2015 年 64 巻 8 号 p. 655-661
Stress corrosion cracking (SCC) of extruded magnesium alloy AZ80 in 0.004wt% sodium chloride (NaCl) solution at 298K was studied by slow strain rate tensile technique. The alloy was treated with naturally or artificially aging heat treatment. The eutectoid phase was precipitated by artificially aging. The specimen was machined from different orientations. One is loaded in the transverse direction with crack propagation in the longitudinal direction (i.e., T specimen). The other is loaded in the longitudinal direction with crack propagation in the radial direction (i.e., L specimen). The strain rate was changed from 8.33×10-6 to 8.33×10-3 s-1. The susceptibility to SCC was evaluated by fracture energy obtained by slow strain rate tensile tests. The SCC susceptibility of magnesium alloy increased with a decrease in strain rate irrespective of heat treatment and specimen orientation. The SCC susceptibility of L specimen was higher than that of T specimen. This was related with the anisotropy in corrosion resistance. In the case of L specimen, the SCC susceptibility was not affected by heat treatment condition. On the other hand, the SCC susceptibility of artificially aged T specimen is surely higher than that of naturally aged one though the artificially aging improved the corrosion resistance. It was suggested that SCC susceptibility of magnesium alloy is related with texture orientation and distribution of eutectoid phase.