Strain-Rate Sensitivity, Tension-Compression Asymmetry, r-Ratio, Twinning, and Texture Evolution of a Rolled Magnesium Alloy Mg-1.3Zn-0.4Ca-0.4Mn

Abstract

In this work, the deformation response, texture evolution, and twinning development of a magnesium (Mg) alloy, Mg-1.3Zn-0.4Ca-0.4Mn, for biocompatible applications are investigated. Further, the alloy’s formability, by examining the instantaneous r-ratio and strain-rate sensitivity (SRS) as a function of strain and loading direction, is investigated. It is found that after rolling and peak aging, the alloy has a rolled texture of moderate intensity with the basal planes contained in the rolling plane and with a bimodal, fine-grained microstructure. The alloy shows both high room-temperature tensile strength (300 MPa) and ductility (25 pct) in the rolling direction (RD) and, remarkably, r-ratios saturating close to unity in all three in-plane testing directions. It is also found that the SRS is relatively high and uniform, with averages ranging from 0.015 to 0.025, depending on the in-plane testing directions. These are outstanding properties compared to pure Mg and most of its biocompatible alloys. Typical of Mg alloys, this alloy has a propensity for twinning by multiple twin modes, which leads to rapid texture evolution, anisotropy, and tension-compression (T-C) asymmetry in yield stress, with compression having the weaker response. These mechanical characteristics along with their microstructural origins are presented and discussed in this article.