Residual stress and microstructural characterization using Rietveld refinement of a carburized layer in a 5120 steel

Rietveld refinement of X-ray diffraction patterns has been used to provide microstructural information complementary to conventional X-ray residual stress measurements through a carburized layer containing a maximum vol. 25 % of retained austenite. Layers in a simple specimen were removed incrementally by electropolishing and, at each depth in addition to conventional residual stress measurements in both the martensite and retained austenite, data were collected at {Psi} = 0 for Rietveld refinement. The refinements provide accurate values for the lattice parameters in the respective phases that can be related to carbon content and microstructure. Besides to providing qualitative information concerning the microstructure and possible surface decarburization, the c/a ratio of the martensite potentially offers an independent technique for determining carbon content profiles.