Abstract
The 2218 Al-Alloy-5% (Alumina-Titania) hybrid metal matrix composites were developed using stir casting in ambient conditions. A sub-micron powder mixture of Alumina-Titania in a ratio of 1:2 was used as reinforcement. Both in-situ and ex-situ processing including reaction wetting by Titania, were used. To refine the structure and minimize porosity, the alloy-particle slurry was forged at pressures from 0 to 220 N/mm(2), followed by T61 ppt.-hardening to achieve peak hardness. Composites characterized by microstructure, hardness, density, porosity, SEM, and EDS at different forging pressures displayed substantial refinement of structure and almost eliminating porosity at high forging pressure level. Tribological performance of the composites marked significant improvement at high forging pressure. SEM micrographs were analyzed to identify the wear-regime and wear mechanisms. The friction coefficient was reduced slightly with the load at high forging pressure. Based on experimental results, a linear mathematical relationship between the forging pressure, the normal bearing load and the wear rate of hybrid composites is suggested. Relationships between the other process parameters and properties have also been developed. The density, porosity, particle retention and Fe content on worn surface vary with forging pressure following polynomial equations. The temperature of counterface follows logarithmic variation with the forging pressure.