Microstructure and mechanical properties of an ultrafine grained Ti5Si3-TiC composite fabricated by spark plasma sintering

The purpose of this study was to investigate mechanical properties, microstructure and sintering behavior of ultrafine grained Ti5Si3-TiC composite synthesized by mechanically activated self-propagating high-temperature synthesis method. For this purpose, the composite was sintered at 1450 degrees C at constant pressure of 50 MPa and reached to 97% of theoretical density by spark plasma sintering technique. The XRD pattern of the sintered sample is composed of the same peaks as the synthesized sample which means that the composite is stable at high temperature. The microstructure analyses illustrate that the composite retained its fine microstructure during the sintering process. The results also show that the amount of C atoms in the structure of titanium silicide slightly increased during the sintering process. The Young's modulus and nanohardness of the composite reached 281 +/- 15.5 GPa and 16.6 +/- 0.8 GPa, respectively. In addition, Vickers indentation test results show that the composite possesses hardness and fracture toughness of 13.2 +/- 0.6 GPa and 4.7 +/- 0.1 MPa.m(1/2), respectively. Formation of microstructure with low microcracks and homogenous distribution of TiC through the matrix are responsible for relative high mechanical properties of the composite. The crack deflection is observed as the main toughening mechanism. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.