The formation mechanism of TiC/Ni composites fabricated by pressureless reactive sintering

Abstract

TiC/Ni composites were innovatively fabricated by pressureless reactive sintering method using Ni, Ti and graphite as raw materials. According to the sintering shrinkage curve, phase and microstructure evolution process of composites during reactive sintering, the formation mechanism of dense TiC/Ni composites could be divided in two stages. In the first stage, TiC layer is formed on Ti particles by the solid reaction between Ti and graphite, while Ni atom diffuses into Ti particles to generated NiTi, Ti2Ni and Ni3Ti. Besides, the solid-state sintering of Ni particles also occurs. At 1250 °C, the Ti is completely consumed, resulting in the TiC layer on Ni and continuous Ni skeleton in composites. In the second stage, the eutectic liquid phase of Ni-Ti-C is formed, and then shrinkage process begins through the dissolution-reprecipitation of TiC in Ni matrix. The relative density of TiC/Ni composites reaches 98.14% at 1360 °C.