EFFECT OF STIR-CAST PROCESS PARAMETERS ON THE DEVELOPMENT OF BIO-ASH REINFORCED ALUMINUM MATRIX COMPOSITES FOR AUTOMOTIVE APPLICATIONS

Abstract

The development of sustainable lightweight materials with improved mechanical performance has become a major priority in the automotive industry due to increasing demands for enhanced fuel efficiency, reduced emissions, and improved component durability. This study optimized the stir-casting process for the development of hybrid bio-ash reinforced AA6061 aluminium matrix composites using coconut shell ash (CSA) and periwinkle shell ash (PSA) for automotive wheel-rim applications. A Taguchi Design of Experiments (DOE) coupled with Signal-to-Noise (S/N) ratio analysis and Analysis of Variance (ANOVA) was employed to determine the optimum reinforcement composition and processing parameters. Five reinforcement compositions containing 0, 3, 6, 9, and 12 wt% total bio-ash reinforcement were produced through stir casting, while stirring speed (300, 400, and 500 rpm), stirring time (5, 10, and 15 min), and pouring temperature (680, 700, and 720°C) were systematically investigated. The developed composites were evaluated based on tensile strength, hardness, fatigue behaviour, wear resistance, porosity, and overall process stability. The optimization results showed that the optimum reinforcement composition was 6 wt% total hybrid reinforcement (3 wt% CSA and 3 wt% PSA), which produced the highest mean Signal-to-Noise ratio of 43.95 dB. The optimum stir-casting parameters were identified as 400 rpm stirring speed, 10 min stirring time, and 700°C pouring temperature, corresponding to S/N ratios of 43.90 dB, 43.85 dB, and 43.95 dB, respectively. These optimum conditions promoted improved particle dispersion, enhanced matrix–reinforcement bonding, reduced porosity, and greater process stability compared with other parameter combinations. Reinforcement contents above 6 wt% resulted in reduced performance due to particle agglomeration, increased porosity, and poor wettability. The study demonstrates that hybrid reinforcement using coconut shell ash and periwinkle shell ash, combined with statistically optimized stir-casting parameters, provides an effective and environmentally sustainable approach for producing high-performance aluminium matrix composites. The developed optimization framework offers a reproducible manufacturing route for lightweight automotive components and supports the utilization of agricultural and marine wastes as value-added engineering reinforcements. These findings contribute to sustainable materials development and provide practical processing guidelines for the industrial production of bio-ash reinforced aluminium matrix composites for automotive applications.