Bainite in the light of rapid continuous cooling information

Rapid continuous cooling of pure iron can produce three different transformations yielding acicular structures: Widmanstatten alpha, lath martensite, and lenticular martensite. The information on their extensions into binary systems with carbon, nickel, and chromium has been reviewed, and admittedly rough methods have been used for estimating growth rates in order to examine the role of diffusion. The effect of alloying elements on their plateau temperatures and growth rates indicates that Widmanstatten alpha in Fe-C alloys grows under conditions close to local equilibrium for carbon, and it is suggested that the same should hold for edgewise growth of bainite. In Fe-Ni alloys, there are indications that Widmanstatten alpha grows under a considerable solute drag, an effect which may also occur for bainite. In Fe-Cr alloys, the solute drag effect seems to be weaker but may increase with the carbon content.