Effect of grain boundaries and rigid inclusions on plasticity in nickel bicrystals containing helium bubbles and radiation-induced self-interstitial atom clusters

Abstract

We use molecular dynamics to assess the effect of grain boundaries and rigid intergranular inclusions on plastic deformation in nickel (Ni) containing helium (He) bubbles and self-interstitial atom clusters. Our simulations show that plasticity in Ni bicrystals is relatively uniform, with no localized slip bands or nano-twins. We attribute this behavior to grain boundaries, which block dislocations and favor activation of new sources over persistent slip along a single plane. While there is no initiation of intergranular cracks, He bubbles at matrix/inclusion interfaces elongate along the tensile axis and migrate towards regions of high tension, potentially setting the conditions for formation of crack-like flaws via bubble coalescence. We discuss the implications of our work for understanding degradation of mechanical properties in Ni-base alloys in nuclear reactors.