KINETICS OF AUSTENITE TRANSFORMATION DURING THERMOMECHANICAL PROCESSES

One of the most important fundamental problems of thermomechanical pro cessing (TMP) of steel is the transformation kinetics of deformed aust enite, which has a great influence on the final microstructure and mec hanical properties. In the present work, the results of more than 20 y ear's systematic study of deformation effects on the ferrite-pearlite and bainite transformations conducted by the authors and their colleag ues are discussed. The progress of isothermal austenite decomposition was measured by magnetometry, while dilatometry was used to monitor tr ansformation under continuous cooling. From a research base of about 4 0 steel grades, general conclusions of the characteristic features of austenite transformation kinetics during TMP are formulated and the fa ctors responsible for changes in the kinetics are discussed. The accel eration effects of deformation on the ferrite-pearlite transformation and the much more complicated variations in austenite decomposition ra tes in the bainite range are considered depending on deformation param eters (temperature (T), strain, post-deformation delays), transformati on conditions, and carbon and alloying content of the steels. (C) 1998 Canadian Institute of Mining and Metallurgy. Published by Elsevier Sc ience Ltd. All rights reserved.