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Sr变质Mg2Si/Al-Cu-Si复合材料的机理与组织性能
Sr 变质 Mg2Si/Al-Cu-Si 复合材料的机理与 组织性能
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- DOI:
- 作者:
- 刘丹丹 1，2 ，孟丽娜 1 ，孙 瞻 1
LIU Dandan1,2, MENG Lina1 , SUN Zhan1
- 作者单位:
- 1.郑州工业应用技术学院 机电工程学院，河南 郑州 451100；2.河南理工大学 材料科学与工程学院，河南 焦作 454000
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
- 关键词:
- Mg2Si/Al-3%Cu-3%Si 复合材料；变质机理；第一性原理计算；Mg2Si 晶体
Mg2Si/Al-3%Cu-3%Si composite; metamorphic mechanism; first-principles calculation; Mg2Si crystal
- 摘要:
- 采用熔炼法制备了 x%Mg2Si/Al-3%Cu-3%Si(x=15，20，25 和 30)复合材料，并选择 15%和 25%Mg2Si 含量的
复合材料通过添加微量 Sr 进行了变质处理。 结果表明，铸态复合材料组织由多边形块状 Mg2Si 初生、棒状 Mg2Si 共晶、网状
θ-Al2Cu、过剩 Si 和块状 Q-(Al4Cu2Mg8Si7)相组成。 其中，Mg2Si 初 生 的晶粒尺寸约为 31.2 μm。 随着 Mg2Si 含量的增加，
Mg2Si 初生由颗粒状转变为更为粗大的树枝状。 加入 0.04%Sr 对 15%Mg2Si/Al-3%Cu-3%Si 进行变质处理，Mg2Si 初生 的晶
粒尺寸减小至 20.1 μm，尖角状 Mg2Si 初生转变为多边形。 用第一性原理计算变质元素 Sr 在 Mg2Si 中结合能和吸附能揭
示 Sr 的变质机理。 计算结果表明，Sr 优先吸附在 Mg2Si 晶体{111}面，固溶并取代晶格中的 Mg 原子，改变{100}
晶面和{111}晶面的相对表面能，从而抑制 Mg2Si 沿 <100> 晶相的生长速度，实现了 Mg2Si 颗粒的细化。 对 15%和
25%Mg2Si/Al-3%Cu-3%Si 复合材料及其变质态进行 3 点抗弯测试， 结果表明， 经过 0.04%Sr 变质的 15%Mg2Si/Al-3%
Cu-3%Si 复合材料抗弯强度和抗弯应变最高，分别达到 246.9 MPa 和 1.23%。
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%.