Abstract A study was made on the microstrueture, properties and deformation behaviour of intercritically quenched ferrite-martensite dual-phase steel 20 under coldrolling. The results indicate that both structure and properties of martensite and ferrite phases are quite different from those of single-phase ones. The conventional mixture law, which is commonly used to evaluate the strength of the fibre-reinforced composite materials seems to be not applicable. The model of deformation of the dual phase steel 20 in the process of cold rolling may be proposed by a gradual transition from stress-equal model at the starting to strain-ratio-equal model on the later stage. Its work-hardening may be attributed to a change from nonequal strengthening state to strength-ratio-equal state A summarized plot for its deformation behaviour during cold-rolling is also given to understand rather easily the relative variation of the structure and properties of each phase in the whole process.
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