均匀化处理对含钪Al-Zn-Mg-Zr合金组织的影响

采用金相分析、扫描电镜、能谱分析、DSC等手段研究含钪Al-Zn-Mg-Zr合金均匀化态显微组织的演变。结果表明：在合金铸态组织中存在大量的枝晶偏析，在晶界处存在很多低熔点共晶相，主要元素在枝晶内部区域呈周期性变化；合金中元素Zn、Mg和Cu在晶内及晶界分布不均匀；在均匀化过程中，随着均匀化温度的升高或时间的延长，残留相逐渐溶入基体，元素分布逐渐均匀。合金的过烧温度为476.7°C。当均匀化温度升高到480°C时，合金中开始出现复熔球和三角晶界。综合考虑：合金的最佳均匀化制度为470°C，24 h。

Microstructural evolution of Al-Zn-Mg-Zr alloy with trace amount of Sc during homogenization treatment

The microstructural evolution of Al-Zn-Mg-Zr alloy with trace amount of Sc during homogenization treatment was studied by means of metallographic analysis, scanning electron microscopy （SEM）, energy dispersive X-ray （EDX） and differential scanning calorimetry （DSC）. The results show that serious dendritic segregation exists in studied alloy ingot. There are many eutectic phases with low melting-point at grain boundary and the distribution of main elements along interdendritic region varies periodically. Elements Zn, Mg and Cu distribute unevenly from grain boundary to the inside of alloy. With increasing the homogenization temperature or prolonging the holding time, the residual phases are dissolved into matrix α（Al） gradually during homogenization treatment, all elements become more homogenized. The overburnt temperature of studied alloy is 476.7 °C. When homogenization temperature increases to 480 °C, some spherical phases and redissolved triangular constituents at grain boundaries can be easily observed. Combined with microstructural evolution and differential scanning calorimeter, the optimum homogenization parameter is at 470 °C for 24 h.