| 7A04 aluminum alloy,as a relatively mature heat-treatable and deformed aluminum alloy in domestic research and development,has the advantages of high strength,low density and excellent processing properties.After solution and aging heat treatment,it is widely used in aviation,military industry,aerospace,stress parts and other fields.Solution and aging treatment is the purpose of the solution of supersaturated solid solution is obtained by precipitation aging treatment spread small dispersion of strengthening phase,to improve the properties of the aluminum alloy as the application in the field of development,the traditional solid solution aging process is very difficult to meet the needs of existing,and it has complex process,heat treatment for a long time caused by the problems such as low production efficiency.In this thesis,7A04 aluminum alloy extruded bar as the research object,in 7A04 aluminum alloy solution and two-stage aging process respectively add electromagnetic energy,the solution temperature is set at 470℃,the two-stage aging temperature range is110～130 ℃,120～160 ℃.The effect of electromagnetic energy on microstructure and properties of 7A04 aluminum alloy was investigated by changing the solution treatment time,the two-stage aging treatment temperature and treatment time of electromagnetic energy.The morphology and size of precipitated phase were observed by scanning electron microscope,hardness was measured by digital Vickers hardness tester,tensile strength and elongation were measured by microporous electronic universal tensile machine.By analyzing the mechanical properties of 7A04 aluminum alloy under solution and aging heat treatment,the optimal parameters of solution and aging heat treatment were determined respectively.Finally,the electromagnetic energy was applied to 7A04 aluminum alloy under solution and aging heat treatment at the same time.The significance of this study is to maintain or improve the properties of 7A04 aluminum alloy and provide new ideas for its solution aging process to save energy,reduce consumption and improve productivity.The results show that when the magnetic induction intensity is 30.8m T,electromagnetic energy can completely penetrate into the sample,and the electromagnetic energy can be processed by modifying the number of ampere-turns for large aluminum alloy materials.After electromagnetic energy solution treatment at 470℃ for 60 min,the decomposition rate of the insoluble second phase of 7A04 aluminum alloy is improved,the tensile strength is increased by about 96 MPa,the microhardness is increased by about 20 HV,and the elongation is decreased by about 0.9% compared with the conventional solution.After conventional solution treatment at 470℃ for 120 min,primary aging treatment at 110℃ for30 min and secondary aging treatment at 140℃ for 60 min,tensile strength is increased by60 MPa,microhardness is increased by 9HV,elongation is increased by 72% and time is shortened by 65%.Analysis,electromagnetic energy can increase the diffusion coefficient of Cu,Mg and Zn,reduce the critical nucleation work,at the same time,the larmor frequencies of Cu,Mg and Zn atoms are effected to promote their precession,Through the comprehensive effect of diffusion coefficient,critical nuclear work and screw-forward motion,the process of forming nucleus,nucleus growth and diffusion of the reinforced phase is accelerated,thereby shortening the heat treatment time of the solid solution aging process. |
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