Globularisation of α2 phase in (α2 + γ) two-phase lamellar titanium aluminide by thermal cycling

Present work deals with modification of lamellar microstructure of a γ – TiAl alloy to globular concerning α2 phase. For this investigation, cast Ti-48Al-2Cr-2Nb alloy was subjected to cyclic heat treatment. This cycle was consisting of heating and cooling alternatively to order – dis-order (α2 ↔ α) regime. Thermal cycles led to the change of lamellar α2 phase to globular. Additionally, with time of globularisation, average micro-hardness was identified to be decreasing at the expense of grain coarsening with respect to γ and globularised α2 phase. Phase percentage of both phases was observed to be stabilizing with cycling time. Based on phenomena of globularisation with time, a possible mechanism was designed for understanding the mechanism of globularisation.