Li含量对亚快速凝固2A97铝锂合金的性能及组织演变规律的影响

通过亚快速凝固技术铸造2A97Al-Li合金,借助密度和拉伸测试对合金性能进行分析。同时,利用差热分析(DSC),光学电镜(OM),扫描电镜(SEM)及能谱分析(EDS)对合金显微组织演变进行研究。结果表明：通过亚快速凝固技术和合理的热处理工艺可以有效减少2A97 Al-Li合金中存在的粗大第二相,这对于超低密度Al-Li合金的实现具有十分重要的意义。随着合金中Li含量的增加,Cu原子更倾向于捕获Li原子而形成Al2CuLi相；同时,Al2Cu相相对减少,并出现花瓣状共晶相Al2CuMg；另外,亚快速凝固Al-Li合金的铸态显微组织由树枝晶向胞状晶转变,并促进晶粒细化。然而,随着Li含量由1.5 wt. %升到3.5wt. %过程中,热处理的效果逐渐降低,导致粗大共晶相残留于合金的三角叉晶界处,合金力学性能降低。

Effect of Li content on the properties and microstructure evolution of near-rapid solidified 2A97 Al-Li Alloy

2A97 Al-Li alloys with different Li contents have been cast by the near-rapid solidification. After that, perform physical properties analysis by means of tensile and density tests. Simultaneously, use the differential scanning calorimeter (DSC), optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) to explore the microstructure evolution of the Al-Li alloy. The results show that through the near-rapid solidification and a reasonable heat treatment process can effectively reduce the coarse second phase in the 2A97 Al-Li alloy, which is of great interest for obtaining ultra-low-density Al-Li alloys. With the increase of Li content, the Cu element in the alloy is more inclined to capture more Li element to form the Al₂CuLi phase. Accompanied by the relative decrease of Al₂Cu phase and the appearance of the petal-shaped eutectic phase Al₂CuMg. Not only that, the as-cast microstructure of the near-rapid solidified Al-Li alloy transforms from dendritic grains to cellular-like grains, leading to the refinement of the grains. However, with the Li content from 1.5 wt. % to 3.5wt. %, the effect of the heat treatment decreases sharply, resulting in many coarse eutectic phases remaining in the triangular cross boundaries of the alloy and the reduction of alloy mechanical properties.