Effect of C and Al Elements on High Resistivity and High Rigidity of Ultra-High Strength TiC(1−X)/Ti-Metal Matrix Composites Fabricated by Blended Elemental Reactive Sintering

The effects of the C and Al content on the resistivity and rigidity of newly developed ultra-high strength titanium-based metal matrix composites (Ti-MMCs) fabricated using a technique that we refer to as blended elemental reactive sintering (BERS), were investigated. The composition of the MMCs was TiC(1−X)/Ti-6Al-4V and Ti-8.6Al-5.7V, which were compared with those for TiB/, SiC/and AlN/Ti-MMCs. The blended TiC reacted with Ti powder and transformed to TiC(0.50～0.62) during sintering. The resulting TiC(0.50～0.62)/Ti-8.6Al-5.7V exhibited a specific resistance of 2.3 μΩm, a Young's modulus of 135 GPa, and a tensile strength of 1.25 GPa, with a substantial elongation of approximately 2.5％. On the other hand, TiB/Ti-6Al-4V had excellent mechanical properties, but an extremely low electrical resistance because the conducting TiB particles have a resistivity of only 0.07 μΩm. Blended SiC and AlN also reacted with Ti powder during sintering and formed a brittle phase at the interface between the particles and the Ti matrix. As a result, Ti-6Al-4V MMCs that are suitable for use as structural materials could not be fabricated using BERS with SiC or AlN.The reasons for the high specific resistance of TiC(0.50～0.62)/Ti-8.6Al-5.7V are considered to be as follows. First, due to their C deficiency, the resistivity of individual TiC(0.50～0.62) particles is approximately 1.7 μΩm, which is about three times higher than the value of 0.52 μΩm for stoichiometric TiC particles. In addition, the solubility of the excess C and Al in the Ti matrix also increases the specific resistance.