固溶温度对Al-Zn-Mg-Cu系铝合金组织与应力腐蚀的影响

Effects of solution temperature on microstructure and stress corrosion of Al-Zn-Mg-Cu aluminum alloy

对7B50铝合金热轧板在460～490℃范围内进行固溶处理、室温水淬及人工时效,通过室温力学性能测试、慢应变速率拉伸实验及电导率测试,结合光学显微镜,扫描电镜和能谱分析,研究固溶温度对Al-Zn-Mg-Cu铝合金组织与应力腐蚀的影响。结果表明,提高固溶温度能有效减少残留相,增加再结晶的体积分数。当固溶温度从460℃提高到490℃时,屈服强度(σ0.2)和抗拉强度(σb)分别提高20.9%和23.5%,固溶温度从480℃升高到490℃时,强度变化不大,但随着固溶温度升高,伸长率先提高后降低,抗应力腐蚀性能先升高后降低。当固溶温度为480℃时,应力腐蚀敏感性最低,综合性能较好。残留相增多和再结晶程度提高是引起应力腐蚀敏感性提高的主要原因。在腐蚀溶液中,应力腐蚀断口形貌为典型的沿晶断裂。

The hot-rolled plates of 7B50 aluminum alloy were solution-treated at 460~490℃,water quenched and artificial aged.The effects of solution temperature on microstructure and stress corrosion of Al-Zn-Mg-Cu aluminum alloy were investigated by mechanical test at ambient temperature,slow strain rate test（SSRT）,combine optical microscopy（OM） and scanning electronic microscopy（SEM） with energy dispersive spectrum（EDS）.The results showed that the amount of residual phases decreases and the volume fraction of recrystallization increases with the increasing of the solution temperature.With the solution temperature increasing from 460 ℃ to 490 ℃,the yield strength（σ0.2） and tensile strength（σb） increases 20.9% and 23.5%,respectively.The strength has little change when solution temperature increasing from 480 ℃ to 490 ℃.The elongation and resistance of stress corrosion cracking（SCC） increase and then decrease with the increasing of solution temperature.The lowest susceptible of stress corrosion cracking and the best comprehensive performance can be obtained when solution temperature is 480℃.The increasing of amount of large size residual phases and raising of recrystallization are mainly responsible for the increasing of susceptible of SCC.The fracture morphology of stress corrosion cracking is a typical intergranular fracture.