(1. 西安理工大学 材料科学与工程学院，西安 710048；
2. 西安谢赫特曼诺奖新材料研究院，西安 710048；
3. 陕西铁路工程职业技术学院 机电工程系，渭南 714099；
4. 上海航天精密机械研究所，上海 201600)
摘 要: 采用锂盐熔剂保护熔铸Mg-8Li-4Zn-xGd(x=1, 3, 5)合金铸锭，研究钆含量对铸态合金组织和力学性能的影响。结果表明：Mg-8Li-4Zn-xGd合金基体由α-Mg(HCP)和β-Li(BCC)双相构成。随着钆含量的增加，Mg5Gd共晶相和Zn12Gd化合物相逐渐连成网状，将基体α+β双相隔离成20~40 μm的等轴状或类似于铸铁中的共晶团状，可有效细化α-Mg相和连续的β-Li相；组织中大颗粒Mg2Zn11相弥散分布在β-Li相内，Mg51Zn20相分布在α-Mg晶界处；锌元素还可以在β-Li相中析出细小弥散分布的MgZn相，其数量随钆含量的增加而增加，可直接弥散强化β-Li相。此外，锌和钆对合金硬度的影响较大，随着钆含量的增加，合金的抗拉强度提高，但伸长率降低。
关键字: Mg-Li合金；钆；显微组织；相组成；力学性能
（1. School of Materials Science and Engineering, Xi''an University of Technology, Xi’an 710048, China;
2. Xi’an Shechtman Nobel Price New Materials Institute, Xi''an 710048, China;
3. Department of Electrical and Mechanical Engineering, Shaanxi Railway Institute, Weinan 714099, China;
4. Shanghai Spaceflight Precision Machinery Institute, Shanghai 201600, China）
Abstract:As-cast ingots of Mg-8Li-4Zn-xGd(x=1, 3, 5) alloys were prepared by lithium flux protection in an electric-resistance furnace. The effects of Gd addition on microstructures and mechanical properties of as-cast Mg-8Li-4Zn-xGd alloys were investigated. The results show that the matrix of as-cast Mg-8Li-4Zn-xGd alloys is consisted of α-Mg (HCP) and β-Li (BCC) phase. With the content of Gd increasing, the Mg5Gd eutectic and Zn12Gd compound are gradually connected into network, isolating α and β eutectic into equiaxed with a dimension from 20 μm to 40 μm or eutectic-cell similar to those in the cast iron, which can refine α-Mg and the continuous β-Li phase effectively. The large Mg2Zn11 particles are dispersed in β-Li phase and the Mg51Zn20 phases are distribution at the grain boundary of α-Mg phase. Zn can also precipitate the fine dispersed MgZn phases in the β-Li phase and the quantity increases with the increase of Gd content, which can directly dispersion strengthening β-Li phase. In addition, Zn and Gd have a great influence on the hardness of as-cast alloy, and with the Gd content increasing, the tensile strength of Mg-8Li-4Zn-xGd alloys increases, while the elongation decreases.
Key words: Mg-Li alloy; Gd; microstructure; phase composition; mechanical properties
