抄録
An investigation was made on the effect of microstructure on the stress corrosion cracking (SCC) in 3.5% NaCl+0.5% H2O2 solution for Al-Zn-Mg series 7N01-T4 alloy welds. Its susceptibility to SCC is known to be affected by microstructure. The microstructure consisting of G. P. zone has high susceptibility to SCC, and that consisting of η' precipitates and η phase has low susceptibility to SCC. The microstructure in which G. P. zone and a few η' precipitates or η phase are mixed, has lower susceptibility to SCC than that consisting of G. P. zone only. SCC of the welds occurred at the area of G. P. zone microstructure such as the weld bond area and base metal of non-heat affected zone, but the SCC hardly occurred at the area where only a few η' precipitates or η phase existed in the weld heat affected zone. The fracture morphology of SCC in the microstructure consisting of G. P. zone showed intergranular fracture with plain surface, while that of SCC in the microstructure consisting of η' precipitates or η phase seemed to show intergranular fracture associated with grain boundary precipitates.
