Deformation Mechanism Maps for Sub-Micron Sized Aluminum

Abstract

Plastic deformation of sub-μm sized metals is strongly influenced by factors absent in their bulk counterparts, including surface diffusion assisted softening and mechanical/thermal annealing-induced hardening. The test temperature and sample size therefore strongly affect the mechanical behavior, necessitating the construction of new deformation mechanism maps (DMM). Here, based on results from in situ quantitative compression tests on micro-pillars at various sizes and temperature ranges, we have constructed the DMM for single-crystalline sub-micron-scale aluminum. The DMM clearly delineates three regions of elasticity, diffusive plasticity, and displacive plasticity. In the size-stress DMM at a fixed temperature, a strongest size with maximized yield strength is found at the triple junction of the three regions. In the diffusive plasticity region, deformation is localized within the top pillar volume demarcated by a moving front interface, which is impenetrable for impinging dislocations under a critical stress of ~1 GPa.

Keywords: Deformation mechanism maps, Nanomechanics, In situ TEM, Size effect, Strength