Fabrication and characterization of TiB2/TiC composites

• TiB2/TiC nano-sized powder was successfully synthesized by mechanical milling of Ti and B4C blends.
• The phase evolution and reaction mechanism were investigated by XRD and FTIR spectrums.
• The effect of temperatures on the microstructures of TiB2/TiC composites was studied by SEM.
• The mechanical activation was in favor of the coherent interface between TiB2 and TiC.
• The samples fabricated by pressureless sintering at 1800 °C had uniform microstructures and higher relative densities of 98%.

TiB2/TiC composites have attracted enormous interests in the recent years due to their superior properties, such as high hardness, good wear resistance, high electrical and thermal conductivities, and high fracture toughness, comparing to their single-phase ceramics. This paper begins with a fabrication of dense TiB2/TiC composites by pressureless sintering technique using the 48 h milled powders. Diffusion was the main reaction paths for the formation of TiC and TiB2 during the milling process. Due to the higher diffusivity of C than B into the Ti matrix, TiC was formed within 18 h of milling, earlier than TiB2. The powder used for pressureless sintering consisted of nano-sized TiC and TiB2 particles, and the particle sizes ranged from 30 to 50 nm. The samples sintered at 1800 °C for 2 h and exhibited the superior mechanical properties including relative densities higher than 98%, hardness (94.7, HRA), excellent bending strength (487 MPa) and fracture toughness (5.83 MPa · m1/2). The mechanical activation was in favor of the formation of coherency between the (11¯0)TiC and (1¯21¯0)TiB2, which led to the more superior mechanical properties of TiB2/TiC composites, especially in fracture toughness.

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