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properties. One of the important requirements for materials used in bearing production is the coeYcient of friction.4 Fe-Cu-Zn alloys containing solid lubricants of Generally the coeYcient of friction is highly dependent on graphite and talc produced via cold pressing and the compositions used. sintering technology are investigated. The in uence Many of the early works were focused on the study and of composition and sintering temperature on open optimisation of bronze alloys because of the potentially large porosity, density, strength and hardness of these application and excellent antifriction properties exhibited by alloys is studied. The microstructure is correlated with PM bronze materials. The possibility of fabrication of antithe mechanical properties of the sintered materials. friction material containing 31•5 wt-%Cu, 3•5 wt-%Sn, Fe The tensile tests showed that the peak strength was was reported before.5 The main limitations were unsatisfactory observed for samples sintered at å 1000°C. Above this antifriction properties and the high cost of the material. temperature the bending and tensile strength values Another work examined the material containing 44•5 wt-%Cu, decrease. Microstructural analysis of sintered materials 4•5 wt-%Sn, 1•0 wt-% graphite and Bal. Fe.6 Unsatisfactory revealed three phases in the structure: a-Fe, a-brass distribution of components and low mechanical and and talc. Results indicate that the microstructure of antifriction properties were reported. sintered samples is sensitive to process variables such The present study examines the possibility of manuas brass and talc contents and sintering temperature. facturing of iron base Cu-Zn-talc alloys via cold pressing PM/1038 and sintering with a limited amount of added lubricant. The intent is to understand the microstructure development At the time the work was carried out Professor during sintering and the formation of consequent anti-A. T. Mamedov is in the Department of Casting friction and mechanical properties of sintered materials. and Welding Manufacture, Faculty of Metallurgy, Future development of these types of materials can provide

A new technological approach to the fabrication of high density powder metallurgy (PM) parts via single pressing sintering, allowing cold compaction to be performed without admixed lubricants, has been studied. The influence of in pore gas on the compacts' green density and their sintered properties were evaluated. A mathematical expression relating in pore gas pressure in the compacts to the green density was developed. The expression showed that in order to reduce the negative influence of gases trapped in the pores it is necessary to ensure effective air drainage from the compaction zone. In order to ensure sufficient air evacuation during cold compaction, a new design of porous die was developed. The behaviour of powder mixes with different lubricants during cold compaction in porous die was investigated. All the test conditions were evaluated in terms of green and sintered properties, including the ejection force, green and sintered densities, tensile strength and surface hardness. In the context of the experimental work, compaction in porous die promoted the improved combination of green and sintered properties compared with compaction in conventional dies. PM/1116Professor A. T. Mamedov is the Head of the Casting and Welding Manufacture

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