The effect of cobalt additions on the shock response of nickel

Abstract

The effect of the addition of an alloy element to a pure metal upon its behaviour under shock loading had been investigated. Two materials had been chosen: nickel, a face centred cubic material, and nickel–60 wt% cobalt, also a face centred cubic material but with a much reduced stacking fault energy (SFE). The influence on the shock response of cobalt additions had been studied by the plate impact technique (uniaxial strain). The experimental results allowed the determination of characteristic properties of both materials. The Hugoniots of pure nickel and its alloy were established and compared, for the range of stress 0–20 GPa. The dynamic tensile stress (pull-back stress) was then investigated at low-stress amplitudes as a function of specimen thickness to investigate the nucleation of damage. The Hugoniot elastic limit (HEL) was investigated and the dynamic tensile stress under different incident conditions was presented and discussed. The cobalt additions did not modify the shock properties in compression. The sensitivity to the pulse length duration was observed for the alloy in tension.