DESIGN AND MANUFACTURING OF COMPOSITE STRUCTURES AND STUDYING THE EFFECT OF SiCp ADDITION

The fabrication, Physical Properties, microstructure, mechanical properties and wear behaviors under dry conditions of particulate metal matrix composite (Al/SiC) were investigated. The following conclusions have been drawn.1. The MMCs densities at various locations were found to increase as volume fractions of particulate reinforcement were increased but still lower than the theoretical densities.2. The density was also found to increase as the particles size ratio (PSR) was decreased especially near unity.3. The porosity was found to increase as volume fractions of particulate reinforcement were increased. However, decreasing the PSR resulted in significant decrease in porosity.4. The properties of the MMCs fabricated by PM depend not only on volume fractions of reinforcement but also on the PSR. The lower the PSR, the lower the porosity.5. The extrusion process overcomes some SiCp agglomerations (cluster) and voids, and enhances its distribution in the aluminum matrix.6. The extrusion process gives a good distribution of the SiC particles in the aluminum matrix with preferred particle orientation to extrusion axis; thus enhancing the distribution.7. The low PSR (1.2) has also shown relatively more homogenous particle distribution in the matrix at all different volume fractions.8. Fractographic structure showed bimodal distribution of dimples; the larger dimples are associated with reinforcement particle and smaller dimples are associated with the ductile failure of the matrix.9. Some reinforcement particles were pulled out and others showed initiation of cracks across the particles.10. The composite hardness has been improved by increasing volume fractions of SiC reinforced particles and by decreasing the PSR.11. The yield and ultimate tensile strengths of the MMCs have been increased with increasing the volume fractions of reinforcement particles and decreasing the PSR.12. The yield and ultimate tensile strengths of the MMCs have been increased with increasing the volume fractions of reinforcement particles and decreasing the PSR.13. The ductility of the (Al/SiC) decreased by increasing the volume fractions of SiC and decreasing PSR.14. Good mechanical properties of MMCs fabricated by PM when PSR is close to unity.15. The wear properties of the aluminum matrix were considerably improved by the addition of SiC particles and the wear resistance of composites was higher than that of the unreiforced aluminum matrix .16. The wear resistance of the composites increased with increasing SiC particle content and size (decreasing the PSR); the highest wear resistance was obtained in the case of 50 µm size of SiCp at all loads .17. The wear rate increased with increasing the applied load and sliding distance at all volume fractions.18. The wear rate decreased as the hardness of the MMCs increased at all volume fractions.5.2 Future WorkThe following suggestions are recommended for future work:1. Further investigation is suggested to optimize the strength of composites by varying compacting pressure and temperature of sintering.2. It is also suggested to conduct further studies on effect of other extrusion parameters such as die angle, lubrication and extrusion speeds on mechanical characteristics of metal matrix composites.3. Studying the wear resistance of the Al/SiC composites sliding under different environments.4. Studying the effect of surface treatments on the wear resistance of the MMCs produced.5. Studying the effect of sliding speed on the wear resistance of the MMCs.