There has long existed a controversy regarding the formation of the bainite phase in steels. Nonetheless, following the clear identification of bainite in 1930, several characteristic features associated with the bainite transformation became well established. These features include: the classification into upper and lower bainite; the existence of a bainite-start temperature; and the incomplet...

The mechanism of the bainite transformation in carbon containing steels was discussed after presenting our recent experimental results; (1) the bainite transformation has its own C-curve, (2) incomplete phenomenon is a general feature of the bainite transformation, (3) bainitic fenite grows to a limited size, and (4) bainitic ferrite is highly supersaturated with respect to carbon. It was exami...

The kinetics and mechanism of bainite transformation have been studied in Fe-Cr-Mo-V-Ti-C steel high speed dilatometry backed by thermodynamic analysis. The complete transformation of austenite, however, has not occurred at any reported temperature. Obtained results confirm the incomplete reaction phenomenon with the cessation of the bainite transformation well before the paraequilibrium is ach...

The carbon concentration trapped in films of austenite between parallel platelets of bainite is often found to be much larger than that in the larger blocks of austenite between sheaves of bainite. The effect of this non-uniform distribution of carbon on the overall transformation kinetics of bainite is examined theoretically. It is found that the trapping of carbon in the films of austenite ac...

Two experimental high strength steel weld metals were produced with 7 wt-% nickel and either 2 or 0.5 wt-% manganese. Neural network predictions that it is advantageous to reduce the manganese concentration in high nickel alloys have been confirmed, with impact energy increasing from 32 to 113 J at –40uC. High resolution microstructural investigations showed that both weld metals contained main...

The possibility of producing bainite at low temperatures by suppressing transformation using substitutional solutes has been investigated, as an alternative to using large carbon concentrations to achieve the same purpose. It is found that although transformation temperatures can indeed be suppressed in this way, the difference between the bainite and martensite start temperatures diminishes. T...

Two experimental high strength steel weld metals were produced with 7 wt. % nickel and manganese at 2 or 0.5 wt. %. Neural network predictions that Mn reductions increase toughness were confirmed with impact energy increasing from 32 to 113 J at –40 °C. High resolution microstructural investigations showed that both weld metals contained mainly martensite at interdendritic regions and predomina...

During the course of our research on the quantitative design of steels [1,2], an exciting discovery was made, in which carbide–free bainite was obtained by transformation at incredibly low temperatures, as low as 125 ◦C [3]. To put this into context, the random jump distance of an iron atom at that temperature is only 10 m over a period of three weeks. The consequence of the low transformation–...

There are two well-known phenomena associated with the bainite reaction, both of which have been exploited here to enhance the mechanical behaviour of steel. Firstly, the bainite plate size decreases as the transformation temperature is reduced. Secondly, it is bad to have large regions of untransformed austenite in the microstructure; this is because they can transform, under the influence of ...

Several experimental techniques are used for phase identification and microstructure characterization of austempered vermicular cast irons (XRD, SEM, TEM and Mössbauer spectroscopy). Acicular structures were found to be composed by ferrite and austenite with average sizes compatible with those reported for bainitic ferrite in steels. An assessment of the free energy change involved in the auste...