Current Opinion in Solid State and Materials Science, Special Issue on Bainite, Volume 8, 2004

Bainite Transformations (Preface)

Pages 211 to 211

Bhadeshia, Harry

Recent progress: kinetics of the bainite transformation in steels

Pages 213 to 217

Takahashi, Manabu

Abstract: There are two different approaches to model the kinetics of the bainite transformation. The diffusional growth model needs to adopt the solute drag effect, and a quantitative approach is proposed although the diffusion of substitutional alloying elements is not fully accepted experimentally. The nucleation-controlled model based on the displacive and diffusionless nature of the bainite transformation, combined with the kinetics of cementite formation in austenite and in ferrite as the simultaneous reactions.

Partitioning of carbon from supersaturated plates of ferrite, with application to steel processing and fundamentals of the bainite transformation

Pages 219 to 237

Speer, John G., Edmonds, David V., Rizzo, Fernando C., Matlock, David K.

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 and 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 and 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 [alpha]/[gamma] 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.

Reduced-activation bainitic and martensitic steels for nuclear fusion applications

Pages 239 to 250

Klueh, R.L.

Abstract: Reduced-activation steels were developed to enhance safety and reduce adverse environmental effects of future fusion power plants. Martensitic and bainitic steels were developed during the 1985-1990 timeframe, and the feasibility of their use for fusion was investigated in an international collaboration from 1994 to present. Work continues to improve the steels and understand the effect of neutron irradiation on them.

Very strong bainite

Pages 251 to 257

Caballero, F.G. and Bhadeshia, H.K.D.H.

Abstract: Steel with an ultimate tensile strength of 2500 MPa, a hardness at 600-670 HV and toughness in excess of 30-40 MPa m1/2 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.

Transformation-induced plasticity for high strength formable steels

Pages 259 to 265

Jacques, P.J.

Abstract: Recent advances in the development of high performance steels presenting improved properties of strength and ductility rely on the TRIP effect, i.e. on the mechanically-induced martensitic transformation of the retained austenite dispersed in a soft ferrite-based matrix. As a consequence, the stabilisation and retention of austenite at room temperature have become of primary importance, leading to specifically designed steel grades and thermal or thermomechanical treatments. Particularly, carbon enrichment of the austenite during intercritical annealing and bainite transformation was found to be very effective in retaining austenite. This metastable austenite then progressively transforms during straining, bringing about a large increase of the work hardening rate. This increase results from the stress and strain partitioning continuously evolving with the appearance of the hard martensite.

The mechanism of acicular ferrite in weld deposits

Pages 267 to 278

Babu, Sudarsanam Suresh

Abstract: Research has shown that the acicular ferrite microstructure in steel weld metal, which provides an optimum combination of strength and toughness, is indeed intragranularly nucleated bainite. It is possible to maximize the content of acicular ferrite by increasing the intragranular nucleation sites while maintaining a critical weld metal cooling rate and the steel hardenability. This paper highlights recent research related to nucleation and growth of acicular ferrite during decomposition of austenite.

Effects of strong magnetic fields on bainitic transformation

Pages 279 to 284

Ohtsuka, Hideyuki

Abstract: Effects of magnetic fields on bainitic transformation temperature, transformation behavior and transformed structures in Fe-based alloys are reviewed, and compared with corresponding effects on ferrite, pearlite and martensite. Bainitic transformation start temperature is increased and the transformation behavior is accelerated by applying magnetic fields. A magnetic field of 10 T is much more effective than the applied stress of 172 MPa for the acceleration of bainitic transformation. No magnetic effect on the transformed structure was observed so far except that the volume fraction of bainite is much larger in magnetic fields.

Structure-properties relationship in TRIP steels containing carbide-free bainite

Pages 285 to 303

De Cooman, B.C.

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.

Bainitic and martensitic creep-resistant steels

Pages 305 to 311

Abe, Fujio

Abstract: Great advancement has been achieved in the analysis of specific microstructure instability causing a loss of creep strength at 550 [deg]C and above, the prediction of onset time of the creep strength loss and theoretical modeling of precipitation sequences in power plant steels. A number of new alloy-design concepts based on microstructure stabilization have been proposed for the development of highly creep-resistant bainitic 3Cr and martensitic 9-12Cr steels with higher creep rupture strength than existing high strength steels such as T23 and P92.

Superalloys Titanium Bainite Martensite Widmanstätten ferrite
Cast iron Welding Allotriomorphic ferrite Movies Slides
Neural Networks Creep Mechanicallly Alloyed Theses Retained Austenite

PT Group Home Materials Algorithms Any Valid CSS!