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The performance of steel and ductile iron can be improved through a deformation process called transformation induced plasticity (TRIP). New combinations of chemistry and heat treatment to produce microstructures that exhibit TRIP are still being developed. This paper reviews the development of advanced heat treatment cycles (conventional austempering and intercritical austempering) and the resulting properties for a variety of section sizes and steel & ductile iron chemistries.

Neutron diffraction is a powerful tool that can be used to identify the phases present and to measure the spacing of the atomic planes in a material. Thus, the residual stresses can be determined within a component and/or the phases present. New intercritically austempered irons rely on the unique properties of the austenite phase present in their microstructures. If these materials are to see widespread use, methods to verify the quality (behavior consistency) of these materials and to provide guidance for further optimization will be needed. Neutron diffraction studies were performed at the second generation neutron residual stress facility (NRSF2) at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory on a variety of intercritically austempered irons. For similar materials, such as TRIP steels, the strengthening mechanism involves the transformation of metastable austenite to martensite during deformation.