新型Al-Cu-Li合金时效过程中组织和性能的变化研究

通过拉伸试验和透射电镜(TEM)等分析测试手段, 研究了一种新型Al-Cu-Li合金在固溶+预拉伸+人工时效过程中组织和性能的变化。结果表明, 143 ℃下时效65 h后合金的强度达到峰值, 抗拉强度为559 MPa, 屈服强度为472 MPa, 延伸率为6.7%, 塑性损失较为严重;透射电镜(TEM)观察分析表明, 合金中的主要析出相是T1相, δ'相析出较少。2%预拉伸引入的适量密度位错为T1相提供了形核位置, 既提高了T1相的形核率, 又使T1相的分布均匀弥散。T1相的数量密度和尺寸随着时效的进行而增大。峰时效状态下, T1相长大较为明显, 尺寸达到200 nm, 尺寸均匀性减弱。结合显微组织和拉伸性能比较分析, 合金时效35 h后可得到良好的组织和力学性能匹配。

Investigation on Microstructure and Property of Newly Developed Al-Cu-Li Alloy during Aging

The evolution of microstructure and mechanical properties of a newly developed Al-Cu-Li alloy during the process of solution treatment and pre-stretching plus aging was investigated by transmission electron microscopy (TEM) and tensile testing. The results showed that aging at 143 ℃ for 65 h resulted in the strength of  Al-Cu-Li alloy reaching the peak value, the tensile strength, yield strength and elongation being at 559 MPa, 472 MPa and 6.7%, respectively, with great plastic loss. The TEM results showed that T1 phase was the major precipitate with little precipitation of δ' phase. An appropriate density of dislocations introduced by 2% pre-stretching provided a nucleation position for T1 phase, not only increasing the nucleation rate of T1 phase, but also making the T1 distribution homogeneous and dispersive. The number density and size of T1 phase increased with the increase of aging time. Under the peak-aged condition, the growth of T1 phase was apparent with the size reaching to 200 nm. However, the size uniformity of T1 phase was reduced. The comparative analysis of TEM and tensile testing results indicated that a good combination of microstructure and mechanical property for the Al-Cu-Li alloy was obtained after aging at 143 ℃ for 35 h.