Thermo-kinetic characteristics on stabilizing hetero-phase interface of metal matrix composites by crystal plasticity finite element method

Abstract

Using dislocation-based constitutive modeling in three-dimension crystal plasticity finite element (3D CPFE) simulations, co-deformation and instability of hetero-phase interface in different material systems were herein studied for polycrystalline metal matrix composites (MMCs). Local stress and strain fields in two types of 3layer MMCs such as fcc/fcc Cu–Ag and fcc/bcc Cu–Nb have been predicted under simple compressive deformations. Accordingly, more severe strain-induced interface instability can be observed in the fcc/bcc systems than in the fcc/fcc systems upon refining to metallic nanolayered composites (MNCs). By detailed analysis of stress and strain localization, it has been demonstrated that the interface instability is always accompanied by high-stress concentration, i.e., thermodynamic characteristics, or high strain prevention i.e., kinetic characteristics, at the hetero-phase interface. It then follows that the thermodynamic driving force ΔG and the kinetic energy barrier Q during dislocation and shear banding can be adopted to classify the deformation modes, following the so-called thermo-kinetic correlation. Then by inserting a high density of high-energy interfaces into the Cu-Nb composites, such thermo-kinetic integration at the hetero-phase interface allows a successful establishment of MMCs with the high ΔG-high Q deformation mode, which ensures high hardening and uniform strain distribution, thus efficiently suppressing the shear band, stabilizing the hetero-phase interface, and obtaining an exceptional combination in strength and ductility. Such hetero-phase interface chosen by a couple of thermodynamics and kinetics can be defined as breaking the thermo-kinetic correlation and has been proposed for artificially designing MNCs.