G0310705 ショットピーニングした時効硬化Al合金の高湿度中における疲労特性([G031-07]材料力学部門一般セッション:環境と材料,材料力学部門)

Abstract

Fatigue properties of shot-peened high strength Al-Cu-Mg alloys, extruded and drawn 2017-T4, and effect of humidity on the properties were investigated in relative humidity of 25% and 85% under rotating bending. Fatigue strength was increased by shot-peening irrespective of humidity. Although fatigue strength was largely decreased by high humidity in the electro-polished specimen, there is no or little influence of humidity on fatigue strength in the shot-peened one. In the electro-polished specimen of the extruded alloy, the crack propagation changed from a shear mode to a tensile one with decreasing in stress level in high humidity, while the propagation in the shot-peened one was in a tensile mode in both humidity environments similar to the one in the electro-polished specimen in low humidity. Most of fracture surface in low humidity was occupied by striations in both specimens. On the other hand, those in high humidity were covered with slip planes in the shear mode crack, and with a few brittle facets in the extruded alloy or brittle striations in the drawn one in addition to striations in the tensile one irrespective of shot peening.