X-ray diffraction in thermal treatments: Determination of residual austenite by X-ray diffraction

X-ray diffraction allows the analysis of residual austenite either by summation of multiple peak (Co and Mo tubes) for each phase alpha and gamma or from a couple of peaks (Co tube). Some perturbation can occur as carbide peak superposition with ferrite and austenite peaks or as lamination texture effects or as micro-bending due to quenching. Micro-bending enlarge the peaks. This phenomena is underscored when the annealing reduces the stress. The measuring out by x-ray diffraction allows to determine the best thermal treatment according to the expected mechanical properties. The measure of residual austenite allows to assess dimentionnal variation of the treated pieces due to the transformation of austenite in martensite.