新型Al-Cu-Li合金时效过程中组织和性能的变化研究

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

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。

The evolution ol microstructure and mechanical properties ol a newly developed Al- Cu -Lial loy d u r in g the process ol solution treatment and pre-stretching plus aging was investigated by transmission electron microscopy （T E M ） and tensile test ing. The results showed that aging at 143 ℃ for 65 h resulted in the strength ol Al- Cu -Lial loy reaching the peak value,the tensile s treng th,y ie ld strength and elongation being at 559 M P a,472 MPa and 6.7%, re sp e c t ive ly, with great plastic loss. The TEM results showed that T 1 phase was the major precipitate with little precipitat ion ol S＇ phase. An appropriate density ol dislocations introduced by 2 % pre-stretching provided a nucleat ion position for T 1 phase,not only increasing the nucleat ion rate ol T 1 phase, but also making the T 1 distrsibution homogeneous and dispersive. The number density and size of T 1 phase increased with the increase ol aging time. Under the peak-aged condition,the growth ol T1 phase was apparent w i th the size reaching to 200 nm . Howeve r, the size unilormity of Tlphase was reduced. The comparative analysis ol TEM and tensile testing results indicated that a good combination ol microstructure and mechanical property for the Al- Cu -Lialloy was obtained alte raging at 143 ℃ for 35 h .