Theoretical model for the tensile work hardening behaviour of dual-phase steel

Abstract

The modified Crussard-Jaoul analysis was employed to describe the work hardening behaviour (the ln(dσ/dϵ) vs. ln σ curves) of a 1020 dual-phase steel with quenching and quenching plus tempering treatments and with various volume fractions of martensite ( V m), which demonsrated that this dual-phase steel exhibits two stages of work hardening in the range of plastic deformation. The modified law of mixture was used to simulate the tensile stress-strain and the ln(dσ/dϵ) vs. ln σ curves for the steel. The simulations were divided in different ways in terms of the deformation state of martensite. For the steel with quenching treatment and with V m < 50%, the work hardening behaviour in the first stage of deformation can be well simulated with a model in which martensite deforms elastically and ferrite deforms plastically. For the steel with quenching treatments and with V m > 50% and the steel with quenching plus tempering treatments and with V m over the whole test range (33–85%), the work hardening behaviour in the first stage of deformation was well simulated with the assumption that martensite deforms elastically and then deforms partly elastically and partly plastically while ferrite deforms plastically. For the steel in all the above-mentioned cases, the work hardening behaviour in the second stage of plastic deformation was simulated with a model in which both phases deform plastically.