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On the Critical Driving Force for Deformation‐Induced α′‐Martensite Formation in Austenitic Cr–Mn–Ni Steels
Author(s) -
Hauser Michael,
Wendler Marco,
Weiß Andreas,
Volkova Olena,
Mola Javad
Publication year - 2019
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201800676
Subject(s) - martensite , materials science , austenite , diffusionless transformation , deformation (meteorology) , ultimate tensile strength , stress (linguistics) , metallurgy , gibbs free energy , strain energy , thermodynamics , composite material , microstructure , physics , linguistics , philosophy , finite element method
The influence of martensite formation on the mechanical properties of an Fe–16Cr–6Ni–6Mn (concentrations in wt%) austenitic stainless steel is studied by tensile tests between −70 and 300 °C. As‐quenched martensite formation is observed at temperatures below −30 °C. Deformation‐inducedα ′martensite formation, on the other hand, is triggered below 100 °C. The temperature dependence of proof stress, tensile strength, and triggering stress for martensite formation are represented on a Stress‐Temperature‐Transformation (STT) diagram. In order to determine the critical Gibbs free energy for the formation of martensite at temperatures betweenM sandM d , the chemical and mechanical contributions to deformation‐induced martensite formation are determined. The chemical term is obtained from thermodynamic calculations. The mechanical term, on the other hand, is obtained by determining the mechanical energy supplied to tensile specimens to trigger martensite formation. This is done using the model proposed by Patel and Cohen. The magnitudes of shear strain ( γ 0 = 0.23 ) and dilatational strain ( ϵ 0 = 0.023 ), required for the calculations, are obtained based on the martensite crystallography theory of Wechsler‐Lieberman‐Read. The sum of the chemical and mechanical contributions yields the critical driving force for the martensitic transformation. The results indicate a slight increase in the critical driving force for martensitic transformation at lower temperatures.