Two-Mode Phase Field Crystal Study of Evolution of Grain Boundaries and Dislocations in Hexagonal to Square Phase Transformation

A two-mode phase field crystal (PFC) method was employed to focus on hexagonal to square phase transformation. Hexagonal phase with a misorientation of 6 degrees and a tilt angle of 0 degrees, 15 degrees, 30 degrees, and 45 degrees were investigated. Results show that the hexagonal grains grow up, coalesce and form coherent gain boundaries with dislocation sets in two orientations. Square phases nucleate on these dislocation sets and their orientations are determined by dislocation sets. These square grains have two variants at each tilt angle, and the misorientations are 30 degrees, 30 degrees, 10 degrees, and 5 degrees when tilt angles are 0 degrees, 15 degrees, 30 degrees, and 45 degrees, respectively. Square grains with different orientations grow and ripen in different paces, and the grains located in preferential orientation will dominate. Dislocation sets are generated to relieve strain concentration that rises from grain growth in coherent boundaries.