铣削残余应力对Al7075-T6合金应力腐蚀的影响

Effect of Milling Residual Stress on Stress Corrosion of Al7075-T6 Alloy

摘要: 高性能零部件加工残余应力对其后续使用工况具有重要影响，尤其是不合理的应力分布会加剧产品的开裂或失效等缺陷。因此，针对航天零件加工需求，为保证样件厚度和观测面宽度变量一致，本文采用仿真与试验方法，对不同进给速度下铣削加工的Al7075-T6合金薄壁试件进行残余应力测量和应力腐蚀研究，探究工件表面腐蚀形貌和截面腐蚀裂纹的发展与残余应力的关系。结果表明：铣削表面和未铣削表面的连接处最先发生腐蚀破坏，随着进给速度的增加，工件表面残余拉应力增大，腐蚀坑越大，裂纹萌生速度越快，腐蚀状态越明显。当裂纹扩展深度达到残余压应力峰值处时，裂纹沿深度方向扩展速度减缓，逐渐向四周缓慢扩展。由此可知，通过合理的工艺参数优化以改善残余应力分布，能够较好的减弱由于应力引起的开裂及腐蚀等质量问题。

Abstract: The residual stresses in the machining of high-performance parts have an important impact on their subsequent service conditions, especially the unreasonable stress distribution can aggravate the defects such as cracking or failure of the products. Therefore, in order to ensure that the thick-ness of the sample and the width of the observed surface are consistent, this paper uses simulation and experimental methods to measure the residual stress and stress corrosion on thin- walled Al7075-T6 alloy specimens milled at different feed rates to investigate the relationship between the corrosion pattern of the workpiece surface and the development of corrosion cracks in the cross-section and residual stress. The results show that: the connection between milled and un-milled surfaces is the first to experience corrosion damage, and as the feed rate increases, the re-sidual tensile stress on the surface of the workpiece increases, the larger the corrosion pit, the fast-er the crack sprouts, and the more obvious the corrosion state. When the crack expansion depth reaches the peak residual compressive stress, the crack expansion along the depth of the direction slowed down, and gradually to the surrounding slow expansion. It can be seen that through rea-sonable process parameters optimization to improve the residual stress distribution, can better reduce the stress caused by cracking and corrosion and other quality problems.