Microstructure and Properties of 2A97 Aluminum-Lithium Alloy after Different Aging Processes

Natural aging (0-90 d), single stage artificial aging at different temperature (145,165, 185 ℃) and double aging of natural aging (T4) with artificial aging at 185 ℃ for 2A97 Al-Li alloy were carried out. The effects of aging process on hardening curves, microstructure and mechanical properties were studied, and the tensile fracture morphology was observed also. The results show that the main strengthed precipitations of the alloy after natural aging were δ′, GP zone and δ′/β′ composite particles, and in that state the alloy had a preferable plasticity with poor strength and tensile fracture surface with plenty of dimples. The strength of the alloy was enhanced markedly while the plasticity declined distinctly after single artificial aging at different temperatures, and rock candy shape fracture morphology was also shown. Favorable strength and plasticity were obtained after the alloy was aged at 185 ℃ for 10 h, and the tensile strength, yield strength and elongation were 537 MPa, 506 MPa and 7.0%, respectively. Compared with the alloy after single-stage artificial aging at 185 ℃, a reversion phenomenon appeared in the alloy, i.e., the hardness decreased firstly and then increased during further aging when aging at 185 ℃ following by natural aging for 60 days. And its peak time delayed about 20 h, but the strength and plasticity were both improved, and the fracture morphology was mixed intergranular and transgranular fracture.