Effect of particle size on new constitutive relationship of aluminium–iron powder metallurgy composite during cold upsetting

The strain hardening and the strain rate sensitivity of a material are important phenomenons which are required to be studied during the plastic deformation of any material and these also are the important parameters in the study of workability criteria of the metals. The present investigation has been undertaken to propose the constitutive relationship for porous powder metallurgy parts during upsetting operation. The instantaneous parameters namely the work hardening exponent, the strength coefficient, the density coefficient and the strain rate sensitivity were evaluated during the cold working of sintered aluminium–iron composite with different iron particle sizes and percent of iron content under various stress state conditions, namely, the uniaxial, the plane and the triaxial. Sintered preforms with aspect ratios of 0.44 with different initial preform densities ranging from 0.8 to 0.92 were prepared and cold forged. The variation of above-mentioned parameters with respect to the relative density has been proposed for the different percent of iron content and the various sizes of the iron particles, for different initial preform densities and for the different stress state conditions. Studies showed that there is a tremendous variation in the above parameters for different iron particle sizes and iron contents, for different initial preform densities and for different stress state conditions.