Journal ArticleDOI
Partitioning of carbon from supersaturated plates of ferrite, with application to steel processing and fundamentals of the bainite transformation
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TLDR
In this article, a model for carbon partitioning between supersaturated ferrite and retained austenite is presented, where the process involves quenching the remaining austenites below the martensite-start temperature, followed by a partitioning treatment to enrich the remaining Austenite with carbon.Abstract:
A model is reviewed, that describes the endpoint of carbon partitioning between supersaturated ferrite and retained austenite. A new process, quenching and partitioning (Q&P), has been developed recently to intentionally employ such partitioning in creating useful ferrous microstructures containing retained austenite. The process involves quenching austenite below the martensite-start temperature, followed by a partitioning treatment to enrich the remaining austenite with carbon, thereby stabilizing it to room temperature. Recent experimental studies have confirmed that Q&P provides a viable means to create microstructures containing carbon-enriched retained austenite, and attractive property combinations have been achieved in a variety of materials, while opportunities remain for further optimization. Furthermore, some implications of the partitioning model with respect to fundamentals of the bainite transformation are discussed, including the possibility of displacive growth under carbon diffusion control, with an austenite composition at the α/γ interface represented by the (adjusted) T0 composition. It is suggested that individual movements of iron atoms are likely during growth of Widmanstatten ferrite, and that there may be a need for further consideration of thermally activated iron-related processes in general.read more
Citations
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Quenching and partitioning martensite-a novel steel heat treatment
TL;DR: In this paper, a novel concept for the heat treatment of martensite, different to customary quenching and tempering, is described, which can be used to generate microstructures with martensites/austenite combinations giving attractive properties.
Journal ArticleDOI
Carbon partitioning to austenite from martensite or bainite during the quench and partition (Q&P) process: A critical assessment
Amy J. Clarke,Amy J. Clarke,John G. Speer,Michael K Miller,Robert E. Hackenberg,David V. Edmonds,David K. Matlock,Fernando Rizzo,Kester D. Clarke,E. De Moor +9 more
TL;DR: In this article, two proposed mechanisms for carbon enrichment during partitioning include carbon transport from martensite and/or the formation of carbide-free bainite, and experimentally measured austenite fractions are difficult to explain.
Journal ArticleDOI
Driving Force and Logic of Development of Advanced High Strength Steels for Automotive Applications
TL;DR: In this article, the authors present the driving forces and logic of development of various high strength steels for automotive applications since 1980s and highlight the importance of crash performance, weight saving, formability, and rigidity.
Journal ArticleDOI
Enhanced ductility and toughness in an ultrahigh-strength Mn-Si-Cr-C steel: The great potential of ultrafine filmy retained austenite
TL;DR: In this article, the formation process of the bainitic microstructure as well as martensite and retained austenite was revealed by conducting dilatometry, X-ray diffraction, scanning electron microscopy, electron backscatter diffraction and transmission electron microscope (TEM).
Journal ArticleDOI
Bainite and martensite start temperature calculated with exponential carbon dependence
TL;DR: In this article, the start temperatures of bainite (Bs) and martensite (Ms) formation exhibit an exponential carbon dependence and empirical models are proposed to describe this specific carbon dependence.
References
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TL;DR: It is shown how advanced thermodynamic calculations have become more accessible since: - A more user-friendly windows version of Thermo-Calc, TCW, has been developed, and there is an increasing amount of thermodynamic databases for different materials available.
Journal ArticleDOI
A general equation prescribing the extent of the austenite-martensite transformation in pure iron-carbon alloys and plain carbon steels
D.P. Koistinen,R.E. Marburger +1 more
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Steels, Microstructure and Properties
TL;DR: In this article, the authors studied the effects of alloying elements in iron-carbon alloys and the formation of martensite, bainite reaction and acicular ferrite reaction.
Journal ArticleDOI
Carbon partitioning into austenite after martensite transformation
TL;DR: In this paper, a model is developed to describe the endpoint of carbon partitioning between quenched martensite and retained austenite, in the absence of carbide formation.
Book
Bainite in Steels
TL;DR: The mechanism of the bainite transformation in steels is reviewed in this paper, with a summary of the early research and concluding with an assessment of the transformation in the context of the other reactions which occur as austenite is cooled to temperatures where it is no longer the stable phase.