Solidification microstructure characteristics of Ti-44Al-4Nb-2Cr-0.1B alloy under various cooling rates during mushy zone

Beta-solidifying TiAl alloy has great potential in the field of aero-industry as a cast alloy. In the present work, the influence of cooling rate during mushy zone on solidification behavior of Ti-44Al-4Nb-2Cr-0.1B alloy was investigated. A vacuum induction heating device combining with temperature control system was used. The Ti-44Al-4Nb-2Cr-0.1B alloy solidified from superheated was melted to beta phase with the cooling rates of 10, 50, 100, 200, 400 and 700 K center dot min(-1), respectively. Results show that with the increase in cooling rate from 10 to 700 K center dot min(-1), the colony size of alpha(2)/gamma lamella decreases from 1513 to 48 mu m and the solidification segregation significantly decreases. Also the content of residual B2 phase within alpha(2)/gamma lamellar colony decreases with the increase in cooling rate. In addition, the alloy in local interdendritic regions would solidify in a hypo-peritectic way, which can be attributed to the solute redistribution and enrichment of Al element in solidification.