First-Principles Study of Chemical and Topological Short-Range Orders in the Mg–Si Liquid Alloys

Dan Liu,Tingkun Gu,Xunming Zhu,Junpeng Duan,Aimin Wang,Jingyu Qin

doi:10.3390/met6040078

Dan Liu, Tingkun Gu + Show 4 more

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https://doi.org/10.3390/met6040078

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Journal: Metals	Publication Date: Mar 30, 2016
Citations: 22	License type: CC BY 4.0

Affiliation: Shandong University, Weihai Science and Technology Bureau

Abstract

The structures of a series of Mg–Si liquid alloys were investigated by means of ab initio molecular dynamic simulation. The pair distribution function analysis manifests a tendency of aggregating for the Si–Si pairs in the Mg90Si10 liquid alloy. Chemical short-range orders are observed around Si atoms between unlike atoms, and the maximum is observed for the eutectic Mg47Si53 alloy. Furthermore, the topological environment changed abruptly near the eutectic Mg47Si53 alloy according to Voronoi polyhedra analysis. The variation of diffusion coefficients of Mg and Si suggests that the dynamical properties of Mg–Si liquid alloys are more sensitive to temperature than to compositions.

Highlights

Mg alloys have exhibited great potential in the automotive and aerospace industries owing to their unique mechanical properties such as low density, high hardness, high specific strength, good vibration performance, etc
The results indicate that the chemical short-range order (CSRO) mainly exist around Si atoms in the form of Si–Mg pairs, and the strongest CSRO arises in the eutectic alloy, which is different from the previous results of Mg–Cu [10] but consistent with those of the Mg–Zn liquid alloys [18]
The structures of liquid Mg–Si alloys were investigated by means of ab initio molecular dynamic (MD) simulation

Summary

Introduction

Mg alloys have exhibited great potential in the automotive and aerospace industries owing to their unique mechanical properties such as low density, high hardness, high specific strength, good vibration performance, etc. The Mg–Si particles mainly exist in Mg–Al (Zn)–Si alloys in the form of Mg2 Si for reinforcement. The high melting point of Mg2 Si (1085 ̋ C) improves the performance of Mg alloys at high temperature. 1.16 atom % Si, which improves the die-cast performance of Mg alloys. The strengthening mechanisms of Mg–Si alloys had been investigated in rapidly solidified Mg–11Si–4Al and Mg–13Si–4Al alloy ribbons [3]. The strength decreases rapidly at 473 K due to diffusion when the Mg2 Si particles are smaller than 1 μm. The microstructures and solidification process of an ingot metallurgy hypereutectic Mg–8 wt % Si alloy was analyzed in experiments by means of electron probe microanalysis (EPMA) [4]

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