Chen Liang, Yang Wenpeng, Cui Hongbao, Wang Ying, Xu Zhichao
School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China.
School of Physics and Electronic Information Engineering, Henan Polytechnic University, Jiaozuo 454000, China.
Materials (Basel). 2024 Apr 15;17(8):1811. doi: 10.3390/ma17081811.
Pb plays an important role in determining the morphologies and mechanical properties of the MgSi phase in Mg-2.5Si-Pb alloys. As the amount of Pb increases from 0.4 wt.% to 1 wt.%, the primary MgSi 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 MgSi {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 MgSi 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 MgSi phase reaches a maximum of 0.4 wt.%, and the hardness of the primary MgSi 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 MgSi phase.
