Effect Of Retrogression And Reaging On Microstructure And Properties Of Spray-forming 7055 Aluminium Alloy

This paper mainly through the mechanical test,conductivity test and room temperature tensile test, by means of optical microscope,scanning electron microscope,energy spectum analysis method of microstructure and composition to research the effect of solid solution treatment,retrogression and reaging on microstructure and properties of spray forming 7055 Aluminum alloy.This paper accumulated data for the optimization of heat treatment process design.The main results are follows:(1) An industrial large-scale 7055 Aluminum alloy ingots with a size of Φ500mm×1600mm was successfully prepared by automatic control of reciprocating spray forming technology.After hot-extruded,solid solution and retrogression and reaging treatment are researched.(2)The optimum single solution process of 7055 Aluminum alloy is:475℃/3h.Through the analysis of Orthogonal experiments, the optimum two-stage solution process is:450℃/2h +475℃/2h. The alloy has excellent comprehensive properties after the this treatment. The tensile strength, the yield strength, the extensibility are 708 MPa,651MPa,11.3%. After the two-stage solution process,the alloy has higher strength and extensibility.(3)After hot-extruded,solid solution and single aging,the highest hardness of spray forming 7055 Aluminium alloy is 219.93 HV.The conductivity of material is 27.3%IACS.So,the optimum single aging process of 7055 Aluminum alloy is 120℃/24 h.After peak aging,the second phase in grain become wee and disperse.The second phase on grain boundary become continuous.(4) After hot-extruded,solid solution and retrogression and reaging,the highest tensile strength,yield strength,hardness and conductivity of spray forming 7055 Aluminium alloy is 695 MPa,680MPa,224.08 HV and 29.66%IACS.After retrogression and reaging,the second phase in grain become wee and disperse.The second phase on grain boundary become discontinuous.After retrogression and reaging,the material has good toughness,the tensile fracture is ductile fracture. It infers alloy after retrogression and reaging treatment has a good corrosion resistance.