Generation of a relief on the surface of a film coating under the surface and volume diffusion
The mechanism of generation of a relief on the surface of a solid with film coating under intensive external heating the surface layer is investigated. The longitudinal remote stresses, surface stress, volume and surface diffusion, and the thickness of the surface layer the elastic properties of which differ from the same properties of the substrate are taken into account. A semi-infinite body with a surface layer is considered under the plane deformation. Wave formation on the surface of the layer is taken up as instability of a flat shape of the surface under the small sinusoidal perturbation of this surface. According to Asaro and Tiller, it is assumed that the chemical potential gradient driving the mass transport along the surface comes from a stress variation along the surface and the surface curvature. Furthermore, it is supposed that volume diffusion that arose under the high temperature due to capillarity and stress variations in the bulk influences the evolution of the surface profile. The flux of diffusing mass through the bulk is determined by the chemical potential as well. Basing on the perturbation technique, the elastic energy at the film surface is derived from the solution of the corresponding problem. The explicit dependence of an undulation amplitude upon the time, physical and geometrical parameters of the problem is obtained. The analysis of influence of this parameters on the critical wavelength perturbed is given.