Dynamic characteristics of the γ→α phase transition of cerium at room temperature

The γ→α phase transition of 99.8% purity cerium was investigated using the passive confined split Hopkinson pressure bar experiment under a hydrostatic pressure up to 1.7GPa and at room temperature, the relationship of the hydrostatic pressure with the volume strain covering the whole process of γ↔α phase transformation was obtained, and the hysteresis loop was observed. The results show that the γ→α phase transition is the first-order with hysteresis rather than the first-order with volume discontinuity as recognized in previous researches. The γ →α phase transition occurs under the hydrostatic pressure ranging from 0.8 GPa to 1.3 GPa, whereas the inverse phase transition occurs under the hydrostatic pressure ranging from 1.1 to 0.6 GPa. The hysteresis loop shows a gap of 0.15 GPa hydrostatic pressure between the curve of hydrostatic pressure and volume strain during the γ→α phase transition and that during the inverse phase transition. The curves of the hydrostatic pressure and volume strain during the γ↔α phase transition were linear with the bulk modulus of 4.2 GPa. The mechanism behind the γ↔α phase transition is that the hydrostatic pressure drives the conversion between the phases of γ and α, which coexist during the γ↔α phase transition. Based on the mechanism of phase transition, a tri-segment linear model was constituted to describe the response of the hydrostatic pressure and volume strain in the process of γ→α phase transition. The modeled curve is found to be in good agree with the experimental curve.