Microstructure and mechanical properties of TiC/Ti–6Al–4V composites processed by in situ casting route

Abstract

TiC/Ti–6Al–4V composites containing various volume fractions of TiC were produced by induction skull melting and common casting utilising in situ reaction between titanium and carbon powder. The microstructure and room tensile properties of as cast and heat treated TiC/Ti–6Al–4V composites were investigated. Bar-like or small globular eutectic TiC were found in 5 vol.-TiC/Ti–6Al–4V composite, whereas the equiaxed or dendritic primary TiC particles were found to be the main reinforcements in 10 and 15 vol.-TiC/Ti–6Al–4V composites. The as cast TiC/Ti–6Al–4V composites have shown higher strength but lower ductility than those of monolithic Ti–6Al–4V alloy. The shape and fracture of TiC particles can strongly influence the fracture and failure of the composites, and so the ultimate tensile strengths and elongations of as cast composites reduce with the increase in volume fraction of TiC. TiC particles appear to be spheroidised, and titanium precipitation can be found within large TiC particles after heat treatment at 1050°C for 8 h, which can promote the resistance to fracture of composites. Therefore, the elongations of the composites increase significantly, and the ultimate tensile strengths also have marginal increase especially for the 10 and 15 vol.-TiC/Ti–6Al–4V composites after heat treatment.