Abstract
A novel TiB 2 -based composite, with metallic vanadium and nano-graphite additives, was fabricated by spark plasma sintering. A comprehensive investigation was carried out to clarify the sintering behavior and interfacial phenomena. The in-situ synthesis of crystalline V 3 B 4 , V 6 C 5 , and TiC phases was proved. The formation of V 6 C 5 was attributed to the ordering phase transformation promoted by carbon vacancies in the initially-synthesized VC. TiC was formed due to the reduction of TiO 2 impurity with graphite additive. Simultaneous addition of vanadium and graphite not only resulted in the reduction of B 2 O 3 impurity, but also the synthesis of V 3 B 4 nano-crystals, which shows the critical role of oxide impurities on the final phase arrangement. The liquid state of B 2 O 3 at high temperatures promoted the possibility of such reactions. The in-situ formation of such phases led to significant improvements in the mechanical properties. Compared to the monolithic TiB 2 consolidated through similar conditions, 50% increase in fracture toughness and 27% enhancement in elastic modulus were observed.
Published Version
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