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采用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射(XRD)以及差示扫描量热仪(DSC)等技术对车用铸态7055铝合金组织及均匀化退火过程中的组织演变进行研究。结果表明:均匀化退火后铝合金枝晶间距明显缩小,晶粒细化。部分金属间化合物以及许多非平衡共晶组织出现在晶界部位,呈现网状片层的连续分布结构,在铸态组织内生成了具有较高Zn、Cu、Mg含量的共晶相。MgZn_2相随着均匀化退火时间增加发生回溶现象。将均匀化退火时间增加到40 h,表现出明显的均匀化效果。确定465℃下处理40 h作为最优的单级均匀化条件。
The microstructure evolution of as-cast 7055 aluminum alloy and its homogenization annealing process were investigated by OM, SEM, XRD and DSC. the study. The results show that the dendritic spacing of aluminum alloy is obviously reduced and the grains are refined after the homogenization annealing. Some intermetallic compounds and many non-equilibrium eutectic structures appeared in the grain boundary, showing the continuous distribution of network sheets, and the eutectic phases with higher content of Zn, Cu and Mg were formed in the as-cast microstructure. MgZn_2 phase homogenization annealing time increases with the phenomenon of backwash. The homogenization annealing time was increased to 40 h, showing a significant effect of homogenization. The optimal single-stage homogenization conditions were determined at 465 ℃ for 40 h.