Diffraction study of the retained austenite content in TRIP steels

The results of a study of using neutron diffraction for determining the retained austenite content of TRIP steels are presented. The study covers a wide area of materials, deformation modes (uniaxial, biaxial and plane strain), strains, and the retained austenite content as a result of these variables. It was determined using basic principles of statistics that a minimum of two reflections (hkl) for each phase is necessary to calculate a phase mass fraction and the associated standard deviation. Texture from processing the steel is the largest source of uncertainty. Through the method of complete orientation averaging described in this paper, the texture effect and with it the standard deviation of the austenite mass fraction can be substantially reduced, regardless of the type or severity of the texture.

Research highlights
► Novel orientation averaging scheme for retained austenite content measurement.
► assumption of random grain orientation generally not justified.
► Averaging scheme allows to disregard texture.
► unlike Rietveld method, averaging method does not orientation density function.
► Two independent (hkl) are necessary for retained austenite content.