Abstract
High temperature flow behaviour and recrystallization kinetics of two high Mn Al-bearing twinning induced plasticity (TWIP) steels, 25Mn6Al and 30Mn4.5Al4Cr (in wt%) have been investigated using hot compression testing and compared with 25Mn and 25Mn3Al steels which were tested previously. Al alloying affected the initial flow stress levels, but, at higher strains, 25Mn6Al and 30Mn4.5Al4Cr showed intermediate or even the lowest flow stresses whereas 25Mn3Al possessed the highest flow resistance. These results are explained by the strengthening influence of the Al addition, but softening by the ferrite at 1100 to 1000 °C and by the intense dynamic recovery in 25Mn6Al and 30Mn4.5Al4Cr steels, where a higher stacking fault energy enhanced dynamic recovery. The activation energies of deformation are about 400 kJ/mol reflecting a small influence of Al. Dynamic recrystallization could only occur at the highest temperatures and the lowest deformation rates. The static recrystallization rate was the fastest while ferrite was present, but otherwise, Al or Cr had only small effects.
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