Experimental Investigations on Plastic Deformation and Densification Characteristics of P/M Fe–C–Cu–Mo Alloy Steels Under Cold Upsetting

Abstract

Powder metallurgy (P/M) alloy steel containing copper (Cu) and molybdenum (Mo) has tremendous potential in various industrial sectors. The present work investigates the effects of Cu and Mo addition on plastic deformation/densification characteristics of P/M plain carbon (Fe–0.5%C) steel. Sintered preforms of 1 and 2% addition of Mo and Cu to the plain carbon steel were subjected to cold upsetting by applying uni-axial load on the preforms. The compressive stress was gradually applied and increased on the alloy steel preforms till fine crack appears on lateral surface of the deformed preforms. Various analytical stresses useful for die design are evaluated using conventional plasticity correlations. The plain carbon steel is observed to exhibit better densification and deformation properties and higher strain hardening exponent value compared to other alloy steels. The basic ferrite–pearlite microstructure coupled with the presence of pore-free copper and Mo particulates is understood to influence the deformation and densification of Cu- and Mo-added alloy steels, respectively. The Cu- and Mo-added alloy steels require more axial compressive stress to attain same level of plastic deformation and densification of the plain carbon steel. Addition of Cu and Mo to the plain steel is observed to reduce the plastic flow and densification level during cold upsetting.