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<p>Friction stir additive manufacturing (FSAM) is an emerging solid-state technique for producing high-strength aluminum composites with refined microstructures. However, challenges such as non-uniform reinforcement dispersion and weak interlayer bonding still limit the performance of multilayer FSAM components. In this study, AA7075 hybrid composites reinforced with zirconium dioxide (ZrO<sub>2</sub>) and graphene were fabricated using a groove-assisted multilayer FSAM technique. The primary objective of this work is to examine the influence of a tapered octagonal pin tool geometry on material flow behavior, microstructural evolution, reinforcement dispersion, and mechanical performance. Optical microscopy, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) were used for microstructural characterization, while hardness, tensile, wear, and friction tests were conducted to evaluate mechanical and tribological properties. Fracture behavior and tool surface conditions were further analyzed using SEM-based fractography and tool wear observations. The results show that the tapered octagonal pin tool promotes improved material flow, leading to a relatively uniform distribution of ZrO<sub>2</sub> and graphene reinforcements with limited agglomeration and improved interlayer bonding. The fabricated composite exhibited enhanced hardness (up to 187.5 VHN) and tensile strength (up to 325&#xa0;MPa) compared with the base alloy. Fractographic analysis revealed predominantly ductile fracture characteristics, indicating effective load transfer between the matrix and reinforcements. In addition, the composite demonstrated improved wear resistance with a reduced coefficient of friction. Tool surface analysis indicated minimal tool degradation during the FSAM process. The findings highlight the role of tapered octagonal pin tool geometry in improving reinforcement dispersion and mechanical performance in FSAM-processed AA7075/ZrO<sub>2</sub>/Gr hybrid composites, providing insights for optimizing tool design in solid-state additive manufacturing.</p>

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Microstructural evolution and particle dispersion in FSAM-processed AA7075/ZrO2/Gr composites using a tapered octagonal tool

  • 期刊论文

  • 发表日期：

    2026年5月12日

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  • Abdhesh Kumar,
  • Vishwajeet Kumar,
  • Rajnish Singh,
  • Sunil Singh Rana,
  • Avinash Ravi Raja,
  • Kuntal Maji,
  • Mohd Zaheer Khan Yusufzai,
  • Yogesh Kumar

摘要

Friction stir additive manufacturing (FSAM) is an emerging solid-state technique for producing high-strength aluminum composites with refined microstructures. However, challenges such as non-uniform reinforcement dispersion and weak interlayer bonding still limit the performance of multilayer FSAM components. In this study, AA7075 hybrid composites reinforced with zirconium dioxide (ZrO2) and graphene were fabricated using a groove-assisted multilayer FSAM technique. The primary objective of this work is to examine the influence of a tapered octagonal pin tool geometry on material flow behavior, microstructural evolution, reinforcement dispersion, and mechanical performance. Optical microscopy, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) were used for microstructural characterization, while hardness, tensile, wear, and friction tests were conducted to evaluate mechanical and tribological properties. Fracture behavior and tool surface conditions were further analyzed using SEM-based fractography and tool wear observations. The results show that the tapered octagonal pin tool promotes improved material flow, leading to a relatively uniform distribution of ZrO2 and graphene reinforcements with limited agglomeration and improved interlayer bonding. The fabricated composite exhibited enhanced hardness (up to 187.5 VHN) and tensile strength (up to 325 MPa) compared with the base alloy. Fractographic analysis revealed predominantly ductile fracture characteristics, indicating effective load transfer between the matrix and reinforcements. In addition, the composite demonstrated improved wear resistance with a reduced coefficient of friction. Tool surface analysis indicated minimal tool degradation during the FSAM process. The findings highlight the role of tapered octagonal pin tool geometry in improving reinforcement dispersion and mechanical performance in FSAM-processed AA7075/ZrO2/Gr hybrid composites, providing insights for optimizing tool design in solid-state additive manufacturing.