The effect of separate solute additions of Al, Zr, Sr, Si, and Ca on grain
size of Mg has been investigated. Increasing the Al content in hypoeutectic
Mg-Al alloys resulted in a continuous reduction in grain size up to 5 wt p
et Al, reaching a relatively constant grain size for higher Al contents (ab
ove 5 wt pet). The effect of Sr additions was investigated in both low- and
high-Al content magnesium alloys, and it was found that Sr had a significa
nt grain refining effect in low-Al containing alloys but a negligible effec
t on grain size in Mg-9Al. Additions of Zr, Si, and Ca to pure magnesium re
sulted in efficient grain refinement. The grain refinement is mainly caused
by their growth restriction effects, i.e., constitutional undercooling, du
ring solidification, but the effect of nucleant particles, either introduce
d with the alloying additions or as secondary phases formed as a result of
these additions, may enhance the grain refinement. A brief review of grain
refinement of magnesium alloys is included in this article to provide an up
date on research in this field.