New developments with bainite have resulted in a steel with an ultimate tensile strength of 2500 MPa, a hardness of 600-670 HV and a toughness in excess of 30-40 MPa m [1]. The novel microstructure is generated in a high carbon (0.98 wt.%) high silicon (1.46 wt.%) steel austenitized for 15 min. at 1000 oC, and then isothermally transformed at temperatures of ∼200 oC. Iron does not diffuse durin...

For several decades, the question of carbon supersaturation in bainitic ferrite has attracted the attention of physical metallurgists. Originally, this was associated with excess carbon due to the displacive nature ofphase transformation and its subsequent trappingatdefects inbainitic ferrite. The development of advanced experimental techniques, such as atom probe tomography and in situ synchro...

A bainitic microstructure with fine ferrite plates (20 to 40 nm) in a matrix of high-carbon retained austenite, obtained by isothermal transformation at 200°C, was characterized with an energy-compensated optical position-sensitive three-dimensional atom probe. The average carbon concentration in the austenite was found to be 8.0±1.6 at.% and in the bainitic ferrite 1.1±0.7 at.%. The latter con...

Knowledge of carbon content in retained austenite (RA) with different neighbouring phases is essential to understand the chemical stability of RA, which is useful for microstructure tuning of transformation-induced plasticity (TRIP) steels. The present study investigates different morphologies and chemical compositions of RA by correlating electron backscattering diffraction, transmission elect...

Low-temperature bainite, obtained by the transformation of austenite at temperatures as low as 200oC for times as large as several days, has been reported to have extraordinary mechanical properties including the highest reported hardness of any bainitic steel. The unusual properties are a consequence of the fine scale of the microstructure, which contains bainite plates with thickness in the r...

The first evidence is provided for the existence of a tetragonal or slightly orthorhombic unit cell of bainitic ferrite. It supports the hypothesis that the excess carbon that persists in the ferrite, which is in contact with austenite, is a consequence of an increased solubility due to the change in symmetry from the conventional cubic unit cell. The deviations from the cubic cell are maintain...

The effect of tempering temperature, within the range of 400 to 700°C, on the microstructure and hardness of two super-bainitic steels, one as the control parent sample and the other with added Co & Al was investigated. Post-tempering examinations of the super-bainitic samples showed that low temperature tempering cycles (400–500°C) resulted in carbides formation, and some increases in the hard...

the unique properties of air-cooled bainitic steels have been described. a series of mn containing air-cooled bainitic steels invented by authors is presented in this paper: including low carbon granular bainitic steels, low carbon grain-boundary allotriomorphic ferrite/granular bainite duplex steels, medium and medium high carbon bainite/martensite duplex steel, and low carbon carbide free bai...

bainitic transformation at low transformation temperatures leads to a microstructure involving fine plates of bainitic ferrite and thin films of retained austenite. this microstructure has shown ultimate tensile strength of about 2.2 gpa, noticeable uniform elongation in the range of 5 to 30%, hardness values of about 600 to 670 hv and impact toughness in the range of 30 to 40 mpa m1/2. with ca...