T6处理工艺对Mg-Y-Cu-Zr合金显微组织和耐腐蚀性能的影响

为研究T6热处理工艺对Mg-6.6Y-2.6Cu-1.2Zr镁合金组织和耐腐蚀性能的影响,对合金进行了不同工艺的固溶处理和相同工艺的时效处理。固溶处理工艺为420℃、440℃和460℃保温12h水冷,时效处理工艺为200℃×12h。采用光学显微镜和扫描电镜观察合金的显微组织,通过电化学法测试合金的耐蚀性能。结果表明:随着固溶温度的升高,合金中β相数量减少,且其形貌从不规则形状转变为条状;LPSO结构的体积分数先增多后减少;合金的腐蚀速率先增大随后显著降低。经460℃×12h水冷随后200℃×12h时效处理的Mg-6.6Y-2.6Cu-1.2Zr合金的耐蚀性能显著提高,为铸态合金的4.6倍,表明合适的T6处理工艺可有效提高Mg-6.6Y-2.6Cu-1.2Zr镁合金的耐蚀性能。

Effect of T6 Treatment Processes on Microstructure and Corrosion Resistance of Mg-Y-Cu-Zr Alloy

In order to investigate the effect of T6 heat treatment processes on its microstructure and corrosion resistance,The Mg-Y-Cu-Zr magnesium alloy was solution treated by processes which consisted of holding at 420 C,440 C,and 460 C for 12 h and cooling in water respectively,then aged at 200 C for 12 h.Microstructure of the alloy was surveyed by means of optical microscope and scanning electron microscope,and corrosion resistance of the alloy were tested by an electrochemical method.The results showed that as the solution temperature became higher,βphase in the alloy decreased in amount and changed from irregular shape to strip,volume fraction of long period stacking ordered(LPSO)structure firstly increased and then decreased,as well as corrosion rate of the alloy first increased and then reduced significantly.The Mg-Y-Cu-Zr alloy undergoing solution treatment consisting of soaking at 460 C for 12 h and water cooling followed by aging at 200 C for 12 h exhibited considerably improved corrosion resistance which was 4.6 times better than that of the as-cast alloy,indicating that reasonable T6 treatment process can effectively improve corrosion resistance of Mg-Y-Cu-Zr magnesium alloy.