(1. 西安理工大學(xué) 材料科學(xué)與工程學(xué)院，西安 710048；
2. 河南科技大學(xué) 材料科學(xué)與工程學(xué)院，洛陽 471023；
3. 河南工學(xué)院 材料工程系，新鄉(xiāng) 453003)
摘 要: 研究稀土La對Zn-Cu-Ti合金顯微組織和力學(xué)性能的影響。結(jié)果表明：適量添加La有利于固液界面前沿成分過冷區(qū)的形成，促進(jìn)形核，細(xì)化晶粒，阻滯枝晶的進(jìn)一步生長；大部分La與Cu生成高熔點(diǎn)、高穩(wěn)定的LaCu6和LaCu4；隨著La添加量的增加，硬脆、粗大的初晶相εp轉(zhuǎn)變?yōu)楦蛹?xì)小彌撒的εⅡ相，且共晶組織TiZn16相層片間距更加細(xì)小，推遲裂紋的萌生和發(fā)展，提高合金的塑性，合金的斷裂機(jī)制由脆性向韌性過渡；當(dāng)添加0.1%La及 0.5%La(質(zhì)量分?jǐn)?shù))后，合金的平均晶粒尺寸分別降低70%和72.3%，而塑性則分別增加7%和33.33%；Zn-Cu-Ti合金中第二相的強(qiáng)化效果遠(yuǎn)大于細(xì)晶的強(qiáng)化效果，這也是合金強(qiáng)度先降低而后升高的原因。
關(guān)鍵字: Zn-Cu-Ti 合金；稀土 La；顯微組織；第二相；力學(xué)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
