In-situ synthesized TiC/Ti-6Al-4V composites by elemental powder mixing and spark plasma sintering: Microstructural evolution and mechanical properties

Abstract

Titanium matrix composites synthesized using powder metallurgy methods have attracted significant attention due to their extraordinary mechanical properties. In this study, cost-effective and high-performance TiC/Ti-6Al-4 V matrix composites were synthesized and characterized using a combined elemental powder mixing and spark plasma sintering method. Studies on the effect of graphene nanoplate (GNP) content on microstructures of Ti-6Al-4 V matrix composites showed typical Widmanstatten structures without apparent pores and microcracks. The grain size of composites was decreased significantly with the increase of GNP content, mainly due to the pinning effect of in-situ generated TiC particles at grain boundaries, which limited the rapid grain growth of the matrix. Mechanical test results showed that their yield strength and ultimate tensile strength were 889.0 MPa and 988.3 MPa, respectively, and their total fracture elongation was maintained at ∼14.2 %. GNPs/Ti-6Al-4 V exhibited superior strength (e.g., yield and ultimate tensile strength of 1028.4 and 1121.6 MPa, which are 14.4 % and 13.5 % higher than those of the matrix) and maintained a good ductility of ∼ 9.8 % with only 0.1 wt% GNP addition. Carbon nanomaterial (such as graphene nanoplates) induced the precipitation of needle-like nano-secondary phases in trigeminal grain boundary β phases, which strengthened the β-Ti soft phase. The reinforced strength of the composite is mainly attributed to the grain refinement, secondary α phases precipitation strength and dislocations strengthening. This work provides a new methodology for fabrication of high-performance titanium matrix composites (TMCs) combination blended elemental powder metallurgy (BEPM) and sintering technology.