Three-dimensional analysis of MMC microstructure and deformation by μCT and FE simulations

A better understanding of micro deformation and damage processes that the microstructure of particle reinforced metal matrix composites (MMCp) undergoes at microscale before macroscopical failure gives the right direction for the microstructural design of these materials. To this end, a μCT-based analysis was performed that combines μCT-experiments and FE simulations: The gauge length of tiny tensile specimens (cross-section A = 2 x 1 mm2) consisting of the MMCp systems Cobalt/Diamond and Al/B4C was imaged by tomography at different stages of deformation. 3D strain tensor fields and displacement vector fields were determined by digital image correlation of the reconstructed tomograms. Based on tomograms of the analyzed volume at the undeformed state, FE meshes were generated that model the microstructure close to reality. Using these meshes and the displacement vector fields measured at the volume boundaries, FE simulations of the deformation and damage behavior were carried out. In both composites volume strains below 1% have been found experimentally. The spatial resolution of deformation fields is limited by the characteristic microstructural length which depends on the particle diameter and the particle spacing. The results of the experiments and the simulations are compared on the basis of 3D-strain fields sampled within the analyzed microstructural region. Additionally, the impact of microstructural features on the localization of strain, the initiation of localized damage and the successive failure of the composite materials is discussed.