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High‐precision face‐centered cubic–hexagonal close‐packed volume‐change determination in high‐Mn steels by X‐ray diffraction data refinements
Author(s) -
Malamud Florencia,
Castro Facundo,
Guerrero Lina Maria,
La Roca Paulo,
Sade Marcos,
Baruj Alberto
Publication year - 2020
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s1600576719015024
Subject(s) - twip , materials science , austenite , diffraction , crystal twinning , diffusionless transformation , close packing of equal spheres , work (physics) , ductility (earth science) , work hardening , lattice (music) , martensite , cubic crystal system , crystallography , thermodynamics , metallurgy , microstructure , chemistry , physics , creep , acoustics , optics
High‐Mn steels attract attention because of their various technological properties. These are mainly mechanical and functional, such as the shape‐memory effect, high damping capacity, high strength with simultaneous large ductility, the TRIP/TWIP (transformation‐ and twinning‐induced plasticity) effect, low cycle fatigue and high work hardening capacity. All these phenomena are associated with the face‐centered cubic (f.c.c.)–hexagonal close‐packed (h.c.p.) martensitic transformation which takes place in these alloys. During this phase transition defects are introduced, mainly due to the large volume change between austenite and martensite. Knowing this volume change is key to understanding the mechanical behavior of these metallic systems. In the present article, a full‐pattern refinement method is presented. The proposed method uses data obtained by means of conventional X‐ray diffraction from regular bulk samples and allows a high‐precision calculation of the lattice parameters of both phases, f.c.c. and h.c.p., under conditions very different from randomly oriented (powder) materials. In this work, the method is used to study the effect of chemical composition on the volume change between the two structures. By applying empirical models, the results enabled the design and fabrication of Fe–Mn‐based alloys with a small volume change, showing the potential of this new tool in the search for improved materials.