Effect Of Solution And Aging Process On Microstructure And Performance Of Spray Forming Aluminum Alloy 7055 Free Forging

7055 aluminum alloy is one of the ultra-high strength aluminum alloy that has been applied,it will have very broad application prospects in the field of aerospace and other fields for its excellent overall performance.In the paper,the effects of single-stage,two-stage solution process,single-stage and two-stage aging processes on the microstructure and properties of 7055 aluminum alloy free forgings were studied systematically by means of OM,XRD phase analysis,DSC analysis,SEM analysis,conductivity test,hardness test,room temperature tensile test and tensile fracture SEM analysis and other methods.The optimal solution treatment process is 460℃/4h when the single-stage solid solution process was used.And the solid solution of MgZn₂ phase at 460℃/4h was sufficient,but the Al₂CuMg solution was un-sufficient and it became sufficient when the temperture more than460℃.But the re-crystallization would reduce mechanical properties of forgings.When the solution temperature lower than 460℃,the solid solution of alloy phase was not sufficient.Compared with the single-stage solid solution,7055 aluminum alloy could get a fuller solution as well as keeping a smaller grain size and no obvious recrystallization happened by the two-stage solid solution.450℃/3h+475℃/2h two-stage solid solution process could make MgZn₂ phase and Al₂CuMg phase dissolved fully into the aluminum matrix and the solid solution with large supersaturation formed.The tensile and yield strength of forging increased from 603.9MPa and 535.5MPa of single-solid solution to 619.5MPa and 555.3MPa after 115℃/8h+155℃/24h aging treatment.The spray forming 7055 aluminum alloy could achieve good aging strengthened effect by single-stage aging process.The strength of 7055 aluminum alloy was 643.7MPa after155℃/24h aging treatment,but the conductivity of alloy is too low under single stage aging and could not meet the requirement.In this paper,conductivity could reflect stress corrosion resistance of the forging,the forging with low conductivity revealed a poor corrosion resistance to stress.7055 aluminum alloy could form a large number of GP regions under low primary temperature and fine precipitates of MgZn₂ region could form in the GP region by two-stage aging process.The optimal two-stage aging process is 125℃/8h+155℃/24h.The best heat treatment process of spray forming 7055 aluminum alloy free forgings is the 450℃/3h+475℃/2h two-stage solution and 125℃/8h+155℃/24h two-stage aging.After the process,tensile strength,yield strength,elongation,Brinell hardness and conductivity of7055 aluminum alloy could reach to 629.2 MPa,561.6 MPa,12.3%,184.3 HB and 40.11%IACS,which could meet the design requirements of open frame firder of heavy-duty helicopter.