Effect of Al-5Ti-1B and Y on Casting Mg-5Al-5Si Alloy

Abstract

Purposes In order to refine the coarse Mg2Si phase in Mg-Al-Si alloy, the Mg-5Al-5Si alloys are modified by adding Al-5Ti-1B and rare earth Y. Methods The Mg-Al-Si alloys with different compositions were prepared by smelting. Various means were used to analyze the composition, microstructure, and mechanical properties of alloys before and after modification, and discuss modification mechanism. Findings The results show that, adding Al-5Ti-1B to the Mg-5Al-5Si alloy transforms the morphology of the primary phase from coarse bulk to fine dendritic or polygon, the number of eutectic phases decreases with the increase of Al-5Ti-1B, while the hardness of the alloys increases significantly, which is attributed to TiB2 phase acting as the heterogeneous nucleation sites for primary Mg2Si phase. On the foundation of adding 1.0% Al-5Ti-1B, rare earth Y can further modify the size and morphology of Mg2Si. When 1.0% Al-5Ti-1B and 1.0% Y are added together, the average size of the primary Mg2Si is decreased to 10.2 μm, the morphology of primary Mg2Si is fine polygonal, and the alloy has the best tensile mechanical properties, with the modification mechanism of rare earth Y mainly adsorption and poisoning.

Keywords

• mg-al-si alloy
• mg2si
• microstructure
• mechanical properties