| Description |
Although the Ti-B system is relatively well established, research in practical applications of systems such as the intermediate compound, Ti3B4, and Ti-TiB composite materials has exposed several areas of limited knowledge which are essential in the design of high performance materials. These gaps in knowledge stem largely from the difficulty in producing large, high density, high purity samples of these compounds for mechanical testing. Ti3B4 is an intermediate compound that has remained relatively under researched since its first production in 1966 and its subsequent confirmation in 1986. Mechanical testing on Ti3B4 is essentially nonexistent despite it existing between TiB and TiB2, two very stiff compounds with a variety of applications. WIEN2k density functional theory was used to estimate the elastic constants of orthorhombic Ti3B4. The nine independent orthorhombic elastic constants were calculated and the polycrystalline Voigt, Reuss, and Hill moduli were determined. The anisotropy of the crystal and its electron bonding characteristics and DOS were analyzed. Ti3B4 was synthesized in order to validate the first principles calculations. Electric field activated sintering (EFAS) was used to produce large, high density (~98% TD) Ti3B4 samples with reasonably high purity (>90%). The material was characterized by X-ray diffraction and optical microscopy, and the directionally dependent elastic modulus was measured by nanoindentation, validating the results from density functional theory iv calculations. The addition of beta-stabilizing element Mo to Ti-TiB composites results in unavoidable formation of Ti1-xMoxB phases due to substitution of Mo into the Ti sites of the TiB crystal. Ti1-xMoxB unit cells at x = 0.25, 0.5, 0.75, 1 were analyzed using WIEN2k in order to determine the effects of Mo substitution into the TiB unit cell. Ti1-xMoxB was found to reach a maximum stiffness near x = 0.5, which is noticeably higher than the stiffness of either TiB or MoB. The electron bonding was analyzed to determine the effects of Mo substitution into TiB. |
