On the effect of the volume fraction on martensite on the tensile strength of dual-phase steel

Dual-phase steels were prepared from thoroughly homogenized Fe-1.5wt.%Mn-0.1wt.%C and Fe-1.5wwt.%Mn-0.2wt.%C steels by intercritical annealing at 720, 740, 760 and 780°C. Their tensile strengths and the volume fractions of martensite and ferrite were determined. The following non-linear relation between the tensile strength and the volume fraction of martensite $\text{ƒ}{}_{\mathrm{m}}$ was derived. $\text{σ = σ}{}_{\mathrm{F}}\text{+ (σ}{}_{\mathrm{M}}{}^0\text{− σ}{}_{\mathrm{F}}\text{) ƒ}{}_{\mathrm{M}}\text{+}\text{K}{}_{\mathrm{M}}\text{(}\text{gC}{}_0\text{ƒ}{}_{\mathrm{M}}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$

The data obtained with the two experimental steels and those measured by N. C. Goel were statistically analysed. Values obtained for various parameters were found to be reasonable. This non-linear relationship described the experimental data more satisfactorily than the linear ones.