| The high-strength,heat-treatable 7075 aluminum alloy is one of the most important structural materials in the aerospace field.In aluminum alloy manufacturing,additive manufacturing technology is valued for its advantages in rapid manufacturing of complex materials compared to other additive manufacturing technologies(Selective laser melting)Electron beam selective melting,etc.),cold spraying technology in the rapid manufacture of metal at lower temperatures,especially suitable for thermal oxidation and heat sensitive materials,such as aluminum alloy magnesium alloy,but relatively poor plastic 7075aluminum alloy powder in the process of cold spraying,due to insufficient plastic deformation brought by high porosity will seriously reduce the mechanical and corrosion resistance.The compactness and comprehensive properties of cold sprayed aluminum alloy can be improved by the composite hot working method after cold spraying.Therefore,this article low cold spraying technology by optimizing the preparation of the Al2O3particles reinforced 7075 aluminum alloy composite material,and take the annealing heat treatment and hot rolling processing of composite materials for subsequent processing,combined with metallographic and scanning electron microscope and microstructure of composite block material tensile properties and corrosion behavior of the test,research on the cold spraying7075 hot working process.The main work of exploring relevant theoretical papers is as follows:The irregular aluminum alloy reinforced 7075 aluminum alloy composite and spherical aluminum alloy reinforced 7075 aluminum alloy composite were prepared by low pressure cold spraying,respectively.The influence of the shape of aluminum oxide on the microstructure and corrosion resistance of cold spraying aluminum alloy composite was analyzed The results show that the structure compactness and corrosion resistance of aluminum alloy composite reinforced by irregular alumina are poor,which is attributed to the fact that irregular alumina particles are easily embedded into the sediment layer and collide with each other,which leads to the introduction of more holes and defects to reduce the material compactness and corrosion resistance.The spherical alumina is easy to rebound and has the effect of in situ tamping,which increases the plastic deformation of aluminum alloy powder and makes the structure of cold-sprayed aluminum alloy composite more compact,thus showing higher corrosion resistance.The effect of annealing temperature on microstructure mechanics and corrosion resistance of 7075 aluminum alloy composites reinforced by spherical alumina was analyzed at different temperatures.It is concluded that the degree of interfacial fusion of particles in the microstructure increases with the increase of heat treatment temperature from 300?to500?The interfacial defects are reduced,the grains grow up and the second phase is precipitated.The elongation of 500?annealed samples is 4.19%,which is twice of that of unannealed samples.The tensile strength did not change much with the increase of annealing temperature,but the compressive strength of 500?annealed samples decreased,which was attributed to annealing softening.The pitting corrosion occurred in the annealed samples at different temperatures,and the corrosion resistance of the annealed samples at 400?is the best.After 400?annealing,the spherical alumina reinforced 7075 aluminum alloy composite block was processed by hot rolling under different pressing amount.The influence of the pressing amount on the structure mechanics and corrosion resistance of the aluminum alloy block was analyzed.The results showed that the density of 7075 aluminum alloy block was significantly improved by hot rolling,porosity decreased obviously,tensile strength The elongation and corrosion resistance increased with the increase of pressure.The tensile strength of the sample with 30%pressure was 349MPa and the elongation reached 6.18%.Therefore,the 7075 aluminum alloy composite prepared by low pressure cold spraying method with spherical alumina as reinforcement phase combined with subsequent heat treatment and hot rolling process can obtain dense structure and better strength,toughness and corrosion resistance. |
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