Abstract
In order to investigate effects of texture and humidity on fatigue properties of Al alloy under ultrasonic loading, fatigue tests were carried out using plain specimens cut out from two kinds of age-hardened Al alloys 2017-T4, extruded and drawn bars, in relative humidity of 25% and 85%. The extruded Al alloy had a marked texture of a (111) plane, but a specified orientation was not observed in the drawn Al alloy. The retardation of a crack growth yielded at the surface length below about 1 mm in low humidity of both alloys. Although the crack growth was accelerated in the early growth process by high humidity, there was no or little influence of humidity on the growth rate of a crack over the above retarded length in both alloys. After the retardation of the crack growth, most of fracture surfaces were covered with many slip planes and voids in the extruded alloy and many flat facets in the drawn one, and striations being a main fracture mechanism under rotating bending fatigue of the conventional frequency were very limited.
