Study on alloying element distribution and compound structure of AZ61 magnesium alloy with yttrium

Abstract

To investigate the microstructural changes in AZ61 magnesium alloy with rare-earth yttrium, alloys with different Y contents were prepared, and the alloying element distribution and compound structure were studied by microstructural analysis. The results show that the added Y in the alloy is mainly formed into Al2Y and the amount of solution in α-Mg is very small. Moreover, with increasing Y content, the quantity of Al2Y increases and the size of Al2Y becomes larger. Y can refine the α-Mg grains because of the undercooling of the composition and hindrance to the diffusion of elements caused by Y enrichment at the crystallization front. In addition to the formation of Al2Y, Al in the alloy mainly exists in the form of a solid solution and eutectic β-Mg17Al12. The solid solution of Al increases with increasing Y content in the alloy. The significant decrease in β-Mg17Al12 amount is due not only to the production of Al2Y, which consumes a part of the Al, but also to the increase in the amount of Al solid solution by the dissolution of Y. The solution amount of Zn in α-Mg is much lower than the average content of Zn in the alloy, mainly in β-Mg17Al12. Zn can replace Al in β-Mg17Al12, which results in β-Mg17Al12 lattice distortion and a larger lattice constant.