Dual-phase steel (DPS) is a high-strength steel that has a ferrite and martensitic microstructure. DPS starts as a low or medium carbon steel and is quenched from a temperature above A1 but below A3 on a continuous cooling transformation diagram. This results in a microstructure consisting of a soft ferrite matrix containing islands of martensite as the secondary phase (martensite increases the tensile strength). The desire to produce high strength steels with formability greater than microalloyed steel led the development of DPS in 1970s.
The steel melt is produced in an oxygen top blowing process in the converter, and undergoes an alloy treatment in the secondary metallurgy phase. The product is aluminum-killed steel, with high tensile strength achieved by the composition with manganese, chromium and silicon.
- Low yield strength
- Low yield to tensile strength ratio (yield strength / tensile strength = 0.5)
- High initial strain hardening rates
- Good uniform elongation
- A high strain rate sensitivity (the faster it is crushed the more energy it absorbs)
- Good fatigue resistance
- Chakraborti, P.C.; Mitra, M.K. (2007-10-27), "Microstructure and tensile properties of high strength duplex ferrite-martensite (DFM) steels", Materials science & engineering 466 (1–2): 123–133, doi:10.1016/j.msea.2007.02.042.
- Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, ISBN 0-471-65653-4.
- Fallahi, A. (2002), "Microstructure-Properties Correlation of Dual Phase Steels Produced by Controlled Rolling Process" ([dead link]), Journal of material science & technology 18 (5): 451–454.