Microstructure and Strength of Ni-TiB₂ Composites Containing TiB₂ Different Powder Sizes

Abstract

TiB₂ is challenging to sinter to high density due to its low self-diffusion coefficient and high melting point. Typically, metals are used as a binder phase to lower the sintering temperature. In previous research, metal-TiB₂ composites were prepared using the SPS sintering method at temperatures exceeding 1500°C. In this study, TiB₂ powders of 3μm (denoted as S-TiB₂) and 63μm (denoted as L-TiB₂) were utilized. The powders were mixed in proportions where L-TiB₂ constituted 0%, 25%, 50%, 75%, and 100% of the total TiB₂ mass. TiB₂-10Ni composites were then prepared by the SPS sintering method at 1100°C under a pressure of 50 MPa. At this temperature, TiB₂ grains did not grow, and the composites contained only TiB₂ and Ni phases. where the hardness of the composites with 25% of L-TiB₂ can reach 2122 HV, while the relative density of the composites with 50% of L-TiB₂ exhibited a hardness of 1904 HV, while the composite with 50% L-TiB₂ achieved a relative density of 99.6%. Observations indicated that the composites with 25% and 50% L-TiB₂ had smaller Ni-rich areas. The L-TiB₂ particles adsorbed a portion of the Ni, inhibiting its aggregation, which in turn improved the density and hardness of the composites.