利用SEM, EPMA, XRD和DSC, 对Mg-Zn-Ca系镁基固溶体400 ℃时的溶解度以及镁基固溶体与化合物之间的平衡相关系进行了研究. 结果表明, 在Mg-Zn系中加入Ca后, T1和T2相在400℃ 时依然是富Mg角的主要三元化合物, 但只有T1相与镁基固溶体相平衡, 且α-Mg+T1两相区明显缩小. 400 ℃时, Mg-Zn-Ca系低Ca侧存在一个可与镁基固溶体相平衡的液相区, 其含Ca量小于 8.4%(原子分数); 但Zn/Ca值小于1.7的三元合金中不会有液相存在. Mg-Zn-Ca系低Ca侧400 ℃等温截面相图中存在着4个三相区: α-Mg+Mg2Ca+T1, α-Mg+T1+Liq, Liq+T1+T2和Liq+T2+Mg2Zn3.
Zn addition to the magnesium alloys could result in the age-hardening, and the age-hardening response of Mg-Zn alloys could be further enhanced by the ternary addition of Ca. In order to better understand the mechanism of the Mg-Zn-Ca base alloy design, the solubility of Mg-based< solid solution and relative phase equilibrium at 400 ℃ in low-Ca side of the Mg-Zn-Ca system have been investigated by SEM, EPMA, XRD and DSC. It has been shown that T1 and T2 are still main ternary compounds in the Mg-rich corner at 400 ℃ with the addition of Ca to Mg-Zn system, but only T1 phase could be in equilibrium with the Mg-based solid solution, and the two-phase field of α-Mg+T1 becomes narrow. The liquid phase with the Ca content less than 8.4\% (atomic fraction) exists in the low-Ca side at 400 ℃, which could be in equilibrium with α-Mg. But liquid phase could not exist in the Mg-Zn-Ca α-Mg+Mg2Ca+T1, α-Mg+T1+Liq, Liq+T1+T2 and Liq+T2+Mg2Zn3 in the Mg-Zn-Ca system, respectively.
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