Studies on fatigue strength and porosity formation in aluminum silicon eutectic alloy subjected to modification and vibration during solidification

摘要

The effect of the addition of modifier and the use of vibration during solidification on the fatigue strength and porosity of Aluminium-Silicon Eutectic Alloy (LM-6) has been studied. It has been observed that the addition of a modifier and the use of vibration during solidification influence the fatigue properties significantly. Addition of 1.5% sodium modifier has improved the fatigue properties by about 120%. The use of vibration is found to increase the fatigue strength by about 160%. The morphology of the modified and the modified - vibrated alloy has been studied using SEM. It is found that the silicon morphology has reduced to finer type compared to that of the modified alloy. The fatigue-fractured surface of modified vibrated alloy has revealed more smooth and silky areas, reflecting a change towards ductile behaviour. Also more number of fine striations are seen in the fractured surface in this case compared to the modified and unmodified alloys. The microporosity distribution of the new structure has been studied and quantified using a universal measuring microscope (UMM). It is found that in the case of modified-vibrated alloy, the number of distributed micropores are more, when the alloy is solidified under a vibration frequency of 15 Hz. However, the porosity has been found lower, making it suitable to yield better castings.