应力水平对2219铝合金腐蚀损伤力学性能的影响

为明确应力水平及暴露时间对2219铝合金腐蚀损伤力学性能的影响，选择在不同应力水平作用下暴露于EXCO腐蚀溶液中，经不同时间加速腐蚀后的2219铝合金试样，开展表面蚀坑深度测量、力学性能测试、拉伸断口形貌观察试验。结果表明，应力水平、暴露时间都是影响试样应力腐蚀损伤发展从而影响材料力学性能变化的重要因素。在腐蚀的初期阶段，即0.0~1.5 h，应力水平因素的影响有限；当暴露时间大于等于2.0 h，应力水平引起的以蚀坑平均深度为表征的腐蚀损伤更加显著。但在试验时间（2.5 h）内，应力水平对腐蚀损伤所产生的影响小于暴露时间，因而对材料力学性能变化的影响也小于暴露时间。腐蚀损伤造成的点蚀坑、微裂纹破坏了材料的连续性，使试样材料的抗拉强度、延伸率、弹性模量等力学性能指标下降，是促使材料在拉伸试验中没有经过充分的塑性变形阶段就发生瞬间断裂的重要原因。深度大的点蚀坑、微裂纹，可能成为断口主裂纹的起源。

Effect of stress level on mechanical properties of 2219 aluminum alloy caused by stress corrosion damage

In order to identify the effect of stress level and exposure duration on corrosion damage mechanical properties of 2219 aluminum alloy, some specimens exposed to EXCO corrosion solution under different stress levels and accelerated corrosion at different duration were selected to carry out surface pit depth measurement, mechanical properties testing and tensile fracture morphology observation. The test results show that both stress level and exposure duration are important factors affecting the development of stress corrosion damage thus affecting the change of mechanical properties of the material. At the initial stage of corrosion, i.e. before 1.5 h, the effect of stress level is limited. When the exposure duration reaches 2.0 h or more, the corrosion damage characterized by the average depth of pits caused by stress level is more significant. However, within the test time (2.5 h), the effect of stress level on corrosion damage is less than that of exposure duration, so the effect on the change of mechanical properties of materials is also less than that of exposure duration. Pits and microcracks caused by corrosion damage destroy the continuity of the material and decrease the mechanical properties of it, such as tensile strength, elongation and modulus of elasticity, which is an important reason for the instantaneous fracture of the material without sufficient plastic deformation stage in the tensile test. A larger pit or a deeper microcrack may be the origin of the main crack in the fracture surface.