The crystal internal stress and texture evolution of six-pass hot rolled ZK61 magnesium alloy plate are studied by means of combining macroscopic finite element simulation and microscopic crystal plasticity analysis. According to the rolling experiment and tensile test， the corresponding synchronous hot rolling model is established and simulated， and the simulation results are entered as boundary conditions in the polycrystalline plasticity model based on Voronoi diagram. Then the crystal plasticity finite element method is used to simulate the synchronous hot rolling of the polycrystalline model， and the plastic parameters and texture pole figures of the hot-rolled ZK61 magnesium alloy in each pass are obtained. Compared with the tensile test results and the texture pole figures derived from the electron backscatter diffraction experiment， the crystal plastic deformation and texture evolution mechanism of the hot-rolled ZK61 magnesium alloy under different passes are summarized. The results show that there are a large number of twins and dynamic recrystallization in the ZK61 plate after multi-pass hot rolling， the grain homogenization and refinement effect is obvious. The pole intensity of basal texture is correlated with the whole rolling passes， the peak misorientation angle of the alloy under different passes has a quite diversity （8°， 28°， and 88°）， and the mechanical properties of the alloy are improved. The alloy strength is increased by 7.55%， and the elongation is achieved by 19.5%. The results can provide reference for improving the plastic processing ability of magnesium alloy.

Defects are the main factors affecting fracture behavior of casting materials. The fracture behavior of high pressure casting aluminium alloy is predicted using Gurson-Tvergaard-Needleman （GTN） damage model combined with finite element simulation software. The results show that damage parameters suitable for high pressure casting aluminum alloy materials are obtained through finite element reverse fitting， with a nucleated void volume fraction f_{\mathrm{N}} = \mathrm{0.12}， critical void volume fraction f_{\mathrm{c}} = \mathrm{0.001}， and fracture void volume fraction f_{\mathrm{F}} = \mathrm{0.001}. At the same time， fracture behavior prediction based on microscopic features is carried out by simplifying the pore morphology as ellipsoids and ignoring pores with volumes less than 0.001 mm³， to avoid low efficiency and non convergence in finite simulation calculations. The applicability of the two models in predicting the fracture behavior of casting materials is compared， and it is concluded that the finite element simulation combined with damage mechanics has higher computational efficiency， but the finite element simulation based on microscopic characteristics has higher prediction accuracy.

A wire-based friction stir additive remanufacturing （W-FSAR） method is proposed to address large cracks and material loss in aluminum alloy components during production and service. The W-FSAR tools consist of a wire feeding device， a stationary sleeve， and a screw-structured stirring head. This method effectively fills and repairs 10 mm-width and 2 mm-depth groove defects in aluminum alloy components. The results indicate the repaired sample has high repair efficiency， smooth morphology， homogeneous microstructure， and excellent mechanical properties. The dynamic recovery and recrystallization processes refine the grain size to 1.59 μm. The ultimate tensile strength and elongation of the repaired samples are （410±8） MPa and （11.9±0.9）%， respectively， which increase by 26% and 159% compared to the worn-out specimens. There are numerous dimples on the fracture surface， exhibiting typical ductile fracture characteristics.

As lightweight and high-performance structural materials， nano-Al₂O₃ reinforced aluminum matrix composites can achieve lightweight energy saving and emission reduction， and have broad application prospects in aerospace， automotive industry， shipbuilding， national defense， and 5G electronic communication. In this paper， high energy ball milling powder metallurgy method， ultrasonic assisted casting method， friction stir method， additive manufacturing method， in-situ reaction method and other nano-Al₂O₃ reinforced aluminum matrix composite preparation technologies are introduced. The effects of nano-Al₂O₃ reinforcement， the interface microstructure between the reinforcement and aluminum matrix， the size and content of the reinforcement， the grain size of the aluminum matrix，the dispersion of the reinforcement， and the microstructure design on the mechanical properties of nano-Al₂O₃ reinforced aluminum matrix composites are analyzed and summarized. The main strengthening mechanisms of nano-Al₂O₃ reinforced aluminum matrix composites and the coupling forms of each strengthening stress are also summarized. Finally， the future development direction of nano-Al₂O₃ reinforced aluminum matrix composites in the aspects of large-size preparation technology with high reinforcement volume fraction， heterogeneous configuration optimization， and the integration of high-strength and heat-resistant structure and function are prospected.

During the wire-arc additive manufacturing process， Al5356 straight-wall components are fabricated by imparting lateral swings of varying frequencies and amplitudes to the welding gun. The impact of these swinging arcs on the forming quality， pore distribution， microstructure， and mechanical properties of the components is evaluated through surface waviness calculations， microstructural analysis， and mechanical tensile tests. The results show that incorporating the arc swing technique in the manufacturing process significantly enhances the forming accuracy， compactness， microstructural uniformity， and mechanical properties of the straight-wall samples. Within the experimental parameters， applying an arc swing reduces the surface waviness of Al5356 straight-wall samples by 60% compared to those produced without an arc swing. Additionally， the porosity and maximum pore diameter are decreased from over 0.65% and 33 µm to below 0.20% and 10 µm， respectively. The average tensile strength in both the X-direction （deposition direction） and Z-direction （build direction） increases by approximately 13% and 15%， respectively， while the average elongation improves by about 27% and 25%， respectively. Notably， the frequency of the arc swing has a more pronounced effect than the amplitude in enhancing surface quality， pore dispersion， and pore diameter reduction in the deposited components. High-frequency arc oscillation exerts a potent stirring effect on the melt pool， leading to a more uniform temperature distribution across the transverse direction of the deposited weld path. The observed enhancement in mechanical properties is primarily attributed to the reduction of pore defects and the homogenization of the microstructure. Therefore， the proper application of the arc swing technique in wire-arc additive manufacturing holds significant promise for improving the forming quality and mechanical properties of components.

The micro-sized second-phase and recrystallized structure has an important influence on the strength and toughness of 5083-O alloy. In order to acquire the morphological feature of the micro-sized second-phase particles and recrystallized particles in 5083-O alloy， multi-slices EDS data at a low acceleration voltage of 5 kV and EBSD data at 20 kV of the alloy are collected based on the double beam microscope system. These multi-slices data are restructured into three-dimensional types by Avizo software. The size， morphology， distribution， and volume fraction of the chief second-phases （Mg₂Si phase and Fe-rich phase） and recrystallized structure are obtained through the restructured data. The results show that the volume fractions of Mg₂Si phases， Fe-rich phases， and recrystallized particles in the studied alloy are 0.46%，0.25%， and 11.7%， respectively. Most Mg₂Si particles have smooth surfaces， with shapes of near-spherical， near-ellipsoid， or rod-shaped， and elongate along the rolling direction. The Fe-rich phases in the alloy are angular or subangular， and have relatively low spherical degrees. The three-dimensional EBSD restructure data show that the smaller size recrystallized particles have the higher spherical degrees， and the bigger size recrystallized particles have the lower spherical degrees. It is found that the recrystallized grains grow up from the small sphere recrystallized particles during the annealing process， and grow fastest along the rolling direction. The morphology of recrystallized particles is more truly reflected by three-dimensional EBSD results.

The 6061 aluminum alloy billets are subjected to solution quenching treatment under a solution heat treatment condition of 550 ℃ for 30 min. After quenching， the billets are artificially aged at 140 ℃ for 6 h to 18 h to obtain pre-hardening （PH） billets. The formability and mechanical properties of the pre-hardening 6061 aluminum alloy billets are evaluated using room-temperature Erichsen cupping tests and uniaxial tensile tests. Additionally， the stamping trials for hat-shaped beam components are conducted to verify the feasibility of this technique for engineering applications. The results show that the yield strength （YS） of the PH-12 h pre-hardening billets is 186 MPa higher than that of the O-temper billets， and the tensile strength （TS） is 215 MPa higher than that of the O-temper billets， while the elongation （EL） and cupping values are comparable to those of the O-temper billets. The PH-18 h pre-hardening billets exhibit a maximum tensile strength of 391 MPa after 10% deformation， significantly exceeding that of the T6-temper aluminum alloy， demonstrating that the pre-hardening billets possess excellent strength-ductility balance. Furthermore， the hat-shaped beam components formed from pre-hardening billets exhibit tensile and yield strengths superior to those of the T6-temper aluminum alloy.

Single point incremental forming （SPIF） is a highly flexible manufacturing process widely utilized in the aerospace industry， particularly suited for customized and small-batch production components. However， the appropriate range of process parameters suitable for different models remains undefined， necessitating extensive parameter testing. An orthogonal experiment is conducted to perform a multi-factor analysis of variance， discussing the influence of parameters such as sheet thickness， angle， incremental amount， feed rate， and rotational speed on the maximum forming depth. Based on the experimental results， a regression model using the Adaboost algorithm is developed to predict the forming depth of 6061 aluminum alloy thin sheets at the forming diameter of 100 mm. The results indicate that the influences of single factors on the maximum forming depth in descending order of significance are： thickness， layer increment， angle， feed rate， and rotational speed. Under the optimal forming conditions achieved at the fastest forming speed， the maximum forming angle is 70°， the sheet thickness is 1 mm， the layer increment is 0.2 mm， the feed rate is 2000 mm/min， and the rotational speed is 2000 r/min. Furthermore， the regression model created based on the orthogonal experiment demonstrates high accuracy， correlating well with both the Abaqus simulation results and the actual experimental outcomes. The maximum error between the four groups of tests and simulations is 4.24%， while the maximum error with the actual forming results is -2.45%.

This paper proposes a non-isothermal solid solution-forging integrated hot forming process for 7075 aluminum alloy. After solid solution treatment， the aluminum alloy is directly placed into the mold for forging， then quenched and subjected to artificial aging treatment. The influence of water entry temperature and aging parameters on the microstructure and properties of 7075 aluminum alloy is studied under this process， through the construction of a temperature-time-property（TTP） curve. Additionally， machine learning techniques are integrated to optimize and match the key process parameters. The results reveal that the nose temperature of the TTP curve is 315 ℃， and the mechanical properties of the alloy increase with the increase of water temperature after aging， a double-peak phenomenon after non-isothermal forging and aging is observed. When the inlet temperature is 380 ℃， the optimal aging parameters are 115 ℃-26 h and the peak hardness is 182HV. After training， the prediction accuracy of the BP neural network model is 94.9977%. Experimental verification of the optimal process parameters predicted by the model shows that its prediction similarity is 96.9%. Compared with traditional forging processes， this process can achieve high mechanical properties than traditional forged T6-state 7075 aluminum alloy while reducing procedural steps and energy consumption.

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.

The 316 stainless steel coatings with different thicknesses （SSC2， SSC4， SSC7， SSC10） were deposited on the magnesium alloy surface by using the HVOF method. The microstructures， deposition characteristics， residual stresses and immersion corrosion characteristics of the coating were investigated. The results reveal that due to the lower melting point and hardness of magnesium alloy， spray particles are prone to invade the substrate and melt its surface， causing particle escape or splashing， resulting in lower deposition efficiency； after depositing thinner coatings （SSC2 and SSC4）， the escape or splashing behavior of deposited particles reduces significantly， and the deposition efficiency increases； when the deposition thickness increases to SSC7 or above， the surface temperature of the deposition increases， particle splashing gradually increases， and the porosity and oxide content of the coating surface increase. Furthermore， as the coating thickness increases， the residual compressive stress of the coating decreases， the stress distribution becomes more uniform， and the number of penetrating pores in the coating decreases significantly， approaching zero. There are penetrating pores inside the SSC2 and SSC4 coatings， and the effective protection time is extremely short. The thick coatings （SSC7 and above） still have a protective effect after soaking in 3.5% （mass fraction） NaCl solution for 720 h.

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.

In order to study the corrosion resistance of three different superhydrophobic coatings (MZS-1, MZS-2 and ZnO@ZIF-8) on AZ91D magnesium alloy surface in 5% (mass fraction) NaCl solution. The microstructure, wettability and corrosion resistance of the superhydrophobic composite coating were tested and characterized by field emission scanning electron microscope, static contact angle tester, electrochemical workstation and salt spray tester, respectively. The results show that the corrosion of the superhydrophobic coatings does not occur until 192 h after salt spray treatment among the three types of superhydrophobic coatings, and the corrosion of the MZS-1 superhydrophobic coating is the most serious. The surface pitting of the MZS-2 superhydrophobic coating doesn't occur until 240 h later, and the contact angle is still high after salt spray treatment, so the corrosion resistance of the MZS-2 composite coating is the best.The polarization curve tests indicate that the corrosion current density of three superhydrophobic coatings are still one order of magnitude lower than that of the metal matrix after salt spray treatment for 240 h, showing excellent corrosion resistance. The superhydrophobic coating can effectively increase the corrosion resistance of metal materials.It can effectively prevent the infiltration of corrosive ions and provide long-term protection for the matrix because of its water repellency.

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.