Interfacial reaction between Ti-47Al-2Cr-2Nb alloy melt and y ₂O₃ shell mold

Interfacial reaction, interfacial microstructure, element distribution and phase constituent of Ti47Al-2Cr-2Nb alloy melt with Y₂O₃ shell mold were investigated in condition of different heating temperature and holding time combining with directional solidification technology. Feasibility of Y₂O₃ shell mold for directional solidification TiAl alloy parts was approached. The results show that, at a given holding temperature or holding time, Al element in the melt is more easily diffused into the mold shell side than Ti element. Meanwhile, infiltrated layer with 40-70f¿m in thickness can be formed on surface of the alloy rod. Formation of infiltrated layer at 1600 "C is attributed to the introduction of Y₂O₃ particle into the matrix alloy as a result of erosion and thermal impaction of liquid alloy to face materials of shell mold, while it is the result of reaction of Y₂O₃ with liquid alloy at 1700 'C because of the occurrence of grey phase containing Y, O, Al around Y₂O₃ particle.