FTMP-Based Kink Deformation and Strengthening Mechanisms for Mille-Feuille Structures

Abstract

Kink-strengthening for mille-feuille structures has attracted many attentions in recent years. This study aims at identifying the kink formation/strengthening mechanisms via numerical reproductions of emerging kink-like morphologies based on FTMP (Field Theory of Multiscale Plasticity)-incorporated FE simulations, considering the Rank1 connection, where the incompatibility-based relevant underlying microscopic degrees of freedom for kinking are introduced. The targeted phenomena here include an experimentally-observed unique feature recently reported based on the combined ND–AE (neutron diffraction - acoustic emission) technique, i.e., scale-free-like energy release before (precursor) and during kink formations. This study uses a Mg single crystal model with alternatingly aligned soft and hard layers in parallel to the basal plane under c-axis plane-strain compression, where the soft/hard regions are controlled by the values of the hardening ratio. Also, we assume that the kink mode is only active, while the basal, prismatic and pyramidal slip and the twin systems are not operative associated with the layered structure. From the simulated results, we confirm kink-like morphologies and the attendant significant misorientation in the basal plane angles. Also, the simulated results are demonstrated to exhibit power-law type distributions in the strain energy fluctuation from the early stage of deformation even before the massive emergence of kink-like regions, which are analogous to the above-mentioned ND–AE observations.