Fabrication, microstructure and mechanical properties of in situ formed particle reinforced titanium matrix composite

Abstract

The field of particulate reinforced titanium matrix composites (TMCs) has seen significant progress and breakthroughs over the last two decades. Among the particulate reinforced TMCs, Ti/TiB composites have been studied and well adopted in the industry. Despite many advantages, Ti/TiB composites, however, do not possess high wear resistance. Contrary to Ti/TiB composites, incorporation of Si3N4 into the Ti matrix can significantly increase the wear resistance. This study makes use of both reinforcements (Ti/TiB composite as core material and Ti/Si3N4 as shell material) to produce a high strength, high wear-resistant hybrid composite system. The resultant composites were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. The results revealed complete decomposition of Si3N4 reinforcement and the formation of needle-shaped TiB whiskers, indicating that in situ reaction occurred during the vacuum sintering of the powder compacts. All the composite samples had a high sintered density. The hardness of the composites increased with an increase in the mass fraction of Si3N4. Tensile strength and tribological properties were determined and found to be dependent on the mass fraction of the reinforcements, respectively. The results show that by combining the two reinforcements, composite with a high-strength core and a high wear-resistant surface can be realized.