Spall strength of shock-heated hafnium and the equations of state of its polymorphic modifications

he spall strength of hafnium heated by a loading shock wave to thousandths of temperatures and subjected to transformation into denser polymorphic modifications has been determined. The following problems are solved. The pressure profiles at the sample-soft barrier interface in the spall experiments with flat one-dimensional loading are measured. The equations of state of three polymorphic modifications of hafnium are constructed in the pressure range up to 100 GPa. The thermodynamic states of hafnium under the conditions of the performed experiments were calculated. These calculations, together with the results of measurements of pressure profiles, made it possible to determine the spall strength of hafnium heated in a shock compression-unloading cycle. The spall strength of hafnium was -4 (1) GPa at a temperature of 1680 (380) K. Mathematical modeling of spall experiments in the framework of a one-dimensional hydrocode was performed.