The Microstructure And Properties Control Of The Aluminum Alloy Al-12.51Zn-2.85Mg-2.83Cu-0.18Zr-0.0598Sr By Strong Plastic Deformation And Heat Treatment

The 7000 series aluminum alloy is widely used in aerospace industry,weapon,car and ship manufacturing areas due to its low density,high specific strength and good corrosion resistance.In this paper,the ultra-high strength aluminum alloy Al-12.51Zn-2.85Mg-2.83Cu-0.18Zr-0.0598Sr(wt.%)was used as the experimental material.The properties and structure of the aluminum alloy which has been processed by extrusion,Equal-Channel Angular Pressing(ECAP),Twice ECAP by route Bc,compression and heat treatment was investigated by observing its microstructures,EBSD,XRD,fracture characteristics and testing its micro-hardness,electrical conductivity,tensile property,inter-granular corrosion and exfoliation corrosion property.The specific research work and results are as follows(The X direction is the axial direction of the extruded alloy.The Y direction is parallel to the shear plane of ECAP):A method of preparing an ultra-high strength aluminum alloy by conventional casting(non rapid solidification)-extrusion-rolling process and subsequent heat treatment(recovery,solution,T7X-2 aging)was studied.The tensile strength of the alloy made by this method is up to 716 MPa and the alloy has good corrosion(inter-granular corrosion,exfoliation corrosion)resistance.When the alloy researched in this paper was treated by rolling-recovery-solution-T7X-2 aging(121?×5 h+133?×16 h),the hardness of the Z direction was up to 232.8HV,the inter-granular and exfoliation rank of the Z direction of the alloy were fourth and EC respectively.The tensile strength and elongation of the X direction of the alloy were 716.39 MPa and 8.76% respectively.The recovery annealing treatment can improve the tensile strength of the rolled alloy.And the inter-granular and exfoliation corrosion resistance of the alloy under T7X-1(121?×5 h+153?×16 h)is better than T6(121?×24 h)and T7X-2 aging.A method of preparing an ultra-high strength aluminum alloy by conventional casting(non rapid solidification)-extrusion-ECAP-compression along Y direction process and subsequent heat treatment(solution,T6 aging)was studied.The tensile strength of the alloy made by this method is up to 696 MPa and the alloy has good corrosion(inter-granular corrosion,exfoliation corrosion)resistance.When the alloy researched in this paper was treated by ECAP-compression along Y direction-solution-T6 aging(121?×24 h),the hardness of all the direction was beyond 220 HV.In the X,Y,Z direction,the depth of inter-granular corrosion was less than 131?m and the exfoliation corrosion resistance rank was up to EC.The tensile strength and elongation of the X direction of the alloy are 696.76 MPa and 7.67% respectively.The strength,conductivity and corrosion resistance of the alloy after compression along Y direction is higher than the process by compression along Z direction.That is because the angle between compression along Y direction and cut direction of ECAP is close to 90 degree.A method of preparing an ultra-high strength aluminum alloy by conventional casting(non rapid solidification)-extrusion –Twice ECAP by route Bc-compression process and subsequent heat treatment(recovery,solution,T7X-1 aging)was studied.The tensile strength of the alloy made by this method is up to 688 MPa and the alloy has good corrosion(inter-granular corrosion,exfoliation corrosion)resistance.When the alloy researched in this paper was treated by twice ECAP by route Bc-compression along Z direction-recovery-solution-T7X-1 aging,the hardness of all the direction was beyond 214 HV.In the X,Y,Z direction,the depth of inter-granular corrosion was less than 126?m and the exfoliation corrosion resistance rank was up to EA.The tensile strength and elongation of the X direction of the alloy were 688.20 MPa and 6.67% respectively.The different compression after ECAP has no obvious influence on the hardness,conductivity and corrosion resistance of the alloy.This difference can be explained that the twice ECAP by route Bc can eliminate the anisotropy of the extruded alloy on microstructure and corrosion resistance.The extruded alloy researched in this paper has obvious difference on inter-granular and exfoliation corrosion resistance under T6 and T7X-1 aging.And the corrosion resistance of the alloy under T7X-1aging is better.