Phase quantification in nanobainite via magnetic measurements and X-ray diffraction

Author-Highlights
• Magnetic phase quantification of nanobainite is presented for the first time.
• Results are compared with x-ray diffraction.
• Expression obtained that relates ferrite fraction and saturation magnetization.
• Equation derived to calculate intrinsic saturation magnetization of ferrites.
• These values agree with experimental data of the literature.

Accurate phase quantification of nanostructured bainitic steel is of importance because of the nature of its percolating structure that controls many of its mechanical properties. X-ray diffraction is the technique of choice for such analysis, but magnetic methods can be more rapid and less sensitive to defect structures. In this study, the phase volume fractions measured using both of these techniques for the specific mixtures associated with nanostructured bainite have been compared and contrasted. An expression which relates the volume fraction and the saturation magnetization is obtained and its form is found to be consistent with previous work done on duplex stainless steels and TRIP steels. The fitting constants used in many of such analyses vary significantly so an attempt is made to rationalize the differences by considering the factors that determine the intrinsic saturation magnetization of ferrite.