Effect of cooling rate and manganese concentration on phase transformation in Ti–45 at.% Al based alloys

The microstructural evolution in various Ti–45Al based alloys during varying heat treatment conditions was studied. Detailed microstructural investigation of the alloy samples, heated at 1350 °C for 0.5 h and subsequently cooled at different cooling rates, suggested that the alloyʹs susceptibility to massive transformation increases with increasing the severity of cooling. However, this transformation is quenched by α→α2 disorder–order transformation at very high cooling rates (water quenching). It was also observed that cooling rate dependence of transformation modes depends on the composition of the alloy; higher the amount of Mn in the alloy, higher is the cooling rate required for complete massive transformation.