Volume 110, Issue 6

The effects of partial pressure of sulphur dioxide on the gas/slag/matte/tridymite equilibria in the Cu–Fe–O–S–Si system at 1 200 °C have been experimentally investigated and compared with the previous studies at various P (SO 2 ). The experimental procedure includes equilibration of the sample and silica substrate at high temperature for the designated time, rapid quenching to preserve the equilibrium phases, followed by measuring the composition of the condensed phases with electron probe X-ray microanalysis. A set of graphs were constructed to present the compositions of slag and matte as a function of copper concentration in matte. The present study confirmed that the chemically dissolved copper and sulphur for the given Cu in matte are independent of the partial pressure of SO 2 . However, the experimentally measured liquidus (Fe/SiO 2 ) are different for various P (SO 2 ). The new data provide an important, accurate and reliable quantitative foundation for improvement of the thermodynamic databases for the chemical systems containing copper matte and slag. The present study is a part of a broader overall research program on the characterisation of the multi component (Cu–Fe–O–S–Si–Al–Ca–Mg), multi-phase (gas/slag/matte/metal/solids) systems with minor elements.

On the basis of the experimental phase equilibria of the Bi–Mg–Zn ternary system, the thermodynamic assessment of the Bi–Mg–Zn ternary system was carried out by means of the CALPHAD (CALculation of PHAse Diagram) technique. The Gibbs free energies of the solid solution phases (Rhombohedral_A7, Hcp_A3 and Hcp_Zn) were described by the substitutional solution model, and that of the liquid phase was described by the associate model with the constituent species Bi, Bi 2 Mg 3 , Mg and Zn. The non-stoichiometric compound, α-Bi 2 Mg 3 as well as its high temperature allotrope β-Bi 2 Mg 3 were described by the sublattice models, (Bi,Zn,Va) 2 (Mg,Zn) 3 and (Bi,Zn) 1 (Bi,Zn,Va) 3 (Mg,Zn) 6 , respectively. In order to obtain a set of self-consistent thermodynamic data, the thermodynamic parameters of the phases, including liquid, α-Bi 2 Mg 3 and β-Bi 2 Mg 3 , of the Bi–Mg–Zn ternary system were optimized while the thermodynamic data of other phases were adopted directly from the literature reports of the constituent binary systems. With this newly developed thermodynamic database, the CALPHAD results can well reproduce the experimental phase diagram information of the Bi–Mg–Zn ternary system. The solidification processes of a typical Bi–Mg–Zn alloy are calculated and analyzed using the phase equilibrium approach and the Gulliver–Scheil model in comparison with the experimental investigation.

Uniaxial tension creep tests were carried out along the [001] direction for as-heat treated Ni-based single crystal superalloy with cubic γ′ phase and pre-rafting samples with N-type rafted γ′ phase at 980 °C and 300 MPa. By comparing the differences in the creep curves between the as-received and pre-rafting samples, the influence of pre-rafting on creep properties was studied. It was demonstrated that the sample with the cubic γ′ phase exhibited a lower creep rate and a longer rupture life compared to the rafted γ′ phase. This paper discusses the evolution of the microstructure, especially the matrix channel width. The influence of rafting on creep deformation was incorporated into the modified crystal plasticity model via the dependence of the Orowan stress on the matrix channel width. Finite element calculation was performed to predict the creep behavior, which agreed well with the experimental data.

The cold rolling and subsequent annealing of microstructures with a high percentage of bainite is one of the promising thermomechanical treatments for grain refinement in low-alloy steels. In this research, the bainite microstructure was formed in the steel DIN 1.5715 by austenitizing at 1143 K followed by quenching in a salt-bath at 688 K. The specimens were then cold rolled to 90 % reduction in thickness followed by annealing at 773–923 K for different times. An ultrafine grained ferrite microstructure was developed possessing the best strength–ductility balance after 90 % cold rolling followed by annealing at 923 K for 2 400 s.

The present study deals with the hot deformation behaviour of as-cast Mg alloys AM30 and AM50. The alloys have been investigated for mechanical and microstructural evolution in the temperature range 423–623 K and strain rate range of 10 −3 –10 s −1 . A safe processing domain is identified for as-cast AM30 and AM50 alloys from the strain rate sensitivity map. The deformed microstructure of both AM30 and AM50 alloy reveals the occurrence of dynamic recovery and recrystallization for temperature above 523 K. Although the two alloys show similar behaviour in the hot deformation regime, they deviate at 623 K and low strain rate, where AM30 is fully recrystallized while AM50 attains necklace structure after deformation. This is likely due to the difference in the rate of dynamic recovery in the two alloys owing to the difference in Al concentration. Continuous dynamic recrystallization was the recrystallization mechanism active in the processing regime as deduced from the EBSD investigation.

The present research investigated the tribological and the thermal properties of Mg-3Al- x GNP alloy nanocomposites, fabricated through a powder metallurgy route with microwave assisted sintering followed by hot extrusion. Graphene nanoplatelets (GNPs) were incorporated as reinforcements in different amounts (0.1 wt.%, 0.3 wt.%, and 0.5 wt.%) into pure Mg and Mg-3Al alloy. The values of coefficient of friction and wear rate of pure Mg, Mg-3Al alloy, and Mg-3Al/ x GNPs ( x = 0.1 wt.%, 0.3 wt.%, and 0.5 wt.%) nanocomposites were evaluated on a pin-on-disc tribometer under dry sliding conditions, and scratch testing was performed under a vertical load of 9.8 N. The ignition temperatures of Mg-3Al-0.1GNP, Mg-3Al-0.3GNP, and Mg-3Al-0.5GNP were respectively increased by 2.31 %, 5.34 %, and 5.7 %. It was noticed that the reinforcement of 0.3 wt.% GNP yielded the best mechanical and tribological properties.

Rolling temperature is thought to have a significant effect on the cold workability of Ti-6Al-4V alloy. To investigate the extent of this effect, four Ti-6Al-4V strips were hot rolled at different rolling temperatures in the range of 650–950 °C while other process parameters were invariant. The specimens revealed an increase in work hardening capacity with increase in rolling temperature, based on tensile and plane strain compression testing. After 10 % cold rolling, the same annealed samples exhibited propagation of edge cracks in specimens that had been hot rolled at 650, 750 and 850 °C while no cold rolling defect was found in the specimen hot rolled at 950 °C. The results of finite element method reveal that during cold rolling, the von Mises stress field is decreased as a result of increasing previous hot rolling temperature. In accordance with X-ray diffraction results, increasing previous hot rolling temperature is associated with lower lattice strain storage during subsequent cold rolling.

This study presents the synthesis of new aluminosilicate (Al-MSU) materials with different Si/Al ratios. Two substrates, Aerosil 200 V and silicon dioxide, were used as a silicon source for the synthesis. Following synthesis, the surface morphology and pore sizes of the new mesoporous materials were determined by low-temperature nitrogen adsorption. The Si/Al ratio was estimated using scanning electron microscopy/energy-dispersive X-ray spectroscopy. The surface properties of the studied aluminosilicates were characterized by means of inverse gas chromatography. The surface area, pore diameters, dispersive component of surface energy, and basic/acidic parameters were found to depend on the Si/Al ratio; a higher Si/Al ratio led to increased surface area of the materials, but their average pore diameter decreased and a change in sorptive properties was observed. The adsorption properties of the examined materials were evaluated by solid-phase extraction. The selected hydrocarbons were found to be adsorbed on the aluminosilicates and were desorbed using elution solvent.

A novel approach has been successfully developed to synthesize Pd@Au core/shell nanosheets by using lemon extract as a biological reducing agent and microwave heating. This approach is suggested to be an eco-friendly, rapid and simple method for the synthesis of Pd@Au core/shell nanosheets. The Au shells that covered the Pd nanosheet surfaces were formed at 80 W in microwave for 20 min. The prepared Pd@Au core/shell nanosheets were characterized by UV–vis spectrophotometry, X-Ray diffraction, transmission electron microscopy, energy dispersive X-ray, energy dispersive X-ray elemental-mapping and energy dispersive X-ray line profile. A highly self-assemblage surface-enhanced Raman scattering methodology was developed by applying Pd@Au core/shell nanosheets for trace fluorescent dye detection. The highest R6G signal was attained with an Au layer of about 3 nm thickness. The results show that the SERS technique is able to detect trace fluorescent dye within a wide concentration range from 10 −8 M to 10 −17 M, with an extremely low limit of detection of 10 −17 M. The study offers a low-cost route to the fabrication of sensing devices capable of use for monitoring cancer progression in natural matrices such as blood.

Solution annealing followed by quenching in carbon nanotubes (QCNT) nanofluid treatment was applied to generate very high interstitial carbon content,≈0.30 wt.%, in an austenitic stainless steel (ASS). The high interstitial carbon content leads to remarkable improvement in mechanical properties with essentially no loss of ductility, with no chromium carbides and/or martensite formation. To evaluate the localized corrosion tendency and passivity behavior, 3.5 wt.% NaCl and borate buffer solutions were used, respectively. Based on the electrochemical corrosion results, both high carbon and low carbon (0.030 wt.%) QCNT-treated ASS alloys show comparable passivity and localized corrosion performance. In addition, Mott–Schottky plots revealed that the anodic films on QCNT-treated samples exhibit similar semiconducting characters.

In-situ Al 2 O 3 (14.8–31.3 wt.%) reinforced Fe–Cr–Ni alloys were prepared using reactive hot pressing at a temperature of 700°C and pressure of 30 MPa for 2 h. X-ray diffraction showed that the obtained metal matrix composites (MMCs) mainly comprised Al 2 O 3 , Fe–Cr and Cr 0.7 Fe 0.36 Ni 2.9 phases. Vickers hardness values of the composites with varying Al 2 O 3 contents were all around 4.28 GPa. Scanning electron microscopy images showed that the Al 2 O 3 particles in the MMCs (with Al 2 O 3 content of 14.8 wt.%) were ultrafine and uniformly distributed. Moreover, the metal matrix composite with 14.8 wt.% Al 2 O 3 exhibited the highest values of fracture toughness and bending strength, which were 15.2 MPa · m 1/2 and 529 MPa, respectively.

A novel method is presented for the synthesis of Ti 2 SC powder by heating FeS 2 /Ti/TiC mixtures. The phase evolution of Ti 2 SC was explored in detail with X-ray diffraction, thermo-gravimetry/differential scanning calorimetry, and scanning electron microscopy analysis. It was found that FeS 2 began to decompose into activated FeS and released molecular state sulphur at around 500 °C. Subsequently, FeS and Ti underwent a reaction that formed Fe and TiS at 700 °C. Finally, the reaction of both TiS and TiC to form a Ti 2 SC phase could be triggered at 900 °C. It was confirmed that the Ti 2 SC phase was obtained with only trace impurity of TiC remaining after acid treatment by microwave hybrid heating of 1.1FeS 2 /2Ti/2TiC mixtures at 1 300 °C for 3 min. The fine powder with a mean diameter of approximately 1 μm was mainly composed of quasi-spherical particles. Compared to the conventional method, Ti 2 SC powder was synthesised at a temperature some 300 °C lower and required only 10 % of the heating time.