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In this study, the eect of milling speed on particle size and morphology of Cu25W composite powder produced by high-energy ball milling was investigated. For this aim, commercial elemental copper and tungsten powders were milled in a planetary-type ball mill for dierent milling durations. Ball-to-powder weight ratio was selected as 10:1. Three dierent milling speeds, namely 200, 300, and 400 rpm were used throughout the tests. In order to avoid agglomeration and to decrease the tendency of cold welding among powder particles, stearic acid in amount of 2 wt.% was used as a process control agent. The morphological and microstructural evolution of the milled powders was evaluated by scanning electron microscopy. In addition, the variation of particle size and powder morphology as a function of milling duration was determined. As a result of this eort, the milling duration was found to have strong eect on the structural evolution of the powder, and the optimum particle size as a function of milling speed was determined.

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A series of binary Zn -Al and ternary Zn -Al -Cu alloys were produced by permanent mould casting. The fatigue behaviour of the alloys was examined using a rotating bending fatigue machine, which was designed and built for the present work. The stress -number of cycles to failure (S -N) curves of the alloys were obtained. It was found that both fatigue strength and fatigue life of the binary Zn -Al alloys increased with increasing aluminium content. It was also observed that copper additions of up to 2% increased the fatigue strength of the binary alloys. However, above this level, the fatigue strength of the ternary alloys decreased with increasing copper content. In addition, it was observed that the fatigue strength of the ternary alloys was dependent on their tensile strength, rather than on their hardness. Correlation of the fatigue data showed that Basquin's law can be used to express the fatigue behaviour of these alloys.MST/4418

This study is based upon the optimization of production parameters of Cu25W electrical contact material. Commercial elemental copper (Cu) and tungsten (W) powders were synthesized to produce Cu25W composite powder by mechanical alloying technique at various amounts of stearic acid via using a planetary type ball mill. The effect of amount of stearic acid on production of Cu25W composite powder was evaluated. In order to achieve true alloying among powder particles, it is necessary to establish a balance between cold welding and fracturing. Hence, different types of process control agents (PCA) were used to reduce excessive cold welding. Here, the effect of various amounts of stearic acid, namely 0, 0.5, 1, 2 and 3 wt.% on morphology and some properties of Cu25W composite powder were studied. The microstructural evolution of the milled powders was characterized by using scanning electron microscopy. The test results showed that the morphology and particle size distribution of the milled powders were changed considerably depending upon the variable amount of PCA. In addition, holding the same milling duration, different microhardness values were obtained for various amounts of PCA.