Microstructure and texture evolution with Sm addition in extruded Mg–Gd–Sm–Zr alloy

Abstract

We prepared as-extruded Mg-10Gd-xSm (x = 1, 3, 5)-0.5Zr alloys by indirect extrusion, and the microstructure, texture and mechanical properties of as-extruded Mg-10Gd-xSm-0.5Zr alloys were investigated. The results indicate that the microstructure, texture and strength of as-extruded Mg-10Gd-xSm-0.5Zr alloys take a great variation with Sm addition. Dynamic recrystallized grain size is decreased with increasing Sm content, and the average grain size rapidly reduced to 1.4 μm in as-extruded Mg-10Gd-5Sm-0.5Zr alloys due to abundant Mg5(Gd, Sm) and Mg41(Gd, Sm)5 precipitates and their pinning effect on grain boundaries. With an increasing Sm content, the texture has a significant variation. The fiber texture with 〈10-10〉 axis of Mg matrix parallel to extrusion direction (ED) in as-extruded Mg-10Gd-1Sm-0.5Zr alloy transformed into an abnormal texture with 〈0001〉 axis of Mg matrix parallel to ED in as-extruded Mg-10Gd-3Sm-0.5Zr alloy. The tensile yield strength and Brinell hardness gradually increase with Sm addition due to soild solution strengthening, refined grain boundaries strength and numerous precipitates strengthening. However, the as-extruded Mg-10Gd-5Sm-0.5Zr alloy exhibits the poor ductility due to stress concentration caused by abundant precipitates.