Stability of retained austenite in multi-phase microstructure during austempering and its effect on the ductility of a low carbon steel

The contribution of multi-phase microstructure and retained austenite on mechanical properties of austempered and intercritical annealed Fe–0.23C–1.8Mn–1.35Si (wt%) steel was studied. The multi-phase microstructure comprised of intercritical ferrite (IF), bainite/martensite, and retained austenite....

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Bibliographic Details
Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2014-05, Vol.603, p.69-75
Main Authors: Xie, Z.J., Ren, Y.Q., Zhou, W.H., Yang, J.R., Shang, C.J., Misra, R.D.K.
Format: Article
Language:English
Subjects:
Annealing
Applied sciences
Cross-disciplinary physics: materials science
rheology
Ductility
Elasticity. Plasticity
Exact sciences and technology
Hardening. Tempering
Heat treatment
Martensitic transformations
Materials science
Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology
Mechanical stability
Metals. Metallurgy
Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
Physics
Production techniques
Retained austenite
TRIP effect
Work hardening
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Summary:The contribution of multi-phase microstructure and retained austenite on mechanical properties of austempered and intercritical annealed Fe–0.23C–1.8Mn–1.35Si (wt%) steel was studied. The multi-phase microstructure comprised of intercritical ferrite (IF), bainite/martensite, and retained austenite. During austempering, the retained austenite was stabilized, which was studied using a combination of experimental (XRD, TEM) and thermodynamic analysis. The termination of bainitic transformation combined with carbon rejection into residual austenite during the second step austempering treatment is believed to be the underlying basis for stabilization of retained austenite. This led to significant increase in uniform and total elongation (25% and 36%, respectively) and the product of tensile strength and % elongation was 33GPa%. The work hardening behavior of retained austenite exhibited a three-stage process such that necking was delayed. The increased work hardening rate is attributed to the multi-phase microstructure and TRIP effect.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2014.02.059