Hot deformation behavior of two C–Mn–Si based and C–Mn–Al based microalloyed high-strength steels: A comparative study

• We compared the hot deformation behavior of a high Al steel to a high Si steel.
• The flow stress of high Al steel is higher.
• The activation energy of high Si steel is higher.
• The peak strain of high Al steel is higher.
• The dynamic recrystallization kinetics of high Al steel is faster.

The compressive deformation behaviors of two new 0.26C–1.56Mn–1.72Si(wt%) based and 0.23C–1.50Mn–1.79Al(wt%) based microalloyed high-strength steels were investigated and compared with each other at the temperatures from 900 °C to 1100 °C and strain rates from 0.01 s−1 to 30 s−1 on Gleeble-1500 thermo-simulation machine. It was found that the flow stress of high Al steel is higher than that of high Si steel at the same hot deformation condition due to the higher solute strengthening parameters (SSPs) of Al than that of Si. The flow stress constitutive equations of hot deformation were developed for both steels, and it was found that the activation energy Q about 396 kJ/mol for the high Si steel was higher than that (310 kJ/mol) for the high Al steel. The dynamic recrystallization behavior of both steels was also investigated and found that Al alloying delayed distinctly the onset of dynamic recrystallization, however, the dynamic recrystallization kinetics of high Al steel was faster than that of high Si steel.