Dynamics of Ga penetration in textured Al polycrystal revealed through multimodal three-dimensional analysis

Abstract

We investigate in situ the penetration of liquid Ga in a polycrystalline Al rod at a temperature of 31.9°C. Our study is made possible with the aid of a novel, multimodal laboratory-based X-ray imaging platform, which enables us to characterize the three-dimensional (3D) grain structure, Ga wetting behavior, and correlations of the two. Our sample shows a strong texture along [001] and a higher fraction of low-angle grain boundaries (LAGBs) compared to a random distribution, signifying a poor connectivity of high-angle grain boundaries (HAGBs). We detect channels of Ga along HAGBs after 1-hour of exposure to the liquid metal, but such channels gradually disappear upon prolonged annealing. We interpret this phenomenon in the lens of geometric percolation theory and diffusion theory, which point to the synergistic effects of a limited HAGB connectivity and the enhanced Ga leakage from HAGBs into the bulk through dislocation-pipe diffusion. This work provides detailed insight into the influences of texture and grain boundary connectivity on the dynamics of liquid metal embrittlement, with relevance to grain boundary engineering of embrittlement-resistant materials with high stacking fault energy.