Ductile damage of tantalum under spalling effects. Experimental and metallurgical analysis

Abstract
In this paper, we examine the experimental and metallurgical features of ductile damage of some high purity tantalum under dynamic uniaxial strain loading. This particular sollicitation is obtained by performing plate impact experiments using a single stage light gas gun. Such spall tests are performed in the 5 GPa - 12 GPa range of shock pressures for a 1.5 µs pulse duration. On the one hand, free surface velocity has been measured by means of a Doppler Laser Interferometer in order to quantify the spall stress levels as a function of shock pressure. Theses results are compared to those of litterature and we found a good agreement. On the other hand, tests with soft recovery of shocked samples have been achieved for metallurgical analyses. These ones allow us to better understand the different stages of nucleation, growth and coalescence of microvoids. The advanced analysis performed in this work quantifies the size, shape and evolution of microvoids, which give us precise informations to propose well defined hypotheses fo further modelling of damage phenomena for tantalum.