Characterization of deformation stability of medium carbon microalloyed steel during hot forging using phenomenological and continuum criteria

In the analysis of any hot forming process the knowledge of interaction between microstructural behaviour and control process parameters such as temperature, strain rate and strain is very important. In the last decades, processing maps have been used to design, control and optimize hot workability of a wide range of materials. In the present work, in order to study the hot workability of a medium carbon microalloyed steel, during hot compression test, two types of processing maps have been constructed on the basis of phenomenological and continuum criteria. The studied steel does not undergo any type of unstable flows manifestations. However, all the instability maps at strain of 0.6, which is roughly the strain corresponding to steady state, reveal a domain of dynamic recrystallization, which may be considered as the optimum hot working domain. This domain is centered at about 1150 degrees C and strain rate of 10 s(-1). Also these maps reveal a domain of dynamic recovery. The comparative study of the obtained results shows the difference between the positions of stability domains predicted by the two criteria. (C) 2007 Elsevier B.V. All rights reserved.