An investigation of the plastic failure of spheroidized steels

The mechanical properties, fracture behaviors and micro-mechanism of damage have been studied for three spheroidized steels, respectively. It is shown that void formation and growth induced by decohesion at the interface between the ferrite matrix and non-metallic particles or by particle cracking are the main reasons for the failure of these materials during plastic deformation. Experimental results show that the void volume fractions of these materials increase as strain increases, with the increasing rate being larger for the material with more carbide particles. The strain -hardening exponent and fracture strain decrease with the volume fraction of second-phase particle increasing. Based on the concepts of effective stress and strain softening induced by void evolution during plastic deformation, analytical expressions of strain hardening exponent and fracture strain for plastically damaged materials with second-phase particles are derived, respectively, and shown to be in good agreement with experimental data.