回归时间对7150铝合金力学性能与组织的影响

Influence of Retrogression Time on Mechanical Properties and Microstructure of 7150 Aluminum Alloy

采用硬度、常温拉伸、恒载荷拉伸、剥落腐蚀及透射电镜等方法研究回归时效时间对7150-T77铝合金性能和组织的影响。结果表明:随回归时效时间的延长,晶内η′相先回溶再重新析出η相,并不断粗化,导致合金最终力学性能先升高后降低,η′相回溶与η相析出的临界时间为30min,此时合金最终力学性能最高;晶界η相不断粗化且不连续,大幅提高合金的抗腐蚀性能;再时效阶段存在硬度峰值,且回归时效时间越长,达到硬度峰值时间越短。对比实验表明,较优的T77制度为105℃/17h+190℃/30min+120℃/23h,其抗拉强度(σb)、屈服强度(σ0.2)和伸长率(δ)分别为608,544MPa和10.4%,剥落腐蚀评级为EA级,恒载荷实验中抗拉强度和伸长率损失分别为4.9%和5.0%。

The influence of the retrogression time on properties and microstructure of 7150-T77 aluminum alloy was studied by hardness testing, tensile property testing, exfoliation corrosion test and TEM. Results indicate that the matrix precipitated η′ phase re-dissolves first, and then η phase re-precipitates and becomes coarsened with the extending of retrogression time. The ultimate mechanical properties increase first then decrease as retrogression time increases. The critical time of the η′ phase re-dissolution and the η phase precipitation is 30min, At this point, alloys have the highest ultimate mechanical properties, and the grain boundary precipitated η phase becomes coarsened and discontinuous, leading to lower mechanical properties and better corrosion resistance, peak hardness exists at re-aging stage. With the retrogression time extending, the time for the alloy to reach the peak hardness becomes shorter. Optimal T77 aging treatment is 105℃/17h＋190℃/30min＋120℃/23h. With this treatment, the ultimate tensile strength （ σ b ）, yield strength （ σ 0.2 ） and elongation （ δ ） are 608,544MPa and 10.4%, respectively, the exfoliation corrosion test gets EA level, the σ b and δ loss in constant loading tensile testing is 4.9% and 5.0%, respectively.