Preparation, microstructure and mechanical properties of metal-particulate/glass-matrix composites

Composites with a borosilicate glass matrix containing different concentrations of vanadium particles were fabricated by powder metallurgy and hot-pressing. The mechanical properties and fracture behaviour of the composites were assessed by a range of techniques. Young's modulus, fracture strength in bending, and fracture toughness increased with vanadium content. By virtue of the good interfacial bonding and low residual internal stresses, an effective crack-particle interaction during fracture was achieved. The fracture toughness of composites containing 30 vol. % of vanadium inclusions was approximately 65 % higher than that of the unreinforced glass. Experimental values for the fracture toughness increment were in good qualitative agreement with the predictions of theoretical models in the literature. Extensive plastic deformation of the vanadium inclusions was not found, however. This was attributed mainly to the constraint imposed by the rigid matrix surrounding the particles and to possible embrittlement of the particles during composite fabrication at high temperatures. The brittleness index (B) of the composites was calculated and its relevance for characterisation of the ductile versus brittle behaviour of brittle-matrix composites is discussed.