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G-phase strengthened iron alloys by design

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Title: G-phase strengthened iron alloys by design
Authors: King, DJM
Yang, M
Whiting, TM
Liu, X
Wenman, MR
Item Type: Journal Article
Abstract: Density functional theory (DFT) calculations were used to model G-phase precipitates of formula X6M16Si7 where X is Cr, Hf, Mn, Mo, Nb, Ta, Ti, V, W and Zr and M is either Fe or Ni. It was found that the occupancy of the d-orbital is correlated to the formation enthalpies of each structure. Past thermal expansion coefficient data was used to predict the lattice misfit between each G-phase and body centred cubic (BCC) Fe. All except Hf and Zr containing G-phases were predicted to have zero misfit between 581−843 K. Of the Ni containing G-phases, Mn6Ni16Si7 was predicted to have the most similar elastic properties to BCC Fe. DFT calculations of the substitution energies of Al, Cr Cu, Fe, Ge, Hf, Mo, Nb, P, Ta, Ti, V, Zr, and vacancies onto the Mn6Ni16Si7 G-phase from BCC Fe were performed. It was predicted that Cu, P and vacancies favour G-phase substitution. Suppression of the G-phase is predicted when Si content is reduced by half, at which point the BCC phase is favoured. It is hypothesised that including Zr to form a (Mn,Zr)6Ni16Si7 precipitate will allow for higher ageing temperature and expediate nucleation in an Fe alloy. Thermocalc was used to predict that a mixture of FebalCr9Ni4Si2(Mn0.6Zr0.4)1.2 (at.%) will produce a G-phase strengthened Fe alloy with potential for a good balance of strength, ductility and oxidation/corrosion resistance at room temperature. This alloy composition was experimentally determined to precipitate the G-phase in ≤24 h with cube-on-cube orientation to the BCC Fe matrix.
Issue Date: 15-Jan-2020
Date of Acceptance: 2-Nov-2019
URI: http://hdl.handle.net/10044/1/80015
DOI: 10.1016/j.actamat.2019.11.007
ISSN: 1359-6454
Publisher: Elsevier
Start Page: 350
End Page: 361
Journal / Book Title: Acta Materialia
Volume: 183
Copyright Statement: © 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor/Funder: Rolls-Royce Plc
Engineering and Physical Sciences Research Council
Funder's Grant Number: 5003023643
EP/P005101/1
Keywords: Science & Technology
Technology
Materials Science, Multidisciplinary
Metallurgy & Metallurgical Engineering
Materials Science
G-phase
Solute clustering
Density functional theory
Duplex steels
Ferritic
ATOM-PROBE
CRYSTAL-STRUCTURE
2-STEP NUCLEATION
FERRITIC STEELS
HIGH-NICKEL
PRECIPITATION
DUPLEX
NI
EMBRITTLEMENT
SEGREGATION
Science & Technology
Technology
Materials Science, Multidisciplinary
Metallurgy & Metallurgical Engineering
Materials Science
G-phase
Solute clustering
Density functional theory
Duplex steels
Ferritic
ATOM-PROBE
CRYSTAL-STRUCTURE
2-STEP NUCLEATION
FERRITIC STEELS
HIGH-NICKEL
PRECIPITATION
DUPLEX
NI
EMBRITTLEMENT
SEGREGATION
0204 Condensed Matter Physics
0912 Materials Engineering
0913 Mechanical Engineering
Materials
Publication Status: Published
Online Publication Date: 2019-11-16
Appears in Collections:Materials