Delta-Ferrite in the Novel High Silicon Ferritic/Martensitic Steels

The microstructures of novel high silicon ferritic/martensitic steels were studied by optical microscope,scanning electron microscope and transmission electron microscope,also the mechanical properties were investigated.It is found that the addition of silicon in the steel can increase the fraction of the delta-ferrite.However,the delta-ferrite will be eliminated by increasing the carbon content to 0.25%.Delta-ferrite will reduce the strength but not decrease the toughness.Meanwhile,the matrix continuity is interrupted by the stripe-like delta-ferrite distributed along the rolling direction,which makes the fractographies of impact specimens show lamination characteristic.