Abstract:The WC/Co and WC/CoCe interface models were constructed, and the interfacial energy, elastic constants, and charge distribution characteristics were calculated using first-principles calculations. WC-10Co, WC-10Co-0.5Ce, and WC-10Co-1Ce cemented carbides were fabricated via liquid-phase sintering. Microstructural analysis, mechanical testing, and friction and wear testing were conducted to investigate the influence of the rare earth element Ce on the overall performance of the cemented carbide. The calculated results indicate that doping with Ce promotes the formation of strong covalent bonds between W and Ce atoms at the interface, which increases the interfacial bonding energy, reduces the interfacial energy, and improves structural stability. Based on the elastic constants and electronic properties, it is predicted that the hardness, toughness, and wear resistance of the cemented carbide are enhanced. Experimental findings demonstrate that the optimal performance is achieved when the Ce content is 0.5wt%. At this concentration, the Vickers hardness reaches 1484 HV₃₀, the fracture toughness is 10.55 MPa?m^1/2, and the wear rate is 1.067×10^–5 mm³?N^–1?m^–1.

Abstract:The microstructural evolution during the laser welding and subsequent post-weld heat treatment processes of laser welded TB9 joints was investigated. Results show that, during the laser welding process, the average size of β grains in the fusion zone increases with the increase in laser power. During the aging treatment, the size of the α phase increases with the increase in temperature. Concurrently, the quantity of the α phase decreases. The size of the α phase also increases with the prolongation of holding time. Meanwhile, the morphology of α phase transforms from a needle-like structure to an elliptical one. After the heat treatments, the precipitation-free zones (PFZs) are observed in the fusion zone, heat-affected zone (HAZ), and base metal of the welded joint. The formation of PFZs is due to the inhomogeneous precipitation and growth of α phase. PFZs exist between the dendrite arms in the fusion zone, near the grain boundaries in HAZ, and near the low angle grain boundaries (LAGBs) and grain boundaries of the base metal. In the fusion zone, the formation of PFZs is due to the enrichment of element Cr between dendrite arms. In HAZ and base metal, the formation of PFZs is attributed to vacancy depletion around grain boundaries as well as LAGBs.

Abstract:Based on the highly radioactive service environment of spent fuel reprocessing, the influence of gamma irradiation on the structure of Ti35 alloy was studied by applying gamma rays at different irradiation doses, and the structure-activity relationship between irradiation-induced structure and performance was established. The results show that gamma irradiation induces a large number of defects in Ti35 alloy, and the defect density increases with the increase in irradiation dose. The rapid migration of Ti atoms in the Ti35 alloy matrix caused by irradiation results in the formation of a body-centered cubic Ta-rich second phase in the granules, and the Ta content and size of this phase further increase with the increase in irradiation dose. Gamma irradiation significantly reduces the elongation of Ti35 alloy, which is related to the deformation and interface failure mechanism dominated by Ta-rich soft phase according interface analysis. The Ti35 alloy shows ductile fracture mode before and after irradiation, and it is found that gamma irradiation significantly increases the size and density of fracture micropores by observing the fracture morphology.

Abstract:A low-cost Ti-6Al-4V (TC4) alloy fabricated by remelting TC4 scrap using electron beam cold hearth melting (EBCHM) combined with a short-process hot-rolling route was investigated. Two heat treatment conditions, namely stress-relief annealing and solution treatment followed by aging were adopted to study the influence of microstructure on the tensile properties and high-cycle fatigue (HCF) performance of the alloy. The results indicate that the stress-relieved alloy exhibits a typical basketweave α+β lamellar microstructure. After solution treatment and aging, the microstructure transforms into a heterogeneous structure consisting of coarsened α lamellae, equiaxed α grains, and transformed β. Compared with the annealed condition, the solution-aged alloy shows a significant improvement in ductility while maintaining relatively high strength, leading to a favorable strength-ductility synergy. This enhancement is primarily attributed to the cooperative deformation of coarsened α lamellae and equiaxed α grains, which effectively accommodate dislocation slip and promote the activation of higher-order slip systems, thereby improving the plastic deformation capability of the alloy. High-cycle fatigue tests reveal that the annealed alloy exhibits a higher fatigue strength. This behavior is associated with the basketweave lamellar microstructure, which facilitates crack deflection and prolongs the fatigue crack propagation path, thereby improving resistance to fatigue crack growth.

Abstract:The low-cycle dwell fatigue behavior and fracture characteristics of a cost-effective Ti-2Fe-0.1B alloy with lamellar microstructure were investigated. Strain-controlled low-cycle fatigue tests incorporating tension-compression with dwell time of 0, 2, and 10 s were conducted under various strain amplitudes. The results reveal that at lower strain amplitudes (Δε_t/2=0.6%), specimens with all dwell durations exhibit continuous cyclic softening during initial cycles. Conversely, at higher strain amplitudes (Δε_t/2=1.4%), an initial cyclic hardening phase precedes subsequent softening, which is primarily attributed to dislocation multiplication and entanglement, forming temporary barriers that impede plastic deformation in early stages. The fatigue life of Ti-2Fe-0.1B alloy demonstrates significant strain amplitude and dwell time dependence. At high strain amplitude (Δε_t/2=1.4%), the life reduces (710→426 times). At intermediate strain amplitude (Δε_t/2=1.0%), specimens maintain stable fatigue life under short dwell periods (1604→1610 times), while low strain amplitude (Δε_t/2=0.6%) testing reveals non-monotonic life variations (15 478→8543→8887 times) with the prolongation of dwell time. Comparative analysis with conventional titanium alloys (TA15, Ti80) demonstrates that dwell fatigue resistance of Ti-2Fe-0.1B alloy is better. Microstructural characterization of fracture profiles reveals the presence of precipitated TiB phases. These high-strength and high-hardness precipitates contribute to enhanced matrix strength and can provide effective crack propagation resistance through reinforcement mechanisms, which improves the overall fatigue performance of alloy's.

Abstract:Channel segregation in Nb47Ti alloy is prone to occur during vacuum arc remelting (VAR), which significantly degrades its processability. Molecular dynamics simulations reveal that for the Ti-Nb system under isothermal holding at 1170 ℃, the mean squared displacement (MSD) of Ti and Nb increases with the increase in Nb content, indicating that homogenization treatment effectively alleviates microsegregation. In Nb47Ti alloy, solute atoms Nb exhibit significantly stronger displacement amplitudes and diffusion trajectories than the Ti matrix. The effects of homogenization heat treatment at 1170 ℃ for 5.5 and 10 h on the microsegregation and channel segregation of Nb47Ti ingot with diameter of 520 mm were analyzed. The results show that the segregation index of microsegregation decreases by 0.27% and 0.53% after homogenization, but no significant improvement is observed in the morphology, quantity, or size of channel segregation. Increasing the heat treatment temperature or prolonging the duration has an extremely minimal effect on reducing channel segregation, and may lead to excessive hydrogen content issues.

Abstract:The cross piercing (RP) TC4-0.55 Fe titanium alloy seamless tube was taken as the research object. The microstructure was controlled by solid solution and aging treatments. The tensile properties at room temperature and impact properties at –20 ℃ were tested. The effects of microstructure evolution on mechanical properties were analyzed by scanning electron microscope, X-ray diffractometer, and transmission electron microscope. The results show that the size of α_C and the average grain thickness of α_L increase significantly, and the orientation and uniformity of the microstructure are also significantly enhanced. The tensile strength, yield strength, and elongation of RP samples are 904±1.23 MPa, 793±2.62 MPa and (14.2±0.72)%, respectively. The impact energy and impact toughness at –20 ℃ are 66.2±1.62 J and 82.7±1.03 J/cm², respectively. After solution and aging in the two-phase region, the tensile strength, yield strength, and elongation of STA910 sample increase to 984±8.92 MPa, 904±9.93 MPa and (16.2±0.93)%, respectively. The impact energy and impact toughness at –20 ℃ decrease slightly, but still maintain at 52.8±1.77 J and 64.9±1.78 J/cm², respectively. The α/β interface is increased by the precipitation of α_S and ω phases in the STA910 sample, which increases the dislocation slip and motion resistance and improves the segregation of alloying elements. The dual effects of grain boundary strengthening and solid solution strengthening are achieved, thus improving the strength and plasticity of the alloy. On the other hand, all TC4-0.55Fe alloys show excellent impact toughness. The fracture modes of the alloys are mainly ductile fracture and transgranular fracture. The coarsening of α phase grain size, the decrease in β phase stability, and the precipitation of α_S and ω phases in β_t lead to the decrease in impact properties of the alloys.

Abstract:The anisotropic mechanical behaviors of TA1 commercially pure titanium (CP-Ti) rolled plates with two different initial orientations (bimodal texture and dispersed texture) under uniaxial loading, including stress-strain curves, tension-compression yield asymmetry, strain hardening, plastic strain ratio (r-value), and texture evolution were investigated using macroscopic mechanical property testing, microstructural characterization, and crystal plasticity modeling. The simulation results based on the VPSC-PTR model are well agreement with the experimental data. Compared to the plate with dispersed texture, the plate with bimodal texture presents more prominent anisotropy and tension-compression asymmetry, accompanied by more significant changes in the r-value and more intense texture evolution during deformation. Combining with the Schmid factor distribution, the relative activity of slip/twinning system, and critical resolved shear stress, the effect of initial texture on competition between slip and twinning during the deformation is clarified, revealing the influence mechanism of the initial orientation on the anisotropy of the rolled CP-Ti plates. The prismatic slip is the dominant mechanism of plastic deformation in CP-Ti. And extension twinning is more easily activated in plate with bimodal texture, while basal slip and pyramidal slip are more active in plate with dispersed texture, leading to different anisotropic characteristics. Moreover, the r-value of plate with bimodal texture is higher than that with dispersed texture during deformation, which is related to the decrease in activity of prismatic slip and the increase in activity of extension twinning.

Abstract:The effect of withdrawal rate on microstructure and creep performance of directionally solidified (DS) Mar-M247LC superalloy was investigated. Results show that an increase in withdrawal rate of DS specimens leads to a reduction in primary dendrite arm spacing (from 479 μm to 322 μm), and the average size of γ' precipitate decreases from 460 nm to 345 nm in interdendritic region and from 298 nm to 203 nm in dendritic core. In addition, the carbide morphology changes from blocky to script-like. The heat treatment leads to the formation of distinct cuboidal γ' precipitates. And the volume fraction of γ' precipitates in heat-treated microstructure has a significant increase compared to that in DS microstructure. The DS superalloy under the withdrawal rate of 40 μm/s exhibits elongated raft-like γ' structure with narrowed matrix channels and regular dislocation networks, synergistically prolonging creep rupture life to 96.6 h. Fractographic analysis confirms that the superalloy exhibits a transgranular ductile fracture mode, with cracks initiating at decomposed MC carbides.

Abstract:This study employed a field emission scanning electron microscope, an energy dispersive spectroscope, and ABAQUS finite element analysis to investigate the oxidation behavior of DD6 single-crystal superalloy at a constant temperature of 1000 ℃, focusing on the effects of various processed drilling processes and adjacent hole spacting. The results show that the trend in oxidation mass gain of the DD6 single-crystal superalloy processed by different drilling techniques with different adjacent hole spacting is relatively consistent, following the order: 0.75 mm>0.95 mm>0.55 mm>0.39 mm. Compared with drilling process, adjacent hole spacting emerges as the primary factor affecting oxidation mass gain. The high-temperature oxidation behavior differs between the two drilling processes. The change in microstructure and elemental redistribution in the recast layer produced by electrical discharge machining may cause a variety of elements at different states to react at different rates simultaneously. In contrast, after femtosecond laser processing, there is almost no recast layer on the inner wall of the holes, and the oxide layer forms directly on the single-crystal alloy matrix. Finite element analysis reveals that oxide layer developed on hole surfaces is primarily governed by shedding stress. As adjacent hole spacing increases, the areas of stress cancellation diminish, while shedding stress escalates to a peak under the adjacent hole spacing of 0.75 mm, at which point oxide film shedding is the most pronounced, and then decreases.

Abstract:Taking an Inconel 718 (GH4169) turbine disk with an accumulated service time of approximately 60 000 h from a specific model of aircraft as the research object, the microstructure evolution of various regions of the service turbine disk was investigated. Detailed characterization of the microstructure was conducted using research methods such as optical microscopy, scanning electron microscopy, electron probe, extraction phase analysis, inclusion scanner, and nano-indentation. The results show that after long-term service, there is no significant change in the strengthening phases γ' and γ' of the turbine disk. However, the quantity, size, and morphology of primary MC carbides from the center to the edge have noticeable changes. The content decreases from 0.166wt% to 0.106wt%, and the morphology gradually changes from sharp and regular blocky at the interface to irregular near-circular ones. The nano-hardness decreases, and there is a significant redistribution of elements, with elements Nb, Ti, and C released and diffused into the matrix. The primary MC carbides are prone to dissolution and decomposition during long-term service, leading to a decrease in concentration and hardness of the carbide elements. The diffusion of carbide-forming elements into the matrix may cause a disturbance to the comprehensive mechanical properties of the alloy during the long-term service performance.

Abstract:Effects of initial grain morphology on anisotropy of microstructure and mechanical property in Inconel 738 alloy prepared by laser powder bed fusion (LPBF) under different scanning strategies after hot isostatic pressing (HIP) treatment were studied. The results show that the initial grain morphology is highly heritable. The initial grain morphology of Inconel 738 alloy formed by scanning strategy 90° (As-built 90 alloy) presents elongated columnar grains and irregular fine grains. After HIP treatment, the recrystallized grain morphology of HIP 90 alloy presents elongated columnar grains and a few equiaxed grains. The As-built Inconel 738 alloy formed by scanning strategy 67° (As-built 67 alloy) initially has short columnar and equiaxed grains, and the recrystallized grain morphology of HIP 67 samples shows similarly equiaxed and equiaxed grain morphology. The main reason is that the initial grain morphology determines the strain distribution. The strain distribution of As-built 90 samples is in the shape of “bar”, while that of As-built 67 samples is in the shape of “net”, and the strain distribution is more uniform. During HIP treatment, the strain concentration region preferentially provides nucleation location for recrystallized grains, which determines the morphology of recrystallized grains in HIP samples. The mechanical anisotropy of HIP 90 alloy is larger than that of HIP 67 alloy, which is mainly related to the grain morphology of HIP 90 alloy. The equiaxed grain morphology of LPBF-Inconel 738 alloy after HIP treatment requires appropriate LPBF process parameters.

Abstract:The Mar-M247 nickel-based superalloy turbine blade was investigated by tensile tests conducted from room temperature to 980 ℃. The microstructure, tensile properties, and fracture mechanisms of the alloy were analyzed. Results indicate that the alloy's microstructure primarily consists of γ phase, flower-like γ′ phase, γ/γ′ eutectic structure, and carbide phases. The alloy strength initially increases and then decreases with increasing temperatures. At low temperatures, fracture exhibits a mixed mode dominated by transgranular fracture with intergranular fracture as a secondary component, where cracks preferentially initiate at carbide/matrix interfaces. When the temperature reaches 980 ℃, the fracture mechanism transitions to microvoid coalescence-induced ductile fracture, accompanied by an increase in elongation to 6.4%. Deformation mechanism analysis reveals that stacking fault shearing dominates in the low-temperature region (<400 ℃), forming Lomer-Cottrell (L-C) dislocation locks. The intermediate temperature range (400–760 ℃) displays Portevin-Le Chatelier (PLC) effects coupled with intermediate-temperature brittleness. Above 760 ℃, widening matrix channels and increased stacking fault energy promote a synergistic interaction between antiphase boundary (APB) shearing and Orowan bypassing mechanisms, leading to a significant decrease in deformation resistance.

Abstract:Electrode induction-melting gas atomization (EIGA) is a crucial technique for producing ultra-high-purity metal powders, as it is a crucible-free powder production method. This study focused on the nickel-based superalloy FGH96 and the titanium alloy TC4, and the effects of atomization pressure and gas temperature on the particle size, morphology, and hollow powder content of the alloys were investigated. The study combined atomization experiments with powder characterization. The results show that at a gas temperature of 25 ℃, increasing the atomization pressure from 2.5 MPa to 4.0 MPa reduces the median particle size (D₅₀) from 96.3 μm to 75.5 μm. The sphericity reaches 0.9805 at an atomization pressure of 3.5 MPa. The powder volume porosity also exhibits a trend of first increasing and then decreasing. At an atomization pressure of 4.0 MPa, when the gas temperature increases to 100 ℃, the powders are further refined, with the D₅₀ values for FGH96 and TC4 powders decreasing to 63.8 and 86.0 μm, respectively. The gas heating effect is more pronounced for the superalloy powders. As the gas temperature rises, the powder sphericity of the superalloy remains unchanged, while the powder sphericity of the titanium alloy increases slightly. The powder volume porosity of the superalloy slightly increases. Due to differences in viscosity, surface tension, and density between the two alloy melts, powder characteristics such as particle size and morphology exhibit distinct variation trends. This study provides a theoretical basis for the customization of powder preparation processes for different types of alloys.

Abstract:In response to the need for in-situ repair of deep cracks in a naval ship, a 4 mm-deep 30° U-shaped groove was prepared on 921A steel. Groove filling experiments were conducted using local dry underwater oscillating laser wire feed welding under the conditions of air and shallow water. The microstructure and properties of the welds were analyzed. The results indicate that sound welds without significant defects are obtained in both air and shallow water. Owing to the effective shielding gas protection within the local dry cavity and the rapid cooling effect underwater, the shallow water weld exhibits a bright white surface with densely distributed fish-scale patterns. The air weld includes a higher fraction of acicular ferrite, whereas the rapid cooling in water promotes the formation of lath martensite. The main alloying elements under both environments exhibit a smooth transition near the fusion lines with good metallurgical bonding. However, due to the higher cooling rate in the shallow water compared with that in air, there is a greater fluctuation in elemental distribution, along with higher contents of Si, Mn, and Mo and a slightly lower Cr content in the shallow water weld. The shallow water weld shows higher overall hardness than the air weld, though the hardness distribution trends across different zones are similar in both cases. Tensile tests reveal that fracture occurs in the base metal under both environments, with the tensile strength and yield strength ranking as follows: shallow water weld>air weld>base metal. However, electrochemical corrosion tests indicate that the shallow water weld has inferior corrosion resistance compared to the air weld.

Abstract:The thermal barrier coatings (TBCs) are prepared using spraying technique of 8YSZ particles. In this process, H₂ is often added to the plasma torch discharge system. In order to study the effect of H₂ content on plasma discharge, this study emplyed particle velocity capture diagnostics, optical emission spectroscopy, and finite element simulation to validate the relationship between H₂ content and coating quality. The results indicate that adding H₂ increases the temperature and velocity of plasma, which in turn improves the efficiency and in-flight velocity of molten 8YSZ particles. However, when the H₂ /(Ar+H₂) is increased to 50%, the instability of arc root disturbs the arc plasma discharge, posing a challenge to maintaining the physical state of the in-flight particles. With an increase in H₂ flow rate, the coating quality shows a trend of first increasing and then decreasing, with the optimal flow rate ratio being H₂/(Ar+H₂)=37.5%. The findings of this work can serve as a theoretical guidance and reference for the preparation of TBCs via plasma.

Abstract:The high-purity Mo₂BC bulk was synthesized via spark plasma sintering (SPS) technique. Results show that the Mo₂BC bulk prepared by optimized SPS process exhibits exceptional structural homogeneity, with a Vickers hardness of 19 GPa. This considerable mechanical hardness is attributed to the strong covalent bonding network within the Mo₂BC crystal structure. Simultaneously, magnetic and electrical characterization confirms that the Mo₂BC bulk has superconductivity with a transition temperature of 7.8 K and a high upper critical field of 6.3 T. The coexistence of such notable mechanical properties and robust superconducting characteristics in Mo₂BC bulk reveals a promising candidate for advanced applications under extreme conditions. This study not only provides crucial insights into the non-centrosymmetric bulk materials, but also establishes SPS as an efficient route for developing novel superconductors with high hardness.

Abstract:Asynchronous rolling reduces rolling force through the cross-shear effect, significantly influencing the plastic deformation behavior of zirconium alloys, and serves as an effective approach to optimize texture characteristics in Zr-Sn-Nb alloys. In this study, Zr-Sn-Nb alloy sheets were subjected to asynchronous rolling at a speed ratio of 1.13 along the RD-TD (0° sample) and RD-ND (90° sample) directions. By combining electron backscatter diffraction and intra-grain misorientation axis (IGMA) analysis, the effects of initial orientation and deformation amount on microstructure evolution, slip system activation, and deformation mechanisms during asynchronous rolling were investigated. The results demonstrate that with the increase in deformation, both oriented samples exhibit significant grain refinement and a progressive rise in the fraction of low-angle grain boundaries. Throughout rolling, the 0° sample retains a bimodal texture, whereas the 90° sample undergoes a texture transition from <0001>∥TD to a bimodal texture. IGMA analysis reveals that prismatic <a> slip dominates the early deformation stage in both samples. As strain accumulates, competition arises between prismatic <a> slip and basal <a> slip. In the 0° sample, prismatic <a> slip remains the predominant deformation mode, with negligible contributions from other mechanisms. In contrast, plastic deformation in the 90° sample is cooperatively accommodated by {102} twinning, prismatic <a> slip, basal <a> slip, and pyramidal <a> slip.

Abstract:The Zr/Re co-modified PtAl coating was fabricated by electroplating Pt vacuum diffusion annealing and composite electroplating Ni-Zr/Re layer+arc ion plating Al layer vacuum diffusion annealing. The isothermal oxidation experiment was carried out at 1100 ℃ for 200 h. The phase composition and microstructure of the as-annealed coating and the oxidized coating were characterized by SEM, XRD and EPMA, and the distribution law of the modified elements and the evolution law of the coating microstructure during oxidation were investigated. The results show that the Re-rich precipitates dispersed in the coating aggregate and grow during oxidation and form volatile oxide Re₂O₇. The Zr solid-solved in the coating co-precipitates with the Ta element diffused into the coating from the substrate alloy, and some Zr enters the Al₂O₃ scale to form Zr-rich oxides, reducing the growth rate of the Al₂O₃ scale. In addition, with the mutual diffusion of elements between the coating and the substrate, the β phase in the coating undergoes martensitic transformation. The precipitates in the mutual diffusion zone change from plate-like to particle-like, and the coexistence relationship of Cr-rich precipitates and Re, Cr and W-rich precipitates is found in the secondary reaction zone of the coating.

Abstract:Porous CoCrNi medium-entropy alloy (MEA) with porosity of 60.6%–78.1% and pore size of 1.8–2.4 mm were prepared by powder sintering-dissolution method. Results show that the pore distribution is uniform, and the metallurgical bonding is good. The dynamic compression test results show that the material has a significant strain rate strengthening effect, and the impact resistance is the best at strain rate of 500 s^–1. The yield strength increases by 52.8% (from 22.9 MPa to 35.0 MPa) with the increase in strain rate from 200 s^–1 to 800 s^–1. The dynamic yield strength increases by 25% compared with the quasi-static yield strength. The energy absorption value reaches 35.4–14.5 MJ/m³ (6.6%–14.0% higher than the quasi-static result), and the maximum ideal energy absorption efficiency is close to 0.9. At the same time, under the condition of low temperature (–100 ℃), the elastic modulus and platform stress are increased by 2.4%–10.5% and 2.5%–9.8%, respectively, compared with those at room temperature. The energy absorption value is 41.3–15.2 MJ/m³, which is twice that of magnesium alloy foam, and the maximum ideal energy absorption efficiency is 0.8. In summary, the porous CoCrNi MEA has both dynamic strengthening and low-temperature strengthening characteristics, and it has good energy absorption capacity and high ideal energy absorption efficiency, showing significant application potential in the field of actual working conditions and extreme environments.

Abstract:The cold metal transfer (CMT) butt welding was conducted on AlSi10Mg alloy thin sheets prepared by the powder bed fusion laser beam/metal (PBF-LB/M) technique using two types of filler wires, including ER4043 (Al-Si5) and ER4047 (Al-Si12). The effects of the two wires on weld geometry, porosity, microstructure, and mechanical properties of the welded joints were evaluated. Results indicate that the adding ER4043 wire effectively reduces porosity rate and pore size of the weld metal. In contrast, the ER4047 wire exhibits improved mechanical performance. The ultimate tensile strength of joints welded with ER4047 wire reaches 211.7 MPa, representing a 6.7% increase compared to the 198.4 MPa achieved with ER4043 wire. The average microhardness of the ER4047 weld (76.8 HV) increases by 15.5% compared to that of ER4043 weld. These findings suggest that the higher Si content in ER4047 filler wire is more conducive to achieving superior joint properties. Microstructural analysis attributes this enhancement to a combination of solid solution strengthening, fine grain strengthening, texture strengthening, nanoscale Si precipitation, and the load-bearing contribution of the eutectic Si network.

Abstract:To fabricate high-purity tantalum target billets with uniform grain size, preferential orientation, and homogeneous hardness distribution, a series of high-purity tantalum target billets were prepared by electron beam melting and multi-pass rolling technique. The effects of rolling modes (cold rolling/hot rolling) and multi-pass rolling reduction on the microstructure, and mechanical properties of tantalum target billets were investigated. The results indicate that compared with that prepared by hot rolling, the sample prepared by cold rolling exhibits smaller and more uniform grain size. Under cold rolling condition, the multi-pass rolling reduction decreases from 20% to 2%, and the grain size and standard deviation of the tantalum target billets change significantly, varying from 46.01 μm to 58.92 μm. Meanwhile, the proportion of (100) and (111) crystal planes gradually increase, while the proportion of (110) crystal plane rapidly decreases. When the multi-pass rolling reduction is 2%, the growth of the (110) crystal plane in the tantalum target blank sample is certainly inhibited, a high proportion of (100)-(111) mixed random texture is obtained, and the Vickers hardness of the tantalum target increases to 147.68 HV. These research findings provide an important reference for the development of high-quality tantalum target billets.

Abstract:As a strategic critical metal, niobium is widely used in the fields of aerospace, nuclear industry, and superconductors owing to its superior properties. With the requirement of sustainable development, the energy consumption in niobium melting processes has attracted increasing attention. Green, low-carbon, and energy-saving practices have become the new development direction. In addition, microelectronics technology requires high-purity niobium as a sputtering target material. Although niobium with a purity of up to 5N has been achieved, a low-cost high-purity technique is still challenging. This review summarized a variety of pyrometallurgical methods for the preparation and purification of crude niobium. As a traditional method for producing crude niobium, the key challenge of thermal reduction is how to reduce energy consumption. As a technique with industrial propects, molten salt electrolysis has been developed into a variety of methods, but the efficiency needs to be further improved. In addition, some new purification techniques are constantly emerging, such as fully-automated melting technique assisted by the digital twin and artificial intelligence. In the future, a variety of technical means will be combined to purify niobium metal. This review also briefly introduced the current status of niobium recovery and further explored the full lifecycle of niobium based on the concept of urban mine, to provide direction for achieving niobium recycling.

Abstract:As a representative γ'-strengthened nickel-based superalloy, GH4099 is widely used in hot-end components under extreme service environments such as aviation, aerospace, and nuclear due to its excellent high-temperature performance, thermal stability, corrosion resistance, as well as fatigue resistance and fracture toughness. Laser powder bed fusion (LPBF) technique has effectively solved the technical bottlenecks such as prolonged processing cycle, insufficient process synergy, low material utilization, and high cost in the forming process of complex components by the traditional manufacturing technique. This review presents a comprehensive overview of the recent advancements in LPBF technique for the formation of GH4099 and delved into various aspects of GH4099 superalloys prepared by LPBF, including its technical principles, solidification defects, microstructure, and high-temperature mechanical properties. Furthermore, it focused on the influence of powder characteristics, process parameters, post-treatment techniques (including heat treatment and hot isostatic pressing technique), and other factors on the solidification defects and high-temperature mechanical properties of GH4099 superalloys prepared by LPBF. Finally, it summarized and outlined the application potential and development trends of this technique in future manufacturing.

Abstract:TiAl alloy has important application value in aerospace and other high-temperature structural components due to its low density, high specific strength, and excellent creep resistance at high temperature. However, the high-temperature oxidation resistance of TiAl alloy in the environment above 750 ℃ is poor and the service life of some high-temperature service components under the condition of hot corrosion and high-temperature wear is reduced, which restrict its application. Double glow plasma alloying surface technology is an important way to enhance the surface protection ability without changing the overall performance of the substrate. The basic mechanism of the double glow plasma surface alloying technology was reviewed. The unit infiltration, dual infiltration, multi-component co-infiltration, and the composition and structure of infiltration coatings on high temperature oxidation resistance, hot corrosion resistance, and wear resistance were discussed. Finally, it outlined the future developing trends in the view of theoretical research, preparation process, and engineering applications.

Abstract:With the rapid development of human society, the discharge of various types of sewage has increased year by year, and environmental problems such as water pollution have become increasingly serious. Seeking effective sewage treatment methods has become an urgent need. Due to its excellent surface activity, low oxidation-reduction potential, and outstanding catalytic degradation performance, amorphous alloys are regarded as effective catalysts for solving various types of wastewater, such as dyeing wastewater. Currently, extensive research has been conducted on the treatment of wastewater containing organic pollutants such as dyes and pesticides, as well as inorganic pollutants such as heavy metals and acid-base salts. However, the degradation mechanism of amorphous alloys varies greatly depending on the type of wastewater and the amorphous alloy system, resulting in different degradation rates. Therefore, selecting suitable amorphous alloy components and appropriate material modification methods is crucial for achieving efficient degradation of wastewater. This review summarized the conventional techniques for wastewater treatment, the characteristics and potential of amorphous alloys, their applications in wastewater treatment, and the existing problems. It also reviewed the influence of various chemical parameters and other factors on the catalytic performance of amorphous alloys, as well as various material modification methods, aiming to provide valuable references for the research of new catalysts.