Transactions of Nonferrous Metals Society of China最新文献

An optimized microcrystalline wax-based feedstock was used to fabricate 3D 7075 Al alloy through metal fused deposition modeling (Metal-FDM). The affinity between the wax-based binders and powders was evaluated by a hot-press experiment. The phases, morphology evolution, tensile strength and friction performance of the sintered Al alloy were studied. The feedstock displayed shear-thinning behavior for a smooth extrusion process, resulting in a satisfactory surface quality and minimal stacking pores in the 3D structure. The morphology evolution of Al alloy sintered in nitrogen could be divided into four stages, including the precipitation of fine Mg₂Si and Si at 500 °C, appearance of Mg₂Si phase over 560 °C, nitridation of the oxide layers on alloy powders and enhanced grain growth via the diffusion process over 620 °C. The 3D 7075 Al alloys achieved a high relative density of 95%, exhibiting a tensile strength ranging from 120 to 141 MPa and a tensile strain of 1.0%−2.5%.

The Nakazima method was applied to performing bulging experiments of annealed TA2 pure titanium/ Q235B carbon steel composite plate samples with different sizes. The effects of acting surfaces on forming limits and interface damage behavior of TA2/Q235B composite plate were investigated. It is found that when the steel contacts with the concave die, the bulging height and forming limit of the composite plate increase due to the different contact materials, coordination deformation ability of the interface, and strain state. The bulging height of the R140 specimen reaches the maximum value (46.17 mm), and the thickness reduction and interfacial crack of the R60 and R180 specimens in three directions are larger. In addition, due to the difference in hardness and tensile stress, all horizontal and inclined holes in both groups extend toward the pure titanium.

In order to improve the manufacturing efficiency of high-chromium superalloys, an innovative extreme high- speed laser metal deposition (EHLMD) process was used. The growth behavior of precipitated phases, high-temperature mechanical properties, wear resistance, and corrosion resistance of EHLMD K648 superalloy were investigated and compared with conventional laser metal deposition (CLMD) using transmission electron microscope, tensile tester, wear tester and electrochemical workstation, respectively. The results reveal that the precipitated phase size in EHLMD K648 superalloy is significantly smaller than that in CLMD K648 superalloy. Moreover, EHLMD K648 superalloy demonstrates higher tensile strength at 700 °C, superior wear resistance, and excellent corrosion resistance compared to CLMD K648 superalloy. Consequently, the K648 superalloy manufactured through EHLMD technique exhibits favorable comprehensive properties.

Synchrotron radiography was performed during the solidification of Al−20wt.%Cu hypoeutectic alloy to study the competitive grain growth dynamics and a mathematical model consistent with the experimental results was established. The experimental results showed that for the diverging competitive growth, the “normal elimination” rule played a role. For converging competitive growth, the growth rate of the primary dendrite arms in the non-preferentially oriented grains was accelerated due to constitutional supercooling, resulting in the phenomenon of “abnormal elimination” in which the non-preferentially oriented dendrites would eliminate the preferentially oriented dendrites. The critical conditions between “normal elimination” and “abnormal elimination” of converging competitive growth were explored using a mathematical model. The mathematical model named the “secondary dendrite arm blocking model” among dendrite growth rate, dendrite arm spacing and dendrite inclination angle was established, which could quickly predict the orientation of grain boundaries and the type of elimination.

Additive manufacturing (AM), as a revolutionary technology, enables the fabrication of complex shape memory alloy (SMA) components with unprecedented degrees of freedom, thus providing tremendous opportunities for developing modern manufacturing and transforming traditional manufacturing. Herein, this review aims to broaden ideas for preparing AM-built SMAs with high performance and multifunctionality through elucidating of the current advancements from the perspectives of the microstructure, properties, and prospects. It is concluded that the columnar grains formed by epitaxial solidification, and the prominent microstructure characteristics during printing, are modulated by different scanning parameters. The combined effects of microstructures, such as precipitates, dislocations, twins and stacking faults, can lead to desirable materials with excellent and stable shape memory effect and superelastic effect. Finally, further breakthroughs in materials, technologies, properties and methods are needed to facilitate applicability in various industries.

Zn−4Ag−Mn alloy was successfully prepared by high-pressure solid solution (HPS) method to achieve high strength and antibacterial implant materials which can degrade uniformly. Microstructural characterization showed that HPS treatment on Zn−4Ag−Mn alloy resulted in 57.9% grain refinement, and the average size of the second phases was reduced to 10.2 μm compared with as-cast (AC) alloy. The compression, Vickers hardness and wear and friction tests showed particularly high mechanical properties of HPS alloys, including a compressive yield strength of 333.5 MPa and a Vickers hardness of Hv 89.5. Electrochemical corrosion, and immersion corrosion tests showed that HPS treatment optimized the corrosion resistance of the alloy with homogenous corrosion. Furthermore. The HPS-treated Zn−4Ag−Mn alloy exhibited excellent antibacterial properties through antibacterial testing, with an antibacterial rate of 71.6%. These results suggest that the HPS-treated Zn−4Ag−Mn alloy can be considered as a promising biodegradable implant material.

The corrosion kinetics, surface microstructure, and corrosion mechanism of Sn−3.0Ag lead-free solder were investigated using mass-loss method in the temperature range from 283.15 to 323.15 K in polyvinyl chloride fire smoke environment. The results show that the Sn−3.0Ag solder exhibits an increase in mass-loss from (22.09±2.01) to (44.66±1.20) g/m² as the temperature increases from 283.15 to 323.15 K. Moreover, the corrosion kinetics is in accordance with Arrhenius law. The surface corrosion products of Sn−3.0Ag solder show a superposition growth trend. At 283.15 K, the surface of Sn−3.0Ag solder shows significant corrosion products. The corrosion process of Sn−3.0Ag lead-free solder is an electrochemical corrosion. Hydrogen evolution and oxygen abstraction reactions occur in the cathode, and the dissolution of the Sn-rich phase occurs in the anode. The corrosion products are Sn₂₁Cl₁₆(OH)₁₄O₆, SnO₂, and SnO.

The corrosion behavior of Ti−6Al−4V fabricated by selective laser melting (SLM) in simulated spent fuel reprocessing environment was investigated. The microstructure and corrosion resistance of SLM Ti−6Al−4V alloy were characterized by optical microscopy, X-ray diffraction, scanning electron microscopy, electron backscatter diffraction and electrochemical tests. It can be found that SLM Ti−6Al−4V alloy has a better corrosion resistance than the cast counterpart in 6 mol/L hot nitric acid with oxidizing ions. Further analysis indicates that SLM Ti−6Al−4V alloy exhibits α'+β microstructure with smaller grain size and higher grain boundary density in comparison to the cast counterpart, and a higher β-Ti phase content with uniform distribution is also observed in SLM alloy, which is conducive to enhancing its passivation ability in nitric acid with oxidizing ions, contributing to an improved corrosion resistance. It is indicated that SLM Ti−6Al−4V alloy has the potential to be used in spent fuel reprocessing process.

Particle erosion induced by foreign object damage (FOD) is an important factor that restricts the working life of thermal barrier coatings (TBCs). A dense α-Al₂O₃ overlay was prepared by magnetron sputtering and vacuum treatment on the surface of 7YSZ TBCs sprayed by plasma spray-physical vapor deposition (PS-PVD) to improve the erosion resistance of the TBCs. The FOD behavior of the TBCs was systematically studied and the interface of α-Al₂O₃/c-ZrO₂ was investigated by first principles calculations. The experimental results show that the erosion rates of the PS-PVD, atmospheric plasma spraying (APS), and electron beam-physical vapor deposition (EB-PVD) TBCs were 324, 248, and 139 μg/g, respectively, while the erosion rate of the Al₂O₃-modified PS-PVD TBCs was reduced to 199 μg/g. In addition, the highest interface adhesive energy of 3.88 J/m² observed in the top configuration model of Al₂O₃/ZrO₂−O is much higher than that of ZrO₂/Ni (2.011 J/m ²), which results in improved interface bonding performance.

A unified constitutive model is established to predict the plastic flow behavior of face-centered cubic (FCC) metal in the ultrasonic vibration (UV) assisted forming. The model describes UV softening behavior based on the dislocation dynamics in the UV combined with the stress superposition mechanism. The interaction among dislocation density, grain size and UV is considered, and the residual behavior of UV-assisted forming can be predicted by modelling with dislocation density and grain size as internal state variables. UV-assisted compression tests were performed on oxygen-free high-thermal conductivity (OFHC) copper to verify the predictive ability of the model. The results show that OFHC copper exhibits obvious softening behavior and residual softening behavior in the UV. The model prediction is in good agreement with the experimental result, which effectively captures the softening effect and residual effect of copper.