Modelling of Microstructure and Flow Stress Evolution during Hot Forging

A phenomena based description of the microstructure and flow stress evolution of metals subjected to hot working is presented. The change in dislocation density with time was determined from the dislocation generation and recovery rates. Dynamic recrystallization was assumed to initiate when the dislocation density became greater than a critical value. The flow stress was calculated as a function of the overall dislocation density of the deformed and the recrystallized grains. To validate the model a set of single hit hot compression tests were carried out on two different AFP (Ausscheidungshartende Ferritisch-Perlitische or precipitation hardened ferritic-pearlitic) steels at different strain rate and temperature combinations. The agreement between the calculated and experimental flow curves is quite encouraging.

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