【摘要】 采用CALPHAD （CALculation of PHAse Diagrams）方法重新对Mg-Al-Gd三元系进行评估，获得一套自洽的热力学参数。用Mg_x（TM,Mg）₆（RE,Mg）₈热力学模型（TM=过渡金属，RE=稀土金属）描述长周期堆积有序相14H和18R。计算代表性的等温截面、垂直截面、液相线投影图和相关的零变量反应，与实验数据进行比较，表明所得热力学参数的可靠性。绘制了整个三元体系的反应图，并对几种Mg-Al-Gd合金的Scheil凝固路径和相分数进行计算和分析，清楚地描述了凝固过程中各相的形成以及γ和LPSO相的相分数随Gd成分的变化，这些是影响Mg-Al-Gd合金的显微硬度、极限抗拉强度和屈服强度的重要因素。更多还原

【Abstract】 The Mg-Al-Gd ternary system was re-assessed by the CALPHAD（CALculation of PHAse Diagrams） method and a set of self-consistent thermodynamic parameters of the system were obtained. The long-period stacking ordered（LPSO） phases, 14H and 18R, were described by thermodynamic model of Mg_x（TM,Mg）₆（RE,Mg）₈（TM=Transition Metal, RE=Rare Earth）. Representative isothermal sections, vertical sections, liquidus projections and the related invariant reactions were calculated and compared with the experimental data, showing the reliability of the obtained thermodynamic parameters. Reaction scheme for the whole ternary system was also presented. The Scheil solidification paths and the phase fractions of several Mg-Al-Gd alloys were calculated and analyzed. The phase formation during solidification and the phase content of γ and LPSO phases are clearly described with the increase of Gd content, which is crucial to the microhardness, ultimate tensile strength and yield strength of Mg-Al-Gd casting alloys.更多还原