A Study on the effect of Martensite Morphology on Mechanical Properties of High-Martensite Dual- Phase Steels

The effect of martensite morphology on the mechanical properties of high-martensite dual phase microstructure obtained by intermediate quenching(IQ)and stepquenching (SQ) of a low carbon microalloyed steel is dealt with.
The IQ-treatment results in formation of fine and
fibrous martensite morphology uniformly distributed in
the ferrite matrix. In contrast, SQ-treatment yields blocky and banded martensite and ferrite morphology. Suitable variation of intercritical annealing temp-eratures adopted for both the treatments allowed the evolution of different volume fraction of martensite within a range between 0.26 to 0.71. A carefully condu-cted comparison of tensile results and fracture surfaces of the representative samples obtained after IQ- and SQtreatments indicates that the morphology of martensite formed by the IQ-treatment offer better formability and toughness in the present dualphase steels with an increased volume fraction of martensite (>0.25).