CHARACTERIZATION AND SYNTHESIS OF GRADED COPPER-ALUMINA COMPOSITES BY POWDER METALLURGY & EXPLOSIVE FORMING TECHNIQUE

Abstract

Specific and complex application of parts require materials that can fulfill the desired requirement. Gradient materials, well known functionally gradient materials (FGMs), are used for such applications where common materials can not yield satisfactory results. In the present work, powder metallurgy and explosive forming techniques have been used to synthesize a Cu/A1203 gradient composite. In the powder metallurgy technique, powders were mixed in ball mill followed by hand mixing with addition of camphor as a binder. These mixed powders were compacted using 25kg load. Each pellet consisted of four layers differing in Alumina content from 1% to 10%. After preheating, sintering of pellets was done in vacuum. Sintering cycles were 1000°C for 2hr, 3hr and 4hr respectively and 800°C for 3hr, 6hr and 9hr respectively. 1000°C specimens show maximum electrical conductivity (54.1 %IACS). 800°C specimens show lower conductivity but higher density than 1000°C specimens. Scattering in hardness was found during measurement. Characterization was done using optical microscopy and SEM. In the explosive forming technique, two tubes of 40mm and 55mm inner diameter and 3mm thickness were used. Mixed powders were filled in 40mm inner diameter tube. Alumina content in successive layers varied from 0% to 100% in one specimen and 1% to 6% in another specimen. This filled tube was kept inside the 55mm inner diameter tube. This assembly was exploded and was characterized in a similar way as used in powder metallurgy specimens. Density of specimen obtained was 8.20 g/cm3. Due to presence of porosity it shows no electrical conductivity. The objective of this work is to synthesis a graded material whose one end would be insulator and other end would be conductor.