Impact Response of Pure Iron Between 150 and 1273 K

Yield and spall strengths of pure polycrystalline iron (99.995{\%} Fe) were studied in a series of VISAR-monitored planar impact experiments with initial sample temperature ranged from 150 to 1273 K. It was found that decaying with temperature yield strength of $\alpha $-iron has two local maxima; the first one in the vicinity of the iron Curie point, 1030 K, and the second one just below the temperature of the $\alpha -\gamma $ transition in iron, 1180 K. It was also found that both the pressure and the volume effect of the shock-induced $\alpha -\varepsilon $ transformation (revealed by the two-wave structure of the recorded waveforms) decrease with the test temperature achieving their minima in the vicinity of the $\alpha -\gamma $ transformation. Heating of the iron above the temperature of the $\alpha -\gamma $ transformation is accompanied by the increase of both the $\alpha -\varepsilon $ transformation pressure and its volume effect.