A new approach for fabrication of titanium-titanium boride periodic composite via additive manufacturing and pressure-less sintering

This study proposes a new additive manufacturing (AM) based methodology to fabricate periodic metal matrix composite architectures, with a focus on titanium (Ti)-titanium boride whisker (TiBw) composites. The manufacturing method includes binder jetting AM of the titanium matrix reinforced periodically by the extrusion of a custom-developed highly loaded resin, containing titanium di-boride (TiB2) particles. A low-temperature pressure-less sintering method was then applied to increase the mechanical strength of green samples produced from the additive manufacturing step. The sintering process also fosters the chemical reaction between the matrix and ceramic, resulting in the growth of titanium boride whisker (TiBw). The ceramic volume fraction and sintering protocol were studied as two main input variables in the design and fabrication steps. Investigating the influence of input parameters on the volume fraction and morphology (whisker formation) of TiB determined that the physical properties of the specimens, such as stiffness, were affected. The data analysis suggested a higher possibility for the formation and growth of TiBw as the temperature elevated in the sintering step (1400 °C). The ranges of 1.6 ± 0.2 GPa-3.7 ± 0.4 GPa and 83.9 ± 18.7 MPa-165 ± 13.2 MPa for the Young's modulus and Yield stress of the specimens were obtained, respectively. The stiffness of the samples was enhanced significantly by increasing the temperature and volume fraction. In particular, those samples sintered up to 1400 °C displayed 6.4%-15.2% improvement in the stiffness, although only a small fraction of the ceramic material was incorporated into the design: 2% and 4%, respectively. The similar trend of the improvement in density of the porous matrix was observed (i.e., 4.5%-19%). The range of mechanical and structural properties of the periodic composite developed in this study demonstrated the relevance of applying this method to the fabrication of biomedical and other lightweight titanium composite structures.