Damage initiation in model metallic materials:: X-ray tomography and modelling

Effects of matrix elastoplastic properties and reinforcement volume fraction on damage initiation in model heterogeneous metals have been studied using in Situ tensile tests coupled with high resolution X-ray tomography. The materials consisted in two kinds of alurninium matrices (commercially pure Al and A12124 alloy) reinforced by 4 vol% or 20 vol%,, of spherical hard ceramic particles. The main damage mechanisms were found to change from particle/matrix interface decohesion to particle cracking as the matrix got harder. Quantitative analyses of experimental observations have been performed using the three dimensional images. These measurements were linked to a Weibull statistic based on different local mechanical quantities (stress, strain or energy) calculated by Finite Element in the particle or at the particle/matrix interface. The results obtained for particle cracking confirmed that this damage mechanism is intrinsic to the chosen ceramic reinforcement and the theoretical approach allowed to determine mechanical parameters such as the particle critical stress. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.