7050铝合金半连续铸锭在DSC分析过程中组织的变化

Microstructural evolution of a 7050 semicontinuous casting ingot during DSC analysis process

采用DSC(differential scanning calorimetry)、金相、扫描电镜及其能谱分析等方法,研究了7050超高强铝合金φ200 mm半连续圆铸锭中非平衡凝固共晶体在DSC实验过程的变化.结果表明:7050超高强铝合金φ200 mm半连续铸锭中仅有一种非平衡凝固的低熔点共晶体,其开始熔化温度为477℃;当DSC分析的加热速度低于20℃/min时,在其加热过程,半连续铸锭中的非平衡凝固共晶体发生向具有更高熔化温度的Al2CuMg(S相)的转变,该合金中平衡S相的熔化温度为490℃;采用DSC方法研究非平衡凝固产物时,应考虑其在加热过程发生的转变.

The evolution of the nonequilibrium solidified eutectic of φ200 mm semicontinuous casting ingot of 7050 aluminum alloy during DSC analysis has been studied by differential scanning calorimetry （DSC） , optical microscopy （OM） and scanning electron microscopy with energy dispersive X -ray spectroscopy （SEM -EDS）. The results show that only one kind of nonequilibrium solidified eutectic presents in the semieontinuous casting ingot of 7050 aluminum alloy, whose initial melting temperature is 477 ℃. When the heating rate is below 20 ℃/min, the nonequilibrium solidified eutectic transforms to Al2CuMg （S phase） the initial melting temperature of equilibrium S phase bein5 490 ℃. It is suggested that transformation should be considered during the heating process when a nonequilibrium solidified product is investigated by DSC analysis.