Severe Brittleness in a Peak-Aged Mg-Gd-Sn Alloy Caused by Segregated Β Precipitates Along Grain Boundaries

Abstract

This work elucidates the mechanism of brittle fracture in coarse-grained Mg-Gd-Sn alloy after aging. The results indicate that the Mg-14Gd-0.2Sn alloy extruded at 320°C with a ratio of 28, exhibits a fully recrystallized microstructure with equiaxed grains of approximately 9.8 μm and a randomized texture. The elevated temperature extrusion process suppresses the formation of dynamic precipitates, resulting in a high elongation of 15.4%. However, after aging, the alloy exhibits a significant age-hardening response arising from the high number density of β′ nano precipitates within matrix but much poor ductility, experiencing severe intergranular fracture due to the precipitated β phase along grain boundaries.

Keywords: Coarse-grained, Aging, Intergranular fracture, Precipitate, Grain boundary