Materials Science Forum Vol. 996

Abstract: Inconel718 has been widely used in various fields for its good performance, but it is difficult to machine with traditional machining methods. Electrical discharge machining is an alternative competitive process to machine Nickel-based alloys by electrical erosion. In order to improve reduce the electrode loss and improve the machining efficiency, the horizontal ultrasonic vibration of the workpiece and the cryogenic cooling of the tool electrode were applied into the EDM process. Material removal efficiency, surface roughness, surface topography, and microhardness have been characterized.

Abstract: Cu-14Fe-0.05C alloy was prepared by using the vacuum melting process and then multipass drawing deformation was performed. The results showed that with rise of drawing strain, iron-rich phases in the Cu-14Fe-0.05C alloy gradually change from irregularly distributed coarse dendritic phases in the as-cast state to slender fibrous ones distributed parallel along the drawing direction. The higher the strain is, the slender and denser the fibers are and the more uniform the distribution is. Moreover, more interfaces are found between copper matrix and iron-rich phases and the hardness and resistivity of the alloy become higher.

Abstract: The accurate description of the interfacial heat transfer coefficient is of great significance for the accurate measurement of the temperature field in the process of casting cooling. In this paper, the solidification process of metallic tin in refractory mould was studied by physical simulation experiment, and the on-site temperature measurement of the mold structure was carried out. According to the temperature record, the numerical simulation method is used to realize the fitting of the calculated temperature and the measured temperature. The reversible method was used to calculate the interfacial heat transfer coefficient between the casting and the mould, and then the evolution of the internal temperature field of the casting during the cooling process was determined. The results show that the melt has a large shrinkage during the cooling process, and the interface heat transfer coefficient can reach 300 W·m^-2·K^-1, which provides a mathematical model for the annealing process of fused-cast refractories.

Abstract: The process of producing active vacancies on a hydrogen-terminated diamond surface is the most important rate-limiting stage in CH₄/H₂ and CH₄/H₂/CO₂ atmospheres. Hydrogen atom and the hydroxyl group can bone to the hydrogen atom on the diamond surface and create an active vacancy. Density functional theory (DFT) was used to study the extraction reaction by two reactants both hydrogen atom and the hydroxyl group. The result indicated that the hydroxyl group could reduce the energy required for diamond surface activation. What is more, the activation rate of the surface by the hydroxyl group was livelier at low temperature, while the activation rate of the hydrogen atom predicts on the contrary. The scanning electron microscope (SEM) and Raman spectra demonstrated that the introduction of CO₂ in the CH₄/H₂ atmosphere could reduce the deposition temperature and raise the deposition rate at low temperature.

Abstract: As the ancient metal, Sn is widely used in all aspects of human life. Nowadays, S, as the vulcanizing agent, is used in the process of refining tin to separate Cu and Sn. However, there are few reports about the other agent of removing copper from stannum. In this study, SnS, a new sulfiding agent to separate Cu and Sn, was investigated. During the process, SnS replaces the combination of Sn and Cu. The variables considered in the experimental study were reaction temperature, time and the ratio of reactants. The experimental data indicated under certain conditions, the removal rate of Cu reach 94.3%. At last, we studied the vacuum reaction of Cu₂S and Sn, results indicated that under appropriate conditions, the Cu is detected. The SnS is formed. And after the vacuum reaction, the SnS could be used recycling. This work presented a promising technology for separating Cu from tin.

Abstract: The removal of magnesium from garnierite in Yuanjiang area of Yunnan was performed by carbothermal reduction in vacuum. The effects of reduction temperature and reduction time on the removal rate of magnesium were investigated. The kinetics of the removal of magnesium by carbothermal reduction in vacuum was studied. The thermodynamic calculation results show that it is feasible to remove magnesium from garnierite by carbothermal reduction in vacuum. The experimental results show that the removal rate of magnesium in garnierite can reach 93.23% under the conditions of 1823K for 120min. The reduction process conforms to the chemical reaction kinetics model, which indicated that the reduction process is controlled by chemical reaction and whose expression is 1-(1-α)^1/3=(-22850.1/T+2.6296) t, the apparent activation energy (Ea) and the pre-exponential factor (A) are 189.97 kJ/mol and 13.87 s^-1, respectively. The results of XRD and SEM analysis show that the condensate obtained by carbothermal reduction in vacuum of the garnierite is magnesium, which is mainly obtained by the reduction reaction between magnesium silicate produced by the decomposition of serpentine in minerals and coal. At the same time, it is proved that it is feasible to directly extract magnesium metal from the garnierite.

Abstract: A novel Co-WC composite coating was deposited on the surface of high speed steel (HSS) substrate by an energy-efficient method of electrodeposition. The effects of process parameters on friction and wear properties of the composite coatings were evaluated, and the worn morphologies of Co-WC composite coatings were investigated by scanning electron microscopy. Results revealed that the incorporation of WC particles can significantly improve the wear resistance of the coating. As the current density was increased to 6.5Adm^-2 and the WC concentration was increased to 35g/L, the Co-WC composite coating had the lowest friction coefficient and wear loss.

Abstract: This paper introduces the characteristics of titanium mineral resources in Yunnan Province and the production situation of titanium-slag smelting, The article puts forward the necessity of constructing a project of producing 80,000t/a of high-titanium. The process is advanced production technology of a company in South Africa, the process has a large capacity, gas utilization, energy, and low electrode consumption, the article carried out economic evaluation of the project.

Abstract: The hot rolled single sided stainless steel clad plate of 316L stainless steel and Q345C steel was carried out in a hot rolling line by the technology of “electron beam vacuum welding and hot rolling”. High quality single sided stainless steel clad plates were produced by asymmetrical compound billet and asymmetrically rolling. The productions of stainless steel clad plate have reached the requirements of GB / T 8165-2008. The interface shear strength is greater than 320 MPa. The yield strength is greater than370 MPa. The tensile strength is greater than 520 MPa. The elongation is greater than 30%, A good metallurgical bonding between stainless steel and carbon steel was achieved. The bonding rate reached 100%. The composite interface is straight and perfect. The pilot production in the study has laid down the certain basis for the production of the single-side dissimilar-material composite board.

Abstract: In order to alleviate the shortage of global nickel resources, it is imperative to develop low nickel stainless steel. This paper presents a novel approach based on increasing nitrogen and reducing nickel for smelting economical stainless steel. Taking 06Cr19Ni10 stainless steel as the object, the test steels with different nitrogen and nickel content were smelted using vacuum induction furnace (ZG-0.01) under the laboratory conditions, and the effects of alloy content on microstructures, mechanical properties and corrosion properties of the economical stainless steel were investigated. The results show that the microstructure of the tested steel which nitrogen content 0~0.28% and nickel content 5.98~9.63% is still the single austenitic, and the grain size decreases as the nitrogen content increases. Nitrogen deteriorates the impact toughness of the tested steel, and the room temperature impact absorption energy is reduced from 267 J at the nitrogen content of 0 to 228 J at nitrogen content of 0.28%. Rockwell hardness, tensile strength and yield strength increase with the increase of nitrogen content. When the nitrogen content is 0.28%, the optimum mechanical properties of 06Cr19Ni10 steel are obtained. The Rockwell hardness is 95.4 HRB, the tensile strength is 814 MPa, the yield strength is 437 MPa, and the elongation after fracture is 52.5%. The degree of intergranular corrosion of the tested steel is reduced significantly with the increase of nitrogen content, from 0.023 μm to 0.008 μm. The experimental data prove that the composition design concept of increasing nitrogen and reducing nickel is feasible for smelting economical stainless steel.