抄録
In order to investigate effects of a texture and loading frequency on fatigue properties of an extruded and a drawn alloys of 2017-T4, fatigue tests were carried out under ultrasonic loading frequency (20kHz) in relative humidity of 25% and 85% and rotating bending (50Hz) in nitrogen gas. The extruded alloy had a marked texture of a (111) plane, but a specified orientation was not observed in the drawn alloy. Most of fatigue life was occupied by the growth life of a small crack in both alloys regardless of humidity. In low humidity, the growth of a crack retarded at about 0.3- 0.5mm in length in both alloys. Although the crack growth was accelerated by high humidity in the early growth process, there was no or little influence of humidity on the growth rate of a crack after the retardation in both alloys. After the retardation of the crack growth, fracture surfaces were covered with many slip planes in the extruded alloy and many facets in the drawn one.
