对2A97铝锂合金进行自然时效(0~90 d)、不同温度的单级人工时效(145, 165, 185 ℃)和自然时效(T4)+185 ℃人工时效的双级时效处理, 研究了时效工艺对合金硬化曲线、组织和力学性能的影响, 并分析了拉伸断口形貌。结果表明: 试验合金经自然时效(T4)处理后的主要强化相为δ′、GP区和δ′/β′复合粒子, 此时合金的强度较低、塑性较高, 拉伸断口上分布着较多韧窝; 经不同温度单级人工时效处理后, 合金抗拉强度显著提高的同时塑性明显下降, 断口形貌呈冰糖状, 其中185 ℃×10 h单级时效处理后的强塑性均较好, 其抗拉强度、屈服强度和伸长率分别为537, 506 MPa和7.0%; 与185 ℃单级时效的相比, T4(60 d)+185 ℃双级时效后, 合金的硬度出现了先下降后上升的现象, 并且达到峰值的时间推迟了20 h, 但强度和塑性均有所提高, 断口为沿晶、穿晶约各占一半的混合型断裂, 塑性有所改善。

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.