Effect of two-stage aging on superplasticity of Al-Li alloy
(1.湖南省长沙市中南大学材料科学与工程学院
2.School of Materials Science and Engineering, Central South University, Changsha 410083, China)
2.School of Materials Science and Engineering, Central South University, Changsha 410083, China)
Abstract: The effect of two-stage aging on the microstructures and superplasticity of 01420 Al-Li alloy was investigated by means of OM, TEM analysis and stretching experiment. The results demonstrate that the second phase particles distributed more uniformly with a larger volume fraction can be observed after the two-stage aging (120 ℃, 12 h＋300 ℃, 36 h) compared with the single-aging(300 ℃, 48 h). After rolling and recrystallization annealing, fine grains with size of 8？10 μm are obtained, and the superplastic elongation of the specimens reaches 560% at strain rate of 8×10？4 s？1 and 480 ℃. Uniformly distributed fine particles precipitate both on grain boundaries and in grains at lower temperature. When the sheet is aged at high temperature, the particles become coarser with a large volume fraction.
Key words: Al -Li alloys; superplasticity; two-stage aging; grain refinement