Orientation relationships of impact-induced phase transformation in high entropy alloy HfZrTiTa0.53

Phase transformation in a metastable body -centered cubic (BCC) high entropy alloy HfZrTiTa0.53 is investigated via plate impact along with in situ free surface velocity measurements, postmortem microstructure characterizations and first -principles calculations. Impact -induced BCC to hexagonal close -packed transformation is observed. Compared to the single orientation relationship (the Pitsch-Schrader relationship) under quasi -static loading, an additional orientation relationship with higher phase transformation activation barrier is also involved, given the ultrahigh strain rates and complex stress condition under planar impact.