Shock response of iron between 143 and 1275 K

Abstract

The shock response of polycrystalline iron of 99.995% purity was studied in a series of planar impact experiments using laser interferometer monitoring of the free surface of preheated/precooled samples. On the basis of the recorded waveforms, the dynamic yield and tensile (spall) strengths of iron were determined over the 143–1275 K temperature range. Part of the recorded waveforms had a three-wave (PEL, P1, and P2 waves) structure reflecting a stress-induced phase transformation in the impacted samples. By estimating the stress σtr and the temperature Ttr on the top of the P1 wave, it became possible to determine the upper borders of stability with respect to the shock loading for both the α- and the γ-iron phases. The analysis of the P2 waves of the recorded waveforms showed that irrespective of its initial, α or γ, state the high-pressure phase of iron is the ε-phase. The same analysis yields the width, 5.18 GPa, of the mixed phase region, above which the three-wave structures are substituted by two-wave ones (PEL and P2) with solely the ε-phase behind the front of the overdriven P2 wave.