Development of Alumino-Silicate Investment Shell Moulds to Cast 6061 Al-Alloy

The investment shell moulds were fabricated with ceramic slurry containing alumino-silicates as filler materials and colloidal silica binder. The investment shell moulds were characterized in terms of hot bending strength and thermal shock. The flow time of slurry solution through the Ford cup is directly proportional to the amount of filler added the liquid binder. The Al2O3 / SiO2 ratio of 60/40 has greater bonding strength than those of ratios of 50/50 and 40/60 respectively. As the Al2O3 content in the filler material, the metastability of the investment shell mould increases leading cracks. The microstructure of 6061 Al-alloy reveals some undissolved Mg2Si.