固溶处理时间对Al-5.7Zn-0.7Mg铝合金型材组织及压溃性能的影响

Effect of solid solution time on microstructure and crushing performance of Al-5.7Zn-0.7Mg aluminum alloy profiles

对汽车用Al-5.7Zn-0.7Mg铝合金薄壁型材进行了470℃不同时间的固溶处理和双级时效处理,采用光学显微镜(OM)、EBSD测试、轴向静态压缩试验和室温拉伸试验等方法研究了晶粒组织和再结晶程度对其平均载荷(F_(m))、峰值载荷(F_(p))、吸能(U)等压溃性能的影响,同时分析了压溃变形特征和开裂原因。结果表明:随固溶时间的延长,铝合金型材的再结晶程度逐渐上升,强度逐渐下降,铝合金薄壁梁的峰值载荷、吸能及平均载荷也逐渐降低;在线水淬试样的峰值载荷和吸能分别为406 kN和33.3 kJ;经120 min固溶处理试样的压溃峰值载荷与吸能分别为359 kN和30.7 kJ,较在线水淬试样分别降低了11.5%和8.0%;当固溶较长时间时,铝合金试样再结晶程度显著升高,再结晶晶粒间一般为大角度界面,裂纹更易沿晶界扩展,试样更容易开裂。

Solid solution treatment at 470℃for different time and two-stage aging treatment for Al-5.7Zn-0.7Mg aluminum alloy thin-walled profiles were carried out to investigate the effects of grain microstructure and recrystallisation on the crushing performance such as average load(F_(m)),peak load(F_(p)),energy absorption(U)by means of optical microscopy(OM),electron backscattered diffraction(EBSD),quasi-static axial crushing test and room temperature tensile test,and the characteristics of crushing deformation and the causes of cracking of the alloy were studied.The results show that the recrystallization degree of the aluminum alloy profiles increases with the solution time increasing,while the strength decreases gradually,and the peak load,energy absorption and average load of the aluminum alloy thin-walled beam also decreases gradually.The peak load and absorbed energy of the aluminum alloy profiles after online water quenching are 406 kN and 33.3 kJ,respectively.After solid solution treated for 120 min,the peak load and energy absorption are 359 kN and 30.7 kJ,which reduced by 11.5%and 8%compared with onhine water quenching,respectively.When solid solution for a long time,the recrystallization degree of the aluminum alloy profiles increases significantly,and the recrystallized grains are generally with large-angle grain boundaries along which the cracks are more likely to propagate,and the specimens are more likely to crack.