Strain-induced phase transformation during thermo-mechanical processing of titanium alloys

Strain-induced phase transformation studies have been conducted in a Ti–6Al–2Sn–4Zr–6Mo alloy. This alloy was subjected to β sub-transus deformation upon slow cooling from the β-phase field and the effect of strain on the extent and morphology of the phase transformation during hot-deformation was determined. In addition, the transformation kinetics and the morphology of the newly formed α-phase were studied following deformation under different cooling conditions. By applying strain, the rate of the β-to-α phase transformation increased significantly during deformation as well as during slow cooling following deformation. This increase in the kinetics of the β-to-α transformation can be ascribed to strain-induced phase transformation. Also, the extent of deformation of the β-phase had a marked effect on the resulting morphology and size of the newly formed α-phase. Transformation of un-deformed β-phase rendered α-phase of acicular morphology only. However, following deformation of the β-phase, acicular as well as globular α-phase morphologies have been observed upon cooling.