Abstract
Effects of a texture and a slip characteristic on fatigue properties of Al alloys in high humidity were investigated using plain specimens of an extruded bar and a drawn one of age-hardened Al alloy 2017-T4 and an Al alloy which annealed the extruded one in relative humidity of 25% and 85%. The extruded alloy and the annealed one had a marked texture of (111) plane, but there was no specified orientation in the drawn one. Fatigue strength was decreased by high humidity in all of the alloys, especially in the extruded alloy. The decrease in fatigue strength in the extruded alloy was mainly caused by the acceleration of a crack growth due to the change in growth mechanism of a crack from a tensile mode in low humidity to a shear one in high humidity, though the effect of humidity on the growth mechanism was very small in the drawn and the annealed alloys. The shear mode crack in the extruded alloy was related to the marked texture and the planner slip property and caused by high humidity.
