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

Abstract:

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.