晶界预析出处理对Al-Zn-Mg合金抗腐蚀性能的影响

摘要

通过常温拉伸、晶间腐蚀、慢应变速率应力腐蚀等试验，并结合电子显微观察，研究常规固溶后在不同温度下高温预析出处理对7005铝合金力学性能、腐蚀行为及显微组织的影响。结果表明：合金的维氏硬度随着预析出温度的降低而逐渐下降，而电导率则呈现出相反的变化趋势，并以此选择440和420°C进行预析出对比研究。高温预析出能显著增加晶界粗大析出相的不连续分布程度，且随着预析出温度的降低，晶界析出相的粗化和不连续程度增加，致使合金抗晶间腐蚀和应力腐蚀性能得到显著提高，而强度略有下降。%High temperature pre-precipitation (HTPP)took place in7005 alloy at various temperatures after solution treatment and itsinfluence on mechanical properties, corrosion behaviors and microstructure of the alloy was investigated using tensile test, intergranular corrosion (IGC) test, slow strain rate testing (SSRT), together with microstructural examinations. It is found that Vickers hardness of the aged alloy decreases gradually with decreasing the HTPP temperature, and almost a reverse trend of electrical conductivity is found compared to the hardness changes. Depending on the changes, two HTPP temperaturesof 440 and 420°Cwere chosen for comparative study. Results reveal that HTPP alloy tempers exhibit higher resistance to stress corrosion cracking (SCC) and IGC than none pre-precipitate one with an acceptable strength loss due to the substantial enhancement of distribution discontinuity of the coarse grain boundary precipitates (GBPs), and the coarsening and interspacing effect on GBPs becomes more obvious with decreasing the pre-precipitation temperature.