Reactive-Sinter-Processing and Attractive Mechanical Properties of Bulk and Nanostructured Titanium Boride


  • Based in part on the thesis submitted by Shawn Madtha for the M.S. degree in the department of metallurgical engineering, The University of Utah, Salt Lake City, UT 84112.

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An approach to synthesize bulk nanostructured titanium boride (TiB) ceramic material having a whisker-like microstructure with a very attractive combination of mechanical properties is presented. The material is made of a three-dimensional network of high aspect ratio TiB whiskers that are created in situ during reaction sintering of micron-sized component powders at pressures of 15–20 MPa and at relatively low temperatures (<1400°C). It is shown that the properties are sensitive to the amount of titanium used in the reaction-sintering process. The mechanism of formation of nanostructured TiB whiskers and the process of densification, both facilitated by tri-modal powder particle packing and liquid/β-phase regions, are illustrated. Mechanical property evaluations indicate that, unlike conventional nanoceramics, a good combination of hardness, strength, and toughness can be achieved by the control of microstructure. For example, the best TiB composition synthesized here resulted in a Vickers hardness of 16 GPa, an elastic modulus of 425 GPa, a mean flexural strength of 800 MPa, and a SEPB fracture toughness of 5.2 MPa√m. This combination of properties, from the perspective of room temperature applications, places the material on par with certain grades of silicon nitride (Si3N4) indicating that the material offers significant potential for further development.