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Indentation Simulation of Single Crystal Magnesium using Crystal Plasticity and Molecular Dynamics

Shailendra Joshi (National University of Singapore), Balaji Selvarajou (NUS), Ramin Aghababaei (NUS)

From Atomistics to Reality: Spanning Scales in Simulations and Experiments Symposium B

Wed 1:30 - 2:50

CIT 227

Magnesium is an excellent structural material for a wide gamut of applications, ranging from fuel-intensive automotive components to biocompatible implants. However, it is imperative to understand the interactions between myriad deformation mechanisms in magnesium under complex loading for successful design of such applications. Recent indentation experiments on single crystal magnesium exhibit several salient characteristics that are important from a modeling perspective. They provide valuable information that point toward the intriguing slip-twin nexus and their resulting hardening responses. These are deemed crucial for developing robust coarse-grained modeling approaches that have predictive abilities under complex stress states. With this motivation, we investigate the orientation-dependent indentation response of magnesium single crystals using our recently developed finite element based crystal plasticity (CP) framework [1]. Systematic analysis of the contributions from the basal and non-basal slip modes and the effects of twinning-induced lattice reorientation are performed and correlated with the experimental observations. While experiments provide the post-indentation forensic information, the CP simulations enable interpreting its evolution during the indentation process. It also provides relative importance of the slip modes and orientation dependent spatial evolution of the twin activities. The orientation-dependent activation of particular slip and twin modes profoundly influence the nature of material pile-up around the indenter. Further, we investigate the same orientations using molecular dynamics simulations, which provide a fundamental insight into the atomistic processes governing the evolution of the slip and twin activities. The analyses at these two modeling length-scales together provide important information toward understanding the response of magnesium under complex stress states. [1] Zhang, J and Joshi, SP (2012). JMPS, 60; 945-972.