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In this experimental study, tensile and fatigue properties of the Alumix 431 alloy (Al, Zn, Mg and Cu alloys) produced using the conventional press and sinter processes in different pressures and temperatures are investigated. The results clearly showed that the warm compacted specimens can reach the mechanical properties of the cold compacted ones under less pressure. In the fatigue tests it was observed that fracture started from large pores as shown in all scanning electron microscope (SEM) examinations and ductile fracture occurred. 85% of the 180 MPa/80°C and 77% of the 230 MPa/RT specimens fractured at the machined surface. Tensile and fatigue properties of warm compacted (180 MPa/80°C) and cold (230 MPa/RT) compacted specimens are almost equal at these same densities. This result indicates the economic benefit of warm compaction by the much lower applied compaction pressure

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

integrity due to dense and very stable oxide layers covering the powder particles.6 The former factor has been addressedThe eVects of warm compaction on the green density by the development of various internal and external and sintering behaviour of aluminium alloys were lubricants.7 DiVerent approaches have been suggested to investigated. Particular attention is paid to prealloyed overcome the second factor.8,9 Anyhow, the conventional powders, i.e. eutectic and hypereutectic Al-Si alloys, press and sinter approach produces properties that are regarding their potential applications in the autosuited to a limited range of applications. motive industry. The eVects of chemical composition, During the last decade, a considerable amount of research alloying method, compacting temperature and the work has been directed towards the employment of the amount of powder lubricant were studied. The comadvantages of powder metallurgy by establishing the nal paction behaviour was examined by an instrumented desired alloy composition in the melt followed by atomdie enabling simultaneous measurement of density, isation and rapid solidi cation of the powder.1 This results die wall friction coeYcient, the triaxial stresses acting in signi cant extensions of the property capability for on the powder during the course of compaction and aluminium alloys due to the microstructural re nements as ejection pressure. The sintering behaviour was studied well as extended solid solubility of the alloying elements. via dilatometeric analysis as well as normal batchUnfortunately, the high strength of prealloyed powders also sintering. The results show that warm compaction makes them extremely incompressible. Therefore, vacuum could be a promising way to increase the green density degassing of the powder and special consolidation techniques, of aluminium alloys, especially prealloyed powders, such as hot pressing or forging, must be used. Clearly, and to decrease dimensional instability during sintering.these techniques are not cost eVective for high volume Moreover, it reduces the sliding friction coeYcient productions. and the ejection force during the powder shaping pro-The idea explored in the present work was to do a cess. This paper presents the signi cant advantages feasibility study in which the inconvenient and expensive and drawbacks of using the warm compaction process steps are avoided by using the warm compaction process. As for commercial PM aluminium alloys.PM/1043 described for example in Ref. 10, this method has been shown to provide increased density in ferrous powder metallurgy Dr Simchi