Abstract
The effect of specimen orientation on the fatigue properties of extruded Al–Zn–Mg–Cu alloy was investigated, and the relationship between tensile properties and fatigue strength was established. The results show that the fatigue properties of specimens vary largely with the orientation. The specimens with 0° orientation (relative to extrusion direction) have the highest fatigue strength, i.e. 301.3 MPa, whereas the fatigue strength of specimens with 45°and 90° orientation was reduced by 13.3% and 33.5%, respectively. The fatigue strength is linearly proportional to the elongation. It was found that the crack propagation modes vary with specimen orientation, a result of the grain orientation and intergranular coarse second phase particles, leading to the difference in fatigue lives. In addition, Basquin equations for specimens in the three directions were proposed for fatigue life prediction.
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