Effect of Li Content on Properties and Microstructure Evolution of Near-Rapid Solidified 2A97 Al-Li Alloy

2A97 Al-Li alloys with different Li contents were cast by the near-rapid solidification. After that, physical properties analysis was performed by tensile and density tests. Simultaneously, the differential scanning calorimeter (DSC), optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were used to explore the microstructure evolution of the Al-Li alloy. The results show that 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 significance 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, the petal-shaped eutectic phase Al2CuMg appears. Besides, 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, as the Li content increases from 1.5 wt% to 3.5 wt%, the effect of the heat treatment decreases sharply, resulting in many coarse eutectic phases remaining in the triangular cross boundaries of the alloy and a reduction in mechanical properties of alloys. Copyright © 2019, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.