Grain refinement of pure magnesium using rolled Zirmax® master alloy (MG-33.3ZR)

Owing to the limited solubility of zirconium in molten magnesium, almost all of the zirconium contained in the Zirmax® master alloy (Mg-33.3Zr) is present in the form of nearly pure zirconium particles. Of them, zirconium particle clusters and individual zirconium particles greater than 5 ��m in dimension account for approximately 70% of the area of all zirconium particles observed in the microstructure. Rolling a Zirmax® master alloy ingot can allow some zirconium particle clusters to fragment. Comparisons were made of the grain-refining ability between as-received Zirmax® and rolled Zirmax® master alloys by adding both forms of master alloy to pure magnesium under the same conditions. It was found that the use of rolled Zirmax® delivered higher total and soluble zirconium contents, and therefore better grain refinement in the final alloy than did the use of as-received Zirmax®. The improved performance of rolled Zirmax® master alloy was primarily attributed to less intense zirconium particle settling.<br>