Study On Cyclic Extrusion Compression And Heat Treatment Process Of 7034 Aluminum Alloy By Spray Forming

Super-strength aluminum alloys such as Al-Zn-Mg-Cu have the characteristics of low density and high specific strength,good toughness and diffusion performance,and excellent fatigue resistance,etc.,which have been widely used in the nuclear industry and the defense industry and other fields.Due to the development of high safety coefficient,low structural weight coefficient,high speed and long life,and cost saving,higher requirements are put forward for the structural materials of aerospace vehicles.The purpose of this paper is to improve the microstructure and mechanical properties of 7034 aluminum alloy by means of reciprocating extrusion process and matching reasonable heat treatment process.In this paper,finite element simulation method was used to study the deformation law of Al-Zn-Mg-Cu alloy under different deformation parameters of reciprocating extrusion,and the reasonable range of deformation parameters was explored.Based on the finite element simulation and optimization results of Al-Zn-Mg-Cu alloy,the jet forming 7034 aluminum alloy was subjected to different reciprocating extrusion experiments.Metallographic microscope observation(OM),X-ray diffraction analysis(XRD),hardness analysis and tensile analysis at room temperature were used.The microstructure and mechanical properties of spray forming 7034 alloy under different deformation conditions were studied.The finite element simulation results show that the equivalent strain distribution of single pass reciprocating extrusion process has obvious geometric symmetry,and the equivalent strain varies greatly in different locations.According to the analysis of the equivalent strain uniformity in different areas of the longitudinal section of the multi-pass reciprocating extrusion specimen,the difference between the strain at the edge of the specimen and the strain in the middle region decreases gradually with the increase of the deformation passes,and the equivalent strain variation coefficient in the radial center region is the lowest and the deformation uniformity is the best.The most suitable deformation parameters are as follows: extrusion ratio 4,upward punch downward pressure speed 0.5 mm /s,deformation temperature 350 ?.The results of microhardness and tensile test show that with the increase of reciprocating extrusion passes,the average microhardness and tensile strength increase first and then decrease,while elongation decreases first and then increase.In the process of deformation,dynamic recrystallization and dynamic recovery process occur simultaneously in 7034 aluminum alloy.In the thired passes of deformation,the dynamic recovery process plays a dominant role,which leads to the decrease of dislocation density,strength and hardness.Compared with the deformed specimens without heat treatment,the hardness,tensile strength and yield strength of the specimens after heat treatment are significantly increased.The maximum tensile strength and elongation of the second-pass reciprocating extrusion deformed sample after single stage solution + single stage aging treatment are 835 MPa and 2.8%.