High-precision face-centered cubic/hexagonal close-packed volume-change determination in high-Mn steels by X-ray diffraction data refinements

F. MALAMUD; F. J. CASTRO; L.M. GUERRERO; P. LA ROCA; M. SADE; A. BARUJ

JOURNAL OF APPLIED CRYSTALLOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2020 vol. 53 p. 34 - 44

0021-8898

High-Mnsteels attract attention due to several technological properties.These are mainly mechanical and functional, such as the shape memory effect, high damping capacity, high strength with simultaneous large ductility, TRIP/TWIP effect, low cycle fatigue and large workhardening. All these phenomena are associated with the FCC-HCP martensitic transformation which takes place in these alloys. Duringthis phase transition defects are introduced mainly due to the large volume change between austenite and martensite. Knowing this volume change is key to understand the mechanical behavior of these metallicsystems. In the present manuscript, a full pattern refinement methodis presented. The proposed method uses data obtained by means ofconventional X-rays diffraction from regular bulk samples and allowsa high precision calculation of the lattice parameters of both phases, FCC and HCP, under conditions very different from randomly oriented (powder) materials. In this work, the method is used tostudy the effect of chemical composition on the volume change betweenboth structures. By applying empirical models, the results enabled usto design and obtain Fe-Mn-based alloys with small volume changeshowing the potential of this new tool in the search of improved materials.