不同温度晶界位错湮没过程的晶体相场模拟

Phase Field Crystal Simulation of Dislocation Annihilation at Different Temperature

关键词:  晶界  位错湮没  应变  晶体相场模型

Key words:  grain boundary  dislocation annihilation  strain  phase-field crystal model

摘要:

[目的]针对不同温度的晶界位错湮没过程进行研究。[方法]采用晶体相场模型模拟中等角度对称倾侧晶界结构在不同温度下的晶界位错演化湮没过程,从位错的运动形式和体系自由能的变化,分析晶界的消失过程和位错的相互作用。[结果]具有二维三角晶格原子点阵结构形成的对称倾侧晶界是由配对的位错对按直线规则排列构成,可以看成由2套位错Burgers矢量组成。晶界湮没主要有如下几方面的特征过程:首先晶界位错攀移,然后发生位错分解,晶界发射位错,位错由攀移运动转化为作滑移运动;接着滑移位错穿过晶粒内部,直到在对面晶界上湮没;剩余的晶界位错继续作攀移运动,然后又出现位错分解,晶界再次发射位错,使得位错转为作滑移运动,与其它作滑移运动的位错在晶内相遇湮没消失。[结论]在低温情况,位错是一对一对地按照一定的顺序发生湮没,而高温情况,位错湮没可以同时出现几对位错一起发生湮没。最后,所有晶界和位错全部消失。

Abstract:

[Objective] The process of dislocation annihilation was studied at different temperature.[Methods] A mid-angle symmetric tilt grain boundary (STGB) associated with emission and absorption of lattice dislocation were simulated under strain at different temperature by phase-field crystal (PFC) model.The decay of STGB and dislocation reactions of separation, annihilation and mergence and their mechanisms were analyzed from the energy point of view.[Results] The research results show that the mid-angle STGB is composed of pair dislocations in a line arrangement in two dimensions of triangular atomic lattice, in which there are two sets of basic Burgers vectors.The evolution process of STGB decay can be divided into some typical stages as follows:A dislocation climbs firstly along the STGB under strain, then the dislocation occurs to break up into two new dislocations after it gets enough energy to overcome the active potential barrier of dislocation, and at this time the STGB emits pair dislocations to move in gliding in grain instead of climbing along STGB; After a while of gliding, the dislocation crosses the grain until it annihilates with another dislocation at the STGB right in the front, i.e.the grain boundary absorbs or merges the gliding dislocation.The remain of dislocation in the STGB can still climb along the grain boundary in which it splits off again into two dislocations, and at the same time it looks as if STGB emits the dislocations and changes the dislocation movement from climbing to gliding again.The dislocation continues gliding until they meet another gliding dislocation in grain to annihilation.[Conclusion] The annihilation of dislocation is one by one in proper sequence at low temperature, while at high temperature the process appears two by two or one by one simultaneously in sequence.And finally the total dislocations are annihilated and the STGB disappears.