| Al-Zn-Mg-Cu ultra high strength aluminum alloy has a very wide range of application in transportation,aerospace,weapon and other fields,because of its excellent comprehensive performance.And nowadays,many scholars at home and abroad have been devoted to the research of the microstructure and properties of the ultra high strength Al-Zn-Mg-Cu alloys in order to meet the high performance requirements.In this paper,t h e e xt r u d ed su p er st r e ng t h a l u mi nu m a l l o y(Al-12.18Zn-3.31Mg-1.43Cu-0.20Zr-0.0435Sr)was used as the experimental material.The influence of the deformation process(rolling,equal channel angular pressing(ECAP),hot compression),recovery annealing and aging process on the microstructure and properties of the alloy was studied in this paper by the optical microscope(OM)microstructure,electron backscattered diffraction(EBSD),X-ray diffraction(XRD)analysis and hardness,conductivity,tensile property,corrosion resistance(intergranular corrosion,exfoliation corrosion)test.The main results are as follows(in the following sections,the X direction is the axial direction and the Y,Z directions are the radial directions of the extruded alloy,the angle between Y and Z direction is 90° and in the ECAP processing,the Y direction is parallel to the ECAP shearing plane):A method of preparing a super strength aluminum alloy by conventional casting(non rapid solidification)-extrusion-rolling(along the X direction)process and subsequent heat treatment(recovery,solution,T7X-2(121?×5h+133?×16h)aging)was studied.The tensile strength of the alloy made by this method is up to 809 MPa and the alloy has good corrosion(intergranular corrosion,exfoliation corrosion)resistance.When the alloy researched in this paper was treated by rolling-recovery-solution-T7X-2 aging,the hardness of the Z direction of the alloy is up to 251.6HV,the intergranular corrosion and exfoliation corrosion rank of the Z direction of the alloy are four and EB respectively,the tensile strength and elongation of the X direction of the alloy are 809.2MPa and 5.8% respectively.The recovery annealing treatment has no obvious effect on the hardness,conductivity and corrosion resistance of the rolled alloy and the recovery annealing treatment can improve the tensile strength of the rolled alloy.The tensile property test and EBSD microstructure analysis results of the alloy show that the alloy has less anisotropy.The rolled alloy researched in this paper has similar intergranular corrosion resistance under the aging condition of T6(121?×24h)and T7X-2 and the intergranular corrosion resistance of the alloy under the aging condition of T7X-1(121?×5h+153?×16h)is the best.The rolled alloy researched in this paper has similar exfoliation corrosion resistance under the aging condition of T6 and T7X-1 and the exfoliation corrosion resistance of the alloy under the aging condition of T7X-2 is the worst.A method of preparing a super strength aluminum alloy by conventional casting(non rapid solidification)-extrusion-ECAP(along the X direction)-hot compression process and subsequent heat treatment(solution,T6 aging)was studied.The tensile strength of the alloy made by this method is up to 763 MPa and the alloy has excellent corrosion(intergranular corrosion,exfoliation corrosion)resistance.When the alloy researched in this paper was treated by ECAP-Z direction hot compression-solution-T6 aging,the hardness of the X,Y,Z directions of the alloy are all over 240 HV,the intergranular corrosion and exfoliation corrosion rank of the X,Y,Z directions of the ally are three and EA respectively,the tensile strength and elongation of the X direction of the alloy are 763.6MPa and 5.0% respectively.The differernce of the two directions of the hot compression after ECAP has no obvious influence on the hardness,conductivity and corrosion resistance of the alloy.The corrosion resistance(intergranular resistance,exfoliation resistance)and hardness test results show that the alloy has less anisotropy.But the Y direction hot compression after ECAP can refine the microstructure of the alloy obviously.The percentage of the grains the size of which are below 10?m of the X direction of the alloy treated by ECAP-Y direction hot compression-solution is 78.1% but when the alloy was treated by ECAP-Z direction hot compression-solution,the percentage is just 55.2%.The reason is when the alloy was compressed along the Y direction,the angle between the deformation direction of the alloy and the ECAP shearing plane is approximately 90°.So compared with the Z direction compression,the deformation of the alloy compressed along the Y direction is more severe.A method of preparing a super strength aluminum alloy by conventional casting(non rapid solidification)-extrusion-(twice ECAP(along the X direction)by route C)-hot 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 778 MPa and the alloy has good corrosion(intergranular corrosion,exfoliation corrosion)resistance.When the alloy researched in this paper was treated by(twice ECAP by route C)-Z direction hot compression-recovery-solution-T7X-1 aging,the hardness of the X,Y,Z directions of the alloy are all over 225 HV,the intergranular corrosion and exfoliation corrosion rank of the X,Y,Z directions of the ally are three and P respectively,the tensile strength and elongation of the X direction of the alloy are 778.4MPa and 6.67% respectively.The differernce of the two directions of the hot compression after ECAP has no obvious influence on the conductivity and corrosion resistance of the alloy but has a certain influence on the hardness of the alloy.The alloy treated by(twice ECAP by route C)-hot compression-recovery-solution in this paper has better intergranular,exfoliation corrosion resistance under the aging condition of T7X-1 than under the aging condition of T6.The corrosion resistance(intergranular resistance,exfoliation resistance)and hardness test results show that the alloy has less anisotropy. |
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