α-Fe〈110〉倾斜晶界上He扩散机理的分子动力学研究

Molecular Dynamics Simulation of Interstitial He Diffusion on 〈110〉 Tilt Grain Boundaries in α-Iron

采用分子动力学结合Juslin等最近建立的Fe-He原子间相互作用势函数研究了300～1 200K范围内α-Fe中具有不同位相差(26°～140°)的〈110〉倾斜晶界的热稳定性、He在各晶界上的结合能及其晶界扩散模式,计算了间隙He在晶界上的扩散系数。研究结果表明:1 200K以下各晶界均具有良好的热稳定性;He与晶界具有很强的结合能;间隙He在不同类型晶界上具有不同的扩散机制,间隙He在晶界上的扩散模式取决于晶界的原子结构及晶界上自由空间的大小。

The migration of helium on different 〈110〉 high angle tilt grain boundaries（GBs） with misorientation angle varied from 26° to 140° in α-Fe was studied using atomistic simulations applying the recently developed Fe-He potentials.Systematic molecular static and molecular dynamics simulations were performed to calculate the binding energy between He and GBs,to estimate the diffusion coefficient and characterize migration mechanisms.The thermal stability of GBs was studied as well.The simulations were performed in the temperature range 300-1 200 K.The results show that all the GBs studied in this work are stable up to 1 200 K;both interstitial and substitutional helium are strongly bound to tilt GBs and the particular binding energy strongly correlates with the excess volume.The obtained results demonstrate that the migration mechanism and diffusivity of interstitial He are extremely sensitive to variations in atomic structure of the GBs.