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针对6xxx系铝合金的主要强化相Mg2Si的力热性能,采用密度泛函理论、第一性原理以及CASTEP软件进行了理论计算,得到了Mg2Si的平衡晶格常数、弹性系数、声子谱、声子态密度以及相关热力学参量,并对计算曲线进行了理论分析.结果表明:合金强化相Mg2Si的刚性较好,脆性较强,在合金中能起到强化作用.通过声子谱及声子态密度曲线可知,存在9条色散关系曲线,其中3条为声学波,6条为光学波,且频率在8.51 THz附近的格波振动较强.随着温度的增加,熵、焓均增加,而自由能减少.当温度低于200 K时,热容量随着温度的增加而明显增加;当温度高于400K后,热容量接近于常量,其计算结果与物理规律一致.
For the thermomechanical properties of the main strengthening phase Mg2Si of 6xxx aluminum alloy, the equilibrium lattice constants, elastic coefficients, phonon spectra, sound and sound of Mg2Si were obtained by using the density functional theory, the first principle and CASTEP software. The density of the daughter state and the related thermodynamic parameters, and the theoretical analysis of the calculated curve is carried out. The results show that the alloy reinforced phase Mg2Si has better rigidity and brittleness and can play a strengthening role in the alloy.By the phonon spectrum and the phonon state The density curve shows that there are nine dispersion curves, of which three are acoustic waves and six are optical waves, and the vibration at the frequency around 8.51 THz is strong. As the temperature increases, the entropy and enthalpy increase, while When the temperature is lower than 200 K, the heat capacity obviously increases with the increase of temperature. When the temperature is higher than 400K, the heat capacity is close to the constant, and the calculation result is consistent with the physical laws.