| Description |
This study focuses on synthesizing cermet materials consisting of a two-phase structure of ductile beta-Ti solid solution phase and a hard titanium boride TiB phase, which appears as a nanostructured TiB whisker network surrounded by a beta-Ti matrix. Iron and molybdenum are used in this Ti-B-Fe-Mo alloy system as stabilizers of the beta-Ti phase to control the proportions of alpha (hcp) or beta (bcc) solid solution phases, and also have some solubility in the TiB phase, forming ternary (Ti,X)B borides. The calculation of phase diagrams (CALPHAD) approach using Thermo-Calc software was used to predict and design sample compositions and processing temperatures. Samples were synthesized by mixing Ti, Fe, Mo, and TiB2 powders at varying concentrations to achieve desired compositions. Electric-field-activated-sintering was used to synthesize samples with a reaction sintering process. This study focused on analysis of samples in the cermet range, between 50 and 70 volume percent TiB phase. Density measurements indicated that fully dense cermet materials were created. Generic two-phase microstructure was confirmed using X-ray diffraction and scanning electron microscope (SEM) techniques. Mechanical properties including flexural strength and fracture toughness were evaluated. Four-point flexural strength varied between 826 MPa and 941 MPa for 50, 60, and 70 volume percent TiB samples. Inclusion particles were responsible for initiation of fracture in flexural testing and led to variations in strength. Precracked beam fracture toughness varied between 10 and 17.8 MPa√m for 50, 60, and 70 volume percent TiB samples, with fracture toughness improving with the addition of more ductile beta-Ti phase and after heat treatment. The mechanical and physical properties of Ti-TiB cermets were compared against commercially available cermets such as WC-Co. The present samples have potential for some practical applications as cutting, shaping, or forming tools. |
