Void growth and coalescence in model materials investigated by high-resolution X-ray microtomography

Abstract

The influences of work hardening behavior of materials on ductile fracture, and especially on void growth and coalescence, have been investigated in model materials by in-situ X-ray computed tomography (XCT) coupled with tensile deformation. The model materials contain an artificial void array embedded in a metal matrix. By producing such materials with different metal matrices (pure copper, brass, Glidcop = copper strengthened by $\text{ Al}_{2}\text{ O}_{3}$ nanoparticles), the influences of the work hardening behaviors on void growth and coalescence/linkage process are analyzed. This set of experiments were performed at Japanese synchrotron radiation facility SPring-8 BL20XU beamline, whereby the X-ray tomography setup with one of the highest spatial resolution in the world is available. This beamline however provides less brilliant X-rays compared to the ESRF ID15 beamline where the our previous experiments were performed Hosokava et al. (Acta Mater, 60:2829–2839, 2012), (Acta Mater, 61:1021–1036, 2013). To compensate for the X-ray absorption problems, the specimens to be tested have to be much smaller, making the experiments more difficult. Nevertheless, the growth and linkage behaviors of the artificial voids were successfully visualized, and the plastic strain whereby the linkage takes place (referred to as the linkage strain, hereafter) were quantitatively captured. The models for void coalescence developed by Thomason and by Pardoen and Hutchinson both predict coalescence rather well for both brass and Glidcop, even though the linkage events were found to be dominated by the meso/macro shear localization process.