The influence of aluminum on hot deformation behavior and tensile properties of high-Mn TWIP steels

The influence of aluminum (0-3 wt.%) on the high-temperature flow stress and recrystallization kinetics of two austenitic 25 wt.% Mn-bearing TWIP steels were investigated and compared with the behavior of a low-carbon steel. In addition, tensile properties were determined over the temperature range from -80 to 200 degrees C. It was observed that the hot deformation resistance is slightly higher for the 25Mn3Al than for the 25Mn steel, but in both steels significantly higher than for the low-carbon steel. The static recrystallization kinetics is significantly retarded in both steels compared to the rate in the low-carbon steel. The activation energies of hot deformation and static recrystallization are higher than those for the low-carbon steel. In contrast to the high temperature behavior, below RT, the 25Mn steel possessed a higher tensile strength and a higher work hardening rate than the 25Mn3Al steel due to strain-induced martensite formation. With increasing temperature up to 200 degrees C, the deformation mode changed gradually to mechanical twinning. In the 25Mn3Al steel, the elongation increased with decreasing temperature as a result of enhanced mechanical twinning. (c) 2007 Elsevier B.V. All rights reserved.