AN INVESTIGATION INTO THE MECHANICAL PROPERTIES OF METALLIC POWDER COMPACTS

Abstract

In this work, an investigation of mechanical properties of powder metallurgy (PM) compacts was carried out. As it is well known, deformation and fracture of PM compacts in forming are quite different than these for solid parts. This is due to the presence of pores in the PM compacts, which gives relative density (compact density/theoretical density) less than 100%. The effect of relative density on the behaviour of PM compacts in upsetting was studied. Two theories characterizing PM compact behaviour during deformation were reviewed :the first developed by Kuhn and Downey (1973) and the second by Hwang and kobayashi (1990). To characterize the deformation of PM compacts, a simple workability index ( P) is proposed in this study considering the effect of both apparent effective stress of powder material and the hydrostatic (mean) stress components of the powder material proposed index is the same as the stress workability index ( ) proposed by Vujovic and Shabaik (1986): more negative value of the index means the addition of a hydrostatic compressive stress to the stress state which leads to a delay fracture; while more positive value of the index means the addition of a hydrostatic