The isothermal compression bonding deformation of 705/706 aluminum alloy laminated materials was carried out on Gleeble-3500 hot-simulation machine at 573~773 K and 0.01~10 s^-1.The hot bonding behavior and hot workability of the materials were analyzed,and the constitutive equation and processing map were established.The results show that in the process of compression deformation of the 705/706 aluminum alloy laminated materials,the flow stress is decreased with the increase of deformation temperature and increased with the increase of strain rate,exhibiting steady rheological characteristics when the flow stress reaches the peak value,so it is characterized by positive strain rate sensitivity. The deformation activation energy of the laminated materials is about 147.2 kJ/mol,which is lower than that of single Al-7.0Zn-2.9Mg alloy.The processing maps with different true strains show that safe deformation zone of 705 and 706 aluminum alloys bonding deformation is mainly attained at high cladding temperatures,moderate strains and low strain rates.The bonding strains range of 0.2~0.4,temperatures range of 723~748 K and the strain rates range of 0.1~0.01 s^-1 are appropriate for bonding deformation of the 705/706 aluminum alloy laminated materials.

The preparation technology and application of copper/aluminum composite were introduced.It was summarized for mechanism of interface combination,formation process of interfacial layer,the formation and growth rule of intermetallic compounds in interface layer and its effects on the physical and mechanical properties of composites.Finally,the research direction and development trend was proposed.

Biodegradable magnesium alloys have good promising applications as biomaterials. Firstly, the main problems of biodegradable magnesium alloys as biomaterials were reviewed. Then, two methods including alloying and surface modification in improving the degradation resistance and biological activity of magnesium alloys were described. Besides, the recent progress in the magnesium alloys as biodegradable cardiovascular stent and bone repair materials were also introduced. Finally, the future development of biodegradable magnesium alloys was pointed out.

The interface bonding mechanism of bimetallic clad pipes was reviewed,and main preparation processes of bimetallic clad pipes at home and abroad were described systematically.According to the difference in the physical state of the substrate and cladding metal at the initial stage,the existing preparation processes are divided into four categories:solid-solid bonding method,solid-liquid bonding method, liquid-liquid bonding method and other bonding method.The forming principles and main characteristics of various preparation processes were analyzed comparatively.Finally,the prospects for the major issues that would be faced in the industrialization of bimetallic clad pipes were forecasted combined with the development status and future industrial application requirements.

Based on formation mechanism of shrinkage cavity in die castings, combined with the actual production, it is found that the origination of shrinkage cavity in LD68 castings is attributed to the higher local mold temperature and the wrapping combustion products of oil and fuel.By improving mold preservation project to ensure reasonable mold temperature gradient and reducing the amount of punch oil and changing the way of supply to avoid its combustion package, the shrinkage rate in LD68 hole is decreased by about 90%.

Rare earth element is widely used in a variety of metal materials due to the effective and stable modification.The modification can refine alloy structure,thus improving mechanical properties,and the modification effect of different rare earth elements on aluminum alloy is different.The influence of several rare earth elements on the microstructure and mechanical properties of aluminum alloys as well as the modification mechanism was mainly introduced.Meanwhile,the present research status of rare earth aluminum alloys at home and abroad was reviewed.The existing problems were discussed and the future research was prospected.

The characteristics and formation mechanism of surface defects such as cold shut,surface segregation layer,surface segregation burl and pull marks in semi-continuous casting aluminum alloy ingot were introduced.The effects of mold structure and casting process parameters on the surface defects during semi-continuous casting were analyzed.On this basis,the technical development and process optimization directions to improve ingot surface quality were presented.

Ceramic sand was used widely in resin sand casting as the features of spherical grain shape,higher refractoriness,inert chemical property,high strength and higher reuse rate.Subsequently,shell investment casting with ceramic sand was used gradually.Now,ceramic sand shell casting was used widely to produce cast iron and cast steel and so on,which can partially replace investment casting.The dimensional precision of the castings can reach CT7~CT6 with surface roughness of 12.5μm,greatly improving the product yield and casting quality as well as greatly decreasing casting cost and exhaustion of scrap.

Copper alloy is considered as the widely used materials in the mintage.Following the rapid development of the economical society and the color of mintage were becoming higher and higher.Study and development of copper alloys were becoming more and more widely,including circulation coin,commemorative coin,signet and so on.CIELAB uniform color space was used to describe the color of alloy. The common copper alloys coin at home and abroad were summarized.The formation mechanism and influencing factors of the surface color of the mintage alloy were analyzed,and the design principles and research summaries of copper alloys with different color coinage were analyzed.The future development direction of the copper alloy was expounded.

The thickness of the solidified shell at different casting speeds was measured by the nail-shooting method. The solidification heat transfer model of the round billet was established and the growth curve of the solid shell was calculated.Based on the results of the nail-shooting experiment and the mathematical model,the optimized installation position of the final electromagnetic stirring(F-EMS)should be located at 10.23 m from the mold level.In consideration of plant conditions for the continuous casting of SWRH82B high carbon steel,the FEMS installation position was moved from 11.1 m to 9.75 m from the meniscus.The results show that after the process parameters optimization,the equiaxed crystal ratio in SWRH82B round billet is increased from 40%~46% before optimization to 50%~64%,and the central carbon segregation index is decreased from 1.08~1.10 before optimization to 1.04~1.06.The quality of continuous casting round billets has been improved significantly. Through tracking the quality of the rolled sheet,it is found that the network carbide in the SWRH82B wire rod is reduced,which indicates that the quality of the rolled sheet is improved greatly.

The micro-structure and mechanical characteristics of the multi-layer nickel-plated copper foil welding by blue light laser with 450 nm were investigated. Nickel-plated copper foil with 20 layers were welded onto nickel-plated copper sheet with 0.5 mm, and the effects of different welding speeds on the weld morphology and tensile strength were investigated. The morphology on the weld failure mode and the micro morphology of the fracture were analyzed, and the electrical conductivity of the weld were tested. The results indicate that during the blue laser welding process, the depth of penetration is easily controlled.With the increase of welding speed, the weld penetration depth is gradually decreased, and the tensile strength of the weld is increased at first and then decreased.When the welding speed is 30 mm/s, the tensile strength of the weld reaches the maximum of 75 MPa. Blue laser can be successfully applied to the welding of multi-layer nickel-plated copper foil and laser welding leads to good mechanical properties.

It was reviewed comparatively for the advantages and disadvantages of traditional electrical discharge machining (EDM), electron-chemical machining (ECM) and long pulsed laser processing on the hole wall quality, accuracy and efficiency of film cooling hole processing.Femtosecond laser provided a solution for high-quality film cooling hole processing.For femtosecond laser drilling, its "cold processing" characteristics and mechanism were described, and the basic theory of damage threshold and experimental calculation method were analyzed.At the same time, numerical calculation models and methods of femtosecond laser ablation mechanism were summarized. It is pointed out that the molecular dynamics method (MD) combined with the two-temperature model (TTM) is the quite promising for numerical simulation.

6013 aluminium alloy sheets obtained by semi-continuous casting and extrusion were investigated,focusing on the effects of extrusion temperature and speed on the structure and properties,by optical microscopy, scanning electron microscopy,tensile and hardness testing.The results reveal that both extrusion temperature and extrusion speed have significant effects on the microstructure and mechanical properties of the 6013 aluminum alloy.Recrystallized structure is trend to be generated at higher extrusion temperature or speed.At a lower extrusion speed,the tensile strength of the alloy reaches its maximum at 500℃.The elongation and hardness of the alloy are decreased with the increase in temperature at various extrusion speed.Moreover,fractographic analysis reveals that the alloy with large and deep dimples accompanied with tearing edges observed in the fractography presents the higher plasticity.

The diamond/Cu composites were fabricated by spark plasma sintering (SPS).The effects of diamond particles on the relative density, thermal conductivity, tensile strength and elongation of the composites were analyzed.The results show that with the increase of diamond content, the relative density, thermal conductivity, tensile strength and elongation of the diamond/copper composites are increased firstly and then decreased.With the diamond content of 1.0%, the tensile strength of the composite can reach the maximum value of 221.35MPa.The maximum density can be obtained with the diamond content of 1.5%, and the thermal conductivity and elongation reach the maximum value when the diamond content is 2.0%.The fractures of diamond/copper matrix composites are characterized by ductile fracture and interfacial debonding.

The high quality integral forming of large-scale structural parts is a difficult problem in the field of parts manufacturing.Squeeze casting becomes a new choice for high-quality integral forming and manufacturing of large structural parts,which can successfully solve the problems of low feeding efficiency and shrinkage defects in traditional gravity casting by integral rheological feeding,and dramatically breaks through the limitation of equipment capacity in traditional forging technology by virtue of the good rheological filling capacity of molten metals.It has been proved that by using special coating and casting die instead of forging module and adjusting the die temperature effectively,they are efficient paths to reduce the cost proportion of die.Moreover,a series of new technologies,such as the local multi-point pressing,compound pressing and flowing semi-solid squeeze casting,are introduced to significantly reduce equipment investment and ensure high-quality forming.

7075 aluminum alloy was prepared by permanent mold casting(PMC),liquid squeeze casting(LSC)and semi-solid squeeze casting(SSC)methods.The effects of different casting processes on the thermal conductivity and mechanical properties of 7075 aluminum alloy were investigated.The results indicate that the grains of the PMC are coarse,and dendrite segregation occurs to reduce the plastic toughness.The tensile strength and elongation are 121 MPa and 2.78%,respectively.However,the coarse grains exhibit a wide heat conduction path,lower electron scattering probability,long mean free path and relatively high thermal conductivity,which reaches139.67 W/(m·K).The tensile strength and elongation of the LSC refined grains are 239 MPa and 5.75%,respectively,while fine grains and more dendritic arms lead to the higher electronscattering,with the lowest thermal conductivity,which is 120.94 W/(m·K).SSC grains are compact fine and round,with the highest tensile strength and elongation of 248 MPa and 7.46%,respectively,and the thermal conductivity is 126.07 W/(m·K).

The action mechanism of oxide layer crack and volatilization of molybdenum oxides in the oxidative kinetics of high entropy alloy Mo₂₅Nb₂₅Ta₂₅W₂₅ was described.An equal mole ratio Mo₂₅Nb₂₅Ta₂₅W₂₅ alloy with a simple BCC structure was prepared by hot-pressing sintering.The oxidation behavior of the high entorpy alloy were analyzed at 800℃、900℃ and 1 000℃, respectively, and the oxidation mechanism was expounded.The oxides were characterized by XRD, SEM and electron probe X-ray microanalyzer (EPMA).The results reveal that at oxidation temperature range, the main oxidation products are Ta₁₆W₁₈O₉₄ and Nb₁₄W₃O₄₇ with some protection in the oxide layer.The kinetics of the tested samples follows the parabolic law at 800℃, while follows the linear law at the middle of 900℃ and 1 000℃, which are attributed to the volatilization of MoO₃ leading to oxide layer loose and porous at higher temperature.

In recent years, with the complexity of the gas-cooled structure and the large-scale size of the single-crystal turbine blade, the production of single-crystal blade is more prone to crystal selection failure, orientation deviation, sliver, large angle grain boundary, stray grain in the platform, recrystallization, freckles and other defects, which lead to the reduction of high-temperature alloy performance of single crystal turbine blade, and eventually cause the scrapping of single-crystal blade. In order to reduce these defects in single crystal blade, improve the quality of single crystal, and obtain a complete structure of single crystal structure, it is very important to be familiar with various common defects in the production of single crystal blade, realize the formation rules of defects, and master the defect inhibition technology. On this basis, the common solidification defects in the production of single crystal blades, as well as the formation rules and inhibition methods of solidification defects were systematically introduced, which lays a solid theoretical foundation for reducing the defects of single crystal blades and improving the quality and qualification rate of blades, and provides a strong technical support.

7000 series high strength aluminum alloys have been widely used in aerospace field.However,due to its poor casting properties,the forming method is mainly adopted plastic deformation,such as rolling and extrusion.Forming products include mainly plates and profiles,while it is difficult to prepare parts with complex shapes.Liquid extrusion casting and semi-solid squeeze casting technology can provide a feasible approach for the casting and forming of 7000 series aluminum alloys and their composites.It is expected to achieve "casting instead of forging",becoming an important direction of the development of high strength aluminum alloy forming technology in recent years.The research progress in squeeze casting 7000 series aluminum alloys and their composites was described,and the current problems were presented.Then the development direction was pointed out.

The theoretical and experimental research of high entropy alloys with various phase structures were reviewed,and the contents and applications of various phase formation criteria proposed on the phase formation rules of high entropy alloys were summarized,which was expected to provide ideas for establishing the phase formation rules of high entropy alloys.

Three generation single crystal superalloys(SRR99,DD32 and DD90)were designed by the combination of directional solidification technology and seeding method.The primary dendrite spacings were calculated by the direct measurement method and the square calculation method.The effects of grain boundary and crystallographic orientation on the primary dendrite spacing were eliminated.The average primary dendrite spacings of three superalloys are increased gradually with the increase of solidification heights,and the ones counted by two methods are similar,confirming the accuracy of the two methods.Moreover,the primary dendrite spacings of the superalloys is varied in a large range and present a normal distribution.The upper limit of the primary dendrite spacing is 5.4~8.5 times higher than the lower limit.

The fatigue strength and fatigue life of typical cast magnesium alloys were reviewed,and the initiation and propagation mechanism of fatigue cracks in cast magnesium alloys were described.The effects of the matrix microstructure,grain size,the second phase,the casting defects and working environment on the fatigue properties of magnesium alloys were expounded,and the methods to improving the fatigue properties of magnesium alloys were pointed out.Finally,the future tendency on magnesium alloy fatigue was put forward.

In view of the investment casting process of turbine rear frame strut, the ProCAST software was adopted to simulate the filling process, cavity pressure evolution, and shrinkage cavity defects and the causes of the defects was analyzed. On this basis, the process was optimized by improving the exhaust passage, adjusting the pouring position, pouring time of the strut, and the solidification sequence of the casting, and the numerical simulation was carried out. The results indicate that the filling process of the optimized process is stable without "suffocation" phenomenon in the cavity and shrinkage and cavity defect in the strut. The actual casting verification demonstrates that the casting quality meets the ASTM E192 standard.

Based on the research status of microbial corrosion of aluminum alloys in recent years, corrosion behavior and mechanism and achievements in the field of microbial corrosion protection, the process of representative bacteria and molds in microorganisms was attached and propagated on a variety of aluminum alloys, and their life activities causing or aggravating the corrosion was reviewed. The corrosion rate of aluminum alloy is controlled by microorganisms shielding, secrete corrosion inhibitors and metabolite inhibition. The microbial corrosion mechanism of aluminum alloy was mainly summarized, including cathodic depolarization mechanism, oxygen concentration cell mechanism, micro cell effect, corrosion compound formation, chloride induction and acid corrosion, as well as the mechanism of microbial inhibition of aluminum alloy corrosion. In conclusion, microbial corrosion of aluminum alloys is synergy of multiple corrosion mechanisms. Finally, the current methods to prevent and control microbial corrosion of aluminum alloys were described, and the research emphasis in the future was prospected, providing theoretical guidance for the prevention and control of microbial corrosion of aluminum alloys.

The segregation of Fe and Si in aluminum alloy castings was analyzed by optical microscope, scanning electron microscope and other equipment, and the influence of Fe and Si segregation on castings together with corresponding solutions were briefly described.

Magnesium alloy is the lightest metal structure material for application at present,which has a good application prospect in the lightweight aspect of aerospace.The aerospace application parts are gradually developed towards precision,thin-walled and integrated aspects with the application techniques and requirements increase.Compared with traditional magnesium casting techologies,the process characteristics of investment casting technology have unique advantages for the production of precision and complex thin-walled parts.The application of investment casting in magnesium alloy can better meet the requirements of aerospace parts.The forming technology of magnesium alloy was introduced,and the investment casting for the Mg alloy was emphatically summarized.The existing issue of metal-mold interface reaction and research status were reviewed.

The effects of different annealing temperature and time on the microstructural evolution and mechanical properties of the oxygen free copper tube were investigated by OM, TEM, SEM and universal tensile tester.The results reveal that:the high energy and high density dislocation of the as-deformed sample are evolved into thin dislocation walls, subgrain boundaries and then high angle grain boundaries with annealing at 260℃ or 300℃ for 60min, resulting in low density dislocation structure. After annealing at 300℃, recovery and recrystallization are fully completed.The tensile strength, yield strength and hardness are decreased with temperature increase, while the elongation is increased.Within the annealing temperature range of 300℃ to 460℃, the change of mechanical properties of the copper tube can be ignored.Increasing the annealing time at 300℃ from 10min to 60min, recrystallization is induced gradually, and the tensile strength, yield strength and hardness are decreased, while elongation is increased.With annealing for 60min, recrystallization is finished, and the tensile fracture morphology is changed from quasi-cleavage surface, tearing edge and dimple characteristics to equiaxial dimples. Compared with those of as-deformed sample, the tensile strength, yield strength and hardness of the copper tube are decreased by 39%, 68.5% and 53.1%, respectively, and the elongation is increased from 1.2% to 50%.With annealing time more than 60min, the grain size is increased slightly before reached a stable value, showing an insignificant effect on the mechanical properties.

Based on the requirement of lightening for an electric vehicle structural part of the shock tower, influence of the aluminum design on weight-reduce was analyzed and a high vacuum die-casting process suitable for the aluminum alloy shock tower was developed.The results reveal that the rational mould design can decrease the weight of the shock tower by about 35% based on assemble, rigidity and die casting process.In addition, the reasonable design of the casting system and the control of the vacuum degree are the important factors affecting the stability of the air-gap and mechanical properties. Based on the analysis of bubble test and mechanical analysis, the design of ingate was optimized.The shock tower part can be achieved with tensile strength higher than 300MPa yield strength higher than 250MPa and the elongation higher than 8%, after T6heat treatment, meeting the requirement of OEM.

Hot compressive characteristics of 6061 aluminum alloy were investigated on Gleeble-3500 thermal simulation machine by performing isothermal compression tests at 300~450℃ and 0.0110s^-1 with the maximum reduction of 60%.The flow stress behavior of 6061 aluminum alloy at high-temperature was analyzed and the hot processing map was established based on the dynamic material model(DMM).Moreover,the hot deformation mechanism was described according to the associated microstructure observation.The results show that the flow stress is decreased by increasing in the deformation temperature and decreasing in the strain rate,and the main softening mechanism of 6061 aluminum alloy is characterized by dynamic recovery.The instability zones of flow behavior appear widely at higher strain rate on the processing map.The optimum process interval of 6061 aluminum alloy for hot working is the deformation temperature at 430~450℃ and strain rate of 0.010.05s^-1,in which some recrystallized grains canbe observed.

The research status and progress of bulk amorphous alloy casting forming,and the principle and advantages-disadvantages of the preparation technology of bulk amorphous alloys were reviewed briefly,focusing on the copper mold casting,vacuum casting method and phase-changed refrigeration casting method.Some problems needing to be solved in casting process of bulk amorphous alloys were put forward.

According to its structure,the die casting process of aluminum alloy heat sink was designed, and then simulated by Flow-3D software.The results reveal that gas-entrapped defects can be observed in its four edges of part bottom.Crack detection and sectioning observation on the test-piece of the trialproduction show that the simulated results are well consistent with practical observation,where many blowholes and pinholes can be observed in the edge parts.Process optimization was carried out to adjust the size of ingate.Its results show that the defects can be eliminated effectively.Based on the optimized process,the samples were produced.The results are well in agreement with the simulated ones,where blowholes and pinholes are eliminated greatly,meeting application requirements and reducing the defective rate.

Air evacuation in vacuum die casting process was analyzed.A new mathematical model was established to calculate cavity pressure,and leakage of die was also taken into acount in the model in order to fit with practical conditions.The model was verified by fitting with actual cavity pressure data recorded by the vacuum system in practical die casting process.Furthermore,influences of evacuation efficiency and die leakage on cavity pressure were discussed.And the fitting equation parameters can be used to assess vacuum system and die sealing.

The damping mechanism,the materials system and reinforce microstructure of magnesium matrix damping composites were described.The preparation and post treatments of magnesium matrix damping composites were summarized.Based on the review and analysis of the research progress,the prospects of the developing directions of magnesium matrix damping composites were proposed.

3D printing titanium alloy is suitable for manufacturing complex shape components, which can reduce production process and improve material utilization. In recent years, the application of 3D printing additive manufacturing technology in the production of titanium alloy components achieves rapid development and significant advantages in order to obtain the more complex structure of titanium alloy components, and further reduce the cost and shorten the production cycle. The application advantages, characteristics of classification and process, status and development direction of 3D printing technology in titanium alloy casting production were systematically introduced.

The progress in WGB repair of superalloy vanes was reviewed,and advanced WGB repair methods at home and abroad were introduced,of which the characteristics was analyzed in depth.In conclusion,the existing problems of WGB technology were discussed and the future development was prospected.

The failure of metal materials usually originates from the material surface. Through strengthening the material surface, the service life of metal components can be proloned and efficiency can be improved. High-entropy alloys (HEAs) attracts extensive attention due to the excellent corrosion resistance, wear resistance, high temperature oxidation resistance and other characteristics. The property diversity allows HEAs to be used as metal surface coating materials.Based on the existing research, the influence of HEAs coating on the surface properties of metal materials was comprehensively reviewed, and the performance characteristics of HEAs as coating as well as the preparation methods of HEAs coating were summarized. The problems and development trend of technology in HEAs coating field were put forward.

The recovery, separation, sorting and recycling of aluminum scrap is of practical significance to solve resource shortage, energy shortage and reduce environmental pollution.The development status of aluminum scrap recycles and resource allocation in domestic and overseas was introduced.The application and investigation of waste aluminum separation and sorting technologies in recent years were reviewed, and the advantages and disadvantages of these technologies in practical applications based on cost, efficiency and environmental impact were briefly summarized. Finally, the challenges and related countermeasures in the field of waste aluminum recycle, separation and sorting were analyzed, aiming to provide reference for scientific research, engineering application and development in related fields.

Eutectic high entropy alloys(EHEA), as one of the most potential high entropy alloys (HEAs) for industrial application due to the excellent comprehensive mechanical properties and desirable castability, have become a hot spot in the research field of high-entropy alloys. The latest research progress in the EHEAs was summarized, and the phase constitutes, microstructure, mechanical properties and methods of designing EHEAs were described in detail. Finally, the challenges of EHEAs were pointed out and the development direction of eutectic high entropy alloys was prospected.

The surface of magnesium alloy is easily corroded to form loose porous magnesium oxide due to extremely active chemical behavior,which limit the wide application of magnesium alloy.Therefore, in order to meet the different market demands and expand the application areas of magnesium alloys,the different surface treatment technologies for magnesium alloys were put forward to improve the corrosion resistance of magnesium alloys and make the parts with good appearance.

The axial and moment loads of concrete-filled steel tubular columns were calculated by different analytical methods, and the load-displacement relation and stress distribution of concrete-filled steel tube with hexahedral, square and circular loading section were analyzed by means of ABAQUS finite element software.The results show that the bearing capacity of concrete-filled steel tube with circular section is the largest of 1 800kN.The stress concentration of concrete filled steel tube with hexagonal section is dispersed with a better comprehensive performance, which can reduce significantly the risk of material failure caused by stress concentration.The analytical results are in agreement with the finite element simulated ones, so that the axial eccentric load model can be provided for a reference for the design and verification of concrete-filled steel tubular structures.