Strain-dependent heterogeneity of microstructure and mechanical properties of 2195 Al-Li alloy during power spinning and heat treatment

The effect of thickness reduction (20% in each pass) on microstructure evolution and mechanical properties of 2195 Al-Li alloy during hot power spinning and the subsequent heat treatment were investigated. As a result, high-performance 2195 Al-Li alloy tube with a thickness of 1.56 mm was successfully fabricated. The results showed that the strain localization of spinning led to the heterogeneity of microstructure and mechanical property along the wall thickness direction of the spun tube. With the increase of thickness reduction, dynamical recrystallization set up from the outer surface and propagated to the inner surface, and thus refined the microstructure, improved the mechanical properties, and reduced the heterogeneity in the microstructure and mechanical properties of the spun tube. However, after heat treatment, abnormal grain growth appeared in the microstructure near the inner surface of the spun tube with a moderate thickness reduction, triggering a severer inhomogeneity in the microstructure and mechanical properties. A large enough thickness reduction could induce sufficient dynamic recrystallization, which led to the disappearance of abnormal grain growth of spun tube during heat treatment. Grain boundary strengthening and precipitation strengthening were the dominant strengthening mechanisms of 2195 Al-Li alloy spun tube.