Investigation of Porosity by Effect of Sodium Addition and Holding Time on Aluminium-11.1 Silicon Alloy

The present investigation pertains to effect of different levels of modifiers (Na) in the Al-11.1Si hypo-eutectic alloy casting process. The investigation deals with the porosity analysis of the hypo-eutectic Al-Si alloy casting with varying master alloy, composition and holding time. The modifiers used for the investigation is sodium. Four levels of compositions addition of modifier as sodium is selected for the casting process which are 0.03%, 0.06%, 0.09%, &0.12%. The holding times selected for each composition are 10min, 20min and 30min respectively. The introduction sodium to an Al-Si alloy results in a complete transformation of Si particles, changing them from coarse plates to fine fibres, irrespective of the cooling conditions. The reduction in eutectic growth temperature due to sodium addition was consistently associated with the degree of modification, regardless of the initial microstructure coarseness. Employing modification treatment significantly enhances elongation to failure, particularly when intermetallic compounds are effectively refined in size. The microstructure of the experimental samples is characterized by using differential interference contrast optical image analyzer and found out the level of modification, and then it compared with the porosity level in the sample. The radiography imaging technique confirms that Na that 0.12% addition is giving very less shrinkage porosity.