(1. 西安理工大学 材料科学与工程学院，西安 710048；
2. 河南科技大学 材料科学与工程学院，洛阳 471023；
3. 河南工学院 材料工程系，新乡 453003)
摘 要: 研究稀土La对Zn-Cu-Ti合金显微组织和力学性能的影响。结果表明：适量添加La有利于固液界面前沿成分过冷区的形成，促进形核，细化晶粒，阻滞枝晶的进一步生长；大部分La与Cu生成高熔点、高稳定的LaCu6和LaCu4；随着La添加量的增加，硬脆、粗大的初晶相εp转变为更加细小弥撒的εⅡ相，且共晶组织TiZn16相层片间距更加细小，推迟裂纹的萌生和发展，提高合金的塑性，合金的断裂机制由脆性向韧性过渡；当添加0.1%La及 0.5%La(质量分数)后，合金的平均晶粒尺寸分别降低70%和72.3%，而塑性则分别增加7%和33.33%；Zn-Cu-Ti合金中第二相的强化效果远大于细晶的强化效果，这也是合金强度先降低而后升高的原因。
关键字: Zn-Cu-Ti 合金；稀土 La；显微组织；第二相；力学性能
（1. Faculty of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048, China;
2. School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023, China;
3. Department of Materials Engineering, Henan Institute of Technology, Xinxiang 453003, China）
Abstract:The effects of La on the microstructures and mechanical properties of Zn-Cu-Ti alloy were investigated. The results show that composition supercooling forms on the solid-liquid interface by adding La, promoting nucleation, refining grain and preventing dendrite growth. La and Cu generate LaCu6 and LaCu4 with high melting point and stability; with the increase of the La content, brittle and coarse εp phase turns into thinner and dispersed εⅡ phase; meanwhile, the layer of eutectic organization TiZn16 becomes thinner. Both of them block the initiation and development of cracks, increase the plasticity of alloy. The fracture mechanism of alloy transits from brittleness to ductility; when the La content is 0.1% and 0.5% (mass fraction), the average grain size of alloy decreases by 70% and 72.3% respectively, while its plasticity increases by 7% and 33.33% accordingly. The strengthening effect of second phase is more obvious than that of the refined grain.
Key words: Zn-Cu-Ti alloy; rare earth La; microstructure; second phase; mechanical property
