预拉伸对峰时效2297铝锂合金应力腐蚀性能的影响

在峰时效前对2297铝锂合金试样施加不同变形量的预拉伸，利用慢应变速率拉伸 (SSRT)、扫描电子显微镜 (SEM)、透射电镜 (TEM) 等手段，研究峰时效前不同预拉伸量对应力腐蚀敏感性的影响。结果表明，5组不同预拉伸量的样品经过峰时效处理后，预拉伸量为5%的样品应力腐蚀敏感因子为5.9%，抗应力腐蚀性能最好；预拉伸量为12.5%的样品，应力腐蚀敏感因子为41.4%，抗应力腐蚀性能最差；随着预拉伸量的增加，晶粒尺寸差逐渐减小，晶粒内部针状T₁相析出量逐渐增大，并且不断细化；T₁相的尺寸、数量以及分布的均匀性这3种因素的匹配度对合金强度及抗应力腐蚀性能有决定性的影响。

Effect of Pre-strain Before Aging Treatment on Stress Corrosion Cracking of 2297 Al-Li Alloy

2297 Al-Li alloy was stretched with varying degrees of deformation and then subjected to peak aging treatment. The influence of pre-strain on the stress corrosion cracking of the aged alloy was studied by means of slow strain rate test (SSRT), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and other methods. Results show that the alloy with 5% pre-strain presents a stress corrosion cracking index of 5.9% and the best stress corrosion resistance. While the alloy with 12.5% pre-strain shows the worst stress corrosion resistance with a stress corrosion cracking index of 41.4%. With the increase of the pre-strain degree, the difference of grain size gradually decreases, and the precipitation of the needle-like T₁ phase inside the grain gradually increases and becomes finer. The matched-degree of the size, quantity and distribution uniformity of the T₁ phase has a decisive influence on the strength and stress corrosion resistance of the alloy.