Magnetostructural Transition Kinetics in Shocked Iron.

A generalized Heisenberg model is implemented to study the effect of thermal magnetic disorder on kinetics of the Fe α-ε transition. The barrier to bulk martensitic displacement remains large in α-Fe shocked well past the phase line but is much reduced in the [001] α-ε boundary. The first result is consistent with observed overdriving to metastable α, while the second suggests structural instability, as implied by observation of a [001] shock transformation front without plastic relaxation. Reconciling both behaviors may require concurrent treatment of magnetic and structural order.