Transformation superplasticity of Ti-6Al-4V and Ti-6Al-4V/TiC composites at high stresses

Isothermal and thermal cycling tensile creep experiments are reported for Ti-6Al-4V and a Ti-6Al-4V/10 vol% TiC composite, in which the thermal cycles span a broad portion of the α/β phase transformation of Ti-6Al-4V. At low applied stresses, cyclic transformations give rise to transformation superplasticity, a deformation mechanism with higher rates of deformation and increased flow stability as compared to isothermal creep. At high stresses this flow stability is lost as a power-law regime is encountered. The experimental results are discussed in light of an analytical model, which considers creep of the weak β-phase under both the internal stresses caused by the transformation and the external stress produced by the applied load.