晶体相场法模拟小角度晶界的位错结构及其演化

Simulating Structure of Dislocation and Its Evolution in Low Angle Grain Boundary by Phase Field Crystal Method

采用晶体相场模型模拟小角度晶界结构和在外加应力作用下晶界、位错的演化过程,从位错的运动形式、体系自由能与应变关系等角度,讨论晶界位错运动和湮没过程。结果表明:在稳定的小角度晶界中,位错间距与位向差成反比。位错和晶界区域具有较高的能量密度;外加应力会导致一个位错组脱离晶界而分解成两个位错组,且有诱发晶界湮没的趋势;晶界湮没过程可以出现4个阶段或2个阶段,且存在敏感位向差角,位向差稍高于5.85°时晶界湮没过程呈4个阶段,位向差稍低于5.85°时晶界湮没过程呈2个阶段;位向差越小,晶界湮没过程越简单快捷。

The phase field crystal model is employed to simulate the structure of low angle grain boundary and its dislocation evolution under an applied stress.The process of a dislocation motion and annihilation is discussed according to its movement and the relation between free energy and strain.The simulated results confirm that the dislocation spacing is inversely proportional to the misorientation angle.It shows that there is higher energy density in the region of dislocations and the grain boundaries than others.An applied stress can induce a double-array dislocation to separate from the grain boundary and split apart into two double-array dislocations and to trend to annihilate at grain boundary.The annihilation process contains four or two stages and also there is a sensitive angle.When misorientation angle is slightly higher than 5.85°the annihilation process contains four stages,while the annihilation process contains two stages when misorientation angle is slightly lower than 5.85°.The smaller the misorientation angle is,the faster the process of the grain boundary annihilation is.