A SYSTEMATIC STUDY OF THE GRAIN REFINEMENT OF MAGNESIUM BY ZIRCONIUM

Abstract A Design of Experiments (DOE) approach was used to conduct a systematic study of the grain refinement of magnesium by zirconium. Variables included the amount of zirconium, the pouring temperature, and the settling time prior to casting. Samples were poured into a special “hockey puck” mold designed to reproduce the conditions in permanent mold casting. Optical microscopy and quantitative image analysis were used to measure the resultant average grain size. The results of this study show thatzirconium additions less than that needed for the peritectic reaction can produce grain refinement, providing an opportunity to engineer a more efficient zirconium-based grain refiner. Introduction Zirconium acts as a powerful grain refiner in magnesium alloys which do not contain elements such as aluminum, manganese and silicon, since zirconium forms stable compounds with these elements. Emley [1] reported that the grain refinement of magnesium by zirconium occurs through a peritectic reactionclose to 0.6 wt% zirconium at 654