Waspaloy合金凝固过程中偏析和液体密度的变化

Segregation and Liquid Density Variation during Solidification of Waspaloy Alloy

利用SEM和EDAX研究了Waspaloy合金不同温度下的凝固组织和合金元素的偏析并计算了液体的密度。结果表明,Waspaloy合金凝固时的偏析元素主要是Ti。随着温度的降低,Ti在液相中的含量从开始凝固时的2.90%上升至最高值8.91%,为正偏析元素;Cr和Co在晶干上富集,为负偏析元素。随着温度的降低和液相中Ti含量的升高,液析η相的形态依次发生下面的变化:颗粒状→条片状→块状。液体密度计算结果显示,液体的密度随着温度的下降而下降。当温度降至1300℃以下时,液体密度稍有上升。研究发现,这和液相中富Ti的η相和碳化物析出有关。液体的最大密度反转为0.01406g·cm-3/℃,较易形成宏观偏析黑斑。

The microstructure and microsegregation of Waspaloy alloy at different temperatures were investigated by SEM and EDAX associated with liquid density calculation. It is found that main segregation alloy element in Waspaloy during solidification is Ti. The content of Ti in liquid increases from 2.90% to the maximum value of 8.91% with temperature decreasing from 1360 ℃ to 1300 ℃. Cr and Co are of negative segregation and enriched in dendrites. The lower the temperature, the lower the content of them in liquid. As the temperature decreasing and increasing of the content of Ti in liquid, the morphology of η changes as follows： granular→rodlike or lamellar →blocky. Liquid density calculation shows that the liquid density is reduced with temperature decreasing but slightly arises below 1300℃ which is related to the precipitation of high-Ti phase of η and MC carbides from liquid. The maximum liquid density inversion is up to 0.01406 g·cm^-3/℃ and the alloy is prone to macrosegregation of freckles.