As-deposited parts of 2024 aluminum alloy are fabricated by cold metal transfer and pulse （CMT+P） hybrid wire arc additive manufacturing. The distributions of pore defects， grain morphology， and secondary phase precipitation of CMT+P wire arc additive manufacturing 2024 aluminum alloy， and the influence of different process parameters on pore defects， grain morphology and secondary phase precipitation， and corrosion resistance are investigated. The results show that the pores of the as-deposited parts of 2024 aluminum alloy are mainly distributed near the fusion line. In the same heat input， the larger wire feed speed and travel speed result in higher porosity. In a deposition layer， the upper part is the equiaxed grain without preferred orientation， and the lower part is the columnar grain with preferred orientation. In the same heat input， the texture is weakened and the percentage of equiaxed grains is increased due to the fine grain region in the higher wire feed speed and travel speed. The precipitated secondary phases are mainly Al₂CuMg， Al₂Cu， and rich-Fe， Mn phases. The secondary phases distribute continuously along the grain boundaries. In the early stage of corrosion， the main factor affecting the corrosion resistance of as-deposited parts is the precipitation amount of Al₂CuMg. The better local corrosion resistance is mainly caused by lower Al₂CuMg phase fraction in lower wire feed speed and travel speed.

The microstructure control and corrosion resistance of aluminum alloys fabricated by wire and arc additive manufacturing（WAAM） are important issues that must be studied in engineering applications. The 5356 deposited part is produced by a CMT （cold metal transfer） system. The microstructure and hardness are characterized by metallurgical microscope， X-ray diffractometer （XRD）， scanning electron microscope （SEM） and micro-hardness tester， and the corrosion resistance behavior is studied by using electrochemical workstation， slow strain rate stress corrosion testing machine. The results show that the microstructure of 5356 WAAM aluminum alloy is composed of α-Al matrix and β（Al₃Mg₂） phase. The grains in the deposition layer are columnar crystals with an aspect ratio of ≤2， and the β（Al₃Mg₂） phase exists mainly as finely dispersed particles， while the grains in the interface layer are recrystallized equiaxed grains with smaller size， and the β（Al₃Mg₂） phase is predominantly distributed in large discontinuous blocks along the grain boundaries， with fewer fine granular β（Al₃Mg₂） phase within the grains， leading to a reduction in the matrix strengthening effect. The self-corrosion current density of the deposited layer is 23% of that of the interface layer， which may be caused by the content and morphology of β（Al₃Mg₂） phase. The stress corrosion sensitivity index at a slow strain rate of 5356 WAAM aluminum alloy is 0.57， and samples experience fracture and failure at the interface layer in both silicone oil and 3.5%NaCl solution medium. This is attributed to the lower strength at the interface layer matrix and shearing effect played by large intergranular β（Al₃Mg₂） phase in silicone oil inert medium， while the β（Al₃Mg₂） phase dissolves preferentially in the 3.5%NaCl aqueous solution， and intergranular corrosion propagation is accelerated under tensile stress.

Based on the response surface design， the optimal process parameters for single-side friction stir welding（FSW） of 2195 Al-Li alloy sheets are studied. It is found that the higher the rotation speed and the lower the welding speed， the higher the tensile strength of the welded joint. The results show that in the single-side FSW， when the pin length is 2/3 length of the thickness of the plate， the root of the weld appears unwelded defects， the fracture form of the welded joint is between brittle and plastic fracture， and the tensile strength of the joint is poor. Based on the optimum process parameters of single-sided welding， double-sided FSW can overcome the unwelded defects at the root of single-sided welding. Under different tool pressures， when the stirring head speed is 1600 r/min， the feed speed is 150 mm/min， and the pressure is 0.1 mm， the double-sided welding can improve the tensile strength of the welded joint by about 10% and the elongation of the welded joint by 10%. In two-sided FSW， the material flow on the forward side is obvious， and the fracture mode of the welded joint is a plastic fracture. In double-sided welding， the plate is subjected to secondary stirring and heating， resulting in increased softening of the material in the welding area.The microhardness of the double-sided welded joint is further reduced than that of the single-sided welding.

Developing aluminum alloys with high strength， high conductivity， and thermal conductivity is the key to applying aluminum alloy materials in electrical， electronic， and heat dissipation industries. Aiming at these requirements， the effect of adding trace Eu to Al-Mg-Si-Fe alloy on the microstructure and properties of vacuum die-casting products are systematically studied. The results show that the alloy modification effect of adding 0.05%-0.25% （mass fraction/%， the same below）Eu first increases and then decreases. When adding 0.15%Eu， the grain is significantly refined， and the precipitation of the brittle （FeSiAl） eutectic phase and long plate-like eutectic Si in the alloy is restrained. The solid solubility of Mg in the aluminum matrix is reduced， and the lattice distortion of the alloy is reduced. Therefore the mechanical properties， electrical conductivity， and thermal conductivity of the alloy have been improved simultaneously. The Al-Mg-Si-Fe-0.15Eu alloy has a thermal conductivity of 68.50 mm²/s， electrical conductivity of 51.4% ICAS， tensile strength of 148 MPa， and elongation of 16.20%. Compared with the original Al-Mg-Si-Fe cast alloy， the thermal conductivity increases by 12.50%， the electrical conductivity increases by 1.4% ICAS， the tensile strength increases by 20 MPa， and the elongation increases by 5.40%. The tensile fracture morphology of the alloy changes from quasi-cleavage fracture to ductile fracture.

The xTiB₂/Al-5Cu-0.85Mn-0.35Mg-0.5Ag（x=0%，1%，3%，5%，mass fraction， the same below） composites are fabricated by a mixed salt reaction method， followed by single-stage and interrupted aging treatments. The effects of differing thermal processing regimes on the microstructural and mechanical properties of the materials are systematically studied. The results indicate that as the TiB₂ content increases， both the hardness and strength of the composites show a continuous upward trend， while the elongation gradually decreases. When the TiB₂ content is 3%， after single-stage aging treatment （175 ℃/3 h）， the composite’s yield strength， tensile strength， elastic modulus， and elongation reach 465.1， 496.8 MPa， 78.9 GPa， and 4.8%， respectively. After undergoing an interrupted aging process at 175 ℃ for 1.5 h followed by 150 ℃ for 13.5 h， the yield strength， tensile strength， and elastic modulus of the composites increase to 479.3， 507.2 MPa， and 79.1 GPa， respectively， representing increases of 5.9%， 2.1%， and 0.25% compared to the single-stage aging treatment， with an elongation of 4.1%. The secondary aging temperature significantly affects the precipitation sequence of aging precipitates， which is the main reason for the substantial improvement in material properties. When the secondary aging temperature is 100 ℃， the θ'-Al₂Cu phase is the primary aging strengthening phase. At a secondary aging temperature of 150 ℃， the Ω-Al₂Cu phase becomes the main aging strengthening phase.

To meet the application requirement of advanced aviation engines for complex shell castings of high-strength and heat-resistant aluminum alloys， the process and mechanical properties of a new type of the Al-Si-Cu-Mg-Sc high-strength and heat-resistant aluminum alloy are analysed in comparison with ZL101A and ZL205A cast aluminum alloys. Design and experimental verification of the metal casting process for the complex casing of the oil pump are carried out by using the high-strength and heat-resistant aluminum alloy， and the quality of the casting products is evaluated. The results indicate that the new high-strength and heat-resistant Al-Si-Cu-Mg-Sc alloy shows better casting fluidity and hot cracking resistance than the ZL205A high-strength cast Al alloy. The qualification rate of the complex shell of its metal casting oil pump is comparable to that of the same type of shell ZL101A. The average tensile strengths at room temperature of the separated test bar of casting and test specimen from casting itself of the new alloy are higher than 420 MPa， which are significantly higher than that of ZL101A alloy， while the tensile strengths at 250 ℃ are superior to ZL205A alloy. The surface quality， internal quality， airtightness， and pressure resistant performance of the casting case all meet the design requirement of the product.

Under certain solid solution time conditions， the solid solution temperature determines the degree of supersaturation and recrystallisation of the matrix after quenching， and is an important factor in enhancing the performance of the material after aging treatment. Through the solid solution heat treatment of 2050 Al-Li alloy extruded bar at different temperatures for 2 h and artificial aging treatment at 170 ℃ for 40 h， combined with a variety of property testing methods and microstructure observation methods， the effect of solid solution temperature on the microstructure and properties of 2050 Al-Li alloy extruded bar was studied. The results show that the residual phase is continuously redissolved with the increase of the solid solution temperature， and the residual phase is mainly iron-containing phase when the solid solution temperature is 525 ℃.The slight overheating structure appears in the bar when the solid solution temperature is 550 ℃， and the serious overheating structure appears in the bar when the solid solution temperature reaches 570 ℃. Local recrystallization occurs when the bar is heated to 500 ℃， and complete recrystallization occurs when the solid solution temperature reaches 570 ℃. When the 2050 Al-Li alloy extruded bars are solution treated at different temperature （450-550 ℃） and aged at 170 ℃ for 40 h， the number of θ′ and T₁ phases increases with the increase of solid solution temperature， and the strength increases rapidly and then slowly，when the solution treatment temperature is 550 °C， the yield strength and tensile strength of extruded rods are the highest， which are 505 MPa and 567 MPa， respectively； the elongation decreases rapidly at first and then remains stable with the increase of solid solution temperature， decreasing from 13.4% at 450 ℃ to 10.7%-10.4% at 500-550 ℃.

The effects of the solid solution on the microstructure and mechanical properties of 6451 Al alloy sheets were investigated by using conductivity and tensile tests， combined with OM and SEM observations. The results show that when the solid solution temperature is 560 ℃， recrystallization occurs in the sheet at 3 s of solution treatment. When the solution time is extended to 5 s， the Mg₂Si particles are slowly dissolved. When the time is extended to 7 s， the equiaxial grains are formed after the complete recrystallization， a large amount of Mg₂Si particles are dissolved， and the strength of the sheet is rapidly increased. With the further extension of the solution time， the growth rate of the strength of the T4P-stated sheet slows down obviously， and the increment of the yield strength after baking is basically unchanged. After the solution time of 30 s， there is no obvious change in the grain size. When the solution time is increased to 60 s， the Mg₂Si particle is completely dissolved， and the yield and tensile strengths of the T4P-stated sheet are improved to 125 MPa and 247 MPa， respectively， with a better elongation of 30%. The functional relationship model between the yield strength and solid solution variation of the T4P-stated sheet based on classical diffusion theory is established according to the research results.

Utilizing Ca and TiH₂ as the thickening agent and blowing agent， respectively， Al-0.16Sc， Al-0.21Sc， and Al-0.16Sc-0.17Zr cellular foams with porosity of （72±0.5）% were successfully fabricated by the melt-foaming method. The microstructure and compressive strength of the foams with isochronal aging treatment were investigated. The results show that during isochronal aging between 200 ℃ and 600 ℃， Al-0.16Sc and Al-0.21Sc foams achieve their peak yield strengths （about 21.4 MPa and 26.8 MPa， respectively） at 325 ℃ due to the precipitation strengthening of Al₃Sc/Al₃（Sc_{1- x} Ti _x ）. Unlike the Al-Sc foam， the yield strength of the Al-0.16Sc-0.17Zr alloy foam reaches 23.7 MPa at 325 ℃ and 24.7 MPa at 400 ℃， representing an increase of 100.8% and 109% than those of the cast alloy， respectively. Zr addition not only significantly enhances the strength of the Al-Sc foams， but also effectively affects the coarsening of the Al₃Sc/Al₃（Sc_{1- x} Ti _x ） precipitate.

The 6061-T6 ultra-thin aluminum alloy with a thickness of 0.5 mm was welded using micro-joint friction stir welding technology. The effects of three kinds of stirring heads with different shaft shoulder morphology on the forming quality， microstructure， mechanical properties， welding thermal cycle， and force process of the 6061-T6 thin-wall butt joint were studied. The flow behavior characteristics of the plastic metal in the three welding cross-sections were analyzed in sequence. The results show that the forming effect of the weld surface is significantly affected by welding heat input. The hardness distribution trend of the joint cross-section formed by three kinds of stirring heads with different shaft shoulder morphology is a “W” shape. The highest hardness values in the center of the nucleation zone and the lowest hardness values in the thermo-mechanical affected zone of the needle-free three-involute diversion groove shaft shoulder welded joint are the highest among the three shaft shoulder welded joints. The mechanical properties of the joint formed by the three-involute guide groove with the needle shaft shoulder are outstanding， and the tensile strength， yield strength， and elongation after fracture are higher than those of the other two. The three tensile fracture forms are mainly ductile fractures. The process parameters of the thermal cycle and force can accurately reflect the changing trend of the welding state. The energy required to maintain the weld metal softening is from the heat generated by friction between the shaft shoulder and the workpiece and the work done by the axial and forward forces of the shaft shoulder. The axial force and forward force changed with the softening degree of the welded metal， playing a dynamic regulating role in the migration of plastic metal in the weld. The shoulder surface has a strong effect on the upper part of the weld， driving the plastic metal migration between the forward side and the backward side. The needle of the stirring head promotes the interaction between the plastic metal and the backing plate， providing a driving force for the flow of the upper and lower parts of the weld metal. The optimal heat generation potential is the combined result of the stirring needle and the involute groove， which work together to form a well-formed weld.

Taking TiC_p/Al-5Cu-1.9Mg-0.9Mn composite materials reinforced with 0.27%（volume fraction）TiC particles as the matrix， the effects of different Sm element contents on the microstructure and mechanical properties of the composite material were investigated. The results show that the addition of the Sm element significantly refines the dendritic microstructure and facilitates the dissolution of the second phase during the solid solution treatment. Consequently， an increase in the density of precipitated phases， including T-Al₂₀Cu₂Mn₃ and S'-Al₂CuMg， was observed in the aged microstructure. When the Sm element content is high （0.3%， mass fraction， the same below）， the microstructure exhibits blocky insoluble rare earth-containing compounds. With the addition of the Sm， the composite materials show a gradual increase in yield strength at both room temperature and 250 ℃. However， it will cause a decrease in plasticity. When the Sm element content is 0.3%， the yield strength at room temperature increases from 246 MPa to 310 MPa， and the yield strength at 250 ℃ increases from 191 MPa to 220 MPa. The analysis suggests that the increase in strength is attributed to the microstructural refinement and the increased density of precipitated phases induced by Sm. Conversely， the reduction in plasticity is attributed to the presence of coarse blocky insoluble rare earth compounds cutting through the matrix， leading to the easy generation of crack sources.

To explore the effect of micro-Zr alloying on the hot deformation microstructure of 6082 aluminum alloy and its subsequent recrystallization during heat treatment， the hot deformation behavior and micro-orientation evolution of 6082 aluminum alloy containing Zr at different strain rates （0.01，1 s^-1） were comparatively studied. The evolution process of grain structure before and after heat treatment was analyzed， and the regulatory effect of Zr addition on the thermally deformed sub-grains and recrystallization of 6082 aluminum alloy was further discussed. The results show that the addition of Zr makes the recrystallization of 6082 aluminum alloy during the hot deformation process mainly perform discontinuous dynamic recrystallization， and the recrystallization generated by the particle stimulated nucleation（PSN）mechanism also occurs， and minor Zr addition also plays a role in inhibiting recrystallization in the hot deformation process. After the micro-Zr alloying， the subgrain size decreases， the dislocation density increases， the recrystallization level decreases， and the recrystallization level of the sample at a higher strain rate is lower， and the addition of Zr promotes the generation of the discontinuous dynamic recrystallization of 6082 aluminum alloy during hot deformation.

Pure Mg has advantages of low density， good shock absorption performance and good biocompatibility， but its strength is low. Alloying is an important method to modify microstructure and properties of pure Mg. Sn has characteristics of low melting point， high eutectic temperature with Mg， high solid solubility in Mg， stable chemical properties and large output， which is appropriate to be an alloying element. The effects of alloying element Sn on microstructures and properties of Mg alloys were reviewed in this paper. Sn enriches at the front of the solid-liquid interface， dissolves in Mg matrix， reduces the ratio of critical resolved shear stress value of the pyramidal plane to that of the basal plane， and elevates the electric potential of Mg matrix. Mg₂Sn precipitates can hinder dislocation and grain boundary movement， and form galvanic corrosion cells with Mg matrix. Therefore， effects of Sn addition include grain refinement， age hardening and strengthening， improving plasticity， accelerating or reducing corrosion rate， enhancing discharge efficiency and discharge potential. At present， the main problems restricting the development of Mg-Sn alloys are slow aging， low hardness and strength. In the future， endeavors should be made to develop rapidly age-hardenable Mg-Sn alloys with high strengths， wrought Sn-containing Mg alloys with good ductility， and Sn-containing structural-functional Mg alloys.

6061 aluminum alloys with different aging states were prepared by rotational friction extrusion （RFE）. The effect of RFE on the microstructure and mechanical properties of 6061 aluminum alloys with different aging states was investigated. The results show that the refractory AlFeMnSi phase of 6061 aluminum alloys can be broken by using RFE， resulting in the fine and uniform distribution of the AlFeMnSi phase in the alloy. Under the combined effects of frictional heat and deformation during RFE processing， the pre-precipitated coarse Mg₂Si phase is dissolved and re-precipitated， resulting in that the pre-precipitated coarse Mg₂Si phase has no effect on the particle stimulated nucleation （PSN） mechanism in the dynamic recrystallization of the material. Therefore， the size of grain exhibits negligible change by RFE. RFE reduces the strength of as-quenched 6061 aluminum alloys， while the strength of 6061 aluminum alloys with a long-term aging state can be increased by RFE. However， there are holes inside the material processed by RFE， which reduce the elongation of the alloys.

The hot deformation behavior and dynamic recrystallization of Al-11.1Zn-2.3Mg-2.0Cu-0.05Sc alloy was explored in the isothermal hot compression test with a temperature range of 653-733 K at strain rate of 10^-3 s^-1. The microstructural evolution of the studied alloy at different temperatures was analyzed by EBSD technology. The dynamic recrystallization（DRX） critical strain， critical stress， fraction， and average grain size equations were established by linear regression. The results show that the fitted equations can accurately describe the DRX characteristics of the studied alloy during hot deformation.The increase in the deformation temperature enlarges the misorientation angle inside the grains， which facilitates the DRX progress. The distributions of crystal orientation tend to be more homogeneous with the increase in temperatures. Moreover， dynamic recovery is the dominant dynamic softening mechanism. With the temperature change， there are three types of recrystallization mechanisms in the microstructure of aluminum alloy， including discontinuous dynamic recrystallization， continuous dynamic recrystallization， and geometric dynamic recrystallization.

High-strength aluminum alloy have become one of the most commonly used metal materials for aerospace and automotive application parts due to its high strength， low density， excellent ductility and corrosion resistance. Wire arc additive manufacturing （WAAM） has the ability to rapidly in-situ form and manufacture complex structural parts， and is very suitable for the manufacturing of medium or large high-strength aluminium alloy parts. The current status of high-strength aluminum alloy WAAM processes and equipment， the inherent properties and defects of high-strength aluminum alloy WAAM， and the main performance optimization methods were comprehensively analyzed in this paper. The inherent characteristics of the microstructure and properties as well as the impact of hybrid additive manufacturing technologies on the microstructure and properties were discussed. Opinions are put forward on issues such as metallurgical defects， characteristic performance requirements， the advantages and disadvantages of various optimization processes in WAAM. Development directions such as a comprehensive evaluation system， composition design and wire development， special heat treatment systems and synergy of composite additive manufacturing technology are proposed. Such proposals are expected to provide references for the performance improvement and application promotion of high-strength aluminum alloys manufactured via WAAM.

Due to the low boiling points of the main constituents of 7075 aluminum alloy and the high surface tension gradient of the molten alloy， combined with the uneven energy distribution of the circular Gaussian （CG） laser beam spot commonly used in directed energy deposition （DED） processes， the forming quality of 7075 aluminum alloy DED specimens is generally poor. This significantly restricts the further application of DED in 7075 aluminum alloy. By regulating the laser mode， it is possible to effectively modify the temperature and flow fields of the melt pool， as well as the corresponding solidification conditions. Thus， the forming quality of laser additive manufacturing specimens and the active control of microstructure are improved. An off-axis parabolic integrating mirror is employed to homogenize the CG laser mode into a circular flat-top （CF） laser mode， which is further tilted to achieve a transversely elliptical flat-top （TE） laser mode. Using these three different laser modes， single-track cladding， single-wall structures， and 7075 aluminum alloy in DED block specimens are prepared. Combined with numerical simulations， the influence laws and underlying mechanisms of the laser modes on the forming quality and solidification structure are revealed. The simulation results indicate that by modulating the laser beam spot from the conventional CG laser mode to the CF and TE laser modes， the uniformity of the heat flux on the surface of the cladding layer is significantly improved， subsequently reducing the temperature gradient of the melt， and increasing the solidification rate. Compared to the CG laser mode， the surface forming quality of single-wall structures and block specimens under the CF and TE laser modes is significantly enhanced. The width variation of the single-wall structures is greatly reduced， and the dimensional accuracy in the horizontal direction of the block specimens is improved. Additionally， the density of the block specimens increases from 95.8% to 97.2% and 97.7%， respectively. In terms of solidification structure， the texture is significantly weakened， the grain size is reduced by approximately 50%， and the number of nano-precipitated η-phase within the grains is also increased.

Wire-arc additive manufacturing is a new type of manufacture using wire as filling material and arc as a heat source， making it easier to manufacture complex-shaped and big-sized parts. The reciprocating and unidirectional process path experiment was conducted. The inclined wall made by unidirectional path has better morphology， less splash， and a smoother surface. The simulation model of AM11 reciprocating and unidirectional manufacturing path was established in finite element software and solved. The simulation results show that the unidirectional path deposition temperature is 267.4 ℃， the deposition thermal stress is 357.4 MPa， the reciprocating path deposition temperature is 307.0 ℃， and the deposition thermal stress is 420.4 MPa， the heat accumulation and thermal stress of unidirectional path are lower than that of reciprocating path. AM11， AM12， and AM21 inclined wall samples with different slope factors by wire-arc additive manufacturing in unidirectional path were prepared， and their microstructure and properties were analyzed. The results indicate that the grain size of AM11， AM12， and AM21 is 35， 39 μm， and 42 μm， there is more precipitated β-Mg₁₇Al₁₂ in AM21 thin-walled grains， which has larger and more dimples than that of the other two samples. The micro-hardness values of AM21 and AM11 are both about 81.5HV， higher than 73.1HV of AM12. The horizontal and vertical tensile strengths of the AM21 inclined wall sample are 255.7，224.4MPa， the yield strengths are 103.8，96.0 MPa， and the elongations reach 13.1% and 8.2%. The tensile strengths and elongations are both greater than those of AM11 and AM12 samples， but the yield strengths are close. The AM21 inclined wall has much better strength and plasticity， and verify that the more perpendicular the inclined wall of magnesium alloy arc additive manufacturing is， the better the mechanical properties such as strength and plasticity.

In view of the problems of high preparation cost and low preparation efficiency of traditional powder metallurgy process, 15%(volume fraction, the same below)SiC/2009Al composite was prepared by cold isostatic pressing combined with pressureless sintering and hot extrusion process. The effect of different sintering temperatures (600, 620, 640 ℃) on microstructure and mechanical properties of 15%SiC/2009Al composite was studied. The results show that sintering at 600 ℃, the bonding between SiC and the matrix is poor, more large-size pores can be observed under the microscopic level, the density of the material is low, and the mechanical properties are poor. Sintering at a high temperature of 640 ℃, the billet produces a large amount of liquid phase, and overflows onto the surface of the billet, which causes the core alloying elements to decrease.In addition, sintering at 640 ℃ will trigger a strong interface reaction, generate more large-size brittle phase, become the source of cracks in the material fracture process, resulting in a decrease in material properties; 620 ℃ is the best sintering temperature, and more liquid phase can fill part of the pores in the billet, thereby improving the density and interfacial bonding strength of the material, and the strength and plasticity of the composite material have obtained the best values, the tensile strength and yield strength reach 505 MPa and 345 MPa, respectively, and the elongation reaches 7.2%.

In order to study the effect of aging strengthening on the wear mechanism and frictional deformation behavior of rare earth magnesium alloys, GW83 (Mg-8Gd-3Y-0.5Zr, mass fraction/%) rare earth magnesium alloy was prepared by extrusion process. The electronic universal testing machine was used to evaluate the alloy's mechanical properties.The optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM) were used to examine the alloy's microstructure.The ball-on-disc dry sliding friction testing machine was used to examine the wear resistance. The results show that after aging treatment (T5), a large amount of β′ precipitated phases are precipitated in the alloy. The hardness and tensile strength of the alloy are 124.1HV and 420.31 MPa, respectively, which are significantly higher than those in the extruded state (O state). As the load increases, the friction coefficient of the alloy decreases and the wear rate increases. Aging treatment can significantly improve the wear resistance of GW83 alloy, which is related to changes in wear mechanism and degree of friction deformation. Under a load of 5-10 N, the main wear mechanisms of both samples are abrasion, oxidation, and adhesive wear. When the load increases to 20 N, the main wear mechanism of the O state sample changes to delamination wear, while the transition load of the T5 sample is 80 N. T5 heat treatment significantly reduces the degree of surface metal deformation and deformation layer thickness caused by friction, thereby reducing the generation of friction cracks.

SiC_p/2024Al composite was prepared by semi-solid stirring casting, and the distribution of SiC_p was regulated by multi-step deformation of hot extrusion and multi-direction forging (MDF). The effects of SiC_p distribution on the microstructure and properties of SiC_p/2024Al composite ware studied. The results show that hot extrusion deformation cause SiC_p to distribute along the extrusion direction (ED). After multi-directional forging, SiC_p distribution is improved significantly, and it changes from directional distribution to uniform distribution. After 1MDF, the SiC_p distribution along the ED changes to disordered distribution, and the mechanical properties of the material are sharply decreased. After 3MDF, the distribution uniformity of SiC_p is improved, and the mechanical properties of the material are greatly improved. When the forging passes increase to 6, the distribution uniformity of SiC_p is further improved, the mechanical properties of the material decrease with the partial SiC_p breaking. When the forging number is 3, the mechanical properties of the composite are optimal, with yield strength, ultimate tensile strength and elongation are 264 MPa, 387 MPa and 7%, respectively. Compared with the directionally distributed composite, the uniform distribution of SiC_p effectively relieves the local stress concentration, and the matrix alloy stores more dislocation. In addition, when the distribution uniformity of SiC_p is improved, the Al₂Cu phase is also refined. The diffuse distribution of Al₂Cu phase hinders the slip of dislocation, resulting in a uniformly distributed composite with a higher work hardening rate and internal stress. In order to study the effect of SiC_p distribution on softening behavior of composites, cyclic stress relaxation experiments are carried out. In the process of stress cycling, the uniformly distributed SiC_p/2024Al composites with uniform distribution of SiC_p and Al₂Cu phases exhibit a better stress relaxation resistance.

To analyze quantitatively various indexes of wire arc additive manufacturing components of 2319 aluminum alloy, the expressions of curved surface between different process parameters, porosity and tensile strength values were fitted, and the "process-structure-property" corresponding rule was established. In addition, a normalized fuzzy evaluation model was developed for process parameters, organizational defects, and mechanical properties using the generalized fuzzy synthesis operation rule. The purpose of this model was to obtain the optimal process parameters. The results show that the porosity generally increases with the wire feeding speed rising.Then the porosity generally decreases with a decrease in scanning speed. When the scanning speed is 0.035 m/s, the correlation between porosity and tensile strength is the lowest, with a correlation coefficient (coefficient of determination, COD) of only 0.6. The comprehensive evaluation score of the expert is the highest when the wire feeding speed is 5.0 m/min and the scanning speed is 0.025 m/s, indicating that this combination of process parameters is optimal.

MIG welding and ER5356 welding wire were used for butt welding of 7075 aluminum alloy with a thickness of 3 mm. The joint was subjected to T6 heat treatment after welding. The microstructure, mechanical properties and corrosion resistance of the joints were analyzed by optical microscope, X-ray diffraction, scanning electron microscope and energy spectrometer combined with room temperature stretching, microhardness and electrochemical corrosion. The results show that the molten pool flow brings Zn, Cu and other alloying elements in the molten part of the base metal into the weld, and precipitates MgZn₂ and AlCuMg phases during the welding process, which become the basis for the heat treatment and strengthening of the weld. After heat treatment, most of the precipitated phase melts into the matrix to form solid solution+aging strengthening, the joint tensile strength increases by 20%, and the weld hardness increases by 18.4%, the corrosion resistance improves. However, due to the limited alloying element content flowing into the weld from the base metal, the difference in mechanical properties between the welding wire and the base metal and the heat-affected zone softening phenomenon cannot be eliminated.

In order to reduce the energy consumption of the reaction, the magnesium alloy samples were immersed directly into three conversion solutions and reacted for 9 hours at 60 ℃ and pH=12.0 used the chelating agent-assisted method by adding three chelating agents, ethylenediaminetetraacetic acid tetrasodium (EDTA-4Na), sodium citrate (SC) and potassium sodium tartrate (PST) to aluminum nitrate (Al(NO₃)₃) solution, and Mg-Al layered double hydroxides (LDHs) films doped with different chelating agents can be prepared on the surface of magnesium alloys. The microstructure, phase composition, and corrosion resistance of each LDHs film were analyzed by SEM, XRD, FT-IR, etc. The results show that the chelating agent-assisted method can successfully prepare LDHs films with typical layered structure on the surface of magnesium alloys under normal pressure and 60 ℃ environment; and three kinds of Mg-Al LDHs films obtained can effectively improve the corrosion resistance of magnesium alloys. Then, by comparing the structural properties of three different LDHs film layers, it is found that the Mg-Al-PST LDHs film prepared by adding PST has the highest density and the largest thickness, reaching up to 1.4 μm. The improvement effect of three coatings on the corrosion resistance of magnesium alloys is as follows: Mg-Al-PST LDHs > Mg-Al-SC LDHs > Mg-Al-EDTA LDHs; The magnesium alloy covered with the Mg-Al-PST LDHs film compared to the blank magnesium alloy, the corrosion current density decreases by about two orders of magnitude, and the total corrosion resistance increases by about one order of magnitude. And based on the analysis of the structure and properties of the obtained LDHs films, it can be seen that the chelating agent-assisted method can prepare Mg-Al LDHs films with better corrosion resistance in-situ on the surface of magnesium alloys under the lower energy consumption condition. The reason may be that the carboxyl group in the chelating agent can accelerate the deposition of Al³⁺ on the magnesium substrate and promote the substitution of some Mg²⁺ in Mg (OH)₂ by Al³⁺ to form LDHs.

Wire arc additive manufacturing (WAAM) has received extensive attention from researchers due to its high deposition rate, high material utilization, low cost, and ability to manufacture large-scale components. It is expected to be widely used in rapid forming of magnesium alloys. The current types and requirements of wires used in WAAM of magnesium alloy were summarized. Then, the current preparation methods suitable for WAAM of magnesium alloy were introduced. The manufacturing technology, deposition mechanism, microstructure and mechanical property of various WAAM-processed magnesium alloys were discussed. Finally, the problems such as the few types of available wires and the uncontrollable shape and property of components for wire arc additive manufacturing of magnesium alloys were analyzed. The optimization of properties and application of components for wire arc additive manufacturing of magnesium alloys were forecasted.

Laser repair technology has the advantages of short time, high efficiency, low cost and good mechanical properties, and has great development potential. Al-7.5Mg-0.3Sc-0.28Zr was used as the repair material to conduct laser repair experiments on 5083-H112 aluminum alloy used in rail transit, and a dense and defect-free repair sample was obtained. The microstructure and properties of the sample were studied, and the feasibility of laser repair of aluminum alloy was discussed. The results show that the transition zone near the fusion line can be divided into repair zone, partial melting zone, heat affected zone and base metal. The grains in the repaired area are completely equiaxed, consisting of a fine-grained band with an average grain size of 4.95 μm and a coarse-grained region of 18.34 μm respectively. In the transition area from the repair zone to the partial melting zone and then to the heat affected zone, the content of Al element gradually increases, the content of Mg element gradually decreases, and the hardness decreases gradually. The heat-affected zone and the base metal are not softened after the repair. Due to the rapid solidification of laser additive manufacturing technology, the fine-grain band near the fusion line has larger stress concentration, and the residual stress in the heat affected zone and partial melting zone is small due to the small heat input. The yield strength of the repaired sample of (152±2) MPa is 89.4% of the base metal, the tensile strength of (305±5) MPa is 100% of the base metal, and the elongation rate of (15.5±0.5)% is 85.2% of the base metal. Fracture occurs in the weaker base metal. Laser repair of aluminum alloys is feasible and has broad application prospects.

In order to obtain high quality AZ31B/stainless steel resistance spot welded joints, the FeCoNiCrMn high entropy alloy was used as the interlayer. The reaction-diffusion behavior of the transition zone and the base material on both sides was analyzed, and the joint performance and the welding process were investigated. The results show that the transition zone consists of FeCoNiCrMn particles which successfully connects two base materials of AZ31B and stainless steel. The interface near AZ31B is mainly Fe₄Al₁₃ intermetallic compounds generated by the reaction around the particles; while the boundary of stainless steel is mainly composed of (Fe, Ni) solid solution and Fe₄Al₁₃ intermetallic compounds. The tensile shear load F shows a tendency that increases first and then decreases with the increase of welding current I, welding force P, and the prolongation of welding time t. The tensile shear load of the added high entropy alloy magnesium/steel spot welded joints are above 3.2 kN in the test process range of 18.2-22.5 kA, 15-35 cycle, and 2.0-10.6 kN, and the maximum tensile shear load is 5.605 kN, which is 397% higher than that of Mg/steel spot welded joints without high entropy alloy. A large number of (Fe, Ni) solid solution are formed in the high entropy alloy transition layer, which reduces the generation of Fe₄Al₁₃ brittle intermetallic compounds and effectively improves the mechanical properties of the joint.

The effects of different process parameters on the segregation behavior and properties of bottom twin-roll casting 2624 aluminum alloy were studied in detail by simulating the flow field in the cast-rolling zone and using SEM, EPMA, DSC, electrical conductivity and tensile properties at room temperature. The mechanism of segregation in the cast-rolling process was analyzed.The results show that the large size banded segregation appears at the edge of bottom twin-roll casting 2624 aluminum alloy, solute elements exhibit macroscopic inverse segregation.The decrease of pouring temperature and casting speed can enhance the peak velocity of vortex and reduce the degree of macrosegregation。The increase of cooling rate can weaken the degree of microsegregation and reduce the conductivity.In addition, the yield strength, tensile strength and elongation of the cast-rolled sheet increase with the decrease of pouring temperature and casting speed, and the mechanical properties of the alloy are improved.

The 6061 aluminum alloy was prepared by powder metallurgy method, and the effects of ball milling time and solution-aging treatment on microstructure and mechanical properties of the extruded alloy were studied by means of optical microscopy, scanning electron microscopy, transmission electron microscopy, hardness test and tensile test, etc. The results show that with the prolongation of the ball milling time, the powder morphology gradually changes from spherical to flat sheet, and the powder particle size gradually increases. The sintered alloy has better density and comprehensive mechanical properties when milling for 2 h, but longer milling time will lead to the decrease of density and mechanical properties of the material. The better solution-aging process of sintered alloy after hot extrusion is 530 ℃×1 h+180 ℃×8 h, at which time the alloy precipitates a diffuse distribution and a fine β″ phase, and the alloy has high strength (442 MPa) and hardness (125HV), as well as suitable elongation. Its excellent mechanical properties are mainly the result of the combination of dispersion strengthening, fine grain strengthening and solid solution strengthening.

SiC_p/AZ91D magnesium matrix composites are widely used in the aerospace field, but there is less report on the distribution of SiC_p particles in SiC_p/AZ91D magnesium matrix composites by ultrasonic testing methods at home and abroad. In this paper, SiC_p particle reinforced magnesium matrix composites with volume fractions of 0%, 2%, 4% and 6% were prepared by squeeze casting. In order to study the particle distribution in composite materials, ultrasonic velocity method, ultrasonic attenuation method, ultrasonic characteristic scanning imaging method and nonlinear ultrasonic testing method were used to study the dispersion of SiC_p particles. The relationship between various acoustic parameters and SiC_p volume fraction, and the difference of detection ability of different detection methods for SiC_p particle distribution were explored and verified by experiments. The results show that ultrasonic characteristic scanning detection and ultrasonic velocity method can quantitatively detect SiC_p macro agglomeration, ultrasonic attenuation method can have a good effect on characterizing both micro agglomeration and macro agglomeration, and nonlinear ultrasonic detection method is more sensitive to detecting SiC_p micro agglomeration. When the particles are uneven, the mechanical properties are most affected, and the tensile strength is greatly reduced.

The lightweight and high strength toughness of materials are of great significance for achieving energy-saving, environmental protection, and sustainable development strategies. Particle reinforced aluminum matrix composites, due to their combined performance advantages of reinforcing phase and matrix alloy, can achieve high modulus, high strength, and high heat resistance, and have become one of the focuses of high performance light alloy research and development.AlN reinforced aluminum matrix composites have high degree of microstructure design and can effectively improve the strength and toughness of the Al matrix, which has attracted extensive attention from scholars at home and abroad. The mechanical property progress of AlN reinforced aluminum matrix composites was focused in this paper. Firstly, the effects of preparation methods, interface structure regulation, hybrid strengthening and configuration design on the strength and toughness of AlN reinforced aluminum matrix composites were introduced. Influence of configuration design on the strength and toughening effect of AlN reinforced aluminum matrix composites was illustrated at room temperature and high temperature strengthening, respectively. Then, mechanism of the heterogeneous induced strengthening at room temperature and load transfer strengthening at high temperatures were emphasized. Finally, the new preparation technology, precise microstructure design and strengthening mechanism of heterogeneous configuration of AlN reinforced aluminum matrix composites were prospected.

The 6061-T651 aluminum alloy was strengthened by torsional deformation with the torsion angles of 90°, 180° and 360°. The quasi-static and dynamic compressive properties of the samples before and after torsional deformation were investigated. The results show that the grain size of the samples remains unchanged at first with the increase of the torsion angle, and then begins to decrease. However, the Kernel average misorientation(KAM) value continues to increase with the increase of the torsion angle. The quasi-static and dynamic compression experiments show a slight increase in the yield strength of the samples with the increase of the torsion angle. For the same torsion angle, the dynamic yield strength is significantly higher than the yield strength at quasi-static loading. The strain rate experiment shows that the yield strength of the sample increases with the increase of strain rate, but compared with the untorsional sample, the strain rate sensitivity of the 360° torsional sample is significantly reduced. Based on the experimental data, the parameters in the Cowper-Symonds constitutive model were fitted. The stress-strain curves obtained from this model are in good agreement with the experimental results.

The microstructure and performance homogeneity of 80 mm thick ultra-wide 7B50-T7751 plate with different widths and thicknesses were studied by means of mechanical testing machine and scanning electron microscope，and the fatigue properties were compared and discussed with 7050-T7451 plate. The results show that the ultra-wide 7B50-T7751 plate has excellent mechanical properties. In L and LT directions， the tensile yield strength of 1/2 thickness reaches up to 568 MPa and 545 MPa，and the tensile strength reaches up to 612 MPa and 591 MPa，the compressive yield strength reaches up to 575 MPa and 587 MPa，the fracture toughness in L-T direction and T-L direction reaches 30.16 MPa·m^1/2 and 26.47 MPa·m^1/2，respectively. The ultra-wide thick plate exhibits certain anisotropy at different width positions，the performance homogeneity in LT direction tends to be better than in L direction. Performance at different width positions with 1/4 thickness shows little difference，while the performance at the edge of 1/2 thickness is better than that of the center. No obvious texture exhibits at 1/4 thickness，however，the main textures at the center of 1/2 thickness are S texture and Brass texture， and the main textures at the edge are R texture，S texture and Brass texture. When the stress ratio is 0.06，the T-L anti-fatigue crack growth rate performance of ultra-wide 7B50-T7751 thick plate is better than 7050-T7451 plate with the same thickness. The fatigue limit of LT smooth sample （K _t=1） is about 7.6% inferior than that of 7050-T7451 plate， while the fatigue limit of notch sample （K _t=3） is about 3.7% higher.

The time-temperature-transformation （TTT） diagrams of 7A36 aluminum alloy extruded plate were determined by an interrupted-quench method. The quenching precipitation behavior was investigated by calculate phase diagram（CALPHAD） combined with optical microscopy（OM），scanning electron microscopy（SEM），transmission electron microscopy（TEM），scanning transmission electron microscopy（STEM） and high-resolution transmission electron microscopy（HRTEM）. The results show that the critical quenching rate for inhibiting the phase transition of 7A36 aluminum alloy by 0.5% is about 15.7 ℃/s. Based on 10%TTT diagram， the nose temperature is determined to be about 338 ℃ with the transformation time of about 22 s. The precipitation of η（MgZn₂），T（Al₂Zn₃Mg₃），S（Al₂CuMg） or Cu-Zn rich Y phases can be found depending on different isothermal holding temperatures and time， and the precipitation behavior is described in the TTT curve， which is described as a time-temperature-precipitation diagram.η equilibrium phase tends to occur at grain boundary（GB） first and then at sub-grain boundary（SGB） and on dispersoids in the interior of grains， at higher isothermal holding temperature， the size of η phase is larger. The electrical conductivity increases first and then decreases with the increase of holding temperature； isothermal holding at 420 ℃，the increase of electrical conductivity is caused by precipitation of η phase and T phase， while at 330 ℃ and 240 ℃，the increase of electrical conductivity is due to the precipitation of η phase， T phase， S phase and Y phase.

Magnesium alloy as the most potential light structural material， has the advantages of high specific strength， specific stiffness and easy recycling， which contributes to the realization of lightweight in the industrial field. Compared with the traditional manufacturing technologies， the new and advanced manufacturing technology of additive manufacturing represent for high manufacturing efficiency， excellent performance， and forming complex structures. The technology of additive manufacturing for magnesium alloy， which has broad application prospects in the industrial field， is urgently required to be studied. In this paper， the recent studies of the three major additive manufacturing technologies for magnesium alloy：selective laser melting， wire+arc additive manufacturing， and friction stir additive manufacturing were summarized and analyzed from the aspects of forming characteristic， defect control， and features of microstructure and property.Finally，the developments in shape and performance control of the additive manufacturing technology for magnesium alloy：simulation analysis， process control， and heat source regulation were discussed.

7075-(0%, 0.5%, 1%, 2%, mass fraction)Li alloy was prepared by hot pressing sintering, and the effects of Li on microstructure and friction and wear behavior of 7075 Al alloy were investigated. The results show that the density of 7075-0.5Li alloy reaches above 99% at sintering pressure of 60 kN. Al alloy consists of α-Al, η and S' phases. With the increase of Li content to 2%, the η phase decreases, δ' and δ phases increase, but α-Al is still the main phase. The hardness and wear rate of Al alloy are 71.25HV and 3.50×10^-3 mm³·N^-1·m^-1, respectively. As the Li content increases, the hardness of Al-Li alloy decreases and the wear rate increases. However, 7075-0.5Li exhibits higher hardness and lower wear rate than those of Al alloy. Both oxidation wear and adhesion wear occurs in 7075-Li alloy. With the increase of Li content, the η phase is reduced, the hardness decreases, the brittleness of Al₂O₃ is high which has a weak bonding with the matrix, and the dendrite spacing of microstructure widens, resulting in the transition from the abrasive wear to adhesive wear of the alloy, and therefore the wear resistance gradually decreases. Compared with Al alloy, 7075-0.5Li alloy prepared by hot pressing sintering shows a better wear resistance.

With the increasing application of Al-Li alloy in the aerospace field, the study of its anisotropy is conducive to the further development and utilization of Al-Li alloy. Scanning electron microscope, transmission electron microscope, X-ray diffractometer and electron back-scattered diffraction were used to observe the microstructure of 2050 Al-Li alloy with T3 status. The three-dimensional anisotropy of tensile mechanical properties of alloy plates was studied by tensile test. The results show that the strength of the rolling middle layer of 2050 Al-Li alloy plate with T3 status is the highest, the yield strength is 370 MPa, The tensile strength is 465 MPa, the elongation is the lowest at 9.6%. The transverse surface strength of alloy plate is the lowest, the yield strength is 325 MPa, the tensile strength is 431 MPa, and the elongation is the highest at 19.2%. The fracture morphology and grain size in different thickness of alloy plate are different. The grains in the surface region are thin and compact with small size, while the grains in the middle region are wide and flat with large size. The anisotropy of different thickness of 2050 Al-Li alloy plate is different: the anisotropy of yield strength and tensile strength in surface and middle region is strong, and the anisotropy of elongation is low, while the anisotropy of yield strength and tensile strength in central region is low, the anisotropy of elongation is strong. The anisotropy of different thickness of 2050 Al-Li alloy rolled plate is mainly formed by the grain orientation and texture. The strongest texture type of surface area and central area is {011}〈211〉 brass texture.

7A85-T74 forged aluminum alloy was chosen as the experimental material, and the microstructure, tensile properties and impact energy of the alloy were investigated after 5 h of thermal exposure at room temperature to 240℃. The mechanism of the influence of the microstructure on the mechanical properties of 7A85-T74 aluminum alloy was also analyzed by transmission electron microscopy. The results show that the grain size of 7A85-T74 aluminum alloy does not change much in the temperature range of 80-240℃, but the precipitation phase changes significantly with the increase of temperature. Below 120℃, the precipitate size, tensile properties and impact absorption energy do not change significantly with increasing thermal exposure temperature, and the precipitation strengthening mechanism is a mixture of dislocation cutting precipitates and dislocation bypassing precipitates. With the increase of the thermal exposure temperature from 120℃ to 240℃, the precipitate average radius increases from 3.8 nm at room temperature to 12.3 nm, and the precipitate changes from η' phase to η phase. The yield strength and tensile strength of the alloy decrease significantly by 45.7% and 33.5% respectively compared with that of room temperature and the elongation, reduction of area and impact energy of the alloy increase significantly. The precipitation strengthening mechanism changes to dislocation bypassing precipitates, and the fracture mode changes from mixed fracture consisting of intergranular fracture and dimple transgranular fracture to dimple transgranular fracture. The effect of precipitate size on the strength and impact energy of the alloy discusses based on the precipitation strengthening theory, and the results of the theoretical analysis are consistent with the experimental results.

USRP (ultrasonic surface rolling processing) was used to change the surface layer of 6061 aluminum alloy, so as to realize the change of the second phase microstructure of 6061 aluminum alloy by USRP under different static pressure conditions to improve corrosion resistant, which was characterized by using scanning electron microscopy, laser confocal microscopy, scanning Kelvin probe force microscopy, etc. Based on the principle of microzone galvanic corrosion and considering the impedance of solution and oxide, the correlation law between the size of the second phase and the development of local corrosion was obtained. The effect of the size of the second phase on the development of local corrosion was verified by in-situ observation using laser confocal microscope. The results show that the initial self-corrosion current density of aluminum alloy in 3.5%(mass fraction) NaCl solution is only 1/15 of that of the untreated sample, the corrosion rate is reduced by 93.04%, when the surface layer is rolled with 0.10 MPa static pressure. The Mg₂Si phase has no significant morphology change during the rolling process, and it has no significant effect on the corrosion performance before and after USRP. The AlFeSi phases with long strip continuous distribution are refined into micro- and nano-scale dispersion distributions under the action of USRP. The fully refined AlFeSi phase weakens the galvanic corrosion effect due to the reduction of the local anode/cathode area ratio of the corrosion microcell, which promotes the metastable pitting nucleation rate of the aluminum alloy matrix, but also cause the rapid dissolution of the aluminum alloy itself. When self-dissolution occurs or Al₂O₃ oxide film is formed in the inner wall of metastable corrosion hole, the electrochemical corrosion effect of AlFeSi relative to aluminum alloy matrix is greatly weakened, so as to improve the corrosion resistance of 6061 aluminum alloy as a whole.

In order to improve the reaction efficiency and rate of Al powder with seawater, highly active Al base powder (Al-Mg-Sn-Bi alloy powder, AMSB) was prepared by adding low melting metal (Sn and Bi) by atomizing. The hydrogen generation rate and open circuit potential of AMSB alloy powder were measured by hydrogen generation test and electrochemical test, and the hydrolysis mechanism was characterized. The hydrogen generation test results show that the hydrogen generation rate of AMSB alloy powder in 3.5%(mass fraction) NaCl solution can reach 214.80 mL·min^-1·g^-1, and the hydrogen generation efficiency can reach 80.45%. The results of electrochemical experiments show that the addition of Sn and Bi can reduce the open circuit potential of AMSB alloy powder and promote the negative shift of the electrode potential of Al powder. The phase composition and microstructure of AMSB alloy powder before and after the reaction were characterized by XRD, XPS and SEM-EDS. Low melting point elements Sn and Bi can destroy the densification of oxide film, effectively improve the reaction efficiency of Al with water and promote the reaction process of Al and water. Moreover, the galvanic cell effect formed between Al, Sn and Bi elements is an important reason for the improvement of the hydrolysis performance of AMSB alloy powder. Therefore, the highly active Al based powder prepared has a certain application value in the field of high energy water reaction metal fuel.