Imaging damage evolution in a small particle metal matrix composite

It is difficult to study effectively microstructural damage in metal matrix composites (MMCs) due to artefacts arising from traditional metallographic sample preparation techniques. The sectioning and imaging capabilities of the focused ion beam (FIB) microscope provide an excellent method for studying damage accumulation in MMCs. The capabilities of the FIB system have been used to carry out a study of damage evolution in a powder-processed/hot-extruded Al2080/SiCp MMC. Microvoid damage is found to be preserved accurately during FIB sectioning, allowing measurements of the fraction of decohered particles and the void area fraction. These microscopic damage measurements are correlated with the macroscopic damage parameter, D, as determined by density measurements. Using transmission electron microscopy, the evolution of dislocation structures at the SiC-matrix interfaces has been examined. A previously unreported decohesion mechanism has been observed.