喷射态7075合金回归再时效工艺研究

针对传统回归再时效(Retrogression and re-aging,RRA)工艺并不能充分发挥合金综合性能的缺点,通过拉伸试验、电导率测试、透射电镜观察等手段,研究适合喷射成形7075铝合金的回归再时效处理工艺。结果表明:120℃,16 h的欠预时效处理更有利于合金晶内析出相在回归处理过程中的回溶,有利于合金再时效后强度的提升;200℃,8 min的回归处理可有效地粗化晶界析出相并使其断开明显,使合金的耐蚀性大幅提升;120℃再时效24 h可再次强化合金的力学性能。采用上述RRA处理工艺可得抗拉强度、屈服强度、伸长率和电导率分别为791 MPa、736 MPa、8.5%和22.9 MS/m的高性能喷射成形7075合金,比传统RRA处理的合金在强度与耐蚀性上均有明显提高。

Study on Retrogression and Re-aging of Spray Formed 7075 Alloy

Conventional retrogression and re-aging (RRA) treatment could not be put to good use for combination property of the alloys. The RRA treatment fitted for spray formed 7075 aluminum alloy is investigated by transmission electron microscope, extension and conductivity tests. The results show that pre-aging treatment which under aged at 120℃ for 16 h is beneficial for the re-dissolution of precipitates in matrix at retrogression treatment. With retrogression at 200℃ for 8 min, grain boundary precipitates are conducive to interrupted distributions and the corrosion resistance of the alloy drastically increases. After re-aging at 120℃ for 24 h, the alloy strengthens again. According above-mentioned RRA treatment, the tensile strength, yield strength, elongation and conductivity of the alloy is 791 MPa, 736 MPa, 8.5% and 22.9MS/m respectively, which is higher than that after conventional RRA treatment.