Sr 变质 Mg2Si/Al-Cu-Si 复合材料的机理与 组织性能

Author of the article:LIU Dandan1,2, MENG Lina1 , SUN Zhan1

Author's Workplace：1. School of Materials and Electrical Engineering, Zhengzhou University of Industrial Technology, Zhengzhou 451100, China; 2. School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China

Key Words：Mg2Si/Al-3%Cu-3%Si composite; metamorphic mechanism; first-principles calculation; Mg2Si crystal

Abstract：In this paper, x%Mg2Si/Al-3%Cu-3%Si (x=15, 20, 25 and 30, %) composites were prepared by smelting method. Firstly, the as-cast microstructures of the prepared materials were analyzed, and the results showed that the microstructures of the as-cast composites were composed of polygonal block Mg2Si primary, rod-shaped Mg2Si eutectic, netting θ-Al2Cu, residual Si and small block Q-(Al4Cu2Mg8Si7) phases. Among them, the size of Mg2Si primary is 31.2 μm. Increasing of Mg2Si content, Mg2Si primary changes from angular polygon to coarse dendrite. The alloy of 15%Mg2Si/Al-3%Cu-3%Si was modified by adding 0.04%Sr, the Mg2Si primary size was reduced to 20.1 μm, and the angular polygon Mg2Si primary was transformed into more rounded polygon. Using first principle to calculate binding energy and adsorption of the metamorphic element Sr in Mg2Si revealed the metamorphic mechanism on Sr. The results show that Sr preferentially adsorbed on {111} plane of the Mg2Si crystal, and dissolved in and replaced Mg atoms from original Mg2Si crystal lattice. Therefore the relative surface energies of {100} and {111} crystal planes of unmodified Mg2Si were changed. As a result, the growth of Mg2Si along the <100> direction was inhibited and finally the refinement of Mg2Si particles was realized. Three point bending tests were conducted on 15% and 25%Mg2Si/Al-3%Cu-3%Si composites and their metamorphism. The results showed that the bending strength and the bending strain of 15%Mg2Si/Al-3%Cu-3%Si composite metamorphized by 0.04%Sr were the highest, respectively reaching 246.9 MPa and 1.23%.