Al-6．5Zn-2．4Mg-2．3Cu铝合金半连续铸锭的均匀化处理

Homogenization Treatment of Semicontinuous Casting Ingot of Al-6.5Zn-2.4Mg-2.3Cu Aluminum Alloy

采用DSC、金相、扫描电镜及能谱分析等方法,研究了Al-6.5Zn-2.4Mg-2.3Cu超高强铝合金半连续铸锭的结晶相及其在470℃均匀化处理过程中的变化规律.结果表明:在均匀化处理过程中,铸锭中含有Al,Zn,Mg,Cu元素的非平衡凝固共晶体在向合金基体溶解的同时还转变形成S相(Al2CuMg),形成的S相在该合金中的熔化温度为490℃;均匀化处理初期,含有Al,Zn,Mg,Cu的非平衡凝固共晶体转变成S相的速度大于S相向合金基体溶解的速度,导致S相数量随均匀化处理时间的延长,先增加随后减少到平衡值,但不能全部溶入合金基体.

The constituents in the semicontinuous casting ingot of the super-high strength Al-6.5Zn-2.4Mg-2.3Cu aluminum alloy and how they change in the process of homogenization treatment at 470 ℃ were studied by differential scanning calorimetry （DSC）, optical microscopy （OM） and scanning electron microscopy with energy dispersive X-ray spectroscopy （SEM-EDX）. The results showed that non-equilibrium freezing eutectic containing Al, Zn, Mg, Cu in the ingot not only dissolves into the alloy matrix, but also transforms into S phase （Al2CuMg） in the homogenization treatment process, and the S phase thus formed melts at 490 ℃ in this alloy. During the initial period of the process, the formation rate of S phase is higher than the rate of S phase＇s dissolution into the alloy matrix, thus resulting in that the quantity of S phase increases at first then decreases to equilibrium value with the prolonged time for homogenization. However, the S phase in the alloy can not be dissolved into its matrix completely.