Behaviour of metal powders during cold and warm compaction

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.