Influence of carbon micro-additions on the high temperature rheology of high purity α-Fe based alloys

Five high purity base Fe-C grades, ranging from 0 to 500 ppm C, were prepared and submitted to hot compression and torsion tests. Addition of 50 ppm C induces a decrease of the apparent activation energy of the flow stress at low strains, but in contrast an increase of the latter at large strains. The compression stress-strain curves are analyzed using the Yoshie-Laasraoui-Jonas equation, which allows the dependence of strain hardening and dynamic recovery on the carbon content to be separately discussed. In the range over 200 ppm C, the carbide precipitation or the austenitic transformation occurs and additional hardening mechanisms are activated. This effect is one of the topics of the discussion