Revista de Ciências e Engenharia de Materiais

Egyptian ball clay quarried in the Aswan area in Upper Egypt contains up to 10% Nubian sandstone. This inclusion causes problems in clay grinding when used in ceramic industries. In the present paper, Nubian sandstone was characterized for mineralogical and chemical compositions using XRD and XRF respectively. Its grinding characteristics were then established using a laboratory ball mill where stone was ground for time periods ranging from 60 to 150 min at speeds ranging from 40 to 90 rpm. The cumulative analysis and specific surface area were determined for all samples. It was found that while an increase in either time or speed favoured higher fineness, the effect of rotating speed was more pronounced than that of grinding time. The findings were then applied to the production of ceramic tiles. It was found that crushed sandstone could be crushed and ground with ball clay without impairing the grinding characteristics of the latter or affecting the composition of the final body.

Electrical Discharge Machining (EDM) is used in cutting special steel accurately; in this paper the effect of electrode material will be studied to avoid the surface cracks. Two grades of tool steels are chosen as test materials, DIN 1.2080 and DIN 1.2379 they are a high carbon, high chromium alloy tool steels with excellent resistance to wear and abrasion four types of EDM electrode material has been chosen, Dura graph 11, Dura graph 15, Poco graphite “EDM-C 3”, and copper electrodes.

Magnesium/aluminum bi-metallic castings offer significant mass saving opportunities in automotive structural applications. A “zincate+galvanizing” surface treatment has been developed for aluminum alloys to provide improved wetting and metallurgical bond with molten magnesium in bi-metallic casting, due to the removal of Al2O3 layer and the formation of with a very thin metallic zinc film on the aluminum surfaces. The bi-metallic experiments using a selfdesigned high-vacuum test apparatus provided valuable understanding of the interfacial phenomena of Mg (AM60)/ Al (6061) bi-metallic samples. The test results show significantly improved shear strength in the bi-metallic samples with “zincate+galvanizing” surface treatment. It is recommended to adjust the pre-heating temperature and time of the aluminum substrates to control the interfacial reactions for optimum interfacial properties in the actual bi-metallic casting processes.