Tailoring the Microstructure and Mechanical Property of AZ80 Alloys by Multiple Twinning and Aging Precipitation

Abstract

AZ80 alloy is a relatively inexpensive age‐hardenable Mg alloy. To improve its precipitation strengthening effect, the discontinuous precipitates generally nucleating from grain boundaries should be reduced. In this study, the authors applied strain‐path change compression on a wrought AZ80 alloy to generate multiple {10‐12} twins and then the pre‐deformed alloy is subjected to aging at 180 °C for different period. The effects of the pre‐generated twins on precipitation behavior and hence the mechanical properties are investigated. It is found that multiple {10‐12} twins are formed in the AZ80 alloy after two paths of compressions along the transverse and rolling directions. Consequently, continuous precipitation is largely promoted during the subsequent aging process. Moreover, the continuous precipitates preferred to form inside the {10‐12} twin lamellae. Discontinuous precipitation is almost inhibited during aging at 180 °C for 4–96 h in the sample containing many multiple twins. Compare to the directly peak‐aged sample, the pre‐twinned and subsequently peak‐aged alloys generally exhibit greatly superior mechanical properties. The yield strength, ultimate strength, and elongation for tension along RD are 242 MPa, 476 MPa, and 19.4%, respectively. These excellent properties are attributed to the combined effects of grain refinement, texture weakening, and enhanced precipitate strengthening.