热矫正次数对7N01铝合金应力腐蚀开裂的影响

采用慢应变速率拉伸试验(SSRT)和透射电镜(TEM)测试分析方法研究了热矫正次数对7N01-T5铝合金应力腐蚀敏感性的影响。结果表明:随着热矫正次数的增加,7N01-T5铝合金应力腐蚀敏感性增加。原因主要在于晶界析出相的转变以及溶质元素Zn和Mg从基体向晶界的不断扩散。基于非平衡偏聚理论可知,三次热矫正的等效恒温时间小于临界时间tc。因此,随着热矫正次数的增加,晶界处Zn和Mg元素含量逐渐增加,增大了晶界与基体间的腐蚀电位差,使7N01-T5铝合金应力腐蚀敏感性增加。

Effect of times in heat straightening on stress corrosion cracking of 7N01 aluminum alloy

Stress corrosion cracking behavior of 7N01-T5 aluminum alloy was investigated using slow strain rate test(SSRT)and transmission electron microscope(TEM).The results show that the stress corrosion cracking susceptibility increases with increasing the times in heat straightening.The main reason lies in the transformation of intergranular precipitation and the diffusion of solute elements Zn and Mg from matrix to grain boundary.The effective time of non-equilibrium segregation of solute elements Zn and Mg during three times of heat straightening is less than the critical time,tc,according to the theory of non-equilibrium segregation.Consequently,the contents of solute elements Zn and Mg at grain boundaries gradually increase with increasing the times in heat straightening,which leads to an increase in corrosion potential difference between the grain boundary and its surrounding substrate,thus results in the increase of stress corrosion cracking susceptibility of 7N01-T5 aluminum alloy.