Formation of helical dislocations mediated by interstitials in ion irradiated FeCrAl alloy

Abstract

Unraveling the interaction of the pre-existing dislocations with irradiation defects is crucial to understanding the microstructural evolution and the strength-ductility trade-off of iron-based alloys under service in an irradiation environment. In this work, the formation of helical dislocations was analyzed by combining an in-situ experiment of 400 keV Fe+ irradiated Fe-13.2Cr-5.6Al alloy at 823 K with molecular dynamics (MD) simulations. A mechanism that irradiation induced interstitial defects would mediate the pre-existing screw dislocation to produce the helical dislocations was revealed. The in-situ formation of helical dislocations and the absence of dislocation loop in the vicinity of helical dislocations were observed. The helical dislocations more likely form in the region with higher pre-existing screw dislocation density, but it will be suppressed by the dislocation loops nucleating near the screw dislocations.