Misorientation mediates dislocation phase boundary interactions in FCC to BCC transformation: A phase field crystal study

Through phase-field crystal simulations, we systematically investigate the effects of grain misorientation angle θ on phase transformation kinetics and defect evolution mechanisms. The results reveal a significant dependence of phase transformation pathways and energy relaxation behavior on θ . For θ was 0°–5°, the phase transformation process exhibits a two-stage characteristic, where dislocation annihilation induced by incoherent interfaces dominates the later stage of energy relaxation; consequently, the rate of energy stabilization lags significantly behind that of phase transformation. At θ was 5°, pinned dislocations form stable structures at subgrain boundaries, resulting in a local maximum in the system's free energy. For θ was 5°–8°, the phase transformation demonstrated multi-stage, spatially selective evolution: the upper and lower phase boundaries (parallel to the X -axis) undergo preferential structural reorganization, while the left and right phase boundaries (parallel to the Y -axis) exhibit delayed transformation due to high migration energy barriers. This study further elucidates the inherent non-synchronicity between the completion of phase transformation and energy stabilization. In systems with 0°–5°, energy relaxation is governed by dislocation migration kinetics; conversely, systems with 5°–8° achieve co-stabilization of structure and energy through defect annihilation at phase boundaries. This study’s defect-interface interaction model offers a theoretical basis for precisely controlling microstructural evolution during phase transformations.