Volume 44, Issue 1

A posterior probability and intra-cluster feature weight online dynamic feature selection algorithm is proposed to address the issues of high dimensionality and high volatility of data in the basic oxygen furnace (BOF) steelmaking production process. First, a genetic algorithm with fixed feature space dimensions is introduced, which narrows the solution space by predefining the number of selected features, thereby enhancing the stability of feature selection. Second, the posterior probability of samples and intra-cluster feature weights are used to weigh and calculate the feature importance of the current sample, obtaining the optimal features that align with the current operating conditions. Finally, the dynamically selected features are used in a regression model to predict the carbon content and temperature of the BOF steelmaking process data. Simulations of actual BOF steelmaking process data showed that the prediction accuracy was 86% within a carbon content error range of 0.02, and 88% within a temperature error range of 10°C.

In this study, thermal effusivity distributions of two polished JSC-1A particles, a lunar regolith-simulating material, were measured using a thermal microscope. The results confirmed that the average thermal effusivity of the JSC-1A single particle was approximately half that of the FJS-1 single particle, a different type of lunar regolith-simulating material measured by a similar method. Also, the thermal effusivities of the existing mineral phases of pyroxene and anorthite in the particles were obtained and were comparable to those reported in the literature. A possible reason for the lower thermal conductivity of JSC-1A than that of FJS-1 could be the differences in the ratio of the mineral phases, and phase boundaries between the mineral phases.

The aerospace industry widely uses titanium diboride, a tough material that is challenging to machine using conventional methods. We, therefore, process titanium diboride (TiB₂) to determine the best process parameters for electrical discharge machining for TiB₂. The study compares four electrode materials: brass, copper, tungsten, and tungsten copper. In addition, water-based deionized (DI) dielectric fluids are studied, and the input parameters are changed to measure the fluctuations of the output parameters through experimental studies and gain insights into the material removal rate (MRR), tool wear rate (TWR), surface roughness (SR), and overcut during machining of titanium diboride. We then verify this result using gray relational analysis and a regression model. Based on these results, we confirm that the discharge current is the most important factor affecting the MRR and SR. The copper electrode achieves a higher MRR, while the tungsten copper-based electrode leads to a lesser TWR. A copper electrode achieves better SR, while tungsten electrodes with DI water-based dielectric fluid show a lower overcut value. After machining, we used SEM to check the surface quality and elemental makeup and to see if there were any microstructural changes, like craters, recast layers, and maybe even microcracks, that were caused by the high-energy discharge process.

At present, the predominant method for magnesium production relies on the Pidgeon process, a straightforward yet inefficient procedure characterized by high energy consumption and substantial greenhouse gas emissions. In order to foster advancements in magnesium production technology, this study explored an approach that consolidates silicon calcination and thermal reduction stages into a single stage. The main raw material used in this process is dolomite powder, which replaces the previously calcined dolomite. The primary objective of this novel approach is to streamline production timelines, enhance coherence between stages, and curtail energy usage in magnesium production. The investigation delves into the impact of dolomite decomposition temperature and forming pressure on the efficiency of the integrated process. Laboratory-scale experimentation revealed that the optimal decomposition temperature is 800°C. While the forming pressure significantly influenced the reduction rate, it did not markedly impact the final reduction efficiency. A forming pressure of 150 MPa yielded the highest reduction rate. This decrease is attributed to the dissociation of reactants during dolomite decomposition, indicating a need for further research to address the reduction in contact area during the degradation stage and enhance the efficiency of this integrated process.

To enhance the high-temperature stability of hot-work die steel, a novel hot-work die steel was designed on the basis of 55NiCrMoV7 steel by increasing the content of Mo and V. The hardness variation trend of the two steels during high-temperature service was investigated through a thermal stability test. Test methods such as X-ray diffraction, scanning electron microscope, high-resolution transmission electron microscope, and energy spectrum analysis were employed to analyze the microstructure and carbide evolution. Combined with the Johnson–Mehl–Avrami equation, the influence of Mo and V on the high-temperature aging kinetic process was analyzed. The results indicated that the evolution of carbide and the matrix recovery process exhibit a coupling appearance. The thermal stability and tempering resistance of material experiment steel (MES) 2 steel at the test temperature were optimized, and its tempering activation energy is 34.9 kJ·mol −1 higher than that of MES 1 steel. Under the same tempering conditions, the matrix recovery of MES 2 steel is slow, and carbide coarsening is effectively inhibited. This is mainly because Mo and V are strong carbide-forming elements that preferentially combine with C to form MC over Cr, Mn, and other elements. As a result, more Cr and Mn dissolve in the matrix. This not only plays the role of solid solution strengthening but also reduces the diffusion rate of C in the matrix at high temperatures and effectively inhibits the precipitation and growth of carbides.

The inherent low-temperature brittleness has restricted the application of tungsten materials. One option for enhancing the tungsten fracture toughness is to use tungsten-based layered composites. In this study, W/(Ti/Ta/Ti) multilayer composites with the application of spark plasma sintering under varying bonding temperatures from 1,000 to 1,400°C were fabricated. The ambient- and high-temperature tensile mechanical performance of W/(Ti/Ta/Ti) samples is investigated to obtain the correspondence of microstructure to tensile performance. The as-fabricated composites exhibit significantly superior comprehensive tensile performance to the original foil. When bonded at 1,200°C, the comprehensive tensile performance of W/(Ti/Ta/Ti) samples is the best, showing an elongation of 5.0% and a tensile strength of 671 MPa. The bonding temperature leads to microstructural changes in the as-fabricated composites, thereby affecting their high-temperature tensile mechanical properties. When bonded at 1,000°C, the ductile–brittle transition temperature (DBTT) is approximately 100°C. When bonded at 1,200°C, the DBTT is approximately between 100 and 200°C. When bonded at 1,400°C, the DBTT is between 100 and 200°C. For W/(Ti/Ta/Ti) multilayer composites having low interfacial bonding strength, the primary energy dissipation modes include intermediate-layer plastic deformation, multi-tunnel crack propagation in the W layer, as well as W/Ti interfacial delamination. As for W/(Ti/Ta/Ti) multilayer composites having high interfacial bonding strength, energy can only be consumed through the principal crack propagation. Meanwhile, a tensile strength model is constructed based on the stress concentration coefficient after the nucleation of microcracks at the W/Ti interface.

To achieve comprehensive recovery and utilization of iron and titanium resources in vanadium titanium magnetite concentrate, the vanadium titanium magnetite concentrate is subjected to metallization reduction roasting, studying the selective enrichment effects on iron- and titanium-containing phases in the reduction products under the influence of additives. Experimental results indicate that elevating reduction temperature, increasing additive concentration, and extending the reduction time promote the aggregation and growth of phases containing iron and titanium in the reduction products. Under the optimized roasting conditions of 1,250°C, addition of 4% of the additive, and a reduction time of 3 h, 92.91% of iron existed in metallic form, and 87.35% of titanium existed as anosovite. The average equivalent circle diameters for iron and titanium particles are 45.3 and 10.1 μm, respectively. By magnetic separation of the reduced products, the obtained magnetic separation concentrate contains 93.06% Fe, with an iron recovery rate of 96.15%. The magnetic separation tailings contain 39.22% TiO 2 , and the Ti enrichment rate of the tailings is 87.75%, indicating a good separation effect of iron and titanium.

In view of the fact that the current experimental method is not very satisfactory to study the solid solution behavior of rare earth elements (RE) in steel, it is an effective and economical method to replace the experimental research with the simulation calculation method. In this article, the Fe-RE (La, Ce, Y) systems were constructed based on the density functional theory, and mechanical properties of doping systems were calculated. The calculation results of the solvation energy show that La, Ce, and Y can form stable solid solutions in α-Fe, and Ce has the highest solid solubility in α-Fe, followed by Y and La. The results of elastic moduli show that the doping of RE (La, Ce, Y) reduces the incompressibility, shear strain resistance, stiffness, and Vickers hardness of the doping system, while increasing the toughness and machinability. The strength properties of the doping systems are Fe–Ce > Fe–La > Fe–Y, and the toughness and machinability are opposite. In Fe–RE (La, Ce, Y) doping systems, RE (La, Ce, Y) reduce the metal bond strength of the Fe system, which is the fundamental reason for the decrease of the strength properties of the doping system. In addition, in doping system, Fe atoms gain electrons and RE (La, Ce, Y) atoms lose electrons. And the increase of electron cloud density in the doping system can be used to explain the improvement of toughness and machinability of the system.

This study analyses the entropy and heat transfer characteristics of couple-stress Casson fluid in a porous vertical microchannel, incorporating the effects of isothermal cubic autocatalytic chemical reactions, variable thermal conductivity, uniform heat source/sink, and thermal radiation. The governing equations are transformed into dimensionless form and solved numerically using the fourth and fifth-order Runge-Kutta-Fehlberg method. Key findings reveal that the inverse couple-stress parameter and variable thermal conductivity, significantly influence temperature distribution and fluid flow, enhancing heat transfer efficiency throughout the microchannel system. The study also highlights that homogeneous-heterogeneous reactions reduce concentration levels, improving lubrication and optimizing thermal performance. Additionally, entropy generation increases with higher Biot number, variable thermal conductivity, radiation, and heat source/sink effects. The Nusselt number decreases with increasing thermal conductivity, while drag force minimizes as the inverse couple-stress parameter rises. These findings contribute to the optimization of microfluidic thermal systems, with practical applications in energy-efficient cooling technologies, microchannel heat exchangers, advanced chemical reactors, and biomedical engineering, where precise heat and mass transfer control is essential for improved performance and efficiency.

The steel metallurgy industry is a high energy consuming and high polluting industry. In order to reduce the consumption of fossil fuels such as coke and coal powder and environmental pollution, it is urgent to develop a new type of clean energy for green metallurgy. Biomass straw energy, as a renewable and clean energy source, has attracted widespread attention from metallurgical researchers. In this work, the corn stalk hydrochars were prepared by hydrothermal carbonization (HTC) method at different carbonization temperatures, carbonization times, and mass ratios, aiming to provide a green and sustainable energy source for the metallurgical industry. In addition, the influences of parameter changes on phase composition, microstructure, and calorific value were also analyzed. Results manifested that the elevation of temperature and time promoted the HTC process, contrary to the solid–liquid proportion. It was worth noting that short carbonization time and high mass ratios were unconducive to the dissolution of harmful phase KCl, which affected the application of hydrochar. Under the optimal carbon process conditions ( T = 260°C, t = 40 min, S / L = 2%), the corn stalk hydrochar has a smaller particle size (<50 μm), higher calorific value (22.34 MJ·kg −1 ), and carbon content (76.46 wt%), which has a great potential to replace anthracite and promote the sustainable development of the metallurgical industry.

In order to improve the oxidation and ablation resistance of carbon materials, Zr–Ta–Si–C–B coatings with different Zr/Ta ratios were successfully prepared on the graphite surface by combining slurry impregnation and reactive melt infiltration (RMI). The coatings after RMI are dense, Zr–Ta–B solid solution, SiC, and Si coexist in the coating where ceramic particles are tightly wrapped by Si. The cycle oxidation test results at 1,600°C for 100 h (5 h × 20 cycles) show that the Zr–Ta–Si–C–B coating with a Zr/Ta ratio of 4:6 has a better anti-oxidation effect; the mass change rate of the coated specimen is −0.26%. Its good oxidation protection performance is mainly due to the generated Zr and Ta oxides on the coating surface, which increase the viscosity of the SiO 2 layer and effectively block the diffusion channels of oxygen. After ablation at 2,300°C for 480 s, the mass ablation rate and linear ablation rate of the Z4T6 coating are 1.48 × 10 −2  mg·s −1 and 0.94 μm·s −1 , respectively. The Zr–Ta–Si–O composite glass layer composed of (Zr,Ta)O 2 and SiO 2 is relatively intact at the early stage of ablation, and it can effectively prevent plasma flame ablation. After four cycles of ablation (120 s × 4 cycles), the (Zr,Ta)O 2 solid solution and SiO 2 generated by the ablation reaction are insufficient to resist the invasion of high-temperature oxygen and flame erosion, ultimately leading to the failure of coating protection.

Incoloy alloy 800, a type of superalloy, is well-suited for industries that require high corrosion resistance. Laser beam welding (LBW) is an effective method for improving the quality of its joints. In this study, Incoloy alloy 800 is joined using Nd:YAG LBW by varying laser power between 2 and 3 kW with a constant welding speed of 2 m·min −1 . Joints were analyzed using microscopic and mechanical testing. The observed weld zone has an hourglass shape and elongated columnar structure as well as dendrites with fine equiaxed grains. Remarkable phase changes occur due to the high cooling rate, which is associated with LBW. The reduction in mechanical properties was observed at high laser power due to the laves formation. The mode of fracture was changed from ductile to brittle while increasing the laser power.

The present mathematical model investigates convective heat transfer in the Darcy–Forchheimer flow of a magneto-Maxwell nanofluid over a porous stretched sheet. The impacts of convective boundary conditions, activation energy, Joule heating, thermal radiation, and energy production are also considered in the flow model. Additionally, the heat transmission process is described using the Cattaneo–Christov heat flow model. A system of highly non-linear ordinary differential equations is built using suitable similarity transformations. The model has been numerically tackled utilizing MALAB’s bvp4c package. Computational findings are calculated for liquid velocity, liquid temperature, nanoparticle concentration, and total entropy creation as functions of transverse displacement for investigating the velocity, mass, and thermal properties of the Maxwell nanoliquid under suitable assumptions and boundary conditions. Oscillations in friction factor, mass, and heat transfer rates have also been examined. It is observed that the velocity distribution improves as the thermal and concentration Grashof numbers increase, whereas it decreases as the suction parameter and Darcy–Forchheimer parameter increase. It is further reported that the concentration upsurges with larger estimates of activation energy in the central component of the geometry. This research has practical applications in escalating thermal transfer systems employed in industrial procedures, freezing technologies, and energy systems. It supports heightening thermal management in reactors, geothermal structures, and polymer processing.

This study uses an artificial intelligence neural network to estimate the solution for a Cross-nanofluid containing gyrotactic microorganisms on an inclined surface. Furthermore, the concept of minimizing entropy has been taken into account. The energy and concentration equations take into account the importance of thermal radiation, convective flow, heat source/sink, and chemical processes. By applying an appropriate similarity transformation, the modeled equations are converted into ordinary differential equations. The equations are solved numerically using an artificial neural network (ANN) that employs the Levenberg–Marquardt approach. To evaluate the correctness of the proposed model, the results of training, testing, and validation are analyzed using the performance charts, error histograms, transition state analysis, comparisons between bvp4c and ANN, and regression plots. In addition, a bigger estimation of the radiative variable and the Biot number results in a rise in the temperature of the fluid. Conversely, greater values of the Prandtl number lead to a diminution in the temperature. Growing the Weissenberg parameter enhances the velocity and decreases both the Bejan number and entropy generation. To showcase the accuracy of the numerical approach that has been applied, a comparison table is provided, which displays a remarkable level of agreement when compared to previously published data.

In order to improve the quality of the bonding interface between dissimilar metals, friction stir lap welding was used to weld TA1/6061Al. The effects of multi-pass welding parameters on the mechanical properties, elements distribution, and intermetallic compounds of the lap interface were investigated. The results showed that the fracture locations of the specimens under multi-pass welding and single-pass welding were different. The latter was sheared from the bonding interface, while the former failed near the thermo-mechanically affected zone on the advancing side of the Al side. Moreover, multi-pass welding significantly improved the tensile-shear resistance of the joints. The maximum fracturing load of multi-pass welding reached 7,150 N when adjacent welds interval ( L ) was 12 mm, which was much higher than single-pass welding 3,861 N. The thermal–mechanical coupling effect of the tool during the welding process resulted in the formation of Ti/Al atomic diffusion layers of different thicknesses and the formation of Ti/Al intermetallic compound (mainly TiAl 3 ) at the bonding interface. Diffusion bonding was the main way for multi-pass welded lap joints to form a reliable connection. The thicknesses of the interfacial diffusion layers at the first weld of multi-pass welding under different L values were approximately the same as that of single-pass welding, in the range of 4–4.4 μm.

Activated carbons are widely used adsorbents for hydrogen sulfide (H 2 S) removal in the field of gas stream purification in industry. Five commercially available wood-, coal-, and coconut shell-based activated carbons, prepared by phosphoric acid activation and steam activation, were chosen as adsorbents in an effort to elucidate the effect of the pore structure on H 2 S adsorption of activated carbons in an oxygen-free gas stream. The adsorption experiments were conducted in an adsorption column, and the breakthrough curves of the activated carbons were examined. The results showed that adsorption of H 2 S by activated carbon under oxygen-free conditions was dependent on the microporous structure, particularly micropores with sizes of <1 nm. The surface area of CS-3 is 1,792 m 2 ·g −1 . The H 2 S breakthrough capacities of WS-1, BS-1, CS-1, CS-2, and CS-3 were 0.006, 0.01, 0.018, 0.021, and 0.026 g·cm −3 under oxygen-free conditions. The adsorption experiments of the KOH- and CuO-loaded activated carbons further confirmed the significance of micropores with sizes of <1 nm for H 2 S removal. Also, it was found that pre-adsorption or co-adsorption of carbon tetrachloride led to poisoning of the activated carbon for H 2 S adsorption due to a remarkable reduction in the micropore volume. Therefore, steam-activated materials with highly developed micropore structures were favorable adsorbents for H 2 S removal because of their high adsorption capacities and reduced fire risk in an oxygen-free gas stream.

This article uses carbon black as a conductive material, polytetrafluoroethylene as a hydrophobic material, and calcium carbonate (CaCO 3 ) as a pore-forming agent. Meanwhile, a gas diffusion layer (GDL) with a gradient pore size was prepared using the spray coating method. The results show that a three-layer gradient pore size GDL has good water vapor transmission ability. When humidity is 40%, the current density and power density of gradient pore size GDL are 127.9 mA·cm −2 and 63.31 mW·cm −2 higher than commercial GDL29BC, respectively. When humidity is 60%, the current density and power density of gradient pore size GDL are 250.3 mA·cm −2 and 127.3 mW·cm −2 higher than commercial GDL29BC, respectively. When humidity is 100%, the current density and power density of the gradient pore size GDL are 255.69 mA·cm −2 and 127 mW·cm −2 higher than commercial GDL29BC, respectively.

In the present work, we added 1.5 and 5% v/v hydrogen gas to an Ar–7% N 2 shielding gas for the gas tungsten arc welding of AISI 304L stainless steel to investigate its effect on the weld microstructure and oxidation rate. By using Ar–7% N 2 as a shielding gas, the weld metal contained 2.1% of delta ferrite in an austenite matrix. The addition of 1.5 and 5% hydrogen gas in the shielding gas provided the welds with a higher ratio of delta ferrite to austenite matrix, ranging from 3.8 to 6.9%, thus helping reduce the risk of hot cracks. The weld metals were further subjected to an oxidation test in synthetic air at 700°C, and the parabolic oxidation kinetics were observed. The parabolic rate constant of the weld metal produced using the Ar–7% N 2 shielding gas was 5.44 × 10 –13 g 2 cm –4 s –1 . When 1.5 and 5% hydrogen gas was added to the Ar–7% N 2 shielding gas, the rate constants were reduced to 64% and 24% of that of the weld produced using only Ar–7% N 2 shielding gas, indicating the promising role of the presence of hydrogen in the Ar–7% N 2 shielding gas on improving the weld metal oxidation resistance for high temperature services.

The present study has potential applications in biomedical engineering, particularly in drug delivery systems and diagnostic imaging of stenotic arteries. The purpose of this study is to explore the key role of Fe 3 O 4 and Cu nanoparticles, which are submerged together in human blood in the presence of magnetohydrodynamics flow through stenotic arteries. The main motive for selecting Fe 3 O 4 and Cu nanoparticles is their importance in drug delivery because they possess potential usefulness in drug transference as well as imaging properties. Therefore, the governing equations that define the flow as well as heat transference of blood are changed from partial differential equations to ordinary differential equations by utilizing the appropriate similarity variables. The shooting technique was applied to achieve the numerical solution in Maple software to observe the influences of the used nanoparticles and the parameters in stenotic arteries. Velocity and temperature profiles, along with engineering interest quantities, skin friction, and Nusselt numbers, were detected for various values of parameters and nanoparticle volume fractions. The main findings show that dual solutions exist for S ≥ 1.7591, λ ≥ −0.82435, and 0 ≤ χ ≤ 0.7385. Moreover, the blood flow performance can be decreased by increasing the suction and magnetic parameters and the rate of shrinking in the stenotic arteries. The temperature of the blood can be raised by increasing the rate of thermal radiation and magnetic parameters. An increase in the thermal slip parameter decreased the temperature of the blood in the arteries. Such modeling and investigation of solutions can play an important role in predicting the reasons for atherosclerosis.

Selective laser melting was used to manufacture the magnesium Mg–Al–Zn–X–Mn (Mg) alloy samples, while outer heat treatment cycles (HTC) and plasma arc transfer (PAT) Ti 54 Al 23 Si 8 Ni 5 X Nb+Ta coating technique were used to improve the outer surface. On selective laser melting (SLM) samples, the hexagonal closed structure, Mg 2 Al 3 , and α′-MgSi structure produced the strong bonding strength. MgOx phase, MgZn structure, and the Al–Mg–Si ternary phase all significantly improved the outer surface layer after heat treatment at 1,200–1,350°C. At PAT coating samples, the Mg–Si phase, Ti–Al–Mg–Mo phase, Ti–Mg structure, and Ti-twin boundaries were observed, while the outer surface was shielded by the AlSi structure, Ti-inter binary phase, and AlMn basket structure. According to the texture image, MgTi 1 <0001>, MgTi 2 <1011>, and MgTi 3 <2110> MgTi 4 <2121> outer layers were shielded by the magnesium lattice ternary phase. HTC samples had an 8% harder surface than Mg-SLM samples, but PAT coated samples had a 21% harder surface in both the inner and outer layers. The (µ/β) Mg-coarse grain boundaries, β-MgTi phase, and Ti–Si–Mn structure steadily increased. HTC samples had an average tensile strength of 8% elongation, but PAT coating samples showed a high yield strength and ductility ratio of 13%. The surface roughness, corrosion rate, and wear resistance of the Mg-SLM sample were studied as the outer layer HTC and PAT coated samples were gradually enhanced.

This study draws on the conventional non-oriented electrical steel (NOES) composition, with different contents of the rare earth element Y, and studies the effects of the rare earth Y on the microstructure and texture of NOES ingots and hot-rolled plates. The results indicate that rare earth Y can purify the melt, form high-melting second-phase particles, and significantly refine the ingot microstructure during the solidification process with pinning action. The effect of rare earth on the hot-rolled plate microstructure exhibits an inverse “structural heredity effect.” The coarse ingot microstructure without rare earth forms a fine gradient organization after hot rolling, with the surface and sub-surface being dynamic recrystallization microstructures, the center layer being a deformation microstructure, and the sub-surface forming a sharp shear brass texture. The fine ingot microstructure formed by adding a rare earth becomes relatively coarse and uniform after hot rolling. An appropriate amount of rare earth Y can significantly pin the brass-oriented grain boundaries, inhibit the development of brass components, and enhance the {100} and its variant hot-rolled textures. Considering the grain size and texture of the hot-rolled plate, it is recommended to add 0.012%Y to prepare NOES.

This research elucidates the high-temperature deformation mechanisms in high-chromium cast steel through integrated constitutive analysis and microstructural characterization across thermomechanical processing conditions (1,150–1,250°C, 0.001–0.1 s −1 ). The developed strain-compensated Arrhenius-type constitutive equation exhibits remarkable predictive capability for flow behavior, with deformation activation energy displaying fourth-order polynomial correlation with true strain. Processing map methodology identifies a stable processing domain (1,190–1,240°C, 0.001–0.005 s −1 ) characterized by maximum energy dissipation efficiency. Electron backscatter diffraction analysis demonstrates that under optimal deformation parameters (1,200°C, 0.001 s −1 ), high-chromium cast steel yields a fine-grained microstructure with 92.2% recrystallization fraction. Additionally, discontinuous dynamic recrystallization nucleation predominantly occurs via subgrain merging and boundary protrusion mechanisms.

This study employs X-ray diffraction, scanning electron microscopy, electrochemical workstations, and hardness testers to evaluate the impact of annealing temperatures (600, 700, and 800°C) on the microstructure and corrosion resistance of the CrVNiAlCu high-entropy alloy. Findings demonstrate that the as-cast alloy is composed of copper-rich FCC and chromium-rich BCC phases. With increasing annealing temperatures, the alloy’s crystals transform into dendritic structures, accompanied by the precipitation of new phases. The as-cast alloy displays a peak hardness of 674 HV, which significantly reduces after annealing. Moreover, annealing treatment reduces lattice distortion and element segregation in the alloy, thereby improving the corrosion resistance of the alloy. Importantly, the alloy attains its highest corrosion resistance after annealing at 800°C.

Zinc-based alloys have attracted increasing interest as absorbable implant metals due to their suitable degradation rate and biocompatibility. However, a high concentration of Zn 2+ due to the degradation process results in high cytotoxicity, and low osteogenesis remains a problem. In this work, a compact coating well integrated into the substrate was fabricated on the surface of zinc via micro-arc oxidation (MAO). The coating is mainly composed of ZnO. The addition of phosphate in the coating reinforced the adhesive strength between Zn and the coating. Electrochemical measurements demonstrate a superior corrosion resistance of MAO-P samples as compared to the substrate. Long-term immersion measurements in simulated body fluid indicate that the coating improved the bioactivity of the substrate, which is promising in view of orthopedic applications.

Resistance spot welding experiments of 304 stainless steel were performed in this study. Orthogonal test and analysis method were used to carry out the experiments and optimize process parameters based on their effects on tensile shear load and nugget diameter of the spot-welded joint. The microstructure and the defects of spot-welded joints were studied. The highest tensile shear load of joint was 9.529 kN produced at optimum parameters, i.e., electrode force of 3.5 kN, welding current of 6.5 kA, and welding time of eight cycles. Microstructure of the nugget of welded spot joint was columnar dendrite grains which contains austenite and δ-ferrite, and the microstructure of the HAZ region was coarse equiaxed grains of austenite that were induced by different heat inputs. The solidification cracks and shrinkage cavities were observed in resistance spot-welded joints which were produced at higher heat input. These defects seriously reduced the strength of spot-welded joint.

In this study, magnetic field–assisted high rotational-speed stir friction welding (MFA-HRFSW) and high rotational-speed friction stir welding (HRFSW) were carried out on a 1-mm-thick 6061-T6 aluminium alloy plate, and the macroscopic morphology, microstructure, corrosion for, mechanical properties and equipment tolerance of the two types of welded joints were studied and compared. By establishing a mathematical model of the MFA-HRFSW process, the temperature field characteristics of this process were analysed, revealing that the application of a rotating magnetic field during the friction stir welding (FSW) process influences the welding quality. The test results show that through the application of a magnetic field during the FSW process, the welding load of the equipment is reduced, and the peak axial force during the stabilization phase is reduced by 18.7%. Electrochemical tests show that the corrosion rate of 6061-T6 aluminium alloys is reduced when using MFA-HRFSW. This is mainly attributed to the presence of the rotating magnetic field in FSW, which endows the 6061-T6 aluminium alloys with finer grains, thereby improving the tensile strength and hardness of the alloys. This study provides new ideas for the development of FSW technology assisted by the application of an external energy source.

Dry gas seals (DGSs) are emerging as advanced forms of sealing under high-speed working conditions owing to their low wear, zero leakage, and long-life characteristics. However, it is difficult to accurately and efficiently achieve the theoretical optimal groove depth and minimum roughness requirements using existing laser technology, which limits their practical application in high-speed working conditions. Using ultrafast laser technology, the minimum laser power corresponding to the ablation threshold of the material was taken as the reference to achieve precision machining of the target groove depth. The maximum groove depth error and roughness were controlled within 4.06% and 0.425 μm, respectively. In addition, the relationship between the minimum spot diameter and continuous machining was investigated. Ultrafast laser machining experiments demonstrated that single-direction discontinuous machining could form an ordered texture, which not only improved the sealing performance but also simplified groove processing. The processing time was reduced by ∼30% compared with traditional laser processing. Finally, a quality detection and evaluation method, which can be used to scientifically determine the quality and depth of DGS grooving, is proposed. Our results provide a guideline for DGS processing and manufacturing.

This study introduces a joining procedure applicable to super duplex stainless steel (SAF2507) alloys through the microwave hybrid heating (MHH)-based process using nickel (Ni) and stainless steel (SS304) filler powders. Mechanical test results of the Ni-filler joints revealed an average value of microhardness of 432 HV and an ultimate tensile strength value of 442 MPa. Similarly, SS304 filler joints showed an average value of microhardness of 461 HV and an ultimate tensile strength of 534 MPa. The hardness of SS304 filler joints was 6.71% more than that of Ni-filler joints. Increased hardness leads to better ear properties, which are required in many engineering applications. Furthermore, the tensile strength of SS304 filler joints was 20.81% better than that of Ni-filler joints. Better tensile strength of joints is a major requirement from a design safety point of view. Energy-dispersive spectroscopy results revealed the presence of iron, chromium, molybdenum, nickel, manganese, and carbon elements in the weld zone. Furthermore, the microstructural analysis performed using scanning electron microscopy showed a robust metallurgical bonding among the two interface surfaces, leading to the formation of good quality joints with no interfacial cracking.

In this investigation, cobalt-based composite coatings with varying concentrations of spherical tungsten boride (WB) were fabricated via laser cladding technology, specifically focusing on two compositional systems: Co + 15% WB and Co + 45% WB. The electrochemical behavior of these coatings was systematically evaluated in a low-temperature hydrochloric acid environment to elucidate the influence of WB content on the corrosion resistance mechanisms of cobalt-based coatings and to reveal the electrochemical corrosion mechanisms of WB-reinforced cobalt-based coatings. Experimental results demonstrated that all coatings, including pure Co, Co + 15% WB, and Co + 45% WB, exhibited distinct passivation behavior in 0.5 mol·L −1 HCl solution. The passivation range for WB-containing coatings was predominantly observed between −0.1 V and 0.2 V. Comparative analysis revealed that the Co + 15% WB coating exhibited the most favorable corrosion resistance properties, characterized by the highest corrosion potential and the lowest corrosion current density ( i corr ). Furthermore, this coating composition demonstrated superior passive film resistance, charge transfer resistance ( R ct ), and film resistance ( R f ), indicating optimal protective performance in acidic environments. In contrast, the EH40 substrate exhibited significant corrosion susceptibility in acidic solutions, with the corrosion process primarily dominated by anodic dissolution. These findings provide valuable insights for the design and optimization of corrosion-resistant coatings used in marine vessels operating in corrosive acidic environments.

White marble, renowned for its high resistance to natural conditions and aesthetic appeal, is extensively utilized in stone components like ancient tablets and carvings. Over time, these artifacts undergo complex aging; key factors include atmospheric temperature, humidity, light exposure, and acid rain. Among these, thermal effects play a crucial role in altering white marble’s properties. This study employs white marble rock samples from the Fangshan area in Beijing to examine the impact of temperature on its aging characteristics. Key parameters, including color, mass loss rate, porosity, ultrasonic wave velocity, and mechanical properties, are measured before and after heating the samples. Scanning electron microscopy was used to analyze the morphological changes in samples after heating, and the effects of thermal exposure on the marble’s lattice structure are investigated using X-ray diffraction. Specifically, the study explores how temperature influences the efflorescence of white marble. Findings indicate that heating at 300°C causes the lattice of the sample to transform, significantly affecting its physical properties such as the Leeb hardness decreases by 30.66%, and the ultrasonic velocity reduces by 35.08%. At the same time, the Leeb hardness and ultrasonic wave speed of the samples heated at 300°C are similar to the values of stone relics at the cultural relics site.