In-Situ Grain Resolved Stress Characterization During Damage Initiation in Cu-10%W Alloy

The evolution of stress during damage initiation and accumulation in a two-phase alloy consisting of a ductile copper (Cu) matrix with a randomly dispersed brittle tungsten (W) phase was studied using multiple non-destructive experimental probes. Neutron diffraction measurements were performed to examine the macroscopic strain partitioning between the two phases during a uniaxial tension test. The same material was then examined with high-energy x-ray diffraction microscopy (HEDM) and micro-computed tomography ( μ -CT ) measurements to monitor micromechanical field evolution. The neutron diffraction data indicated a redistribution of load between the Cu and W phases as deformation proceeds. Using HEDM to monitor individual grain micromechanical behavior, an increase followed by decrease in hydrostatic stress and a similar stress triaxiality behavior were found to occur in a subset of W grains. These same W grains were found to be in close proximity to voids observed via tomography at later stages of deformation. From these observations, we conclude that high stress triaxiality development in the W particles leads to decohesion of the interface between the Cu and W phases. The debonded regions eventually grew and coalesced with neighboring voids leading to material failure.