Fatigue crack initiation life prediction of ultra-fine grain chromium–bronze prepared by equal-channel angular pressing

Ultra-fine grain (UFG) Cu–0.69 wt.% Cr alloy with the average grain size ranging from 320 nm to 550 nm was prepared by equal-channel angular pressing (ECAP) with 4–6 passes. The high-cycle fatigue behaviors were studied experimently by loading in stress-control at a frequency of 30 Hz. The relevant coefficients on the energetic approach for fatigue crack initiation (FCI) life assessment were also tested and estimated with the conventional mechanical data for UFG Cu–0.69 wt.% Cr alloy. Two different models, the energetic approach and the Basquin's expression, were selected to compare and found that the fitted values of parameters based on the energetic approach are much closer to the experimental points than those of Basquin's expression. Based on the energetic approach, excellent agreement was obtained between the theoretical prediction of the fatigue crack initiation life and the experiments for the UFG materials. The fatigue limit, Δσc, and the equivalent endurance limit (Δσeqv)th, increase with increasing number of ECAP passes.