Microstructure and Mechanical Property of Mg-13Gd-0.2Ni Alloy Processed by Extrusion and Aging

Abstract

In this work, a good combination of strength and ductility is achieved in a Mg-13Gd-0.2Ni alloy by conventional extrusion and following aging treatment. The aged Mg-13Gd-0.2Ni alloy exhibits a yield strength (YS) of 363 MPa, an ultimate tensile strength (UTS) of 433 MPa, and an elongation of 11.9%. The aged Mg-13Gd-0.2Ni alloy contains a microstructure with a 95% proportion of dynamically recrystallized (DRXed) grains with a micron size, weak texture, and a high number density of prismatic β′ precipitates within grains. The bulk compounds enriched with Ni element which are mainly formed during casting and stable in the extruded and aged samples. Few dynamic compounds are formed during extrusion, and a high density of prismatic β′ precipitates are formed during aging. The high density of prismatic β′ precipitates results in a significant increase in the strength of the Mg-13Gd-0.2Ni alloy, and the YS and UTS are increased by 153 and 136 MPa, respectively. The high proportion of DRXed grains with a weak texture contributes mainly to the high ductility and the fine compounds with a low density at grain boundaries formed during aging have no significant adverse effect on ductility of the aged Mg-13Gd-0.2Ni alloy. These findings for the novel Mg-Gd-Ni alloy can provide guidance for the design of wrought Mg alloys with superior mechanical properties.