Fatigue-induced grain growth and formation of slip bands in Cu processed by equal channel angular pressing

Abstract

In order to elucidate the effect of the microstructure on fatigue behavior of ultrafine grained copper, fatigue tests were conducted using copper processed by equal channel angular pressing through 4, 8 and 12 pass numbers. The evolution of microstructure and surface damage during cyclic stressing was monitored. For samples processed by 8 and 12 passes, dynamically recrystallized grains were formed and these grew with subsequent stressing. Slip bands were initiated inside such grains. For samples processed by 4 passes, the formation of slip bands was likely to occur inside dynamically recovered coarse grains. The physical basis on the phenomena leading to the initiation of fatigue cracks was discussed from the viewpoint of microstructure and surface damage evolution.