Microstructure evolution and precipitation characteristics of spray-formed and subsequently extruded 2195 Al-Li alloy plate during solution and aging process

Al-Li alloys are being successfully employed for manufacturing the structural components of lightweight aircrafts. In this work, the microstructures and precipitation characteristics of the spray-formed and subsequently extruded 2195 Al-Li alloy plate during solid solution and aging treatments were investigated and compared by using different material characterization methods. The grains of the spray-formed alloy were equiaxed without obvious crystallographic textures, whereas in the as-extruded, solution-treated, and aging-treated alloys, the grain morphology changed from being strip shaped near the center of extruded plate to equiaxed near the surface. The grain size increased after the solution treatment, but the aging treatment had no obvious influence on the grain size. A rolling-type texture with a very dominant Brass orientation was observed at the center of the plate, whereas the textures near the surface were rotated, and the crystallographic texture was not sensitive to the solution and aging treatments. The precipitated T-1 and theta' phases, which played a strengthening role in the alloy, gradually formed and developed with increasing aging duration. Besides, the Al-Cu phase in the alloy dissolved and re-precipitated during the heat treatment process, while the Fe-containing particles always remained stable. By applying the uniaxial tension test, a good balance between ultimate tensile strength and elongation was achieved after aging treatment at 170 degrees C x 6 h.