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 β phase with the cooling rates of 10,50,100,200,400 and 700 K·min-1,respectively.Results show that with the increase in cooling rate from 10 to 700 K·min-1,the colony size of α2/γ lamella decreases from 1513 to48 urn and the solidification segregation significantly decreases.Also the content of residual B2 phase within α2/γlamellar 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.