Strength of liquid and solid aluminum at ultra-high strain rates produced by femtosecond laser pulses

Ablation and spallation of aluminum film irradiated by femtosecond laser pulses has been investigated both experimentally and theoretically. A new combined experimental--computational approach has been implemented to determine the parameters of laser-induced shock waves in metal films. Ultrafast time-resolved interferometric microscopy was applied to trace displacement of rear-side surface of film with picosecond-nanometer accuracy. Dynamics of the melting of a surface layer, propagation of melting front, formation of shock and rarefaction waves in aluminum films were investigated by two-temperature hydrodynamics modeling and molecular dynamics simulation. Good agreement between experimental displacement history and simulated one validates theoretical representation of processes taking place inside a film. Tensile strength of melt and spall strength of solid at an ultra-high deformation rates ~10⁹ s-¹ produced by rarefaction waves at frontal and rear-side layer of aluminum film have been obtained.