INFLUENCE OF AN APPLIED STRAIN FIELD ON MICROSTRUCTURAL EVOLUTION DURING THE α_2 → O- PHASE TRANSFORMATION IN Ti-A1-Nb SYSTEM

摘要

We investigate the influence of an applied homogeneous strain on the coherent α_2 (DO_19) to O- phase transformation in Ti--Al--Nb alloys using a phase--field approach. The emphasis is on the effect of the applied strain on the two-phase morphology, as well as the equilibrium volume fractions of different orien- tation domains of the O-phase. It is found that the applied homogeneous strain field does not change the essential features of the morphological patterns, but does alter the relative amount of each orientation domain and the equilibrium volume fraction of the O-phase. When the applied strain is of the same order of magnitude as the stress--free transformation strain, the initial two-phase mixture becomes unstable and transforms into a single O--phase.