过时效态Al-Zn-Mg-Cu合金断裂韧性与显微组织分析

Analysis of fracture toughness and microstructure of Al-Zn-Mg-Cu alloy in overaged condition

采用室温拉伸、断裂韧性测试、扫描电子显微镜和透射电子显微镜等手段研究Al-Zn-Mg-Cu合金在不同过时效状态下的力学性能和断裂行为,探讨合金断裂韧性与屈服强度的关系,分析组织中的析出相特征对合金断裂韧性的影响机理。研究结果表明:在双级过时效态下,Al-Zn-Mg-Cu合金断裂韧性与屈服强度近似呈反比关系;随着一级和二级时效时间延长,晶内析出相和晶界析出相的尺寸逐渐增大,晶内和晶界强度差异减小,断口形貌显示穿晶断裂比例增加;加工硬化指数提高,合金变形均匀性增加,合金断裂韧性提高。

The mechanical properties and fracture behavior of an overaged Al-Zn-Mg-Cu alloy were investigated by tensile test,fracture toughness test,scanning electron microscopy and transmission electron microscopy.The relationship between the fracture toughness and yield strength of the studied alloy was studied,and the mechanism that the precipitates affected the fracture toughness was revealed.The results show that the fracture toughness of alloy is approximately inversely proportional to yield strength.With the increase of aging time,the precipitates within grain and on grain boundary becomes coarse and the work hardening exponent increases.Furthermore,the discrepancy of strength between the grain boundary and matrix diminishes with the coarsening of matrix precipitates,which promotes the homogeneity of deformation and therefore increases the fracture toughness.