双模晶体相场研究六方四方相变过程晶界和位错演化

A two-mode phase field crystal study of evolution of grain boundaries and dislocations involved in hexagonal to square phases transformation

摘要:

对于晶粒，晶界，应力和位错的交互作用的深入理解有助于优化材料组织和提升材料性能。本文采用双模晶体相场法研究六方相向正方相的转变。分别针对倾侧角为0°，15°，30°，和 45°，晶粒取向差为6°的六方相体系做了系统研究。六方晶粒长大、溶合、并形成共格晶界，位错组沿六方晶界均匀分布，并有两种取向。正方相在位错组处形核，并且其取向取决于位错组取向。每一种倾侧角的体系种均形成两个取向正方相的变体。针对倾侧角为0 °，15°，30°，和 45°的六方相体系生成的四方相相变体之间的取向差分别为30°, 30°, 10°, 和5°。不同取向的正方相晶粒长大熟化的方式有差异，位于有利取向的晶粒将会优先生长占据主导地位。以共格晶界形式长大的晶粒，晶界处有位错组生成以松弛晶粒长大的应力集中。

Abstract:

A comprehensive understanding on interaction among grains, boundaries, strain and dislocations are beneficial for microstructure optimization and properties enhancement. A two-mode phase field crystal (PFC) method is employed to focus on hexagonal to square phases transformation. Hexagonal phases with a misorientation of 6° and tilt angle of 0 °, 15°, 30°, and 45° are checked. The hexagonal grains grow up, coalesce and form coherent grain boundaries with dislocation sets in two orientations. Square phases nucleate on these dislocation sets and their orientations are determined by these dislocation sets. These square grains of each case have two variants, which the misorientations are 30°, 30°, 10°, and 5° when tilt angles are 0 °, 15°, 30°, and 45°. Square grains of different orientation grow and ripen in different pace, the grains that locate on preferential orientation will dominate. Dislocation sets are generated to relieve strain concentration that rises from grain growth with coherent boundaries.