Detwinning/twin growth-induced phase transformation in a metastable compositionally complex alloy

Extensive experiments have shown that the transformation from the face-centered cubic to hexagonal close-packed ε phase usually occurs around coherent Σ3 boundaries. However, in this letter, we reveal a different transformation mechanism in a metastable dual-phase compositionally complex alloy via a systematic high-resolution scanning transmission electron microscopy analysis. The face-centered cubic γ matrix can be transformed to the hexagonal close-packed ɛ phase (as small as one unit) around an incoherent Σ3 boundary (~30 nm), i.e., the facet of the coherent Σ3 boundary. This transformation is assisted by the detwinning/twin growth of a coherent Σ3 boundary during annealing treatment (900 °C for 60 min)