High-pressure strength and compressibility of titanium diboride (TiB2) studied under non-hydrostatic compression

The high-pressure strength and plastic properties of titanium diboride (TiB2) were investigated using synchrotron angle-dispersive x-ray diffraction (AXRD) under non-hydrostatic compression up to 42 GPa in a diamond-anvil cell (DAC). The AXRD data yielded a bulk modulus K0 = 308 ± 10 GPa with a pressure derivative K′0 = 3.4 ± 1. The experimental data are discussed and compared to the results of first-principles calculations. The compressibility of TiB2 demonstrates a strongly anisotropic property with increasing pressure. In addition, the microscopic deviatoric stress and grain size (crystallite size) were determined as a function of pressure from the line-width analysis. We can seen that the strength increases while the crystalline size decreases steeply as the pressure is raised from ambient to about 22 GPa. In other words, TiB2 starts to yield a plastic deformation at around 22 GPa, and the yield strength of TiB2 increases with pressure, reaching a value of ∼27 GPa at the highest pressure in our experiment.