The connections of dissimilar materials LA103Z magnesium-lithium alloy and 1060Al alloy were achieved by electromagnetic pulse welding (EMPW). The effects of discharge energy on interface morphology, wave formation mechanisms, and element diffusion were systematically investigated through numerical simulations and experiments. The results indicate that the induced magnetic field and current are determined by the welding current's magnitude and rate of change, respectively. The increase in discharge energy enhances the Lorentz force experienced by 1060Al, thereby increasing the impact velocity, while the impact angle almost remains unaffected. The rebound phenomenon, which alters the contact state between the flyer plate and the target plate, is identified as the key factor in forming the annular weld seam. Both the simulated and actual interface morphologies are sinusoidal, with the amplitude increasing from 3.02 μm at 32 kJ to 6.48 μm at 38 kJ. The wave formation is attributed to shear-induced instability and metal-plastic flow triggered by high-speed collision. No melting is observed at the interface. The maximum shear strength of the joint reaches 90.38% of that of the aluminum base material. Numerical simulations confirm that the interface temperature remains below the melting points of both base materials, which is critical for improving the mechanical performance of the joint.

Al-Ga-Mg-Sn soluble aluminum alloy was selected for a one-step hydrometallurgical technique. Acid leaching agents, including organic acid solutions (e. g., oxalic, malic, and acetic solutions) and inorganic acid solutions (e. g., nitric acid) were used. The type of leaching agent, pH value, temperature, and solution concentration are key factors influencing the recovery of Ga during hydrogen production. Recovery results show that under the temperature of 70 ℃ and the agent concentration of 0.2 mol·L^-1, the organic acid solution successfully recovers gallium, with oxalic acid exhibiting the highest recovery efficiency (86.88%), followed by malic acid (73.40%) and acetic acid (13.17%). In contrast, the inorganic acid (nitric acid) solution fails to recover gallium. Oxalic acid, with an initial pH value of approximately 3.8, achieves a recovery efficiency of 94.38% under 70 ℃/0.3 mol·L^-1 and 93.78% under 90 ℃/0.2 mol·L^-1. The leaching behavior of gallium was then tested and analyzed based on changes in pH value, shape of the recovered gallium, solid particle size and Zeta potential of the product during the hydrolysis process. The results show that the recovery of gallium from oxalic acid leachate increases with the decrease in particle size of the product and increase in absolute value of Zeta potential. The highest recovery efficiency (94.38%) is achieved with a product particle size of 155 nm and a Zeta potential value of -31.29 mV.

To design a porous titanium alloy structure suitable for cervical spine implants, according to different stress conditions of cervical spine, such as compression, compression-shear, compression-torsion, and compression-bending, four types of unit cell structures, TO-C, TO-CS, TO-CT, and TO-CB, were constructed by combining topology optimization and computer-aided design. The mechanical properties were analyzed by compression simulation. Finally, the quasi-static compression test of porous samples with porosity of 60% prepared by laser powder bed fusion technique was conducted. The results of finite element simulation and compression test show that the compressive properties and elastic moduli of the four porous structures meet the requirements of human bone implants. Among them, the TO-CB structure has the best compressive performance and is suitable for porous titanium alloy cervical spine implants.

The distribution and evolution of the internal grain structure of large-scale GH4738 alloy during the complex continuous deformation cogging process, based on the process sequentiality and organizational heredity, were investigated by employing a finite element model combined with secondary development methods, providing a general approach for process design and outcome prediction. Finite element simulation calculations were conducted based on the actual billet preparation process of GH4738 superalloy with Ф660 mm grade, comparing the simulation results with the grain size at corresponding positions of the actual billets to verify the reliability and accuracy of the established model. Utilizing this model, typical upsetting and cogging processes were analyzed, and the effects of process parameters on the microstructural evolution of the billet during multiple deformation passes were discussed, along with methods for process formulation. Results show that during the upsetting process, as the upsetting speed increases, the deformation temperature decreases, the reduction amount decreases, and the degree of dynamic recrystallization within the billet decreases. In the cogging process, as the upsetting speed decreases, the cogging temperature increases, the feed amount decreases, and the degree of dynamic recrystallization within the billet increases. Furthermore, based on the specific analysis, it is recommended to control the upsetting speed during the upsetting process between 5 and 12 mm/s; the initial upsetting temperature should be 1160 ℃; the single-pass reduction amount should be controlled between 25% and 35%. The cogging process is more complex than the upsetting process. Taking into account the factors such as grain refinement within the billet, surface temperature drop during the cogging process, and the occurrence of the "concave center" phenomenon, the upsetting speed is controlled between 60 and 90 mm/s; the second cogging temperature is chosen between 1120 and 1130 ℃; the feed amount is controlled between 200 and 350 mm.

Inconel617 alloy has significant application potential in Generation IV nuclear energy systems. The effects of Mo content on carbide precipitation at grain boundaries (GBs) and high-temperature tensile properties of Inconel617 alloy were studied by mechanical testing and advanced techniques such as scanning electron microscope, transmission electron microscope, and electron backscatter diffractometer. The results show that there are only fine granular M₂₃C₆ carbide at GBs when the Mo content ranges from 8wt% to 9wt%. However, as Mo content increases from 9.3wt% to 9.6wt%, massive M₂₃C₆ and M₆C carbides could be predominantly observed at GBs. As Mo content increases from 8.0wt% to 9.6wt%, the elongation increases initially and then decreases, and the alloys with the Mo content of 8.5wt%-9.3wt% achieve optimal strength-ductility balance. The fractographic analysis reveals that the precipitation of granular M₂₃C₆ at GBs effectively strengthens grain boundaries, resulting in the transgranular fracture features on the high-temperature tensile fracture surface. When massive M₂₃C₆ and M₆C carbides precipitate at GBs, the initiation of intergranular crack is promoted and the intergranular fracture features are observed on the high-temperature tensile fracture surface. The Mo content of Inconel617 alloy for high-temperature components in Generation IV nuclear systems cannot exceed 9.3wt% and it should be controlled with in the range of 8.5wt%-9wt%

Diverse heat treatment schedules were designed and their effects on microstructural evolution and tensile properties at 750 ℃ were investigated by SEM, EDS, TEM, and mechanical testing. The results demonstrate that multi-stage heat treatment schedules lead to a multi-modal size distribution of γ' precipitates within the alloy, where fine γ' precipitates contribute to strength, while coarse γ' phases enhance ductility. At 750 ℃, the alloy subjected to the heat treatment of 1030 ℃/4 h, AC+1000 ℃/4 h, AC+875 ℃/16 h, AC+725 ℃/16 h, AC develops a trimodal γ' phase distribution. This microstructure balances the strength between intragranular and grain boundary regions, facilitating the transfer of dislocation slip and enhancing the ductility of the alloy. The alloy exhibits the best overall mechanical properties, with a tensile strength of 706 MPa and an elongation after fracture of 9.3%.

The effects of different heat treatment processes, alloy states, and stress relief annealing processes on recrystallization defects in 4777DS superalloy were studied using SEM and EBSD. SEM observation shows that the γ' phase near the surface of the sandblasted sample undergoes deformation, changing from an initial butterfly shape to a long strip distribution on the alloy surface. The observation of recrystallization of the alloy after insulation at different heat treatment temperatures shows that the temperature at which recrystallization occurs is 1055 ℃. When the heat treatment temperature is higher than the dissolution temperature of the γ' phase, recrystallization presents an equiaxed morphology, while when the heat treatment temperature is lower than the dissolution temperature of the γ' phase, it presents a cellular recrystallization morphology. With the prolongation of heat treatment time, the proportion of large angle grain boundaries decreases, and the resulting annealing twins help to reduce distortion energy. A comparison of recrystallization behavior under different initial alloy states reveals that the as-cast alloy exhibits the highest tendency for recrystallization. In line with practical engineering requirements, a shorter annealing time can effectively reduce the recrystallization degree of alloys.

Through controlling forging and heat treatment processes of nickel-based wrought superalloy, the microstructures with coarse grain volume fractions ranging continuously from 0% to 100% were prepared, and the stress rupture properties of different mixed-grain structures were tested under the condition of 730 ℃/530 MPa to explore the influence regularity and mechanism of mixed-grain structures on the stress rupture properties. The research results show that the mixed-grain structures with coarse grain volume fractions from 0% to 100% exhibit significantly different stress rupture properties. The mixed-grains structure with coarse grain volume fraction of 15% presents the shortest stress rupture life, while the coarse-grained structure with coarse grain volume fraction of 100% possesses the longest stress rupture life. The high-temperature stress rupture fracture surfaces of the mixed-grain structure specimens with low coarse grain volume fraction from 0% to 15% show typical ductile fracture characteristics, whereas those of the specimens with high coarse grain volume fraction from 50% to 100% present intergranular fracture characteristics. The high-temperature stress rupture deformation mechanisms of all mixed-grain structure specimens take the form of intragranular deformation governed by dislocation motion and grain boundary sliding. However, with the increase in coarse grain volume fraction, the high-temperature stress rupture properties of the superalloy are improved as the strong textures on the {111} crystal planes is changed, the internal dislocation distribution in coarse and fine grains is inhomogeneous, and the tendencies of stress concentration and cavity nucleation induced by dislocation pile-up and grain boundary sliding are significantly changed.