Powder Compaction Dies and Compressibility of Various Materials

Abstract

Powder compaction is the most crucial process in powder metallurgy since almost all the desired properties of a material, such as a shape, size, density, porosity, hardness, and other mechanical properties, can be controlled during this process. The powder compaction can be performed differently depending on the type of die (single-piece or split), the punch movement, and processing parameters. According to the punch movement, there are two types of compaction, uniaxial or multiaxial. Uniaxial compaction can also be divided into single-action and double-action subtypes. Thus, single-action uniaxial compaction implies that only the upper punch can move, and the lower one remains fixed. When both the upper and lower punches are moving, the process is called a double-action uniaxial compaction. If, at the same time, the powder is compacted from more than one side, then compaction is said to be multiaxial. During isostatic pressing, pressure is exerted on powder in all directions, implying a multiaxial compression. Properties of a powder metallurgy green compact depend on the type (uniaxial or isostatic) and pressure of powder compaction, as well as the type of matrix material and reinforcing agent (metallic, carbonaceous, or ceramic). This work involves a comparative study of different types of powder compaction dies. Also, the compressibility of different matrix materials (i.e., Al6061, Mg, and Cu) and various reinforcing agents (metallic, carbonaceous, and ceramic) was examined experimentally. The analysis of different powder compaction dies revealed that the isostatic pressing ensures uniform densification but is more costly. The compressibility of Al6061 was the greatest, and the compressibility of Cu 10% B₄C was the lowest. The addition of metallic and carbonaceous reinforcements enhanced compressibility, while ceramic reinforcing agents contributed to its reduction