| Abstract: | An elastic-plastic axisymmetric increment finite element program based on f inite deformation theory has been applied to calculate the stress-strain curves of 12CrMo ferrite-martensite steel with different martensite contents The fraction and shape of martensite in the finite element meshes should be the same as those in actual materials. The calculated stress-strain curves are consistent with experimental ones. The flow stresses at low strain stage are directly proportional to the martensite content, but at high strain stage, the effect of martensite content dies down. The strength of the steel increases slightly with decreasing martensite size. When the martensite content is 50%, the strength of steel becomes higher than that of those with ferrite matrix. At uniform strain stage, the calculate stress-strain curves on Log-Log scales show two straight lines with slopes n_1 and n_2. The strain hardening exponent n_1 at the first strain hardening stage is sensitive to the character of matrix, while n_2 at the second stage is sensitive to that of particle phase. |
