Molecular dynamics study of hardening induced by helium bubbles impeding edge dislocation motion in α-Fe

The interaction between 1/2 a0 < 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 super jog and is repelled from the bubble since there both are compressive stress fields around the dislocation jog and over-pressured helium bubble. (authors)