Orientation dependent stress-induced martensitic and omega transformations in a refractory high entropy alloy

Deformation behavior of a single-phase body centered cubic refractory high entropy alloy, namely HfTaTiVZr, was evaluated by micropillar compression as a function of two different grain orientations, namely [101] and [111]. The [111] oriented micropillars demonstrated higher strength and strain hardening rate compared to [101] oriented micropillars. The [111] oriented micropillars showed transformation induced plasticity (TRIP) in contrast to dislocation-based planar-slip for the [101] oriented micropillars, explaining the difference in strain hardenability for the two orientations. These differences in deformation behavior for the two orientations were explained using Schmid factor calculations, transmission electron microscopy, and in-situ deformation videos. The insights gained from this study may help guide alloy design strategies by utilizing deformation induced phase transformations.