7055铝合金恒载荷应力腐蚀性能及机理研究

采用室温拉伸、光学显微镜和扫描电镜研究了不同恒载荷条件下7055铝合金型材的应力腐蚀性能。结果表明,在腐蚀周期内,随着应力腐蚀载荷的提高,试样的强度并未出现明显的下降,而塑性下降40%。应力腐蚀载荷越接近材料的屈服强度,塑性下降就越明显,抗拉应变和延伸率均有降低。应力腐蚀试样表层部分区域有明显的点蚀、沿晶腐蚀空洞和裂纹;拉伸时,腐蚀缺口处会产生明显的应力集中而成为起裂源,拉伸断口边缘被腐蚀区域为明显的沿晶断裂。

Mechanism Study and Stress Corrosion Property of 7055 Aluminum Alloy under Constant Load Condition

The stress corrosion resistance of 7055 aluminum alloy under different constant loadings was studied by tensile test under optical and electron microscopy observation. The results show that the tensile strength presents no obvious decline while the plasticity decreases 40% during the test cycle. The closer load approaches yield strength, the severer decrease of plasticity (i.e. elongation and tensile strain) is. Pittings and intergranular voids and cracks are observed on surface layer of specimen. During the tensile test, the stress concentration in voids could become crack source, leading to deterioration of plasticity. Intergranular fracture is observed on the edge of fracture surface.