Utilization of Microalloying with Rare Earth Elements and Hot Extrusion for Remarkable Grain Refinement and Enhancement of Mechanical Properties of as-Cast Magnesium Alloy

The effects of micro-addition by rare earth (RE) elements (via cerium-based mischmetal) and hot deformation (via extrusion process) on the microstructure and mechanical properties of Mg-۰.۵Zn-۰.۵Zr alloy were studied. Optical microscopy, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and tensile testing were used for characterization of alloys in the as-cast and wrought conditions. It was found that the addition of ۰.۵ wt% RE combined with the hot extrusion process could remarkably refine the grain size from ۱۳۲۰ µm for the as-cast Mg-۰.۵Zn-۰.۵Zr alloy to the recrystallized grain size of ۱.۳ µm for the extruded Mg-۰.۵Zn-۰.۵Zr-۰.۵RE alloy. Compared to the as-cast counterparts, the ultimate tensile strength (UTS) and total elongation to failure were significantly enhanced by the extrusion process. Quantitatively, the UTS of ~ ۳۰۰ MPa with the total elongation of ~ ۱۸% was obtained for the extruded Mg-۰.۵Zn-۰.۵Zr-۰.۵RE alloy, which reveals the favorable effects of the ultra grain refinement on the enhancement of the mechanical properties of magnesium alloys.

کلیدواژه ها:

Mg alloys ، Ultrafine grained microstructure ، Recrystallization ، Mechanical Properties