Effect of Y addition on microstructure and mechanical properties of extruded Mg-Mn alloys

Two homogenized as-cast magnesium (Mg)-1 wt% manganese (Mn) alloys containing 1.0 and 4.0 wt% alloying yttrium (Y) were processed at an extrusion ratio of 17:1 at 400 degrees C using a ram speed of 0.3 mm/s. The effect of yttrium additions on the microstructure and mechanical properties of the extruded alloy was analyzed and compared. The average grain size of the extruded Mg-1Mn-4Y (MW14) alloy was much smaller than that of the extruded Mg-1Mn-1Y (MW11) alloy. In addition, the tensile strength of the MW14 alloy was higher than that of the MW11 alloy at the investigated temperature ranging form RT to 200 degrees C, although the former exhibited a lower elongation to failure. The fracture surface of the MW14 alloy exhibited the cleavage fracture mode. Conversely, a dimple was observed in the MW11 alloy which the significant differences in performance between the two alloys are attributed to their Y contents.