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

In this paper, we examine the experimental and metallurgical features of du ctile damage of some high purity tantalum under dynamic uniaxial strain loa ding. This particular sollicitation is obtained by performing plate impact experiments using a single stage light gas gun. Such spall tests are perfor med in the 5 GPa - 12 GPa range of shock pressures for a 1.5 mu s pulse dur ation. On the one hand, free surface velocity has been measured by means of a Doppler Laser Interferometer in order to quantify the spall stress level s 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 so ft recovery of shocked samples have been achieved for metallurgical analyse s. These ones allow us to better understand the different stages of nucleat ion, 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.