Compaction and sintering characteristics of composite metal powders

Abstract

The compaction and sintering characteristics of composite metal powders are examined using aluminium-copper, aluminium-iron and copper-iron powders. The density of a composite green compact is predicted based on the compacting pressure-density curve of each powder. The effects of the volume fraction of the mixed powders and the sintering temperature on the density and hardness of a sintered part are also examined. Experimental results show that the density of the composite green compact can be predicted by the law of mixtures. The density change in the sintering of the composite green compact depends on the combination and the volume fraction of the composite powders as well as on the sintering temperature. For copper-iron mixed composite powders, the density of the sintered part increases with increasing sintering temperature and volume fraction of copper powders, whilst, for the combination of aluminium-copper powders, anomalous behaviour is found; when the green compact (50 vol.% aluminium-50 vol.% copper) is sintered at a temperature of about 800K, the density of the sintered part becomes smaller than that of the green compact. However, the hardness of the sintered part increases remarkably; the micro-Vickers hardness of the sintered part is about 600, which is approximately 15 to 20 times that of the sintered pure copper and aluminium, respectively. This should be emphasized as one of the important characteristics of sintered aluminium-copper composite material.