Fe-Al alloys exhibit excellent mechanical properties, low cost, and moderate magnetostriction, making it a promising magnetostrictive material. The polycrystalline (Fe₈₁Al₁₉)_100-xCe_x (x=0, 0.05, 0.10, 0.20, 0.30, 0.40, at%) alloys were prepared by arc melting. The effect of trace doping rare earth elements Ce on the microstructure, texture, and magnetostrictive behavior of Fe₈₁Al₁₉ alloys was investigated. Results show that the trace doping of the Ce element transforms the equiaxed crystals into columnar crystals, thus significantly improving the volume fraction of favorable η texture. The columnar crystal characteristics gradually weaken with the increase in Ce content, leading to weakening of η texture and an increase in the volume fraction of α and γ texture. With the increase in Ce content, a large amount of Ce-rich phases form at grain boundaries and within the grains. Among them, the phases at grain boundaries are mainly composed of Ce-Al-rich phases, while the phases within the grains is a composite secondary phase of Ce-Al wrapped around the Fe-Ce-rich phase. The magnetostriction of Fe₈₁Al₁₉ alloy is significantly enhanced by trace doping of Ce element. The peak magnetostriction of 153 ppm is obtained at the Ce element of 0.05at%, with an enhancement of 89% compared to the magnetostriction of a binary alloy. This improvement in magnetostriction is attributed to more columnar crystals containing ηtextures and the formation of more nanoheterogeneous phases owing to solid solution of trace Ce element.

The effect of heat treatment on the microstructure and mechanical properties of a high-boron Ni₃Al-based superalloy was investigated by scanning electron microscope, tensile test and stress rupture test. The results show that when the solid solution temperature increases from 1080 ℃ to 1150 ℃, the volume fraction of γ' phase in dendrite trunk decreases gradually, the morphology changes from blocky to spherical, and fine tertiary γ' phases are precipitated inside the γ channel. When the temperature rises from 1080 ℃ to 1120 ℃, the skeleton-like primary borides are partially dissolved, and the granular secondary borides are precipitated. The precipitation tendency of secondary borides is increased with the increase in temperature, and the borides are completely dissolved when the temperature rises to 1150 ℃. After aging at 900 ℃ for 10 h, the alloy solid-solution-treated at 1080 ℃ achieves the ultimate tensile strength of 900 MPa during the tensile test at 800 ℃ and the stress rupture life of 144.5 h under the condition of 580 MPa/800 ℃, exhibiting the best comprehensive mechanical properties. Therefore, the optimal heat treatment process of the test alloy is 1080 ℃×4 h→air cooling+900 ℃×10 h→air cooling.

Taking β-Ti as the research object, the first-principles calculations based on density functional theory were performed to construct a model of Ti-V system with different V contents by substituting Ti atoms with V atoms and to calculate the mechanical properties and electronic structures. The calculation results indicate that the addition of V atoms decreases the elastic constant and elastic modulus of β-Ti and improves the plasticity and toughness of the system. This is because during the formation of the Ti-V system, both atoms lose electrons. Therefore, the electronic mobility of the system increases, the bonding strength of the metallic bond is enhanced, and the plasticity and toughness of the system are improved. In addition, the 3d-orbitals of Ti and V atoms are mainly involved in bonding, which is the key reason for the improvement of plasticity and toughness. Meanwhile, there are also some electrons with directivity gathered around the two atoms, which indicates that there is also a covalent bond within the system. The existence of covalent bond is the key to enhancing the mechanical stability of the system.

The surface composition and microstructure evolution of a second-generation Ni-based single crystal superalloy were investigated during vacuum solution heat treatment. The effects of adding argon partial pressure and not adding argon partial pressure on the surface layer of casting were studied. Results show that during the high-temperature vacuum heat treatment of the test bars, when argon partial pressure is applied during solution heat treatment, a Cr-depleted layer forms on the surface, exhibiting three-layer structure: transition layer (adjacent to the substrate) composed of γ' phase and topologically close-packed (TCP) phase; sub-surface layer composed of γ' phase, TCP phase, and β phase; surface layer composed of γ' phase and β phases. In this case, Al and Ni are deposited on the surface. Conversely, when heat treatment is conducted without argon partial pressure, a Cr-depleted layer still forms, but with a two-layer structure: transition layer composed of γ' phase and TCP phase and surface layer composed of γ' phase, TCP phase, and β phase. During vacuum heat treatment, reactions such as volatilization, deposition, oxidation, and diffusion of surface elements occur simultaneously. Depending on the temperature, vacuum level, and argon partial pressure, condensation layer, depletion layer, and interdiffusion layer may be formed on the surface. This study analyzed these phenomena in detail based on the thermodynamics and kinetics of relevant reactions.

N36 zirconium alloy specimens were prepared by the severe plastic deformation process of equal channel dual angle pressing (ECDAP), followed by annealing and aging treatment. The initial microstructure was observed by OM. The types and morphological characteristics of the precipitated phases were analyzed by SEM and TEM. The bonding mechanism at the interface between the α-Zr matrix and the (Zr, Nb)₂Fe precipitated phase after aging treatment was analyzed by combining the difference of valence electron density and the tensile strength. The influence of the precipitation behavior of the (Zr,Nb)₂Fe on the microstructure and properties of N36 zirconium alloy prepared by the ECDAP process was investigated. The results indicate that the ECDAP process can significantly refine the grain and promote the uniform distribution of the precipitated phase in N36 zirconium alloy, which mainly consists of Zr(Nb,Fe)₂ and (Zr,Nb)₂Fe with a large number of internal striated dislocations. The difference of valence electron density at the interface between the α-Zr matrix and the (Zr,Nb)₂Fe precipitated phase is 91.02%, and the lattice mismatch leads to increased resistance and instability of interfacial dislocation motion, which can generate susceptibility to relative motion and laminar dislocation initiation. Interfacial dislocations can induce matrix dislocation shifts to meet deformation demands. The increment in tensile strength after aging for 4 and 8 h reaches 2.14% and 10.36%, respectively, which is due to the increase in the reinforcement of the precipitated phase resulting from the strong electronic discontinuity between the precipitated phase and the matrix.

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.

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.

Ti-47.5Al-6.8Nb-0.2W-xY (x=0,0.1,0.2, at%) alloys were prepared by high-energy ball milling and spark plasma sintering processes, and the effects of Y microalloying on the high-temperature compression creep properties of Ti-47.5Al-6.8 Nb-0.2W alloys were investigated by SEM, EBSD and TEM. Creep experiments were carried out at 800-850 ℃, with a stress of 250 MPa and a time of 50 h. The results show that the Ti-47.5Al-6.8Nb-0.2W-xY alloys are all composed of equiaxial γ grains, the bulk α₂ and B2 phases at γ grain boundaries, and α₂/γ lamellar colonies. The added Y mainly exists in the form of Al₂Y particles at the grain boundaries to form a chain structure and Y can refine the grains and increase the α₂/γ lamellar colonies. When the Y content is increased from 0 to 0.2at%, the grain size is reduced from 12.1 μm to 7.8 μm, exhibiting the most significant refining effect. After creep, γ grains in the alloy are slightly flattened, accompanied by lamellar bending and degradation phenomena, and a large number of fine recrystallized grains and spherical B2 phase appear within the lamellar clusters. Creep temperature increase can promote the formation of dynamic recrystallisation. The addition of Y significantly improves the compressive creep properties of the alloy. At 800 ℃, the maximum creep strain of the 0.2Y alloy is 8.96%, and the steady creep rate is 4.01×10^-7 s^-1, reduced by 32.83% and 38.31% compared with those of the alloy without Y, respectively. The improvement in the mechanical properties of the alloys is attributed to the precipitation strengthening of the second phase Al₂Y particles, lamellar refinement, and reduction of the B2 phase.