Original Article | 2009, Vol.31, No.5, pp. 463-470
Two stage S-N curve in corrosion fatigue of extruded magnesium alloy AZ31
M.S. Shahnewaz Bhuiyan and Yoshiharu Mutoh
pp. 463 - 470
Abstract
Tension-compression fatigue tests of extruded AZ31 magnesium alloys were carried out under corrosive environments: (a) high humidity environment (80 %RH) and (b) 5 wt. %NaCl environment. It was found that the reduction rate of fatigue strength due to corrosive environment was 0.12 under a high humidity and 0.53 under a NaCl environment. It was also observed that under corrosive environments, the S-N curve was not a single curve but a two-stage curve. Above the fatigue limit under low humidity, the crack nucleation mechanism was due to a localized slip band formation mechanism. Below the fatigue limit under low humidity, the reduction in fatigue strength was attributed to the corrosion pit formation and growth to the critical size for fatigue crack nucleation under the combined effect of cyclic load and the corrosive environment. The critical size was attained when the stress intensity factor range reached the threshold value for crack growth.
