7055铝合金T型型材的应力腐蚀行为研究

通过拉伸性能测试、C环应力腐蚀试验、金相分析、扫描电镜和透射电镜观察等研究了7055铝合金T型型材的应力腐蚀开裂(SCC)行为。结果表明:7055铝合金T型型材纵向试样的抗拉强度、屈服强度、伸长率及断面收缩率均大于横向试样的;在间浸腐蚀和恒温恒湿环境下,纵向C环试样的开裂时间均长于横向试样的。型材纵向截面晶粒变形特征明显,主要呈拉长状,横向试样的裂纹沿纵向扩展,裂纹一旦形成,沿着拉长晶界迅速扩展,裂纹平直,开裂时间短;型材横向截面晶粒呈等轴状,纵向试样的裂纹沿横向扩展,裂纹扩展过程中会沿着晶界发生偏折,开裂时间长。7055型材应力腐蚀机理为氢脆和电化学理论的共同作用。 

Study on Stress Corrosion Cracking Behavior of T Profiles of 7055 Aluminum Alloy

The stress corrosion cracking(SCC) performance of 7055 aluminum alloy were investigated by using tensile testing, C-ring stress corrosion experiment, metallographic observation, scanning electron microscope and transmission electron microscope. The results show that longitudinal test specimen of 7055 aluminum alloy had higher tensile strength, yield strength, elongation and reduction of area than those of the transverse specimen. The cracking time of longitudinal C-ring specimens was longer than that of transverse specimens under intermediate immersion and constant temperature and humidity environment. The deformation grains were mainly elongated in the longitudinal section. The crack of the transverse sample grew along the longitudinal direction. Once the crack was formed, it grew rapidly along the elongated grain boundary, the crack was straight and the cracking time short. The grains of transverse section were equiaxial, and the crack of longitudinal sample grew along the transverse direction. In the process of crack growth, deflection along the grain boundary occurred, and the cracking time was long. The stress corrosion mechanism of 7055 alloy consisted of hydrogen embrittlement and electrochemical theory.