On the AlN precipitation and grain refinement in the Al(N)-added medium C-Mn steels

Abstract

The precipitation of AlN particles and grain refinement in the Al(N)-added medium C-Mn steel have been studied using a Gleeble hot-deformation simulator and extraction replica TEM technique. No significant grain refinement occurs during either hot-rolling or hot-deformation/isothermal-holding, which is due to the absence of AlN precipitation; the lack of precipitation is caused by an unusually high-energy barrier for nucleation. Abrupt grain refinement occurs on reheating because of the copious precipitation of AlN during reheating. The copious precipitation of AlN during reheating is possible because thermally unstable Fe-rich sulphides act as precursors for AlN precipitation during reheating.