Prediction of dynamic recrystallisation behaviour of AISI type 4140 medium carbon steel

The aim of the present work was to establish quantitative relationships between the flow stress and the volume fraction of dynamic recrystallisation (DRX) as a function of processing variables such as strain rate, temperature, and strain for AISI type 4140 medium carbon steel, by means of torsion tests. Torsion tests were carried out in the temperature range 900-1100 C and the strain rate range 5.0 x 10(-2)-5.0 x 10(0) s(-1) to study the high temperature softening behaviour. For the exact prediction of flow stress, the effective stress-effective strain curves were divided into two regions, the work hardening and dynamic recovery region and the DRX region. The flow stress of the DRX region could be expressed in terms of the volume fraction of DRX. It was found that the calculated results were in agreement with the experimental flora stress and microstructure of the steel for any deformation condition.