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用原位内生法制备了Al-15%Mg_2Si(质量分数,下同)复合材料,通过XRD测试,定性和定量地分析材料中的相成分和相含量。利用Reflex模拟Al-Mg-Si系合金的XRD图谱,并与XRD测试结果对比。利用CASTEP中基于密度泛函理论的第一性原理方法,对Al-Mg_2Si复合材料中的Mg_2Si相和Mg_(17)Al_(12)相的平衡晶格常数,热力学参数和弹性性质做了系统的研究,分析两相的稳定性和力学性能。XRD分析结果显示,Al-15%Mg_2Si复合材料中仅含有α-Al相和Mg_2Si相,且Mg_2Si相的质量分数为14.9%。模拟与实验中,相同晶面指数的XRD标定值相差很小,实验值验证了模拟值的可靠性。模拟值证实Al-Mg_2Si复合材料中,理论上只形成α-Al相和Mg_2Si相。CASTEP计算结果表明,Al-Mg_2Si复合材料中的Mg_2Si相较Mg_(17)Al_(12)相易于形成,且稳定性较好。Mg_2Si相的弹性模量E,剪切模量G,体模量B均大于Mg_(17)Al_(12)相,Mg_2Si相的力学性能较好,但脆性较大,且塑性较差。
Al-15% Mg 2 Si (mass fraction, the same below) composites were prepared by in situ method. The phase composition and phase content were qualitatively and quantitatively analyzed by XRD. The XRD patterns of Al-Mg-Si alloys were simulated by Reflex and compared with the XRD results. Based on the first principles method based on density functional theory in CASTEP, the equilibrium lattice constants, thermodynamic parameters and elastic properties of Mg 2 Si phase and Mg 17 Al 12 phase in Al-Mg 2 Si composites were systematically investigated Study and analyze the stability and mechanical properties of two phases. The results of XRD analysis showed that Al-15% Mg 2 Si composites only contained α-Al phase and Mg 2 Si phase, and the mass fraction of Mg 2 Si phase was 14.9%. In the simulation and experiment, the XRD calibration values of the same crystal plane index are very small, and the experimental results verify the reliability of the simulation values. The simulation results confirm that only the α-Al phase and the Mg_2Si phase are theoretically formed in the Al-Mg 2 Si composite. CASTEP results show that the Mg 2 Si phase in Al-Mg 2 Si composites is easier to form than the Mg 17 Al 12 phase and the stability is better. The elastic modulus E, shear modulus G and bulk modulus B of Mg_2Si phase are larger than that of Mg_ (17) Al_ (12) phase. The mechanical properties of Mg_2Si phase are better, but the brittleness and the plasticity are worse.