Effect of rare earths on the recrystallization behavior of T91 heatresistant steel

The effect of rare earths on the dynamic recrystallization behavior of T91 heat-resistant steel under different deformation conditions was investigated on a Gleeble-1500 thermo-mechanical simulator. The true stress-strain curves, recrystallization-temperature-time (RTT) map, dynamic recrystallization map and power dissipation map were drawn for the steels with and without rare earths. The recrystallization activation energies of these two kinds of steels at elevated temperatures were also calculated in this paper. It is found that under the deformation condition of the temperature of 850 to 1100℃ and the strain rate of 0.004 to 10 s^-1, dynamic recrystallization happens at higher temperatures and lower strain rates. Rare earths dissolve in the matrix, resulting in solid solution strengthening. Rare earth elements interact with carbon and segregate at grain boundaries or around the matrix, leading to the increasing of peak stress and peak strain as well as the improvement of recrystallization activation energy from 354.6 kJ·mol^-1 to 397.2 kJ·mol^-1. In addition, rare earths delay the starting time of recrystallization greatly, extend the time interval of recrystallization, and postpone the recrystallization kinetic process.