Phase transition and abnormal spallation in pure iron

An experimental setup, containing the pure iron flyer and sample with the same thickness, was applied to carry out symmetric impact tests on pure iron. The free-surface velocities of the pure iron samples were obtained by VISAR. The X-ray diffraction and metallographic examination of the recovered samples exhibit that abnormal multiple spalling behaviors happen in the pure iron samples as the impact pressure is above the phase transition pressure 13 GPa. By referring the experimental results by L.R.Veeser, et al, the spalling mechanism was explored by analyzing the interaction process of stress waves. It is found that the shock-induced phase transition, release-induced reverse phase transition and rarefaction shock wave lead to the abnormal (secondary) spalling phenomena in the pure iron samples.