{^{\prime} } precipitates when heating before extrusion. These precipitates pinned dynamic recrystallized grain boundaries in the subsequent extrusion, resulting in fine gains and dispersed spherical precipitates. By the cryogenic treatment before extrusion, the extruded ZK60 alloy showed good tensile strength and elongation balance. Especially, elongation was improved by 29%.

In this paper, the temperature-dependent proportional limit stress (PLS) of SiC/SiC fiber-reinforced ceramic-matrix composites (CMCs) is investigated using the micromechanical approach. The PLS of SiC/SiC is predicted using an energy balance approach considering the effect of environment temperature. The relation between the environment temperature, PLS, and composite damage state is established. The effects of the fiber volume, interface properties, and matrix properties on the temperature-dependent PLS and composite damage state of SiC/SiC composite are analyzed. The experimental PLS and interface debonding length of 2D SiC/SiC composites with the PyC and BN interphase at elevated temperatures are predicted. The temperature-dependent PLS of SiC/SiC composite increases with the fiber volume, interface shear stress and interface debonding energy, and the matrix fracture energy and decreases with the interface frictional coefficient at the same temperature.

The effect of the addition of 2CaO·SiO 2 solid particles on dephosphorization behavior in carbon-saturated hot metal was investigated. The research results showed that the addition of 2CaO·SiO 2 particles have little influence on desilication and demanganization, and the removal of [Si] and [Mn] occurred in the first 5 min with different conditions where the contents of 2CaO·SiO 2 particles addition for the conditions 1, 2, 3, 4, and 5 are 0, 2.2, 6.4, 8.6, and 13.0 g, respectively. The final dephosphorization ratios for the conditions 1, 2, 3, 4, and 5 are 61.2%, 66.9%, 79.6%, 63.0%, and 78.1%, respectively. The dephosphorization ratio decreases with the increase of 2CaO·SiO 2 particles in the first 3 min. The reason for this is that the dephosphorization process between hot metal and slag containing C 2 S phase consisted of two stages: Stage 1, [P] transfers from hot metal to liquid slag and Stage 2, the dephosphorization production (3CaO·P 2 O 5 ) in liquid slag reacts with 2CaO·SiO 2 to form C 2 S–C 3 P solid solution. The increase of 2CaO·SiO 2 particles increases the viscosity of slag and weakens the dephosphorization ability of the stage 1. The SEM and XRD analyses show that the phase of dephosphorization slag with the addition of different 2CaO·SiO 2 particles is composed of white RO phase, complex liquid silicate phase, and black solid phase (C 2 S or C 2 S–C 3 P). Because the contents of C 2 S–C 3 P and 2CaO·SiO 2 in slag and the dephosphorization ability of the two stages are different, the dephosphorization ability with different conditions is different.

In this study, the parameters of 44 sticker breakout samples were analysed. The research mainly focused on the steel grades and slab thickness of stickers. Other processing parameters, such as slab width, casting speed, mould fluctuation, heat flux and operation, were also discussed. The results show that the number of stickers of low carbon steel and low alloy steel was 16 and 28, respectively. The stickers of low carbon steel were less than those of low alloy steel regardless of the thickness and width. The ratio of stickers per 1,000 casting heats of 220, 260 and 320 mm thickness slabs was 2.5, 0.5 and 0.6, respectively. The higher casting speed of 220 mm thickness slabs made the casting status unsteady and caused more stickers. From the perspective of width, the stickers were gradually increased along with the increase in width due to the worse mould slag. This study provides a foundation to reduce slab stickers and is helpful for a more efficient technology of continuous casting.

The formation of acicular ferrite (AF) in steel containing Lanthanum (La) with different contents of Aluminum (Al) has been investigated. It has been found that the amount of AF in La treated steel killed by Al is less than the one with little content of Al. The reasons are as follows: first, Al can change the type of La-containing inclusions and may reduce the effectiveness of La inclusion to induce the nucleation of AF. second, Al can make the cooling rate range of AF nucleation narrower in La treated steel. What’s more, Al can increase the decomposition temperature of austenite, and all these make AF formation difficult. In this study, the content of Al should be controlled to less than 0.018 wt% to obtain a more effective inclusion to induce the formation of AF.

The influence of the additive β-Si 3 N 4 on the formation and oxidation of Si 4 Al 2 O 2 N 6 during the sintering of Al, Si, and Al 2 O 3 powders under flowing nitrogen atmosphere was examined. An increasing molar percentage of β-Si 3 N 4 was shown to alter the morphology of Si 4 Al 2 O 2 N 6 from a fiber-like to a rod-like structure and also shortened the time needed to form a dense, continuous oxide layer, which served as a barrier to the diffusion of O 2. An optimal molar percentage of β-Si 3 N 4 of 29.9 mol% was discovered, at which the grain growth was enhanced, and the surface area was, in turn, reduced, yielding superior resistance to oxidation. Our results provided a theoretical basis for the formation of β-SiAlON and demonstrated the potential of its use in high-temperature oxidizing environments.

Corrosion at elevated temperature is a serious problem in running thermal power plants because of the use of low-grade fuels that contain substantial amounts of sulphur, vanadium, sodium etc. This article reports the high-temperature corrosion of weld metal and heat-affected zone (HAZ) of shielded metal arc-welding (SMAW) weldment in GrA1 steel in a molten salt (Na 2 SO 4 –60% V 2 O 5 ) environment at 900°C under cyclic conditions. The thermogravimetric technique was used to observe the kinetics of corrosion. The corrosion products formed on weld metal and HAZ of SMAW welded steel were characterized by scanning electron microscopy with energy dispersive X-ray analysis (EDX) and X-ray diffraction pattern. Weld metal was found to oxidize at a higher rate than those of HAZ due to the presence of sodium and sulphur in the inner oxide scale as confirmed by EDX, and this leads to high corrosion rate (in terms of weight gain).

The former analysis of the structural data in liquid Pb–Te alloys, based on the neutron diffraction measurements for this system, was insufficient to obtain the microscopic and spatial configurations in this system. In order to obtain these configurations, we have newly analyzed by using the Reverse Monte Carlo simulations and the method of Voronoi polyhedron. The partial structure factors Sij(Q){S}_{ij}(Q) and thereby gij(r){g}_{ij}(r) are newly estimated by using the former data of neutron diffraction measurements, which are now exactly reproduced by the obtained total structure factors S(Q)S(Q). From these results, it is concluded that the liquid Pb 0.5 Te 0.5 is spatially configured by the mixture of some sorts of covalent-type formation of PbTe molecules and dissociated Pb and/or Te ions with conduction electrons, which result is completely consistent with results of electrical resistivity measurements and also with the thermodynamic analysis.

In the present study, the comprehensive analyses based on the numerical simulation, in situ observation, and metallographic detection were carried out for the roll core of GCr15/45 carbon steel composite roll manufactured by the new electroslag remelting cladding (ESRC) method. During the ESRC process, the temperature distributions at the different radial and longitudinal positions of the roll core have great changes due to the different degrees of heat conduction from the slag bath, as a result, various microstructure and properties were obtained at the different positions of the roll core. The results illustrated that the ESRC process tended to be stable as the composite height reached a certain value and the high-temperature austenitization process mainly occurred in the radial regions where R > 60 mm, whereas no significant changes occurred at the areas where R ≦ 60 mm. The coarse grains and few Widmanstatten structures with proeutectoid ferrite were generated in the roll core areas near the bimetallic interface, while the fine grains with more proeutectoid ferrite were obtained in the roll core area away from the interface. Therefore, a higher tensile strength and a better plasticity were obtained for the specimens away from the interface.

To obtain the ultrafine martensite for BR1500HS ultra-high-strength steel, a new preparation process of cyclic heat treatment (CHT) with descending heat temperature and holding time along with cycle steps was developed. First, a series of thermal dilation tests were conducted with the temperature range of 420–730°C and the heat rate of 5 K/s on a Gleeble-3800 thermomechanical physical simulator. According to the experimental data, the temperature ranges and the optimal holding time to completely austenitize BR1500HS were determined. Then, to confirm the optimal parameters of CHT for BR1500HS, several tests with various temperatures and cycle steps were conducted and analyzed by optical microscope and scanning electron microscope. Subsequently, the CHTs with decreasing heating temperature and holding time were studied due to the increasing internal energy of steel along with the CHT process. The lath width was measured as a criterion to evaluate the refinement degree in this article. After several loops of heat treatment, the lath width is reduced to 0.268 µm. Finally, the hardness evolution of the specimens subjected to CHT in this study was analyzed and compared with the lath width test results, which justified the effectiveness of the new developed process.

In this work, the influence of pulse frequency on the corrosion resistance of Cu–Zn binary alloy has been investigated by using electrochemical workstation, scanning electron microscope and X-ray diffraction. The results have shown that after the electric pulse treatment, the average grain size in the microstructure of high-zinc binary brass decreased and the corrosion resistance increased. The thickness of dezincification layer decreased from 49.8 to 30.8 µm. The diameter of capacitive reactance arc increased from 741.1 to 2898.0 µm. The corrosion potential increased from −0.2719 to −0.2378 V, and the corrosion current density decreased from 6.3147 × 10 −6 to 4.6971 × 10 −7  A cm −2 by one magnitude order.

The bonding character of liquid lead telluride PbTe\text{PbTe} is thermodynamically investigated in detail. Its possibility as an ionic melt composed of cation Pb2+{\text{Pb}}^{2+} and anion Te2−{\text{Te}}^{2-} is not acceptable, by comparing the ionization energy of Pb\text{Pb} atom, electron affinity of Te\text{Te} atom and the ionic bonding energy due to the cation Pb2+{\text{Pb}}^{2+} and anion Te2−{\text{Te}}^{2-} with the help of structural information. Solid lead telluride PbTe as a narrow band gap semiconductor might yield easily the overlapping of the tail of valence band and that of conduction one. And on melting, it becomes to an ill-conditioned metallic state, which concept is supported by the electrical behaviors of liquid Pb–Te alloys observed by the present authors. As structural information tells us about the partial remain of some sorts of covalent-type mono-dipole and poly-dipole of the molecule PbTe\text{PbTe}, all systems are thermodynamically explained in terms of a mixture of these molecules and cations Pb4+{\text{Pb}}^{4+} and Te2+{\text{Te}}^{2+} and a small amount of the conduction electrons are set free from these elements based on the ternary solution model.

The effects of the cooling rate after hot deformation on phase transformation, the microstructure of the designed nonquenched and tempered medium-carbon carbide-free bainitic steel have been investigated during the dynamic continuous cooling process. The results show that with the increase of the cooling rate, the morphology of the carbide-free bainite of the experimental steel evolves from granular bainite to lath bainite. Meanwhile, the hardness increases, and the amount of the retained austenite decreases with the increase of the cooling rate. Besides, the morphology evolution of the retained austenite from block to film is revealed by EBSD. Moreover, 0.5°C/s is considered to be the favorable cooling rate to obtain the best strength–toughness matching. Furthermore, the semi-industrial experimental results proved that the tensile strength, yield strength and Charpy impact energy were 1,298 MPa, 847 MPa and 38 J, respectively.

In this article, the influence of electrode tip diameter is investigated for spot welded duplex stainless steel (DSS). Electrode tip diameter and welding current are considered as the major influencing parameters and their values are varied within the feasible range, suitable for 0.8 mm thick sheet, whereas other important parameters such as welding time and electrode force are kept constant. DSS with the chosen thickness range is now becoming a useful material in automotive body-in-white applications and in future it will become one of the key materials replacing the existing materials and hence research outcome of the present work may be beneficial from application view point. In this work, the spot welding quality is inspected through metallurgical aspects (microstructure and microhardness), physical aspects (nugget diameter and electrode indentation), mechanical performance (tensile shear strength [TSS]) and failure mode. The obtained result shows that smaller electrode tip diameter limits nugget diameter due to expulsion phenomena and increases electrode indentation due to higher current intensity. TSS decreases with increase in electrode tip diameter for the same welding current but maximum TSS obtained for particular electrode tip diameter increases with increase in electrode tip diameter up to a specific limit and then it remains constant.

The TC4 titanium alloy powder test piece was prepared by spark plasma sintering. The multi-pass hot deformation of the TC4 titanium alloy was tested by using the Gleeble-1500 experiment machine. Measurement of relative density, X-ray diffraction, optical microscopy, scanning electron microscopy and electron backscatter diffraction were carried out for the TC4 titanium alloy. In order to reveal the evolution of the microstructure, describing its changes systematically is necessary, which has become the focus of this article. The results show that after multi-pass hot deformation, the relative density of the TC4 titanium alloy could reach 99.93%. With the increase in deformation and decrease in temperature, the β-transformed phase was retained, and many fine β-transformed phases were formed between two adjacent lamellar α. During the one-pass hot deformation, the rapid increase in relative density was the main reason for the instability of the flow stress in the stress–strain curve. For two-pass and three-pass hot deformations, more features of dynamic recrystallization and the characteristics of dynamic recovery at high strain rates (5 s −1 ) could be found. The size of the grains was about 15 µm after the three-pass hot deformation.

Corrosion behaviors of 316 stainless steel (316 ss) and Inconel 625 alloy in molten NaCl–KCl–ZnCl 2 at 700°C and 900°C were investigated by immersion tests and electrochemical methods, including potentiodynamic polarization and electrochemical impedance spectroscopy. X-ray diffraction and scanning electron microscopy/energy dispersive spectroscopy were used to analyze the phases and microstructures of the corrosion products. Inconel 625 alloy and 316 ss exhibited high corrosion rates in molten chlorides, and the corrosion rates of these two alloys accelerated when the temperature increased from 700°C to 900°C. The results of the electrochemical tests showed that both alloys exhibited active corrosion in chloride molten salt, and the current density of 316 ss in chloride molten salt at 700°C was 2.756 mA/cm −2 , which is about three times the value for Inconel 625 alloy; and the values of the charge transfer resistance ( R t ) for Inconel 625 were larger than those for 316 ss. The corrosion of these two alloys is owing to the preferred oxidation of Cr in chloride molten salt, and the corrosion layer was mainly ZnCr 2 O 4 which was loose and porous and showed poor adherence to metal.

The chromium valence states in the CaO–SiO 2 –FeO–MgO–CrO x system were investigated by X-ray photoelectron spectroscopy (XPS). The results indicated that the XPS peaks of Cr 2p 3/2 and Cr 2p 1/2 locate at the binding energy of ∼577 and ∼586 eV, respectively. There are three kinds of chromium ions such as bivalent Cr( ii ), trivalent Cr( iii ), and hexavalent Cr( vi ) in the CaO–SiO 2 –FeO–MgO–CrO x slag. Cr( iii ) is the dominant valence state, and more than 77.99% Cr is trivalent Cr( iii ). The fraction of Cr( ii )/Cr is in the range of 11.24–17.22%. The fraction of Cr( vi )/Cr is below 4.80%. The fraction of Cr( ii )/Cr decreases with increasing slag basicity, Cr 2 O 3 content, temperature, or oxygen pressure log(PO 2 ), while the fraction of Cr( iii )/Cr increases with increasing basicity, Cr 2 O 3 content, temperature, or oxygen pressure. The trend of change is opposite. Low log(PO 2 ), high Cr 2 O 3 content, and high temperature are beneficial to reduce the toxic hexavalent Cr( vi ). The slag basicity has little influence on the fraction of Cr( vi )/Cr.

The current state and prospective of electric discharge methods of synthesis of carbon and metal–carbon nanomaterials (CNMs) in different areas of science, technology and industry are considered in the present paper. It was shown that as a result of electric discharge treatment of liquid hydrocarbons, the productivity of CNMs (namely, onion-like carbon, carbon nanotubes, carbon nanofibers and carbon thin films) in terms of the percentage of carbon, released from initial liquid as a nanomaterial, was 6.1% for pentane, 10.2% for hexane, 8.7% for cyclopentane, 14.4% for cyclohexane, 12.0% for benzene and 16.8% for kerosene. Component and phase composition of obtained products depends on the electrode material and composition of initial hydrocarbon liquid.

Soft-contact of molten steel can be achieved by applying a high-frequency electromagnetic field above the mold of continuous casting, which can effectively eliminate surface defects and achieve billets with no cracks and no oscillation marks. It also has some influence on the mold flux. In this study, the effect of a high-frequency electromagnetic field (20 kHz) on a mold flux flow field was simulated using a finite element software, and the slag film was extracted using a slag film simulator. The effect of the high-frequency magnetic field on the microstructure of the mold flux was analyzed using X-ray diffraction, Raman spectroscopy, and mineral phase testing. The results show that the high-frequency electromagnetic field disrupts the orderly movement and increases the movement rate of the liquid flux. The precipitate phase of the slag film did not change, but the silicate dimer Q 1 decreased, the chain Q 2 increased, and the network degree was increased. The slag film structure changed from the original two-layer form of crystalline layer–glass layer into a three-layer form of crystal layer–glass layer–crystal, and the crystallization ratio increased by 35% on average. The grain-size melilite granularity was reduced from the original 0.12 to 0.005 mm.

Heat–cool (H–C) cycle is a serious natural weathering mechanism for rock engineering in temperate desert climate; meanwhile, engineering rocks usually involve responses to impact loads arising from blasting operation, mechanized construction, and seismic oscillation. Considering the universality and destructiveness of rock failure caused by H–C cycle weathering coupled with dynamic loading, split Hopkinson pressure bar tests were conducted for sandstone with various H–C cycles. Additionally, hydrothermal coupled damage ( D ) was defined based on variation of total import strain energy. Energy evolution, damage, and microscopic characteristics of sandstone after diffierent H–C cycles were studied. Finally, the microcosmic structure changes of sandstone after various H–C cycles are compared by means of scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) technology. Results show that decreasing rate of total import strain energy in high temperature group is significantly larger compared with that in low temperature group and moderate temperature groups. Repeated H–C cycles produce the thermal stress at the mineral boundary constantly and fracture along the boundary of the mineral particle according to the SEM and EDS results.

The laser flash technique is a standard method to measure the thermal diffusivity of solid samples especially at high temperatures. To understand the reliability of thermal diffusivity evaluation at high temperature for solid samples with low-thermal-diffusivity values, we analyzed the effect of radiative heat loss using the logarithmic method. The results revealed that when the Biot number was 0.1, the deviation from the input thermal diffusivity value was approximately −1.6%. In addition, when an aluminum silicate (AS) sample was heated to 1,273 K, the maximum deviation was approximately −0.35%. In contrast, the difference between the input value and the thermal diffusivity evaluated by the halftime method when AS was heated to 1,273 K was approximately 2.38%. Thus, since the effect of radiative heat loss was found to be negligible, it is concluded that the normalized logarithmic method should be very useful for the thermal diffusivity analysis of low-thermal-diffusivity solid samples at high temperature.

Kinetics of iron removal from quartz under the ultrasound-assisted leaching was explored in this paper, and the effects of temperature, leaching time, stirring speed and ultrasonic input power on iron removal were studied. The results revealed that the reaction kinetics followed the shrinking core model and the product layer internal diffusion was the rate-determining step in the ultrasound-assisted leaching process. The activation energy of the ultrasonic-assisted leaching reaction was 27.72 kJ/mol, which was 7.28 kJ/mol higher than that of the regular method. Moreover, the kinetic equation and mathematical model of iron removal from quartz were established. Compared with the regular leaching, only 40 min were required for the ultrasound-assisted leaching process to achieve an iron removal rate of up to 74%. Under the optimal parameters, SiO 2 content of concentrate increased from 99.5828% to 99.9047%, and Fe 2 O 3 content reduced from 0.0857% to 0.0223%. Additionally, it was found that the iron removal rate increased with increasing temperature, stirring speed or ultrasonic power.

The oxidizability characterization method of slag system has a decisive influence on the accuracy of the desulfurization model. By carrying out the balance experiments of melting system composed of CaF 2 –CaO–Al 2 O 3 –SiO 2 –TiO 2 –MgO–FeO slag system and Inconel 718 superalloy, the influence of Al 2 O 3 and FeO on desulfurization distribution ratio at 1,773 K was studied. Based on the ion and molecule coexistence theory in slag, the effects of three oxidizability characterization methods, [Fe]–[O] balance, [Al]–[O] balance, and [Fe]–[Al]–[O] balance, on the accuracy of desulfurization thermodynamic model were studied. The results show that the effect of FeO on desulfurization distribution ratio is more significant than that of Al 2 O 3 when the FeO content in slag is greater than 0.014%. When the FeO content in the slag is less than 0.014%, the effect of Al 2 O 3 on the slag oxidizability will be greater than that of FeO. The calculated value of [Fe]–[Al]–[O] balance model is closer to the experimental-measured value compared to [Fe]–[O] balance model and [Al]–[O] balance model alone at 1,923 K.

The development of an environmentally friendly binder can immensely benefit and promote the BF slag fiber industry. Accordingly, in this study, fiber insulation pipes were prepared using water glass, polyvinyl alcohol (PVA), and PVA–glutaraldehyde (GA); moreover, their bulk density, moisture absorption capacity, and thermal conductivity coefficient were measured and compared. The results demonstrated that the values of these three parameters depend on the binder concentration and dosage under certain fiber quality, pipe sizes, and manufacturing process conditions. The best binder composition was proven to be that of PVA–GA, prepared using 3 wt% PVA and 5 wt% GA herein, which facilitated reduction in the bulk density and improvement of the waterproof properties and insulation performance of the slag fiber pipes.

The formation and evolution of nonmetallic inclusions in pipeline steel were investigated by SEM, EDS and INCA Feature Analysis System, with the industrial process of electric arc furnace → ladle furnace (LF) refining → vacuum degassing → continuous casting. The composition, size and amount of inclusions during refining process were discussed systematically. The results show that inclusions at each refining step are mainly small-particle inclusions (below 5 µm), and the total number of inclusions has been reduced significantly due to the refining effect of slag during LF refining. The calcium (Ca) treatment increases the amount of small inclusions. The types of inclusion are mainly Al 2 O 3 and MnO–SiO 2 –Al 2 O 3 before LF, and they are transformed into CaO–Al 2 O 3 , MgO–Al 2 O 3 and CaO–MgO–Al 2 O 3 during LF process. After Ca treatment, inclusions are changed to CaO–Al 2 O 3 –(CaS) and CaO–MgO–Al 2 O 3 –(CaS). Typical inclusions are still mainly CaO–Al 2 O 3 and CaO–MgO–Al 2 O 3 in tundish, but the composition of those inclusions has been changed and located to the low melting point region in ternary phase diagram. Such inclusions will further be removed as continuous casting approaches.

Tunnel water burst is among the common severe geological hazards in deep buried tunnel projects in China and throughout the world. Asphalt grouting is an effective method to block seepage channels in macroporous strata under the condition of flowing water, but it has defects such as a high heating temperature, complex high-temperature construction technology, and poor controllability during the grouting process. A type of “water-in-oil” low-thermal asphalt was developed in this study. It can cool and solidify and not be diluted when encountering water, and its construction temperature can be below 80°C. Experimental research on the physical and mechanical properties of the low-thermal asphalt leakage-blocking material was completed, including proportion experiments, fluidity, sensitivity to temperature, one- and two-dimensional indoor diffusion experiments, and impact experiments, which presented its physical and mechanical properties and can provide guidance for the application of the material in site projects.

The top gas recycling-oxygen blast furnace (TGR-OBF) is a reasonable method used to reduce both coke rate and energy consumption in the steel industry. An important feature of this process is shaft gas injection. This article presents an experimental study on the gas–solid flow characteristics in a TGR-OBF using a two-dimensional cold model. The experimental conditions and parameters were determined using a series of similarity criteria. The results showed that the whole flow area in the TGR-OBF can be divided into four distinct flow zones, namely, the stagnant zone, the plug flow zone in the upper part of the shaft, the converging flow zone and the quasi-stagnant flow zone, which is similar to that in a traditional blast furnace. Then the effects of batch weight and the ratio ( X ) of the shaft injected gas flow rate to the total gas flow rate on solid flow behaviour were investigated in detail. With the increase in batch weight, the shape of the stagnant zone tends to be shorter and thicker. Furthermore, with the increase in X value from 0 to 1, the stagnant zone gradually becomes thinner and higher. The results obtained from the experiments provide fundamental data and a validation for the discrete element method–computational fluid dynamics-coupled mathematical model for TGR-OBFs for future studies.

The cylindrical samples of TC4 titanium alloy prepared by spark plasma sintering (SPS) were compressed with hot deformation of 70% on the thermosimulation machine of Gleeble-1500. The temperature of the processes ranged from 850°C to 1,050°C, and the strain rates varied between 0.001 and 5 s −1 . The relative density of the sintered and compressed samples was measured by the Archimedes principle. During hot deformation, the microstructure of the sample was observed. The results show that the average relative density of the samples was 90.2% after SPS. And the relative density was about 98% after the hot deformation of 70%. Under high temperature (>950°C), the sensitivity of flow stress to temperature was reduced. At low strain rate (0.001 s −1 ), the increase in the deformation temperature promoted the growth of dynamic recrystallization (DRX). At the same temperature, the increase in strain rate slowed down the growth of DRX grains. And the variation tendency was shown from the basket-weave structure to the Widmanstätten structure at a low strain rate (<0.1 s −1 ), with increase in the strain rate.

Ce, Zr and Ce–Zr composite experimentl steel were prepared by vacuum induction furnace and 550 twin-roll reversible rolling mill. Optical microscope (OM), scanning electronic microscopy (SEM) and energy dispersive spectrometer (EDS) were used to observe the rolling microstructure of the experimental steel. The mechanical properties of the experimental steel were tested and analyzed. The effect of cerium zirconium oxide inclusions on nucleation, tensile and impact fracture mechanism of intragranular acicular ferrite (IAF) was investigated. The results show that the rolling microstructure of steel containing 0.0052% Ce and the steel under composite treatment containing 0.0053% Ce and 0.0055% Zr is refined. IAF generation can be induced by Al–Ce–O inclusion of the size of 4 µm or induced by Al–Ce–Zr–O + MnS inclusion of the size of 3 µm. The yield strength and tensile strength of the steel treated by Ce–Zr are 428 and 590 MPa, respectively, the elongation is 23.55%, the longitudinal impact energy at −60°C is 189 J, which are 31, 45, 46 J and 6.25%, respectively, higher than those of the matrix steel. The dimple of the experimental steel at the fracture surface is larger and deeper than that of the matrix steel. The small inclusions in uniform distribution contribute to the high tensile strength of the experimental steel.

Many developed techniques for rare-earths’ (REs) recovery from magnet scraps are highly sensitive to the oxidative roasting process of scraps under high temperature. This study focused on phase evolution, microstructural changes and element distribution during the roasting of the widely used Nd–Fe–B and high-potential Ce–Fe–B scrap powders at 800°C. The sustained oxidation of Fe to Fe 2 O 3 and the constant formation of composite RE oxides were the main reaction processes with increasing roasting cycles for the two scrap powders. The complete oxidation phases consisted of NdBO 3 , NdFeO 3 and Fe 2 O 3 for the Nd–Fe–B scrap powder, while the final products were NdBO 3 , GdFeO 3 and Fe 2 O 3 as well as individual CeO 2 for the Ce–Fe–B scrap powder. An oxygen diffusion front was observed, forming a dark gray oxidized layer with almost the same thickness on the large particle surface. Additionally, a Fe 2 O 3 layer covered the particle surface when the oxidation of the two scrap powders was complete. In oxidized Nd–Fe–B particles, the observed white regions corresponded to the oxidized intergranular Nd-rich phase as indicated by the almost same size and position before and after roasting. In Ce–Fe–B particles, the oxidized intergranular phase appeared to gather and grow, and a RE-rich layer appeared between the oxide/unoxidized layer. Conclusively, the iron-outward diffusion and the oxygen-inward diffusion were dominated by the oxidation of both Nd–Fe–B and Ce–Fe–B particles.

Rock acts as a natural brittle material and demonstrates reactions to various dynamic disturbances and high temperature. Mechanical property fluctuations under high temperature and dynamic load for rock materials including marble, sandstone and granite are studied in an underground project of Qinling Mountain in China, exposed to 1,000°C treatments and different strain rate impact loadings. Two main research issues are explored: (1) variations of strength and failure modes of the same high-temperature rock type under different strain rate impact loadings. (2) Comparison of strength and failure modes of three high-temperature rock types under same strain rate impact loadings. Experimental results indicate that both 1,000°C temperature and the strain rate exert significant influence on dynamic compressive strength, and dynamic compressive increase factor and failure modes of three rock types. However, the influences of high temperature and strain rate on different rock types have obvious differences.

The solution-aging treatment parameters, including solution temperature, cooling rate and aging temperature, have significant influences on the microstructures and comprehensive mechanical properties of titanium alloy. In this work, the detailed microevolution behaviors of Ti–10V–2Fe–3Al alloy under different solution and aging conditions have been investigated through a series of heat-treatment experiments. The results of solution-treatment experiments reveal that the content of α p -phase is reduced to zero as the solution temperature is raised to a certain α → β critical transformation point. Recrystallized β-grains can be observed at the solution temperature of 820°C. In addition, the cooling way (air cooling or water cooling) has little influence on the microevolution behaviors for this alloy during the solution-treatment process. As for the solution-aging-treatment experiments, the results reveal that α s -phases are precipitated from the supersaturated β-phase, and the fraction of α s -phase increases with increasing aging temperature. However, the precipitated α-grains intend to coalesce and coarsen as the aging temperature raises above 510°C. Therefore, the advocated solution-aging-treatment program is solution treatment at 820°C with air cooling followed by aging treatment at 510°C with air cooling.

The mechanism of inclusions precipitation of the E690 offshore platform steel, with and without addition of yttrium, was studied using the thermodynamic calculation method. The results show that in the E690 steel in the absence of yttrium, the MnS inclusions were precipitated in the liquid phase at the solidification front. By adding the yttrium, MnS inclusions were replaced by spindle and spherical yttrium-containing oxide and sulfide complex inclusions, and the precipitation sequence of yttrium-containing inclusions in the liquid steel was Y 2 O 3 , Y 2 O 2 S, and YS. However, Y 2 S 3 inclusions cannot be precipitated in the liquid steel under the experimental conditions. It was also found that Al 2 O 3 inclusions can be formed in the liquid steel with and without addition of yttrium. The thermodynamic calculation results are in accordance with the experimental results.

An innovative rare earth oxide-containing slag for hot metal dephosphorization was proposed, and the factors influencing the efficiency during the dephosphorization of hot metal using rare earth oxide-containing slags were also studied. An increase in the temperature up to 1,550°C is beneficial to the dephosphorization process, and the maximum degree of dephosphorization for slags containing 6 wt% rare earth oxides is 44.49%; further temperature increases would deteriorate the efficiency, and the degree of dephosphorization decreases to 37.38% at 1,600°C. An increase in the basicity of slags up to 3.0, and the rare earth oxide content up to 6 wt%, improves the dephosphorization efficiency; further increase in the basicity and rare earth oxide content, the efficiency has almost no change. It was also found that an increase in the quantity of slags is beneficial to the dephosphorization reaction.

The nonisothermal thermogravimetric analysis was implemented for gasification of sawdust char (SD-char), wheat straw char (WS-char), rice husk char (RH-char), bamboo char (BB-char) and anthracite coal (AC) in the presence of CO 2 . The dependence of activation energy upon conversion for different biochars and AC was obtained by the integral isoconversional nonlinear (NL-INT) method which is a model-free method. Based on the activation energy values from the NL-INT method, a model-fitting method called random pore model (RPM) was used to estimate the kinetic parameters including the preexponential factor and pore structure parameter from the experimental data. The results are shown that the gasification reactivity of different samples from high to low can be sorted as that of WS-char, SD-char, BB-char, RH-char and AC. In the early stage of gasification, the activation energy values of biochars increase generally with an increase in the conversion degree, whereas the value of AC decreases. Thereafter, the activation energy values remain almost unchanged when the conversion is up to some extent. When the conversion degree varies between about 0.3 and 0.9, these carbon materials can be sorted in the order of average activation energy from low to high as WS-char, SD-char, AC, RH-char and BB-char, respectively, 134.3, 143.8, 168.5, 184.8 and 193.0 kJ/mol. It is shown that a complex multistep mechanism occurs in the initial stage of gasification, while a single-step gasification mechanism exists in the rest of the gasification process. The RPM is suitable for describing the gasification of biomass chars and AC except the initial gasification. Additionally, it is found that the kinetic compensation effect (KCE) still exists in the gasification reactions of biochars and AC. However, the AC deviates markedly from the KCE curve. This may be caused by the similarity of carbonaceous structure of biochars and the difference in reactivity between biochars and AC.

CaO–MgO–Al 2 O 3 –SiO 2 glass-ceramics with diopside as the main crystalline phase were prepared by melting blast furnace slag obtained from Baotou Iron and Steel Company. The effect of heat treatment on the crystallization behavior of glass-ceramics, containing a large proportion of melted blast furnace slag, was studied by means of differential thermal analysis and scanning electron microscopy. The optimum heat-treatment regime was obtained by orthogonal experimental results for glass-ceramics in which blast furnace slag comprised 70% of the composition and 1% Cr 2 O 3 and 4% TiO 2 were used as nucleating agents. The nucleation temperature was 750°C for 2.5 h and the crystallization temperature was 930°C for 1 h. Under this regime, the performance of the glass-ceramic was better than that of other groups in the orthogonal experiment.

A series of long-term high-temperature aging tests of ASME A335-P92 steel from 1,000 to 29,000 h at 650°C were carried out. The microstructure evolution of as-received and aging specimens at different stages was investigated using optical microscope observations, scanning electron microscope examinations, and TEM investigations. The static mechanical strength properties (yield strength/ultimate tensile strength) at room and 600°C test temperatures and the plastic performance (elongation/reduction in area) were also analyzed. The experimental results show that the Laves phase can be precipitated rapidly in the early aging period. After a certain aging period, the continuous precipitation of M 23 C 6 and the relatively high coarsening rate of Laves resulted in a rapid decrease of room and high-temperature mechanical properties in the early aging period. However afterwards for the long aging time, a slow decline in tendency of mechanical properties was presented.

Welding and relevant studies are indispensable to employ high-entropy alloys for practical applications. In this study, Al 0.3 CoCrCu 0.3 FeNi high-entropy alloy with single FCC phase was used to make “bead-on-plate” friction stir welds at different rotational speeds, and the effects on microstructure and mechanical properties were studied. Several banded structures containing oxide or nitride particles were observed in the stir zone (SZ), and the chemical wear of the polycrystalline cubic boron nitride tool was confirmed. The microhardness distribution of the welds showed higher hardness in the SZ because of grain refinement and the presence of deformed grains. The electron backscattered diffraction results suggested that the high-entropy alloy with low stacking-fault energy experienced recrystallization during friction stir welding, which was similar to other conventional materials with low stacking-fault energy.

An experimental test is carried out on the 70t converter in Masteel to study the law of middle period dephosphorization in the smelting period. It is found that the dephosphorization rate is slow in the early and middle period of smelting and the content of the final P in steel cannot reach the standard due to the low oxidation of slag. The content of the final P in steel can be controlled within 0.02% by adding ore to the molten bath in the middle period and raising the lance position. The experimental test shows that the dephosphorization can still be achieved by a large margin if appropriate slag conditions are maintained in the middle period when the C and O reactions are strong. By theoretical calculation, it is concluded that the slag content should be controlled between 15 and 23%, and the basicity of slag should be between 2.5 and 2.8 in the middle period of production. Through the observation of experimental slag by SEM, it is found that the limiting factor of dephosphorization in the middle period under the test conditions is that the dephosphorization speed is too slow due to the low oxidation, rather than the solidification of phosphorus.

The 444-type heat-resistant ferritic stainless steel is widely utilized in automotive exhaust pipes and solid oxide fuel cells, due to its excellent properties at elevated temperature. To meet the demands of significantly harsh service environments, rare earths were added in 444-type ferritic stainless steel. For the purpose of evaluating the effect of rare earths on pitting corrosion initiation, the metastable pitting corrosion behavior in 444-type ferritic stainless steel was studied through potentiodynamic polarization and potentiostatic polarization tests. The results demonstrated that pitting corrosion was initiated at the inclusion/alloy interface. The cerium alloying in 444-type ferritic stainless steel decreased the amount of preferential dissolution sites. The beneficial effect of Ce on pitting corrosion resulted from the formation of stable cerium oxides, as well as from the reduction in the amount and size of inclusions in 444-type ferritic stainless steel. In addition, electrochemical impedance spectroscopy test results revealed that cerium alloying enhanced the polarization resistance of passive films through insignificant thickness alteration.

To improve the wear resistance, toughness, and hardness of alloy, the quenching and partitioning (Q&P) technology was applied in the VC particulate (VCp) reinforced wear-resistant alloys, which were prepared by adding different Mn contents (2–5 wt%). The effects of partitioning time on the distribution of alloying elements shown by EDX mapping, retained austenite fraction, microstructure, macro-hardness, and impact toughness were investigated. The results showed that the effect of carbon partitioning time on the hard phase of the wear-resistant alloy was not significant. However, the carbon partitioning time greatly affected the microstructure and the mechanical properties of alloys, such as retained austenite, hardness, and impact toughness, and there was also a strong correlation with the Mn content. When the Mn content was lower (2.51 wt%), the retained austenite content increased with the carbon partitioning time, which resulted in decreased hardness and increased impact toughness. However, when the Mn content was higher (4.52 wt%), the opposite results occurred. This study provided an application of the Q&P technology in a VCp-reinforced wear-resistant alloy.

The Mo/ZrO 2 electrode was prepared by combining hydrothermal synthesis with powder metallurgy, and this new electrode material has a totally different microstructure from the conventional electrode. The grain size of the new electrode was fine, and the size of ZrO 2 in the alloy reached 200 nm. According to the results, the Mo–ZrO 2 electrode has better performance, because the erosion occurs along the grain boundaries. Meanwhile, the new electrode, based on its fine grain, can effectively improve the corrosion resistance of the electrode.

The solidification microstructure of an Fe–Mn–C–Al high-Mn steel with added Nb was studied by optical microscopy and scanning electron microscopy. The results showed that the size of the columnar and equiaxed grains in the solidified structure of the high-Mn steel without added Nb was large. When Nb was added, the size of the equiaxed and columnar grains in the solidification structure of the high-Mn steel decreased. The twin-induced plasticity in the high-Mn steel with added Nb clearly refined the grain size of the solidified structure and simultaneously increased the equiaxed crystallization rate. The high-melting-point second-phase particles increased the heterogeneous nucleation rate, which was beneficial for grain refinement. A large amount of Nb precipitates from the solidification process increased the equiaxed crystallization rate of the solidified microstructure. The increased crystallization rate affected the growth direction of the columnar and equiaxed grains during solidification and indirectly decreased the probability of crack formation, which improved the quality of the twin-induced plastic steel.

In this paper, the damage accumulation and life prediction in fiber-reinforced ceramic-matrix composites (CMCs) subjected to thermomechanical fatigue (TMF) loading are investigated. The relationships between TMF damage mechanisms, fatigue hysteresis-based damage parameters, fraction of broken fiber, and applied cycles are established. Evolution of fatigue hysteresis dissipated energy, fatigue hysteresis modulus, fatigue peak strain, fatigue broken fiber fraction versus applied cycle curves, and the fatigue life S–N curves is analyzed. Damage accumulation and fatigue life of cross-ply silicon carbide/magnesium aluminosilicate composite under in-phase (IP)- and out-of-phase (OP)-TMF and isothermal fatigue (IF) loading are predicted. Under the same fatigue peak stress, the fatigue lifetime decreases from IF loading at 566°C to IF loading at 1,093°C, IP-TMF and OP-TMF. The TMF loading significantly reduced the fatigue lifetime of CMCs.

The morphology evolution from monoclinic molybdenum trioxide (β-MoO 3 ) to orthorhombic molybdenum trioxide (α-MoO 3 ) and quantitative analyses of their mixtures were examined. It was found that the morphology (from spherical to elliptical shape) and color (from green to white) displayed obvious changes when β-MoO 3 converted to α-MoO 3 in ambient air at 773 K. The transformation from β-MoO 3 to α-MoO 3 resulted from a change of the internal crystalline structure. The mass percent of β-MoO 3 in MoO 3 mixtures showed an excellent linear relationship with the relative intensity ratio of the strongest peaks in X-ray diffraction patterns. This approach provides a simple and time-saving method to evaluate the amount of β-MoO 3 , which is a promising material in catalyst and electrochemical applications, in such mixtures. This finding may provide guidance for the analysis of catalytic performance of MoO 3 mixtures. In addition, it was found that β-MoO 3 can be easily decomposed into suboxides such as MoO 2 and Mo 4 O 11 in pure argon gas atmosphere. The possible decomposition mechanism of β-MoO 3 is discussed.

The microstructure of metatitanic acid and its transformations to titanium dioxide during calcination have been investigated previously. However, the detailed microstructure of metatitanic acid has not been elucidated. Herein, we report the high-resolution scanning electron microscopy and X-ray powder diffraction determinations of the microstructure of metatitanic acid and its transformation to titanium dioxide during calcination. It is the first time that the detailed microstructure of metatitanic acid and its transformation to rutile titanium dioxide during calcination have been observed and elucidated. A mechanism of the transformation from metatitanic acid to crystalline titanium dioxide during calcination is described. The basic building blocks of metatitanic acid are the ultrafine crystals with an averaged diameter of a few nanometres, and these ultrafine crystals aggregate to form the porous primary particles. The primary particles further agglomerate to form the porous secondary particle. During the calcination, metatitanic acid undergoes size enlargement of ultrafine crystals, anatase–rutile transformation, merge of primary particles, and the crystal growth of titanium dioxide.

Nickel-based alloys play an important role in the field of high-temperature alloys, which are widely used in nuclear reactors, aerospace and components of turbomachinery. However, the high susceptibility of welding hot crack is a main shortcoming to nickel-based alloys. One of the methods that reduce hot cracking susceptibility is by adjusting element constitution of weld metal and another method is by reducing transient stress. This article used finite element method to study the effect of cooling source on transient stress of the nickel-based alloy weld joint. The selection of appropriate cooling technique can decrease the peak of the transient von Mises stress and make the tensile stress turn into compressive stress, which is beneficial to reduce hot cracking susceptibility. The peak of the transient von Mises stress decreases as the cooling intensity increases from 0 to 15,000 W/m 2  K, but increases if the cooling intensity is ineffective. When the distance between cooling source and heat source reaches 35 mm, the weld can get larger region of compressive stress. The peak of the transient von Mises stress decreases with increasing radius of cooling source and reaches minimum value at 12 mm. Combined cooling is more effective in reducing the peak of this stress than the conventional single trailing cooling source.

Distribution of Ge atoms between tetrahedral and octahedral sites in the spinel-type structure of Fe 2.64 Ge 0.36 O 4 thin films fabricated by radio frequency sputtering with a composite target of magnetite and Ge has been investigated by extended X-ray absorption fine structure analysis. The local structural changes around the Ge atoms in the films induced by annealing at 573 and 873 K are discussed through comparison of the local structure for sintered crystalline Fe 2.7 Ge 0.3 O 4 in which Ge atoms preferentially located at the tetrahedral site of the spinel-type structure. This work provides successful information on the structural change with magnetic property of the thin films as follows: the Ge atoms statistically distributed at the tetrahedral and octahedral sites of the as-synthesized films and preferentially occupied the tetrahedral site by annealing at 873 K corresponding to the increase in magnetization.

In this work, thin aluminum alloy sheets with thickness of 0.8 mm were friction stir lap welded using small shoulder plunge depths of 0 and 0.1 mm. The joint formation, microstructure and mechanical properties were investigated. Results show that voids appear inside the stir zone when the small plunge depth of 0 mm is used because the tool shoulder cannot exert a good material-collecting effect at such low plunge depth. A plunge depth of 0.1 mm causes tight contact between the shoulder and the material and thus results in good material-collecting effect, which is helpful to eliminate the void. Sound joints are attained at a wide range of welding parameters when using the shoulder plunge depth of 0.1 mm. No crack is observed inside the bonding ligament. The joints own higher failure loads when the retreating side (RS) of the joint bares the main load during the lap shear tests. The shear failure load first increases and then decreases with increasing the rotating and welding speeds, and the maximum failure load of 6419 N is obtained at 600 rpm and 150 mm/min. The hardness of the joint presents a “W” morphology and the minimum hardness is obtained at the heat affected zone. The joints present tensile fracture and shear fracture when the advancing side and RS bare the main loads, respectively.

The precise prediction of end-point carbon content in liquid steel plays a critical role in increasing productivity as well as energy efficiency that can be achieved in the basic oxygen furnace (BOF) steelmaking process. Due to numerous and diversity of the studies on BOF end-point carbon prediction, it seems necessary to provide a comprehensive literature review on state-of-the-art developments in end-point carbon prediction for BOF steelmaking. This paper presents the characteristics of different end-point carbon prediction models. The end-point carbon prediction for BOF steelmaking has initially relied on the experience and skill of the operators. With the development of information technology and auto-detection methods, BOF end-point carbon prediction mainly has gone through three stages, such as static prediction, dynamic prediction, and intelligent prediction. Future contributions to the development and application of intelligent end-point carbon prediction in BOF steelmaking are still arduous tasks. However, it is envisaged that the intelligent end-point carbon prediction will witness more frequent applications and greatly improve the high-quality, high-efficiency, and stable production for BOF steelmaking in the future.