Grain boundary effects and void porosity evolution

Abstract

A multiple-slip dislocation-density based constitutive crystalline formulation that is coupled to a kinematic scheme that accounts for grain boundary (GB) interfacial interactions with dislocation densities, and an internal porosity formulation have been used to predict how void porosity is affected by GB interactions, such as dislocation-density pile-ups at GB interfaces, partial and total dislocation-density transmission from one grain to neighboring grains, and dislocation-density absorption within GBs. Void nucleation and growth is represented by a single scalar that is a function of total dislocation density, stress triaxiality, accumulated plastic strains, and temperature. The proposed methodology provides an understanding of how interactions at the GB interface scale affect overall macroscopic behavior due to the interrelated effects of GB orientations, the evolution of mobile and immobile dislocation densities, and porosity evolution, which occur at smaller physical scales. It is shown that the accumulation of pile-ups at GB interfaces and GB absorption at different GB regions are the triggering mechanisms that lead to porosity localization, and subsequently to void nucleation and growth.