Effect of sintering temperature on microstructure and properties of graphene nanoplatelets reinforced TC21 composites prepared by spark plasma sintering.

• The effect of sintering temperature on the mechanical and friction properties of GNPs/TC21 composites were investigated. • A model of the relationship between the interfacial evolution of composites and sintering temperature was established. • The strengthening mechanism of GNPs/TC21 composites was revealed using TEM microstructural analysis. Schematic diagram of microstructure evolution with increasing sintering temperature. (a)Spherical particle sintering model, (b) TC21 spherical particle bonding at lowtemperature sintering, (c) interfacial bonding at medium temperature sintering,(d) interfacial bonding at high temperature sintering. Schematic illustration of the strengthening mechanism of TiC@GNPs bands and TiC particles/plates. (a) Synergistic strengthening mechanism of TiC@GNPs bands and TiC particles/plates, (b) Strengthening mechanism of TiC particles/plates [Display omitted] Graphene nanoplates (GNPs) have been adopted in titanium matrix composite manufacturing and design due to its superior mechanical properties. In this study, Graphene nanoplates reinforced Ti-6Al-2Sn-2Zr-3Mo-1Cr-2Nb-Si alloys (named as GNPs/TC21 composites) were prepared by using spark plasma sintering (SPS), and the effects of sintering temperature on the microstructure, mechanical and wear properties of GNPs/TC21 composites were systematically investigated. The results indicate that the sintering temperatures show a great influence on the interfacial structure. With the increase of sintering temperature from 850 °C to 1050 °C, the interfacial microstructures exhibit three morphographies: (1) The original TC21 particles coated with GNPs (850 °C); (2) A special TiC@GNPs band (900 °C−1000 °C); (3) A discontinuous network structure wrapped by TiC particles/plates (1050 °C). Mechanical and tribological properties of the GNPs/TC21 composites were investigated at room temperature. The optimal SPS temperature was 1000 °C, at which the GNPs/TC21 composites show the best comprehensive mechanical properties i.e. the ultimate tensile strength and yield strength are 1167 MPa and 1041 MPa, the friction coefficient is 0.16275 and the wear loss is 0.0179 g. The improvement of mechanical properties can be attributed to the synergistic strengthening of the load transfer effect of TiC@GNPs bands and the pinning effect of TiC particles/plates. The excellent wear resistance is mainly attributed to the pinning of TiC particles on the surrounding metal matrix and the strengthening and lubrication of GNPs. [ABSTRACT FROM AUTHOR]