Plastic deformation behavior and construction of constitutive model in a wide range of strain rates of 800 MPa grade dual phase steel

•Effect of strain rate strengthening was concluded that Rp0.2 and Rm had maximum enhancements of 35% and 22% respectively.•Deformation mechanism with three stages were analyzed, associating with microstructure.•Affection to ferrite and martensite by various strain rate had been observed.•Affection to fracture by various strain rate had been observed.•A new modified constitutive model was constructed with consideration of modified Hall-Petch equation and grain refinement effect.