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Title: Fcc/hcp martensitic transformation in the Fe-Mn system: Experimental study and thermodynamic analysis of phase stability

Abstract

A new experimental study of A{sub s} and M{sub s} in the Fe-Mn system has been performed by using two complementary experimental techniques, viz., dilatometry and electrical resistivity measurements, which are applied to the whole composition range where the transformation can be detected, i.e., between 10 and 30% Mn. The authors used the A{sub s} and M{sub s} temperatures as input information in an analysis based on thermodynamic models for the Gibbs energy of the face-centered cubic (fcc) and hexagonal close-packed (hcp) phases. In these models, the magnetic contribution to Gibbs energy is accounted for, which allows them to study, by calculation, the influence of the entropy of magnetic ordering upon the relative stability of the phases. The picture of magnetic effects upon the fcc/hcp transformation that emerges from their work is as follows. At low Mn contents, the martensitic transformation temperatures are larger than the Neel temperature of the fcc phase, and both A{sub s} and M{sub s} decrease linearly with increasing Mn. This encourages an extrapolation to zero Mn content, and they use that to critically discuss the available information on the fcc/hcp equilibrium temperature for Fe at atmospheric pressure. At sufficiently large Mn contents, they have M{submore » s} < T{sub N}{sup {gamma}}, which implies that the fcc phase orders antiferromagnetically before transforming to the hcp phase. Since hcp remains paramagnetic down to lower temperatures, the ordering reaction in fcc leads to a relative stabilization of this phase, which is reflected in a drastic, nonlinear decrease of M{sub s}.« less

Authors:
; ;  [1]
  1. Comision Nacional de Energia Atomica, Bariloche (Argentina). Centro Atomico Bariloche
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
109776
Resource Type:
Journal Article
Journal Name:
Metallurgical Transactions, A
Additional Journal Information:
Journal Volume: 26; Journal Issue: 8; Other Information: PBD: Aug 1995
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; IRON BASE ALLOYS; CRYSTAL-PHASE TRANSFORMATIONS; MANGANESE ALLOYS; DILATOMETRY; ELECTRIC CONDUCTIVITY; CHEMICAL COMPOSITION; THERMODYNAMIC MODEL; FREE ENTHALPY; NEEL TEMPERATURE; ANTIFERROMAGNETIC MATERIALS; PARAMAGNETISM; ENTROPY; SHAPE MEMORY EFFECT; PHASE STUDIES

Citation Formats

Cotes, S, Sade, M, and Guillermet, A F. Fcc/hcp martensitic transformation in the Fe-Mn system: Experimental study and thermodynamic analysis of phase stability. United States: N. p., 1995. Web. doi:10.1007/BF02670667.
Cotes, S, Sade, M, & Guillermet, A F. Fcc/hcp martensitic transformation in the Fe-Mn system: Experimental study and thermodynamic analysis of phase stability. United States. https://doi.org/10.1007/BF02670667
Cotes, S, Sade, M, and Guillermet, A F. Tue . "Fcc/hcp martensitic transformation in the Fe-Mn system: Experimental study and thermodynamic analysis of phase stability". United States. https://doi.org/10.1007/BF02670667.
@article{osti_109776,
title = {Fcc/hcp martensitic transformation in the Fe-Mn system: Experimental study and thermodynamic analysis of phase stability},
author = {Cotes, S and Sade, M and Guillermet, A F},
abstractNote = {A new experimental study of A{sub s} and M{sub s} in the Fe-Mn system has been performed by using two complementary experimental techniques, viz., dilatometry and electrical resistivity measurements, which are applied to the whole composition range where the transformation can be detected, i.e., between 10 and 30% Mn. The authors used the A{sub s} and M{sub s} temperatures as input information in an analysis based on thermodynamic models for the Gibbs energy of the face-centered cubic (fcc) and hexagonal close-packed (hcp) phases. In these models, the magnetic contribution to Gibbs energy is accounted for, which allows them to study, by calculation, the influence of the entropy of magnetic ordering upon the relative stability of the phases. The picture of magnetic effects upon the fcc/hcp transformation that emerges from their work is as follows. At low Mn contents, the martensitic transformation temperatures are larger than the Neel temperature of the fcc phase, and both A{sub s} and M{sub s} decrease linearly with increasing Mn. This encourages an extrapolation to zero Mn content, and they use that to critically discuss the available information on the fcc/hcp equilibrium temperature for Fe at atmospheric pressure. At sufficiently large Mn contents, they have M{sub s} < T{sub N}{sup {gamma}}, which implies that the fcc phase orders antiferromagnetically before transforming to the hcp phase. Since hcp remains paramagnetic down to lower temperatures, the ordering reaction in fcc leads to a relative stabilization of this phase, which is reflected in a drastic, nonlinear decrease of M{sub s}.},
doi = {10.1007/BF02670667},
url = {https://www.osti.gov/biblio/109776}, journal = {Metallurgical Transactions, A},
number = 8,
volume = 26,
place = {United States},
year = {1995},
month = {8}
}