Predicting the failure strains of Al/SiC composites with reacted matrix–reinforcement interfaces

The effect of a reacted interface on the fracture behaviour and tensile ductility of Al/SiC composites was studied. Composites with two distinct interfacial microstructures were prepared by varying the contact time between the SiC particles and molten aluminium during processing. The failure strains of the composites were found to be governed primarily by the volume fractions of the matrix phases that could flow plastically during deformation. The formation of a thin reaction layer along the particle–matrix interface was observed to change the fracture pattern from one involving interfacial decohesion to one where particle breakage was dominant. A model was developed to predict the failure strain of the composite as a function of the reaction layer thickness and strain to failure of the unreinforced matrix. The predictions of the model are in good agreement with the experimental results. Thick reaction layers and/or high reinforcement concentrations led to sharp falls in the predicted failure strains. The failure strains were linearly related to the reinforcement content for the range of reaction layer thicknesses and reinforcement volume fractions considered.