Effect Of Multi-forging And Aging Treatment On Stress Corrosion Behavior Of 7075 Aluminum Alloy

7075 aluminum alloy has compact structure,high strength and good heat workability.It is one of the most promising lightweight structural materials in aerospace,marine and vehicle fields.However,the conventional heat treatments are difficult to achieve both high strength and excellent stress corrosion resistance,resulting in a great limitation on the service life and application potential of the alloy.Therefore,7075 aluminum alloy were processed by multi-directional forging and appropriate aging treatment for the purposes of excellent stress corrosion resistance,high strength and good ductivity.The microstructure of the samples was characterized by metallographic microscopy,scanning electron microscopy and transmission electron microscopy.The hardness test,conductivity test,room temperature tensile and slow strain rate tensile were performed.The effects of multi-directional forging and aging treatment on microstructure,mechanical properties and stress corrosion resistance of test materials were investigated.Multi-directional forging with aging treatment process improves the stress corrosion resistance of 7075 aluminum alloy,and the conductivity value is 37.1%IACS:Firstly,the precipitation phase at the grain boundary is discontinuous.Thus it is not easy to form a continuous anodic corrosion channel;secondly,the precipitation phase at the grain boundary is coarse and the precipitation-free precipitation zone is wide,which is not easy to cause hydrogen embrittlement.Meanwhile,multi-directional forging and aging treatment can greatly improve the hardness and strength of the alloy,which values are 185.3HV,604.9 MPa,respectively.Because the forging causes a large number of dislocations inside the alloy,and the grain of the alloy is remarkably refined,then the aging treatment can cause the alloy to precipitate a large number of fine second phase particles dispersed on the substrate.Furthermore,the plasticity of the alloy is still good,the elongation is about 9.4%,which is equivalent to the T6 state.Because the aging treatment can improve the grain boundary state of the forged sample and reduce the residual stress inside the alloy.