S-N Property and Fatigue Damage of Ultrafine Grained Cu Smooth Specimens

Fatigue tests were conducted using copper processed by equal channel angular pressing (ECAP) through 4, 8 and 12 pass numbers. At high and medium stress amplitudes, the largest fatigue life was attained in the specimens processed by 8 passes, whereas the smallest one was given in 12 passes. At low stress amplitudes, S-N curves tended to coincide with a specific value of stress amplitude regardless of pass numbers. The physical background of the effect of ECAP pass numbers on S-N property was discussed from the viewpoints of microstructure and surface damage formation.