Role of second-phase particles in the microstructural evolution and mechanical properties of extruded Mg-Gd-Y-Ag-Zr alloys

Abstract

The role of coarse second-phase particles in the microstructural evolution and mechanical properties of as-extruded Mg-Gd-Y-Ag-Zr alloys was investigated. Results show that the volume fraction of coarse β particles was enhanced by the addition of Ag (0.5 and 1.0) (wt.%) in the Mg-10.5 Gd-5 Y-0.5 Zr (wt.%) alloy. These particles have a face-centered cubic structure phase. In addition to Gd and Y, Ag is also partitioned into particles in the Ag-containing alloys. β particles can promote the dynamic recrystallization via particle-simulated nucleation and effectively suppress grain growth by pinning effects, which are responsible for the grain refinement. With the increase of volume fraction of β particles, the texture and dislocation features have not been changed. Since the coarse β particles can greatly lead to the reduction of grain size, the grain boundary strengthening in Ag-containing alloys with high volume fraction of particles contributes to the significantly improvement of the tensile yield strength. The coupled effect of the increase in the coarse β particle fraction and the reduction in grain size causes a slight decrease in elongation for the Ag-containing alloy.