Anisotropic elastic limits and phase transitions of rutile phase TiO2 under shock compression

Abstract

Anisotropic elastic limits and phase transitions of the rutile phase TiO₂ under shock compression are studied, on the basis of the measurements of particle‐velocity histories and free‐surface motions along the [100], [110], and [001] axis directions in the stress range up to 38.6 GPa. The stresses of Hugoniot elastic limit (HEL) along the [100] and [001] axis directions are determined to be 7.8±0.5 and 4.1±0.3 GPa, respectively. These different HEL stresses are reasonably analyzed by an inherent yield stress of 3.0±0.3 GPa. A Hugoniot kink at 12.2±0.6 or 17.0±0.7 GPa along the [100] or [110] axis direction, respectively, and two kinks at 10.6±0.5 and 33.7±1.3 GPa along the [001] axis direction are observed. Considering the volume changes and the recovery experiments of α‐PbO₂ phase, two former ones and the last one are suggested to correspond to the beginning of phase transitions to a α‐PbO₂ phase and a hexagonal phase, respectively. These anisotropic behaviors clearly show the typical evidences of the uniaxial strain effects of shock wave metamorphism of crystals.