Iron and copper powders are the two most commonly used metallic raw materials for components formation in the powder
metallurgy (PM) industry. The quality of a PM component depends on the ability to achieve high green strength. Most PM
components are susceptible to fracture failure due to unpredictable crack propagation and inhomogeneous density
distribution. In this paper, we examined the influence of the relative density of green iron and copper powder compacts on t he
rate of crack propagation due to shear loading, or the mode II fracture toughness (KIIC). The integrated uniaxial compaction
of a fixed amount of loose powder method was used to produce the modified diametrical compression test technique (MDCTT)
samples used to evaluate the KIIC of the two metal powder compacts studied. The rate of the in-plane crack propagation in the
powder compacts slows down as the powder compacts became denser. The inverse of the fracture toughness, was found
to be related to by constants that are unique to each of the powders. The constants are 33.2 for the iron powder
compacts and 55.5 for the copper powder compacts. Furthermore, the constants were found to be related to the coefficients of
thermal expansivity for solid iron and solid copper. This study has provided a mathematical relation that can be used to
estimate the KIIC for iron and copper based powder compacts from their relative densities. The mathematical relation is also
capable of providing useful information about the thermal properties of the related metals.
Key words: Fracture toughness, relative density, metal powder compact, compression test.
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