This study aims to optimize the process parameters of friction stir additive manufacturing (FSAM) for fabricating sustainable AA6061 eggshell-graphene hybrid metal matrix composites. The research focuses on improving tensile strength and microstructural integrity through systematic control of key processing parameters. The integration of graphene nanoplatelets and eggshell powder (ESP) as hybrid reinforcements is intended to enhance mechanical performance while promoting environmentally sustainable material utilization. This study attempts to optimize the FSAM conditions and correlate process parameters, reinforcement dispersion, microstructure and mechanical properties of the hybrid composite.
AA6061 plates were reinforced with graphene nanoplatelets and ESP and fabricated using FSAM on a vertical machining center. A Taguchi L16 orthogonal array was used to analytically investigate the effects of tool rotational speed, traverse speed and reinforcement weight percentage on tensile strength. Signal-to-noise ratio analysis and analysis of variance (ANOVA) were applied to determine the significance and contribution of process parameters. Under optimized FSAM conditions, the dispersion of the reinforcement, as well as dispersion and interfacial bonding, was evaluated microstructurally using optical microscopy, FESEM and energy-dispersive X-ray spectroscopy.
The results revealed that tool rotational speed had the most significant influence on tensile strength, contributing approximately 78% of the overall variation. Optimal FSAM parameters were identified as a rotational speed of 4000 rpm, a traverse speed of 20 mm/s and a reinforcement content of 10 W%R. Under these parameter conditions, the hybrid composite attained a maximum tensile strength of approximately 387 MPa. Microstructural analysis confirmed refined grains, uniform dispersion of reinforcement and strong interlayer bonding. Fractography revealed ductile fracture with dimples, validating optimized FSAM parameters for high-strength hybrid composites.
This study demonstrates the feasibility of producing sustainable hybrid AA6061 composites reinforced with graphene and bio-derived eggshell particles using FSAM. The work provides a systematic Taguchi-ANOVA-based optimization framework for controlling FSAM parameters and enhancing mechanical performance. The combined usage of graphene and biogenic eggshell reinforcement opens a new avenue for exploring high-strength, lightweight and eco-friendly metal matrix composites. The results are a step forward for solid-state additive manufacturing of hybrid composites with improved mechanical properties and sustainability.
