Stress fields near interfaces of aluminium-based metal-matrix composites

Abstract Large-angle convergent-beam electron diffraction (LACBED) is used to investigate the interfacial strain fields in a short-fibre-reinforced Al-based metal-matrix composite. LACBED patterns are simulated using the dynamic scattering theory with local variations in the scattering vectors caused by lattice distortions. Comparison of experimental and simulated patterns permits local strains to be estimated. Thermal strains and surface relaxation of the thin foil for transmission electron microscopy are considered. Long-range thermal strains caused by the fibre overlapping with localized high strains produced by spinel grains at the fibre boundary are analysed. In Al grains, local stress concentrations are reduced by the emission of dislocations. In Si precipitates, high stresses at the Si-fibre interfaces are maintained. Short-range stresses from inhomogeneities at the Si-fibre interfaces and not the long-range thermal stresses from the whole fibres dominate in Si precipitates.