Synthesis and characterization of Nb5Si3/Nb functionally graded composites

Through simultaneous field-activated reaction and densification, two- and five-layer graded composites of Nb5Si3 and Nb were formed. The product microstructure consisted of Nb particles in a matrix of Nb5Si3 with the composition ranging from 3.4 to 55.8 vol.% Nb (20–90 mol% Nb) for the five-layer samples. The microhardness decreased with increasing vol.% Nb, from 1199 to 732 Hv over the indicated range. Fracture toughness measured by indentation increased from about 21 to 30 MPa m1/2 over the composition range of 3.4–36.0 vol.% Nb. Crack blunting and bridging by Nb particles was observed around a microindentation.