IMPROVEMENT OF MECHANICAL PROPERTIES OF ALUMINIUM ALLOYS WITH MANGANESE IV OXIDE AND CASTING PARAMETERS

Abstract

Aluminium and its alloys are widely employed in engineering applications owing to their excellent corrosion resistance and high strength-to-weight ratio. The abundance of discarded aluminium components - particularly beverage cans and aircraft parts, makes recycling an attractive proposition, offering substantial economic and environmental benefits. This study investigates the use of manganese (iv) dioxide (MnO₂) as a reinforcing additive to enhance the mechanical properties of recycled aluminium alloy, thereby broadening its range of engineering applications. Varying quantities of MnO₂ were introduced into molten recycled aluminium alloy, which was then poured at different temperatures and cooled by different methods. Test pieces were machined from the resulting ingots and subjected to hardness, tensile, and impact strength tests. The experimental design (DOE) was developed using Taguchi methods in Minitab 2020 statistical software, and the effects of varying MnO₂ content and casting parameters were evaluated against the measured responses. Regression equations were generated for each response to enable pre-determination of the exact quantity of MnO₂ and casting parameters required for a desired optimum mechanical property. The highest hardness of 141.1 HV was achieved with aluminium alloy reinforced with 4.8% MnO₂ and cooled in air; the highest ultimate tensile strength (UTS) of 154.59 MPa was obtained with 12.6% MnO₂ and air cooling; and the highest impact strength of 14.94 J was recorded with 2.4% MnO₂ and sand cooling. It was concluded that reinforcing aluminium alloy with an appropriate percentage of MnO₂ and selecting the right cooling medium enhances various mechanical properties for improved engineering applications.