Influence of stacking fault energy and slip planarity on dislocation/grain boundary interactions in FCC metals

The influence of stacking fault energy (SFE) and grain boundary geometric compatibility on the interactions between dislocations and grain boundaries in Ni, austenitic 316L stainless steel, and Al were studied using in situ high-resolution electron backscattered diffraction (HR-EBSD) and electron channeling contrast imaging (ECCI). The results show that the evolution of dislocation pileups is highly dependent on slip planarity, with localized stress fields forming in relatively low SFE materials such as Ni and 316L, while dislocation/grain boundary interactions in high SFE Al lead to the deformation of grain boundary structures and the early formation of sub-grain boundaries. Stress relaxation induced by dislocation/grain boundary interactions was only observed in Ni, while dislocations remained largely confined to discrete slip systems in 316L. The magnitude of the localized stress fields was found to be inversely correlated to the geometrical compatibility in the low SFE materials, but had no relation to the magnitude of stress concentration in Al. At increasing strain levels, the magnitude of local stress in the boundary vicinity was found to increase at the highest rate in 316L.