Ductility Deterioration due to Nonuniform Deformation in Fe-C Alloys

Abstract

The correlation between ductility in tensile test and nonuniform deformation has experimentally been investigated under various conditions (testing temperature: 193∼313 K, strain rate: 10⁻⁵∼10⁻¹ s⁻¹). Total elongation in specimens with large amounts of solute C is decreased by the dynamic strain aging, under the condition of which necking has a tendency to localize. Consequently the magnitude of local elongation after the maximum load point depends simply upon \barv_d⁄(ξv_s) only, low values of which are associated with occurrence of the dynamic strain aging, \barv_d is average velocity of mobile dislocations, v_s is diffusion velocity of C atoms and ξ is a constant depending upon the density and configuration of dislocations. In case of specimens having fine carbides in grains, the ductility deterioration under high strain rates at low temperatures is related to the localization of Lüder’s band.