This study investigates the plastic deformation-induced fcc → hcp → bcc phase transition within nanograins in an ultra-strong gradient nanostructured surface layer on Fe

45

Mn

35

Cr

10

Co

10

compositionally complex alloy (CCA)

subjected to a single point cubic boron nitride turning process. High-resolution transmission electron microscope observations reveal a novel atomic movement mechanism of this transition following a unique Nishiyama-Wassermann orientation relationship. Unlike the previously validated Bogers-Burgers-Olson-Cohen model

which follows different orientation relationships and relies on two shear components

this study demonstrates that the phase transition in this CCA is cooperatively completed by two sets of half-partial dislocation dipoles and associated atom shuffling.

Statement of Novelty

A novel atomic mechanism of fcc → hcp → bcc phase transition

cooperatively completed by two sets of partial dislocation dipoles and atomic shuffling

provides potential implications for advanced structural materials.