時効硬化Al合金押出し材の超音波疲労におけるせん断形き裂の伝ぱ

概要

論文の詳細を見る
Ultrasonic and rotating bending fatigue tests were carried out using plain specimens and specimens with a small blind hole for an age-hardened and extruded Al alloy 7075-T6 in ambient air, oxygen gas, nitrogen gas, oil and water environments. As received Al alloy had a marked texture of (111) plane. The alloy was re-crystallized to make the change in microstructure and then age-hardened at the condition of T6. Their mean grain sizes were about 8μm and 13μm, respectively. Although a crack propagated only tensile mode macroscopically under rotating bending, the one propagated in the tensile mode and then changed to the shear mode propagation under ultrasonic loading in ambient air in both Al alloys. The direction in shear mode propagation was about 35° to the extruded direction, and most of fracture surface in shear mode propagation was (100) plane. The change in propagation mode of a crack also occurred in nitrogen gas, oxygen gas and oil even in rotating bending. From these results, it was concluded that the change in crack propagation mode related to the texture of the material and absorption of water vapor.
2010-07-25