Textural evolution of Fe under shock compression and through the α - ε phase transition

Combined laser-driven dynamic shock compression and X-ray diffraction (XRD) experiments at X-ray Free Electron (XFEL) facilities allow materials to be studied through elastic and plastic deformation, including solid-solid phase transformations, at ultra-fast timescales. The α-ϵ phase transition in Fe is one of the most extensively studied phase transitions, with multiple possible orientation relationships (ORs) reported in literature. Determination of the ORs between the ambient and high-pressure phases of dynamically compressed materials can be achieved using single-crystal or highly textured samples, or by recovery of shocked samples. However, determination of ORs for materials with more complex starting textures has remained elusive.

We have studied the textural evolution of rolled Fe foils shocked during the EuXFEL 2740 community experiment. Fe shocked below the phase transition pressure experiences a textural change consistent with grain rotations caused by slip, with observable fibre splitting. Fe shocked at high pressures above 60 GPa exhibits a preference for one of the six reported Burgers OR variants for the α-ϵ phase transition.