In-situ study of damage mechanisms in Mg-6Li dual-phase alloy

Interfaces play a crucial role in influencing the mechanical properties of Mg alloys. For Mg-Li dual-phase alloy, the type of interfaces is complex, which includes both grain boundary and phase boundary, and the influence of such interfaces on the damage nucleation is yet to be explored. In this paper, in-situ scanning electron microscopy (SEM) based measurements were carried out to investigate the meso-scale damage nucleation mechanisms of the Mg-6Li dual-phase alloy. Results show that 94.8% of cracks are nucleated at the alpha-Mg grain boundary in the post-uniform elongation stage, while 5.2% are at phase boundary and almost no crack at the fi-Li grain boundary. The initiation of alpha-Mg grain boundary cracks is attributed to strain incompatibility, which induces micro-strain localization, and then causes grain boundary sliding (GBS) and crack nucleation. Deformation compatibility analysis reveals that the geometric compatibility factor ( M k ) can be used to predict the nucleation of alpha-Mg grain boundary crack. When M k is lower than 0.075, alpha-Mg grain boundary cracks tend to form. Few cracks are generated at the phase boundary is due to the mild strain partitioning between alpha-Mg phase and fi-Li phase and may also be partly attributed to multiple slip systems in body-centered cubic (BCC)-structured fi-Li phase, which can accommodate well with the deformation of adjacent alpha-Mg phase.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.