Microscopic deformation behaviour of martensitic–ferritic dual-phase steels

Abstract

The deformation behaviour of the two phases of three plain carbon dual-phase steels after various treatments has been studied using a scanning electron microscope equipped with a tensile straining stage. The distribution of strains between the ferrite and martensite phases, as well as among the different grains of each phase, was observed to be inhomogeneous. The martensite/ferrite strain ratio, which defines the degree of uniformity of straining between the phases, depends on the microstructural parameters of the steels: it increases with increasing volume fraction of martensite, but decreases as the carbon content of the martensite increases. Tempering at various temperatures causes a decrease in the martensite/ferrite microhardness ratio and hence causes an increase in the strain ratio. The macroscopic strain of the specimen at which the martensite begins to deform was also found to be dependent on the microstructural parameters. Regions of applicability of the existing theories of the strength of dual-phase steels can be estimated according to the deformation condition of the martensite.MSTj 235

Strain-hardening behaviors of dual phase steels with microstructure features

“…This result can be regarded as mechanical property of microstructure and conforms to the observation of Ref. [44][45][46]. The trend of dislocation mean free path of Martensite in Fig.…”

A unique numerical iterative approach for modelling individual phase stress-strain curves in dual phase steel

“…The strain ratio ε f εm decreases with increasing V m , which indicates that there is lower strain incompatibility between the phases with increasing amount of martensite in DP steels. Similar behaviour was observed experimentally by Shen et al [18] and Su and Garland [19]. The strain ratio ε f εm showed an initially increase during the early stage of deformation, followed by a subsequent decrease after reaching global strain values of around 0.03.…”

Failure mechanisms in DP600 steel: Initiation, evolution and fracture

“…Shen et al [13] determined the strain distribution in the ferrite and martensite phases by measuring the average relative elongations of each phase along the tensile direction in various DP steels. They reported that the macroscopic strain at which martensite deformation commenced depended on the microstructural configuration of the steel.…”

“…The micro-scale deformation of materials has been mainly studied through the observation of microstructural evolution using different techniques including insitu mechanical testing combined with strain measurements at a microscopic scale [9,[13][14][15][16][17].…”