Phase-field study of the solutes-interstitial loops interaction in Fe-Cr alloys

Interstitial dislocation loops are typically formed in post-irradiated materials, such as Ferritic-Martensitic Fe-Cr alloys. These loops demonstrate solute segregation along their perimeters, effectively pinning the dislocation climb and resulting in high-density, small-sized loops that cause embrittlement. Phase-field simulations were conducted to investigate the behavior of Cr segregation in the stress field of a<100> type and various a/2<111> type interstitial dislocation loops in post-irradiated Fe-10Cr alloy. The study considers the long-range elastic interaction of solute Cr within the stress field of dislocation loops in a cubic elastic anisotropic material. The findings reveal a nonuniform stress distribution along the loop's perimeter depending on the included angle of habit plane normal n and Burgers vector b; the nonuniformity becomes more pronounced as the Burgers vector deviates from the normal direction. Furthermore, this nonuniform stress induces Cr segregation within regions experiencing tensile stress and Cr depletion in compression stress regions. Furthermore, a comprehensive analytical solution has been developed to characterize the diverse stress fields and solute segregation induced by interstitial dislocation loops with varying habit planes and Burgers vectors. The proposed analytical model effectively depicts the stress distribution of various dislocation loops, resulting in a Cr segregation profile that closely approximates those obtained through phase-field simulations. A thorough analysis of solute segregation mechanisms also elucidates the dispersed fine-scale nature and high density observed in experimental investigations of dislocation loops.