AbstractUsing the modified Crussard–Jaoul analysis, the strain hardening behaviour of a predeformed 1020 dual phase steel with quenching and quenching plus tempering treatments was examined, showing that this dual phase steel deforms in two stages. The relationships between the maximum uniform strainεu, the stress ratio (true initial stressσ0true maximum stressσu) and the strain hardening exponents in the first stage and the second stage (m1and m2) were derived based on the Swift equation and the Considere instability criterion, which showed good agreement with the experimental results for the present 1020 dual phase steel. The dependence of strengthσuand ductilityɛuof dual phase steel on the exponents m1and m2was discussed using the two derived relationships.MST/1631