初始原子排列对亚晶界湮没影响的晶体相场模拟

Simulation of the Influence of Initial Atomic Arrangement to Sub-grain Boundary Annihilation by Phase Field Crystal Method

关键词:  晶体相场模型  亚晶界  初始原子对齐程度  应力诱发湮没

Key words:  phase field crystal model  sub-grain boundary  initial atomic arrangement  annihilation under strain

摘要:

[目的]研究初始原子对亚晶界湮没机制的影响。[方法]采用晶体相场模型模拟亚晶界结构在应力作用下的湮没过程,并从位错运动和能量变化角度对湮没过程进行分析,同时讨论初始原子在两晶粒交界处的对齐程度对其后亚晶界湮没的影响。[结果]研究表明,初始晶界原子排列错位1/4晶格常数时,首先位错在晶界处攀移,然后位错同时分离成两个,一个分离出的位错停留于原位,另一个则进入亚晶内部进行攀移和滑移直至相遇湮没,之后原来停留于原位的位错在攀移一段时间后也进入亚晶内部进行攀移和滑移,最终相遇湮没,形成单晶。而初始晶界原子排列错位1/2晶格常数时,湮没过程与初始晶界原子排列错位1/4晶格常数时的情况存在很大的差异。[结论]亚晶界湮没过程中,位错直接进入亚晶内部进行攀移和滑移,位错间发生复杂的相互作用,最终位错全部湮没,形成单晶。同时体系能量将随应力的增加而波动下降,形成4个明显的峰谷。

Abstract:

[Objective] The aim of this study is researching the influence of initial atomic arrangement to sub-grain boundary annihilation.[Methods] The phase field crystal model is employed to simulate the annihilation process of sub-grain boundary (SGB) under strain.We have analyzed the process from two aspects of dislocation movement and system energy, then discussed the influence of initial atomic arrangement on the subgrain annihilation.[Results] The simulation result show that, as the lattice misfit is a/4 (a:The distance between atoms), dislocations firstly climb along the SGB under strain, then all dislocations break up into two new dislocations.One of the two dislocations climb and glide into the grain.For a while, the dislocation crosses the grain until it is annihilated with another dislocation moving along opposite direction.At this moment, the other continues to move in the style of climbing.When getting enough energy, they climb and glide into the grain, too.Finally, they are annihilated with another dislocation and the two grain systems with SGB become one grain system.As the lattice misfit is a/2, the annihilation process changes largely compared with that of lattice misfit being a/4.[Conclusion] Although all dislocations climb and glide into the grain at the beginning of the simulation, a complex interaction appear during the process, finally all dislocation are annihilated and the two grain systems with SGB become one grain system.The system energy of the process decreases with strain increasing, and 4 peaks and valleys appear during this process.