Cold upsetting experiments were carried out on sintered Fe-0.8%C steel preforms in order to evaluate the technical relationship that exist between the applied stresses against continuous deformation and densification. Powder preforms of 86% theoretical density and 0.40 of initial aspect ratio were subjected to incremental compressive loading of 0.04 MN under three different friction conditions such as dry, graphite and zinc stearate employed during deformation until fracture appears at free surfaces. Experimental results revealed that the response of applied stresses with induced strain and attained densification exhibits a continuous enhancement but with three different stages. Irrespective of friction conditions the first and third stage shows steep rise, which offers high resistance to deformation, whereas the second stage shows virtually steady state; deformation needed gradual increase in applied stresses but with high rate of densification. Further, preform deformed under without lubricant exhibited maximum strain hardening as well as an enhanced rate of strain hardening through out the deformation in comparison with lubricants employed conditions.
friction conditions; applied stresses; deformation and densification; strain hardening
