High-Resolution Mapping of the Strain Heterogeneity in Heterogeneous and Homogeneous Structured Mg-13gd Alloy

Abstract

The hetero-deformation induced (HDI) stress can effectively promote extra strengthening and strain hardening behavior, which originates from the heterogenous deformation between soft and hard domains. How to quantitatively evaluate the strain heterogeneity at the micron and sub-micron scales remains a great challenge during deformation incompatibility. In this study, the strain evolution at grain level of heterogeneous (HES) and homogeneous-structured (HOS) Mg-13Gd (wt%) alloy was characterized by high-resolution digital image correlation. Both HES and HOS samples show strain heterogeneity related to the physical slip bands inside grains, and the magnitude of local deformation in grain level is much higher than the macroscopic strain, especially at grain boundaries. The HOS sample can also generate HDI stress due to the remarkable difference in Schmid factor and lower geometrical compatibility factor between adjacent grains. The formation of dispersed strain bands in the coarse grains with hard orientation of the HES sample contributes to strain delocalization behavior and the improvement of strain hardening capacity. These results provide us with a new insight for heterostructured design of Mg alloys on a more microscopic scale.

Keywords: Mg-Gd alloy, High-resolution digital image correlation, Microscopic strain, Heterogeneous deformation, HDI stress