Influence of elevated temperature on the wave propagation and spallation in laser shock-loaded iron

摘要

Laser shock experiments have been performed on preheated iron samples to address the role of initial temperature on the elastic limit, wave propagation, and spall fracture in this metal over the temperature range 300.1-000 K at very high expansion rates of the order of 3 x 10~6 s"1. Time-resolved measurements of the free-surface velocity indicate a slight, roughly linear decrease of the spall strength with increasing temperature, accompanied by a clear change from brittle to ductile fracture behavior evidenced from post-shot examination of the recovered samples. The results are discussed on the basis of simulations accounting for laser-matter interaction, pressure wave propagation, and subsequent polymorphic transformations throughout the sample thickness. Over the explored range of loading conditions, the occurrence of such transformations prior to spallation, which takes place near the free-surface under tensile loading after reversion to the a phase, does not seem to strongly affect dynamic fracture.