材料期刊网

用WOL缺口压缩试样研究LC4铝合金在3.5％NaCl水溶液中的压应力腐蚀.有限元计算指出,试样加压缩位移时缺口附近有压应力集中.实验结果表明,当压缩位移大于临界值后产生压应力腐蚀裂纹. 实验测出压应力腐蚀裂纹的门槛值为K_(ISCC*)=27.6MPam~(1/2),等于拉应力腐蚀门槛值的3.5倍.在相同K_I下压应力腐蚀裂纹的孕育期比拉应力高一个数量级.压应力腐蚀时获得带有平行条纹花样的准解理断口,这和拉应力腐蚀的沿晶断口完全不同。

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.