Ultrafine-grain ferrite steel and its mechanical properties

Abstract
Ultrafine-grain ferrite steel with the ferrite grain size of less than one micron has been created though heavy deformation at higher temperature regime of ferrite phase for a low carbon Si-Mn steel. It shows a very good balance of high yield strength and low DBTT in Charpy impact test. However, higher strength steel suffers from lower ductility or easier plastic instability. In order overcome the low ductility, strain hardening rate is raised by an adequate dispersion of iron carbides.