Laser shortpulse heating of a gold-chromium-gold multilayer assembly

Abstract

Laser shortpulse heating of metallic substrates results in non-equilibrium energy transport in the region irradiated by a laser beam. Although the heating duration is short, thermal strain developed due to high-temperature gradients results in high stress levels in this region. In the present study, laser shortpulse heating of a gold-chromium-gold (Au-Cr-Au) multilayer assembly is considered. An electron kinetic theory is introduced when modelling the non-equilibrium energy transport while elastoplastic analysis is carried out to obtain thermal stresses inside the multilayer assembly. A numerical scheme is introduced to discretize the governing equations while the finite element method is employed for the solution of the stress field. It is found that temperature in the Cr layer is higher than the Au layer in the surface region. This is because of a high electron-phonon coupling factor of Cr. The stress levels below the elastic limit of the substrate material are obtained. The displacement of the surface at the irradiated spot centre is in the order of 10⁻⁹-10⁻⁷m.