[en] Ultra-fast cooling of the austenitic phase in low-alloy steel is rapidly gaining importance in controlling the microstructure and properties of the steel. At these high cooling rates, the initial formation of allotriomorphic ferrite undergoes a transition to bainite formation. Of course it is of paramount importance to control the presence of ferrite and/or bainite in the eventual microstructure. Modelling and understanding the transformation process for high cooling rates does therefore not only involve the ferrite formation, but also the bainite formation, and especially the conditions at which the transition occurs. In the present study the acoustic-emission technique is used to determine the point at which bainite formation takes over from the initial ferrite formation. The experimental results are combined with dilatometry data in order to gain a full view of the transformation process and kinetics. Moreover, the acoustic-emission technique provides essential information on the nature of the bainite formation; more specifically to what extent it can be considered displacive or diffusional.
Disciplines :
Materials science & engineering
Author, co-author :
Mertens, Anne ; Delft University of Technology > Laboratory for Materials Science
van Bohemen, S. C. M.; Delft University of Technology > Laboratory for Materials Science
Hermans, M. J. M.; Delft University of Technology > Laboratory for Materials Science
Sietsma, Jilt; Delft Uniervsity of Technology > Laboratory for Materials Science
van der Zwaag, Sybrand; Delft University of Technology > Laboratory for Materials Science
Language :
English
Title :
Acoustic-emission investigations on the ferrite and bainite formation in low-alloy steel during ultra-fast cooling