A structure created by intersecting<i>ϵ</i>martensite variant plates in a high-manganese steel

Abstract

Abstract Microstructural evidence for a new intersection structure, which has been observed in grains oriented to near ⟨101⟩ in a polycrystalline Fe–30Mn–4Si–2Al TRIP/TWIP steel, was obtained by combined use of electron backscatter diffraction and transmission electron microscopy, and the responsible intersection mechanisms are discussed from crystallographic and thermodynamic viewpoints. A γ phase with the orientation 90° rotated from the matrix with respect to the intersection axis is produced at the intersection of two dense ϵ plates, whereas the twinning of the obstacle ϵ plate occurs when the incident plate is a fine γ/ϵ lamella or a stacking fault bundle. The results are compared with various structures reported previously, and the wide variation of the intersection reactions is interpreted by their dependence on thermodynamic stability of the phases, grain orientation and shear amount. Keywords: TRIP/TWIP steelmartensitic transformationintersection reactionTEMEBSD Acknowledgements This work was financially supported in part by Japan Society for the Promotion of Science (JSPS), Grant-in-Aid for Scientific Research (B) (No. 20360318). We should like to acknowledge Materials Manufacturing and Engineering Station, NIMS, for the materials processing, and the Materials Analysis Station, NIMS, for the chemical analysis. We should also like to thank Dr. T. Kikuchi for his valuable support and suggestions for the experimental work.