2011 Volume 60 Issue 4 Pages 339-344
In order to investigate the effect of humidity on fatigue strength of an extruded and age-hardened Al alloy 7075-T6, rotating bending fatigue tests were carried out using plain specimens in environments of controlled relative humidity of 25% and 85%. Both of initiation and propagation of a crack were accelerated by high humidity, causing the decrease in fatigue strength. In high humidity, a crack tended to propagate in a shear mode macroscopically and it was ductile accompanied with glide plane decohesion and void formation microscopically, though the propagation was a tensile mode with striations in low humidity. The shear mode propagation inclined about 35° to the extruded direction due to the marked texture of the alloy.
