中文摘要：

利用磁悬浮真空高频感应加热法熔炼高质量的镁锂合金,通过Si、Nd元素复合添加来研究其对Mg-11Li-3Al合金组织与力学性能的影响。结果表明：加入Si、Nd元素后,组织中主要生成Mg_2Si和Al11Nd3 2种第二相,其中Si的添加能够促使合金组织中形成篆体形貌的黑色析出物聚集区,而Nd的加入能够细化这种黑色棒状的析出物,并减小晶粒尺寸、洁净组织。当Nd的添加量为1%（质量分数）时其晶粒细化的效果最佳。经过XRD和EDS分析发现,这种黑色棒状的析出物为Mg2Si相和Al11Nd3相的结合体。铸态合金的抗拉强度随着Si含量的增加递增,最后趋于稳定;其塑性并不会随某一种或是复合元素的添加而单调变化。实验得到了一种综合力学性能最佳的合金Mg-11Li-3Al-1Si-1Nd,其抗拉强度和伸长率分别为212.3 MPa和46.2%。

英文摘要：

A magnetic high frequency induction heating method was used to prepare high quality magnesium-lithium alloys. The effects of Si-Nd co-addition on microstructures and mechanical properties of Mg-11Li-3Al alloy were studied. The results indicate that two main second phases Mg_2Si and Al11Nd3 are formed in the alloys with Si and Nd addition. The added Si element can promote the formation of the gathering area of black precipitates with Chinese characters morphology, and Nd can refine the rod-like black precipitates and reduce the grain size as well as clean the tissue. When the addition amount of Nd is 1 wt%, the best refinement is obtained. The XRD and EDS analyses find that the rod-like black precipitates are combined phases of Mg_2Si and Al11Nd3. The tensile strength of the as-cast alloys increases with Si content increasing and finally levels off. The plasticity does not change monotonously with a certain or compound element. The Mg-11Li-3Al-1Si-1Nd alloy acquires the best comprehensive mechanical properties, whose tensile strength and elongation reach 212.3 MPa and 46.2 %, respectively.