The development of scanning X-ray diffraction phase mapping techniques using automated Rietveld refinements.

Abstract: A methodology for determining inhomogeneities in microstructural features has been established using scanning X-ray diffraction (SXRD) and automated Rietveld refinements. The method has proven successful for spatially resolved quantitative phase analysis or "phase mapping" of retained austenite on a variety of martensitic steel samples, including carbon case-hardened steel bars and quenching and partitioning (Q&P) steel sheets. In addition, the mechanical stability of retained austenite was investigated in bend tested (Q&P) steels after various loading conditions. The results showed a decreasing austenite content from 7.9 wt% to 0 wt% after fracture. The phase distribution was further investigated using SXRD measurements on the cross-sectional area in the region of the bend, indicating an uneven distribution of retained austenite with higher concentrations in the compression side.