Microstructure and Tensile Properties of Ferritic Lightweight Steel Produced by Twin-Roll Casting

Ferritic Fe-8Al-5Mn-0.1Nb-0.1C lightweight steel has been produced by twin-roll casting (TRC) process. The microstructures, in as-cast condition and during subsequent thermomechanical treatments, and tensile properties of the steel have been investigated and compared to those of the similar steel produced with conventional ingot casting (IC). TRC significantly refines the microstructure of the steel in as-cast condition, with a formation of NbC and kappa-carbide particles within matrix and along grain boundaries. NbC particles inhibit the grain coarsening during subsequent homogenization treatment, while kappa-carbide particles promote recrystallization during final annealing by particle-stimulated nucleation mechanism. Tensile properties of the TRC steel are comparable to those of the IC steel; however, such properties of the TRC steel have been achieved under a much smaller number of processing steps, making TRC as an ideal alternative for the production of ferritic lightweight steels. Graphic