Mg-Zn-Ca系富Mg区域三元化合物及其固态相平衡

来源期刊：金属学报2011年第4期

论文作者：李洪晓 马倩倩 任玉平 蒋敏 秦高梧

文章页码：385 - 390

关键词：Mg-Zn-Ca系； 三元化合物； 结构与成分； 相平衡

Key words：Mg-Zn-Ca system； ternary compound； structure and composition； phase equilibrium

摘    要：利用SEM,EPMA,XRD和TEM对Mg-Zn-Ca系富Mg区域三元化合物的成分、结构及其相平衡进行了研究.结果表明,Mg-Zn-Ca系富Mg区域存在2个可与镁基固溶体相平衡的三元化合物T₁和T₂.其中化合物T₁为线性化合物,成分(原子分数,%,下同)为:Ca约16,Zn 16.8—49.5,Mg余量;晶体结构为六方结构,晶格常数随Zn含量的增大而减小,a=0.995-0.945nm,c=1.036-1.003nm.T₂相的成分范围为:Mg 27.1-29.3,Zn 62.1-64.4和Ca7.6-9.0;也为六方结构,晶格常数a=1.475nm和c=0.879nm.335℃时,Zn的加入并未使得镁基固溶体对Ca的溶解度降低,但Ca元素提高了Zn在镁基固溶体中的溶解度,Zn达到4.6.335℃时,Mg-Zn-Ca系相图富Mg区域存在着三相区α-Mg+Mg₂Ca+T₁,α-Mg+T₁+T₂,α-Mg+T₂+MgZn,MgZn+T₂+Mg₂Zn₃和α-Mg+Mg₇Zn₃+MgZn.

Abstract: The structure,composition range and phase equilibria of the ternary compounds in Mg-rich side of the Mg-Zn-Ca system have been investigated by SEM,EPMA,XRD and TEM. It has been shown that there exist two ternary compounds T₁ and T₂ in equilibrium with the Mg-based solid solution in the Mg-Zn-Ca system.T₁ phase is a linear compound with hexagonal structure, whose structure parameters decrease with the Zn content,i.e.a=0.995-0.945 nm,c=1.036-1.003 nm.Its composition region (atomic fraction,%) is Ca about 16,Zn 16.8-49.5 and balanced Mg.The composition region of the T₂ phase is Mg 27.1-29.3,Zn 62.1-64.4 and Ca 7.6-9.0.T₂ phase also has the hexagonal structure,whose structure parameters are a=1.475 nm and c=0.879 nm. At 335℃,the dissolution of Zn has not decreased the solubility of Ca in the α-Mg solid solution,but the solubility of Zn in the α-Mg solid solution increases with the dissolution of Ca,and the maximum solubility of Zn is 4.6.At 335℃,there are five three-phase fields consisting of α-Mg+Mg₂Ca+T₁,α-Mg+T₁+T₂,α-Mg+T₂+MgZn,MgZn+T₂+Mg₂Zn₃ and α-Mg+Mg₇Zn₃+MgZn in the Mg-Zn-Ca system,respectively.