Isotropic phase transition of single-crystal iron (Fe) under shock compression

The α−ɛ phase transition stresses of single-crystal iron under shock compression along the [100], [110], and [111] crystal orientations were measured to be ∼13.3 ± 0.5, 13.5 ± 0.4, and 12.8 ± 0.4 GPa, respectively. Within the uncertainty of the measurement, the phase transition stresses of single crystal iron do not show obvious orientational dependence. These results differ from the simulation studies of the nonequilibrium molecular dynamics. We suggest that single crystal iron loses most shear stress beyond the Hugoniot-elastic-limit and the phase transition happens under a nearly hydrostatic state.