α-Fe中氦泡阻碍位错移动硬化的分子动力学研究
Molecular dynamics study of hardening induced by helium bubbles impeding edge dislocation motion in α-Fe

基于周期性位错阵列模型，利用分子动力学方法，研究了α-Fe中1/2a0<111>{110}刃位错与3 nm氦泡的相互作用导致硬化的过程，重点研究了不同温度下（300 K和623 K），氦空位比例对位错与3 nm氦泡作用机制影响的差异性。研究结果表明，当氦空位比例在0~1之间变化时，氦空位比例的变化对临界剪切应力的影响微弱，当氦空位比例在1~1.5之间变化时，氦泡内氦原子的数量的增加，临界剪切应力随之降低。氦空位比例升高至1.75时，高温623 K与室温相比，临界剪切应力反常升高，原因是高温引起的位错与氦泡的排斥机制：氦泡严重超压，与位错接触瞬间，沿位错拉伸侧踢出自间隙原子团簇，被位错吸收后产生割阶；由于位错割阶与超压氦泡同为压应力场，割阶被氦泡强烈排斥反弹。
Abstract: The interaction between 1/2a0<111>{110} edge dislocation and 3.0 nm helium bubble with various Helium-to-vacancy ratios (He/V) and temperatures (300 K and 623 K) in α-Fe were studied by using molecular dynamics based on the periodic arrays of dislocations model. The results show that the release stress of dislocation weakly depends on He/V ratios ranging from 0 to 1; when He/V ratio varies from 1.0 to 1.5, increasing the number of helium atoms in the helium bubble has positive effects on the climbing of dislocation; for the helium bubble (He/V = 1.75), when the temperature rises from 300 K to 623 K, the increase of the bubble pressure caused by the increase of temperature changes the interaction mechanism and caused the increase of CRSS. A repel mechanism of dislocation and helium bubble interaction is proposed to elucidate the effect of temperature. When the helium bubble is heavily over-pressured, the edge dislocations absorbs the interstitials and clusters which are punched out from the bubble, thus forms a superjog and is repelled from the bubble since there both are compressive stress fields around the dislocation jog and over-pressured helium bubble.