Evolution of the microstructure and fracture characteristics of a Mg-Nd-Zn-Zr-Mn alloy through heat treatment and extrusion

Abstract

Appropriate mechanical properties are essential for the use of biodegradable Mg-based alloys as structurally supporting materials. However, research studies on the evolution of the tensile fracture pathways and fracture characteristics of as-cast and as-extruded Mg-based alloys are limited. In this paper, the microstructures, tensile properties, fracture pathways and fracture characteristics of the as-cast, heat treated and hot-extruded Mg-1.59Nd-2.91Zn-0.05Zr-0.35Mn (NZKM) alloys were systematically investigated. The results indicated that the hot-extruded NZKM alloy exhibits good mechanical properties with a yield strength and an elongation reaching 212 MPa and 30.7%, respectively. These excellent properties were attributed to its special multiscale microstructure consisting of an α-Mg matrix (2–10 μm), eutectic compound β-Mg4Zn7 (2–10 μm) together with a high density of dispersed nanoscale precipitates, that provide solid solution strengthening, grain boundary strengthening and precipitation strengthening effects. The fracture patterns changed with the evolution of the microstructures. Intergranular and transgranular cleavage fractures were changed to ductile fractures by hot extrusion.