An alternative formation mechanism of {332}BCC twinning in metastable body-centered-cubic high entropy alloy

In this work, the origin of {332}(BCC )twinning was investigated in a body-centered-cubic (BCC) high entropy alloy (TiZrHf)87Ta13 (at.%). Detailed transmission electron microscopy analysis of the deformed microstructure revealed that a special "{351} "< 211 >(alpha) " type II twinning generates in the early deformation stage, and with further straining, the "{351} "< 211 >(alpha) " type II twin variant accommodates into a {351}(alpha) " type I twin variant. The resultant {351}(alpha) " type I twinning exhibits good lattice correspondence with the {332}BCC twinning and further propagates into the retained BCC grain with orientation relationship of {351}(alpha) "//(332)(BCC), structuring into a {332}(BCC) twin-like configuration. Based on the experimental results and twinning analysis through evaluating twinning shear and atomic shuffle mechanism of this specific feature, our findings provide an alternative mechanism for the formation of {332}(BCC) twinning in which a special martensitic type II to type I twinning transformation mechanism took effect.