Kinetics of the ironα−ɛphase transition at high-strain rates: Experiment and model

In this article, we investigate the kinetics of the iron $\ensuremath{\alpha}\ensuremath{-}\ensuremath{\varepsilon}$ transition under laser-driven ramp compression for deformation rates ranging from 3 to $9\ifmmode\times\else\texttimes\fi{}{10}^{7}\phantom{\rule{0.28em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. As in previous work, we observe a plateau in the rear surface velocity profile at the transition. With increasing deformation rate the transition onset pressure raises from 11 to 25 GPa, while the plateau duration decreases. These kinetic effects are well reproduced by an Avrami-type kinetics model of nucleation and growth with a constant, nanosecond scale completion time, which suggests an isokinetic regime over the explored range of strain rates.