Effect of carbon content on instantaneous strain-hardening behaviour of powder metallurgy steels

Complete experimental investigation on the instantaneous strain-hardening behaviour of powder metallurgy preforms of pure iron and steels containing 0.4% and 0.8% carbon were carried out. The above-mentioned powder metallurgy sintered preforms with two different aspect ratios namely 0.39 and 0.59 were cold upset with graphite as lubricant and their strain-hardening behaviour under triaxial stress state condition was evaluated. For all the above-said preforms the stress–strain relationship was established, instantaneous strain hardening index was determined and its variation with respect to the axial strain and the relative density were plotted, studied and discussed relative to their as-sintered microstructures. Also the characteristics of the instantaneous strength coefficient with respect to the relative density was analyzed and presented.