In order to investigate the influence of stress change on the fatigue behavior and fatigue life of an aluminum oxide-dispersion-strengthening copper alloy at elevated temperature, rotating bending fatigue tests were carried out under two-step loading at room temperature and 350°C. Both of static strength and fatigue strength decreased at 350°C. However, at the same relative stress σa, /σB, fatigue life was longer at 350°C than at room temperature. Although the cumulative ratios Σ (N/Nf) were nearly unity for both the low to high and the high to low block loadings at room temperature, Miner's rule did not hold at 350°C. These results were related to the stress dependence on the log l-N/Nf relation. That is, the crack length initiated at the same N/Nf was larger in higher stress level at 350°C, whereas there was no stress dependence in the relation at room temperature. The stress dependence on the relation at 350°C was caused by the suppression of crack initiation due to the surface oxidation.
