通过光学显微镜、扫描电镜和差示扫描量热仪等技术手段研究了Al-0.7Mg-0.9Si合金在 550℃均匀化退火过程中的显微组织演变.结果表明,合金的铸态组织存在严重偏析,晶界析出长条状Al(Fe,Mn)Si相和短棒状Mg2 Si相,晶内析出球状Q-AlCuMgSi相;随着均匀化退火时间的延长,枝晶偏析消失,Q-AlCuMgSi相和Mg2 Si相逐步回溶于基体,Al(Fe,Mn)Si相发生断续化转变.合金导电率呈先降低后缓慢升高的趋势.结合均匀化动力学计算,确定Al-Mg-Si合金合理的均匀化退火制度为550℃8 h.
Microstructure evolution of Al-Mg-Si alloy during homogenization
The microstructure evolution of Al-0.7Mg-0.9Si alloy during homogenization at 550℃was investigated by optical microscopy,scanning electron microscopy and differential scanning calorimetry.The results show that serious dendritic segregation exists in as-cast alloy,with the long-strip Al(Fe,Mn)Si phase and short-bar Mg2 Si phase at grain bounda-ries,and the spherical Q-AlCuMgSi phase in the grain;with the increase of the homogeniza-tion time,the dendritic segregation disappears,and the Q-AlCuMgSi and Mg2 Si phases dis-solve back to the matrix step by step,and the intermittent transformation of the Al(Fe,Mn)Si phase occurs.The electrical conductivity of the alloy shows a tendency of decreasing and then slowly increasing.Combined with the calculation of homogenization kinetics,a reasona-ble homogenization heat treatment system for Al-Mg-Si alloy is determined as 550℃8 h.
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