Effect of adding Sc and Zr on grain refinement and ductility of AZ31 magnesium alloy

Grain size in the microstructure dominates the ductility of Mg-Al-Zn magnesium alloy. The strengthening and grain refinement of aluminum alloys by Sc have been extensively studied recently. As is well known, Zr refines grains in magnesium alloys. This work presents a novel approach for enhancing the grain refinement of magnesium alloy by adding Sc and Zr. Rolling and equal channel angular extrusion (ECAE) are performed to refine the grains. Experimental results indicate that adding 0.03-0.06 wt% of Sc and 0.05-0.15 wt% of Zr reduced the mean grain size of AZ31 to 2.47 mu m. The ductility of AZ31-0.15Zr-0.06Sc modified alloy can be increased to 324% at 300 degrees C. Results of this study demonstrate that both Sc and Zr are important in controlling grain size and ductility. (C) 2007 Elsevier B.V. All rights reserved.