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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 17    Special 1    November 2007

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Different grain refinement mechanisms of minor zirconium and
cerium in magnesium alloys
YU Kun(余  琨), LI Wen-xian(黎文献), WANG Ri-chu(王日初), ZHANG Shi-Jun(张世军)

School of Materials Science and Engineering, Central South University, Changsha 410083, China

Abstract:Zirconium and rare earth element cerium were added in magnesium and magnesium alloys to study their different grain refinement mechanisms. The results show that zirconium has an obvious refinement effect on the cast grain of magnesium and its alloys without the alloy element Al because the crystal structure of zirconium is the same as magnesium matrix, and the lattice parameters are close to magnesium. Zirconium can decrease the grain size of magnesium from 150 to 20 μm. The rare earth cerium also has a grain refinement effect on Mg and Mg-Al alloy. The cerium atoms tend to remain in the liquid rather than solidify with the solvent atoms magnesium at the solid-liquid interface. The liquid constitutional undercooling can provide a heterogeneous crystal nucleation. The grain is refined from 200 μm to 40−80 μm. These two elements have different grain refinement mechanism on Mg alloy. The mechanism of zirconium is that it acts as the nuclei of α-Mg. But the mechanism of cerium is that it increases the liquid constitutional undercooling that can provide a heterogeneous crystal nucleation for the alloy.

 

Key words: Mg alloy; grain refinement; zirconium; cerium

ISSN 1672-7029
CN 43-1423/U

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