Evolution of intragranular stresses and dislocation densities during cyclic deformation of polycrystalline copper

Abstract

We have used the cross-correlation based high resolution electron backscattering diffraction (HR-EBSD) technique to evaluate at high spatial resolution the spatial patterning of the type III intragranular residual stresses and geometrically necessary dislocation (GND) density within polycrystalline Cu after cyclic deformation. Oxygen free high conductivity (OFHC) polycrystalline copper samples were cyclically deformed under stress-control at a load ratio of 0.1 and EBSD measurements were made at points throughout the early stages of fatigue when strain amplitudes and cyclic creep rates are changing most significantly, namely at 0 cycles, 2 cycles, 200 cycles and 2000 cycles. Statistical analysis is presented showing that moderate correlations exist between stored GND density, residual intragranular stress and distance from the nearest grain boundaries and/or triple junctions.