Effect of Humidity on Fatigue Strength of Age-Hardened Al Alloy under Rotating Bending

Abstract:

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%, 50%, 75% and 85% and distilled water. The cross section of the alloy has a marked texture of (111) plane. Although fatigue strength was decreased by high humidity, the decrease by high humidity was very small when the humidity was lower than about 60% -70% and fatigue strength was largely decreased over the humidity. Both of initiation and propagation of a crack were accelerated by high humidity. In high humidity, a crack propagated in a shear mode macroscopically and it was ductile in company with many glide planes and voids microscopically. That is, the propagation was not a tensile mode with brittle facets even in water. The shear mode propagation inclined about 35° to the extruded direction and fracture surface was (100) plane, meaning that the shear mode propagation of a crack was mainly caused by the marked texture of the alloy. The propagation mode of a crack was affected by not only environment but also stress level.

• Periodical: Key Engineering Materials (Volumes 452-453)
• Pages: 745-748
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.452-453.745
• Online since: November 2010
• Authors: Norio Kawagoishi, K. Kariya, Yan Nu, S. Furumoto, Eiji Kondo
• Keywords: Crack Initiation, Crack Propagation, Extruded 7075-T6, Fatigue, Fracture Mechanic, Humidity, Rotating Bending, Texture

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