(1. 西安理工大學(xué) 材料科學(xué)與工程學(xué)院，西安 710048；
2. 西安謝赫特曼諾獎(jiǎng)新材料研究院，西安 710048；
3. 陜西鐵路工程職業(yè)技術(shù)學(xué)院 機(jī)電工程系，渭南 714099；
4. 上海航天精密機(jī)械研究所，上海 201600)
摘 要: 采用鋰鹽熔劑保護(hù)熔鑄Mg-8Li-4Zn-xGd(x=1, 3, 5)合金鑄錠，研究釓含量對(duì)鑄態(tài)合金組織和力學(xué)性能的影響。結(jié)果表明：Mg-8Li-4Zn-xGd合金基體由α-Mg(HCP)和β-Li(BCC)雙相構(gòu)成。隨著釓含量的增加，Mg5Gd共晶相和Zn12Gd化合物相逐漸連成網(wǎng)狀，將基體α+β雙相隔離成20~40 μm的等軸狀或類似于鑄鐵中的共晶團(tuán)狀，可有效細(xì)化α-Mg相和連續(xù)的β-Li相；組織中大顆粒Mg2Zn11相彌散分布在β-Li相內(nèi)，Mg51Zn20相分布在α-Mg晶界處；鋅元素還可以在β-Li相中析出細(xì)小彌散分布的MgZn相，其數(shù)量隨釓含量的增加而增加，可直接彌散強(qiáng)化β-Li相。此外，鋅和釓對(duì)合金硬度的影響較大，隨著釓含量的增加，合金的抗拉強(qiáng)度提高，但伸長(zhǎng)率降低。
關(guān)鍵字: Mg-Li合金；釓；顯微組織；相組成；力學(xué)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
