Mg-Zn-Nd合金中的低Nd三元化合物T_1相的研究

RESEARCH ON A TERNARY COMPOUND T_1 AT THE LOW Nd SIDE IN THE Mg-Zn-Nd ALLOY

利用扫描电镜,电子探针、X射线衍射仪和透射电镜对Mg-Zn-Nd系低Nd三元化合物T_1相的成分、结构及其相平衡关系进行了研究.结果表明,在Mg-Zn-Nd系低Nd侧存在一个六方结构的三元化合物T_1相,其晶格常数为a=b=1.5 nm、c=0.87 nm;其成分(原子分数,%)范围为:Mg 27.0—33.4,Zn 60.2—66.4,Nd 6.1—7.4.该化合物在300—400℃的温度区间与α-Mg存在两相平衡.在300,350和400℃时分别存在T_1+α-Mg+MgZn,T_1+MgZn+L及T_1+Mg_2Zn_3+L三相区.

The structure, composition range and phase equilibrium of a ternary compound T1 at the low Nd side in the Mg-Zn-Nd system have been investigated by SEM, EPMA, XRD and TEM. It has been shown that a ternary compound T1 with the hexagonal structure, a=b=1.5 nm and c=0.87 nm, exists at the low Nd side in the Mg-Zn-Nd system. The composition range（atomic fractiom, %） of T1 phase is Mg 27.0-33.4, Zn 60.2-66.4 and Nd 6.1-7.4. At the temperature range of 300-400 ℃, there exists the α-Mg＋Tl two-phase field, and the Zn content in α-Mg increases with increasing temperature. The three-phase fields Tl＋a-Mg＋MgZn, TI＋MgZn＋L and TI＋Mg2Zn3＋L exist at 300, 350 and 400 ℃, respectively.