| Abstract: | Stress corrosion cracking (SCC) of 7075 Al alloy in a 3.5% NaCl aqueous solution under compressive stress was studied using modified WOL notched specimen. The result showed that SCC could occur if an applied compressive displacement was larger than a critical value. Finite-element analysis indicated that there was a stress concentration and the stress components were negative at the notch tip under the compressive displacement. Since the unload displacements were equal but opposite to the loaded ones, no stress relaxation occurred throughout SCC. Thus, the SCC was induced by compressive stress. The threshold stress intensity nucleating SCC from the notch under the compressive applied stress was 27.6MPa·m~(1/2) but the corresponding value under tensile stress was 8.3MPa· m~(1/2). Besides, the incubation period for SCC under compressive stress was one order of magnitude longer than that under tensile stress in the same K_I The fracture surfaces of SCC under compressive stress were quite different from those under tensile stress. The latter was composed of intergranular but the former was quasi-cleavage characterized by parallel striation pattern. |
