Mechanisms of ductile fracture in ferritic-pearlitic and ferritic-martensitic steels

Abstract

AbstractCarbon-manganese steel wire rods were produced using hot rolling followed by cooling at two different rates to give ferritic-pearlitic and ferritic-martensitic microstructures. The wire rods were then drawn to wires of various diameters. The mechanisms of ductile fracture during tensile testing were studied in the wire rods and wires of two different diameters. Rates of void nucleation and growth at pearlite, cementite, and martensite second-phase particles, and at non-metallic inclusions were evaluated. Models are formulated for the void growth, taking into account the effects of tensile strain and particle deformability. These models are subsequently incorporated into a theory of ductile fracture. This theory, which encompasses void nucleation and growth, and the work hardenability of the material, is used to predict the difference in fracture strain between the ferritic-pearlitic and ferritic-martensitic steels, as well as the effect of wiredrawing strain on the fracture strain during tensile t...