Sound velocity in shock-compressed samples of the mixture of microand nanodispersed nickel and aluminum powders

Sound velocity variation behind a shock wave front is measured in pressed samples of micro- and nanodispersed mixtures of nickel and aluminum powders at pressures of 10, 30, and 60 GPa in order to verify the possibility of a reaction with the formation of nickel aluminide in a submicrosecond time range. It is shown that, in a pressure range of up to 60 GPa, the sound velocity in the samples from a nanodispersed mixture is higher than in the samples from a microdispersed mixture. Moreover, upon reaching 60 GPa, the sound velocities in both mixtures with account for errors are practically equalized, which is related to melting of the samples. Based on the data obtained, it is concluded that there is no noticeable progress of the Ni + Al reaction during less than 1 $\mu$s.