عنوان مقاله [English]
In this research, high bainite dual phase steels, with different ferrite volume fractions, was produced by the proper heat treatment
of AISI 4340 steel. Dual phase steels have been subjected to tension tests at different temperatures, from 25 C$^\circ$ to 500
C$^\circ$, with different strain rates, in order to investigate the effect of temperature on their mechanical properties. The
tensile test data were analysed according to the Hollomon equation and it was found that this steel has two stages of work hardening. The effect of ferrite volume fraction, temperature and strain rate on work hardening exponent, strength coefficient and
onset strain of stage II of the work hardening were investigated. Results showed negative strain rate sensivity and peaks in work hardening at intermediate temperatures, which were identified as two manifestations of dynamic strain aging. Also, the work hardening analysis of flow stress data revealed that, in the DSA regime, the onset strain of stage II work hardening was athermal. Finally, variations of these parameters, with differing ferrite volume fractions, were used to rationalize the deformation mechanisms
activated at different stages.