Effect of the strain reversal on austenite-ferrite phase transformation in a Nb-microalloyed steel

Multipass torsion tests were performed on an Nb-microalloyed steel at decreasing temperatures so as to analyze the effect of strain reversal - in the strain accumulation region - on the gamma -> alpha transformation kinetics. Strain reversal involved a significant delay in the start of the transformation as well as a microstructural transient compared to monotonic strain conditions. However, after several passes with no reversal performed within the inter-critical temperature region, both types of tests led to similar microstructures. (C) 2009 Elsevier B.V. All rights reserved.