The Gibbs-Thomson effect in magnetron-sputtered austenitic stainless steel films

Magnetron sputtering of austenitic stainless steel AISI 316, which has a facecentred cubic structure (gamma), leads to films exhibiting a body- centred cubic (alpha) structure or a mixture of alpha- and gamma-phases. The microstructure of the deposited films was studied by Mossbauer spectroscopy, x- ray diffraction and transmission electron microscopy. With increasing deposition temperature a phase transformation from alpha- to gamma-phase was observed in these films. Instantaneous recording of the electromotive force shows that nickel content and deposition temperature are crucial factors for phase stability and phase formation. In room temperature deposited stainless steel films, the phase transformation after vacuum annealing can be described by the Johnson - Mehl Avrami kinetic model. These phase transformations in stainless steel films during annealing can be explained with the Gibbs - Thomson effect, where the grain boundary energy raises the Gibbs free energy. ( Some figures in this article are in colour only in the grain boundary energy raises the Gibbs free energy.