In situ diffraction measurements of lattice response due to shock loading, including direct observation of the α–ε phase transition in iron

In situ diffraction is a technique to probe directly the lattice response of materials during the shock loading process. It is used to record diffraction patterns from multiple lattice planes simultaneously. The application of this technique is described for laser-based shock experiments. The approach to analyze in situ wide-angle diffraction data is discussed. This is presented in the context of single crystal [001] iron shock experiments where uniaxial compression of the bcc lattice by up to 6% was observed. Above the α–ε transition pressure, the lattice showed a collapse along the [001] direction by 15–18%. Additional diffraction lines appear that confirm the transformation of the iron crystal from the initial bcc phase to the hcp phase.