DC铸造7085铝合金在均匀化过程中的组织演变

摘要

采用光学显微镜、扫描电镜、EDS能谱分析、DSC分析及X射线衍射等手段研究DC铸造7085铝合金均匀化态显微组织的演变。结果表明，7085铝合金的铸态组织中存在严重的枝晶偏析，晶界处存在大量的共晶显微组织及共晶相。共晶α(Al)+T(AlZnMgCu)显微组织在均匀化过程中逐渐溶入基体中。金属间相S(Al2CuMg)沿共晶组织形成长大，并在460°C、24 h的均匀化处理下完全溶入基体中。7085铝合金的原始共晶结构的演变包括α+T共晶显微组织的溶解、T相向S相的转变及S相的溶解。最佳的均匀化制度为470°C、24 h。%The microstructural evolution of a DC cast 7085 alloy during homogenization treatment was investigated by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry (EDS), differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The results showed that serious dendritic segregation existed in the as-cast 7085 alloy. Numerous eutectic microstructures and phases were observed at the grain boundary. During homogenization process, eutecticα(Al)+T(AlZnMgCu) microstructure gradually was dissolved into matrix. IntermetallicS(Al2CuMg) phase formed and grew along the eutectic microstructure and disappeared into the matrix completely when it was homogenized at 460 °C for 24 h. It could be found that the evolution of primary eutectic structure of 7085 alloy consisted of three processes, dissolution of eutecticα+T microstructure, phase transformation fromT phase toS phase and the dissolution ofS phase. The optimum homogenization parameter was at 470 °C for 24 h.