The formation of the Zr-containing phases during the solidification of Mg-Zn-Zr alloy is simulated, the structure of the Zr-containing compounds and the solid solution amount of Zr in α-Mg solid solution as well as the grain size of the as-cast alloy are measured. Based on this, the existing form of Zr element in Mg-Zn-Zr alloy and its action mechanism of grain refinement are discussed. The results show that either α-Zr or α-Mg solid solution precipitates first from melt of Mg-Zn-Zr alloy at the beginning of solidification due to the different Zr content, then some Zn-Zr phases with different Zn/Zr atomic ratios form in the alloy melt during solidification. The Zr element in Mg-Zn-Zr alloy mainly exists in the form of compounds, its solid solution amount in α-Mg is not large and is inhibited by Zn element. The Zr in Mg-Zn-Zr alloy has the effect to refine grain, the reason is that the α-Zr phase and α-Mg formed by peritectic reaction or α-Mg formed from Zr atomic clusters can be used as the nucleus of subsequent α-Mg crystals. In addition, the Zr-containing compound formed during solidification can prevent the growth of grains, the enrichment of Zr in the crystallization front can also promote nucleation by component undercooling.

No abstract

No abstract

No abstract

No abstract