Scanning electron microscopical investigation of the fracture of reinforced magnesiumand aluminum-base composites

Conclusions

As a result of a fractographic investigation of fracture surfaces of Mg/steel, Mg/B, Al/steel, and Al/B composites it was established that during the extension of a composite material consisting of a ductile matrix and ductile fibers (e.g., Mg/steel or Al/steel) in the temperature range 20–400°C the matrix fails in a tough manner and no significant changes are observed in the morphology of structure of its fracture. The fracture of the fibers occurs with waist formation. Raising the testing temperature intensifies the processes of plastic flow in the fibers, and the latter can therefore be regarded as playing a dominant role in the fracture of the material as a whole. In a composite material consisting of a ductile matrix and brittle fibers (e.g., Mg/B or Al/B) the matrix ruptures in a tough manner while the fibers fail in a brittle manner, by cleavage. At higher testing temperatures the matrix deformation processes become intensified, in consequence of which the fibers experience multiple fractures and the strength of the material falls.