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Structure of metal matrix composites with an addition of tuff

100%

Łach M.

Archives of Foundry Engineering

2010

tom Vol. 10, iss. 3 spec.

135--140

The article presents preliminary results of tests of metal matrix composites structure which was modified by an addition of powdered volcanic tuff. Distribution and shape of ceramic particles as well as the quality of the bonding along the tuff- metal matrix interface were studied. Depth of tuff element diffusion in the matrix as well as diffusion in tuff particles were checked. Micro-hardness and porosity of the composites were also tested. The tuff from Filipowice near the town of Krzeszowice was used for the tests. Powder metallurgy was applied to obtain the composites and the matrix materials were copper and 316L steel powders. The tuff was introduced in 2, 5 and 10 % by weight. To remove water from the channels of aluminosilicates, the tuff was baked at 850oC for 4 hours and then cooled together with the oven. The tests revealed good quality of the bonding of the tuff particles and the matrix and their even distribution. The addition of tuff improved the hardness of the composites and reduced their porosity which has great significance because of possible applications of this kind of materials in general and copper composites in particular. This gives grounds for further studies on volcanic tuff use in metal composites.

Microstructural, electrical, thermal and tribological studies of copper-fly ash composites through powder metallurgy

100%

Thanga_Kasi_Rajan S. , Balaji A. N. , Narayanasamy P. , Vettivel S. C.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2018

tom Vol. 66, nr 6

935--940

This research work address the fabrication of copper (Cu) matrix composites, reinforced with fly ash (FA) particulates with 3, 6, 9 and 12 wt.% using the powder metallurgy route. The microstructural, physical, electrical, thermal, mechanical and tribological properties of thus fabricated Cu-FA composites have been studied. Optical microstructural characterization of the composites exposed persuasively uniform distribution of FA reinforcement with minimum porosity. The mixed powder SEM images revealed the homogeneous dispersion of fly ash particulates in the copper matrix. The hardness values showed improvement with increase in the weight percentage of FA in the Cu matrix. Electrical conductivity was measured using the four-point probe method at room temperature. Thermal conductivity was measured with a thermal diffusivity analyzer at room temperature. The fly ash addition leads to weakening the conductivity of Cu-FA composites. The tribological properties of Cu-FA composite specimens were investigated using a Pin-on-disc tribo testing machine against an EN81 steel contour disc. The specific wear rate of the composites tended first to decrease, which was attributed mainly to the formation of a mechanically mixed layer on the worn surface. Then it would increase as the FA content increased because of reduction in ductility and brittle oxide cracks associated with adding more FA particulates. It seems that composites with FA percentages below 9wt.% have optimum properties of microstructure, hardness and wear resistance, which is suitable for applications such as electrical sliding contacts, electrical discharge machining and spot welding electrodes.