Microlaminated dual phase steel presenting with high strength and ultrahigh toughness

Abstract

In the present study, a steel with the chemical composition of Fe–0·15 wt-%C–5 wt-%Mn–3 wt-%Al was designed. Its microstructure and mechanical properties were examined by optical microscopy, scanning electron microscopy and mechanical tests. It was found that hot rolling in the dual phase region of ferrite and austenite at high temperature resulted in microlaminated dual phase microstructure. An excellent combination of high strength (∼1200 MPa) and ultrahigh impact toughness (∼400 J) of the microlaminated dual phase steel was obtained. Based on the measurement of the phase volume fraction and the analysis of the fractography, it was shown that the high strength was mainly dependent on the high martensite volume fraction, while the ultrahigh impact toughness was attributed to the microlaminated microstructure.

Keywords:

• Dual phase steel
• Laminated material
• Multilayer
• Toughness
• Anisotropy