ON THE SOLIDIFICATION CHARACTERISTICS AND MECHANICAL PROPERTIES OF ALUMINUM ALLOY AA 6061/Al2O3-SiCP COMPOSITE PRODUCED BY HIGH PRESSURE DIE CASTING

Abstract

The effectiveness of the high pressure die casting (HPDC) process in facilitating a controlled solidification mechanism during the fabrication of hybrid (Al2O3-SiCp) reinforced aluminum alloy composite is investigated. The aluminum matrix composite was synthesized with 5%, 10% and 20% volume fraction of reinforcements by infiltrating molten aluminum AA 6061 via squeeze casting into prefabricated ceramic preforms. The parameters for experimentation are the casting pressure (80MPa), pouring temperature (740 degree C), die preheat temperature (300 degree C), pressure holding time (15 s) and die cooling rate of 0.2 kg/s water flow rate. The composites were examined by optical microscopy, mechanical properties determined by tensile testing and fractured specimens analyzed by SEM fractography. The results indicate that the sample with 5% volume fraction of reinforcements showed significant variations in temperature profile and intensities of phase transformation at the beginning and the end of solidification, while for samples with 10% and 20% volume fractions, this process occurred at fairly constant temperatures with minimal inflexions in phase characteristics. The solidification time increased progressively with increasing volume fraction of reinforcements as the cooling rates reduce, and the mechanical properties with the exception of percent elongation were enhanced with increasing volume fractions of reinforcements.

Keywords

• Aluminum alloy AA 6061
• HPDC
• Hybrid composites
• Solidification
• Volume fraction of reinforcement