A simple inexpensive technique for enhancing density and mechanical properties of AlSi alloys

Reviewing the effects of subjecting solidifying Al and its alloys to various sources of vibration on the resulting casting quality, a simple inexpensive technique for inducing vibration resulting in enhanced density and mechanical properties is devised. It involves minimising turbulence by tilting of mould while pouring as well as inducing vibrations in a solidifying melt by using a simple, handy and inexpensive technique, i.e., hand tapping of the mould with MS rods. The alloys chosen for this study are long freezing range hypoeutectic alloy, Al7Si0.3Mg (LM25/356) and a narrow freezing range eutectic AlSi alloy, Al12Si (LM6/413). The simple, inexpensive hand tapping of long freezing range Al7Si0.3Mg alloy solidifying in a permanent mould without and with mould tilting has improved its density, hardness, ultimate tensile strength and % elongation. Properties similar to a degassed Al7Si0.3Mg alloy melt have been exhibited by an undegassed melt subjected to vibration by hand tapping with mould tilting. The latter too aids in reducing the turbulence experienced by the aluminium melt during pouring and mould filling and hence in enhancing all the above properties. However, the effectiveness of both mould tilting and hand tapping is less in degassed Al7Si0.3Mg melt compared to undegassed one. On the other hand, there is only marginal improvement in the said properties of narrow freezing Al12Si eutectic.