Behaviour of metal powders during cold and warm compaction

Abstract

An instrumented die was used to investigate the behaviour of metal powders during cold (ambient temperature) and warm (up to 140 degrees C) compaction. This instrument enables simultaneous measurement of density, die wall friction coefficient, the triaxial stresses acting on the powder during the course of compaction and ejection pressure. Commercial iron, titanium, aluminium, 316L stainless steel (SS) and aluminium-silicon powders were employed for investigation. The results demonstrated the advantages of powder preheating on the compaction behaviour of metal powders concerning green density, dimensional changes, frictional behaviour, ejection characteristics and compactibility. However, the outlines also determined that the response of the non-ferrous powders to powder preheating is somehow different from those of the ferrous powders. In this context, the behaviour of prealloy aluminium-silicon powders during compaction was found of particular interest, as their compactibility is strongly affected by powder preheating, whereas the dimensional changes after ejection decrease considerably. This article presents the effect of cold and warm compaction on the consolidation and ejection characteristics of ferrous and non-ferrous metal powders. The influence of compaction condition (pressure and temperature) with considering of the powder characteristics and densification mechanisms are underlined

Influence of Fe content and particle size the on the processing and mechanical properties of low-cost Ti–xFe alloys

“…We attribute the low green densities to the difficulties related to the pressing of Ti powders, which were associated with the poor deformability of the hexagonal lattice structure of Ti. Furthermore, its high resilience and high reactivity led to the development of high friction forces with the die-walls [5][6][7]. Despite the standard deviations of the measurements, a slight increase in green density was observed when Fe content increased.…”

Synthesis of polypyrrole coatings on surface of iron particles

“…Investigations16, 17 of the compressibility of aluminium powder have revealed that the powder with irregular particle morphology possessed a slightly higher ability to compaction than the powder with spherical particles. For the Fe + 0.04 wt% PPy, the morphology of particles was influenced by coating process.…”

PM processing and characterisation of Ti–7Fe low cost titanium alloys

“…However, the high reactivity of Ti gives it poor tribological properties, which leads to the development of high friction forces of the powders with the die walls in comparison with commercial, pure Fe powders, which results in losses in pressing efficiency. [27][28][29] The addition of Fe powder slightly improves this behaviour.…”