Highly toughened dense TiC–Ni composite by in situ decomposition of (Ti,Ni)C solid solution

Abstract

A highly-toughened TiC–Ni composite was produced by the in situ decomposition during sintering of a nonequilibrim (Ti,Ni)C solid-solution phase. The solid solution was synthesized by the mechanical milling of Ti–Ni alloy/graphite mixtures, which then decomposed to finely dispersed TiC and Ni upon heating in a vacuum. To take advantage of the fine microstructure, samples were sintered to facilitate the in situ decomposition. Densification of the (Ti,Ni)C during the sintering was achieved through the coalescence of fine particles and the concurrent decomposition of the nonequilibrium (Ti,Ni)C phase. Additional densification was obtained through liquid-phase sintering by the eutectic melting of Ni. The fracture toughness of the sintered TiC–Ni composite was notably higher than that of conventional TiC/Ti(CN)–Ni or of comparable Ti(CN)–WC–Ni composites. Its fine and dense microstructure is believed to account for the enhanced toughness. The method suggested here might represent a valuable option for the preparation of TiC–Ni composites with desirable mechanical properties.