Book•
Bainite in Steels
01 Jan 2001-
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.
Abstract: The mechanism of the bainite transformation in steels is reviewed, beginning with a summary of the early research and finishing 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. The review includes a detailed account of the microstructure, chemistry, and crystallography of bainitic ferrite and of the variety of carbide precipitation reactions associated with the bainite transformation. This is followed by an assessment of the thermodynamic and kinetic characteristics of the reaction and by a consideration of the reverse transformation from bainite to austenite. It is argued that there are useful mechanistic distinctions to be made between the coherent growth of ferrite initially supersaturated with carbon (bainite), coherent growth of Widmanstatten ferrite under paraequilibrium conditions, and incoherent growth of ferrite under local equilibrium or paraequilibrium conditions. The nature of the so-called acicular ferrite is also discussed.
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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.
1,240 citations
TL;DR: In this article, the authors review the current knowledge about the relationship between the micro-structure of cold rolled intercritically annealed low-alloy TRIP-aided sheet steels and their mechanical properties from a materials engineering point of view.
Abstract: The purpose of the present contribution is to review the current knowledge about the relationship between the micro-structure of cold rolled intercritically annealed low alloy TRIP-aided sheet steels and their mechanical properties from a materials engineering point of view. The focus is on their production in existing industrial lines and on their application in the manufacture of passenger cars with a body-in-white which offers an improved passive safety. The review aims to make clear that although low alloy TRIP-aided sheet steel is by now starting to be an established structural material in BIW manufacturing, there is still room for the further optimization of the composition and the processing. In addition, there are still a number of problems related to their physical metallurgy that require a better fundamental understanding.
753 citations
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TL;DR: In this paper, the structure and properties of bearing steels prior to the point of service are first assessed and described in the context of steelmaking, manufacturing and engineering requirements, followed by a thorough critique of the damage mechanisms that operate during service and in accelerated tests.
729 citations
25 Nov 2006-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
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.
Abstract: A novel concept for the heat treatment of martensite, different to customary quenching and tempering, is described. This involves quenching to below the martensite-start temperature and directly ageing, either at, or above, the initial quench temperature. If competing reactions, principally carbide precipitation, are suppressed by appropriate alloying, the carbon partitions from the supersaturated martensite phase to the untransformed austenite phase, thereby increasing the stability of the residual austenite upon subsequent cooling to room temperature. This novel treatment has been termed ‘quenching and partitioning’ (Q&P), to distinguish it from quenching and tempering, and can be used to generate microstructures with martensite/austenite combinations giving attractive properties. Another approach that has been used to produce austenite-containing microstructures is by alloying to suppress carbide precipitation during the formation of bainitic structures, and interesting comparisons can be made between the two approaches. Moreover, formation of carbide-free bainite during the Q&P partitioning treatment may be a reaction competing for carbon, although this could also be used constructively as an additional stage of Q&P partitioning to form part of the final microstructure. Amongst the ferrous alloys examined so far are medium carbon bar steels and low carbon formable TRIP-assisted sheet steels.
618 citations
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TL;DR: A steel with an ultimate tensile strength of 2500 MPa, a hardness at 600-670 HV and toughness in excess of 30-40 MPa/m 1/2 is the result of exciting new developments with bainite as discussed by the authors.
Abstract: Steel with an ultimate tensile strength of 2500 MPa, a hardness at 600–670 HV and toughness in excess of 30–40 MPa m 1/2 is the result of exciting new developments with bainite. The simple process route involved avoids rapid cooling so that residual stresses can in principle be avoided even in large pieces. The microstructure is generated at temperatures which are so low that the diffusion of iron is inconceivable during the course of the transformation to bainite. As a result, slender plates of ferrite, just 20–40 nm thick are generated, giving rise to the extraordinary properties.
555 citations
References
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Book•
01 Jan 1965
4,036 citations
Book•
01 Jan 1965
TL;DR: In this paper, the authors present a general introduction to the theory of transformation kinetics of real metals, including the formation and evolution of martensitic transformations, as well as a theory of dislocations.
Abstract: Part I General introduction. Formal geometry of crystal lattices. The theory of reaction rates. The thermodynamics of irreversable processes. The structure of real metals. Solids solutions. The theory of dislocations. Polycrystalline aggregates. Diffusion in the solid state. The classical theory of nucleation. Theory of thermally activated growth. Formal theory of transformation kinetics. Part II Growth from the vapour phase. Solidification and melting. Polymorphic Changes. Precipitation from supersaturated solid solution. Eutectoidal transformations. Order-disorder transformations. Recovery recrystalisation and grain growth. Deformation twinning. Characteristics of martensic transformations. Crystallography of martensitic transformations. Kinetics of martensitic transformations. Rapid solidification. Bainite steels. Shape memory alloys.
3,397 citations
TL;DR: Herstellung von teilweise in Martensit zerfallenen Austenitkristallen durch lang-same Erstarrung and nachfolgendes Abschrecken.
Abstract: Herstellung von teilweise in Martensit zerfallenen Austenitkristallen durch lang-same Erstarrung und nachfolgendes Abschrecken. — Veranderungen beim Anlassen. — Gesetzmasige Orientierung der tetragonalen und α-Eisenkristalle zum Austenit. — Flachenpolfiguren. — Beschreibung durch eine 24fache Lage. — Einfache Schiebungen als Mechanismus der Umwandlung. — Ausscheidung des Kohlenstoffs beim Anlassen. — Bemerkungen uber das Wesen der Stahlhartung.
1,093 citations
TL;DR: In this paper, the total strain in a martensite transformation was derived from the orientation relationship and the component strains, together with the correspondence, and the dimensions of the initial and final structures.
891 citations