S-N plots and related phenomena of ultrafine grained copper with different stages of microstructural evolution

Abstract

To elucidate the effect of the number of passes in equal channel angular pressing on the fatigue strength of ultrafine grained copper, fatigue tests of cylindrical specimens were conducted and the formation behavior of surface damage during cyclic stressing was studied. With the exception of extremely high- and low-stress amplitudes, the fatigue life depended on the number of processing passes and decreased according to the following sequence of pass-numbers: 8-4-12. The difference in fatigue life resulted from the crack initiation life. The physical background of different crack initiation lives among samples is discussed from the viewpoint of slip band formation and the growth of dynamically recrystallized grains. (C) 2014 Elsevier Ltd. All rights reserved.