Morphology and Properties of Mg2Si Phase Modified by Pb in As-Cast Mg-2.5Si- x Pb Alloys

Liang Chen; Wenpeng Yang; Hongbao Cui; Ying Wang; Zhichao Xu

doi:10.3390/ma17081811

Morphology and Properties of Mg₂Si Phase Modified by Pb in As-Cast Mg-2.5Si- x Pb Alloys

Materials (Basel). 2024 Apr 15;17(8):1811. doi: 10.3390/ma17081811.

Authors

Liang Chen^{1

2}, Wenpeng Yang^{1

3}, Hongbao Cui^{1

3}, Ying Wang^{1

3}, Zhichao Xu^{1

3}

Affiliations

¹ School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China.
² School of Physics and Electronic Information Engineering, Henan Polytechnic University, Jiaozuo 454000, China.
³ Henan International Joint Research Laboratory for High-Performance Light Metallic Materials and Numerical Simulations, Jiaozuo 454000, China.

Abstract

Pb plays an important role in determining the morphologies and mechanical properties of the Mg₂Si phase in Mg-2.5Si-xPb alloys. As the amount of Pb increases from 0.4 wt.% to 1 wt.%, the primary Mg₂Si phase is refined during solidification. Its morphologies transform from equiaxed-dendrite to polygonal and finally to roughly circular. The key reason for morphology evolution is the preferential adsorption of Pb atoms on Mg₂Si {100} surfaces to suppress the growth rate along the ⟨100⟩ directions, which is demonstrated by the adsorption model based on first principles. In addition, the hardness of the Mg₂Si phase decreases with the increasing solution content of Pb according to the results of the nanoindentation. With the addition of Pb at 1 wt.%, Pb content in the primary Mg₂Si phase reaches a maximum of 0.4 wt.%, and the hardness of the primary Mg₂Si phase reaches a minimum of 3.64 GPa. This reduction in hardness is attributed to the augmented ionic bond ratio resulting from the solution of Pb, which concurrently enhances the toughness of the Mg₂Si phase.

Keywords: Mg2(SixPb1−x) phases; Mg2Si; first-principles calculation; modification; morphology.

Abstract

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