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<p>High-quality Al/Al bimetallic composite tubes were fabricated in this study using 2024 and 5A06 aluminum alloys as feedstock through cylindrical billet assembly followed by indirect isothermal extrusion. Macroscopic observations confirmed that the composite tubes exhibited uniform wall thickness, smooth defect-free surfaces, and strong interfacial bonding along the extrusion direction, with the stable extrusion region accounting for more than 70% of the total length. Microstructural characterization revealed a pronounced grain structure asymmetry between the two alloys: the outer 2024 layer retained elongated banded sub-structured grains due to its high solute content and multiscale second-phase particles, which suppressed recrystallization, while the inner 5A06 layer developed a bimodal grain structure composed of fine dynamically recrystallized grains and coarse residual grains, resulting from heterogeneous strain partitioning and its high dynamic recrystallization sensitivity. Mechanical testing demonstrated that the composite tube achieved a significant improvement in elongation with minimal strength loss in the as-extruded state. After T6 heat treatment, it exhibited an ultimate tensile strength of 420&#xa0;MPa with an elongation of 13.6%, outperforming most previously reported Al/Al bimetallic composites. Based on interfacial microstructural analysis, the effects of microstructural evolution during T6 treatment on mechanical performance were clarified.</p>

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Strength–Ductility Synergy in 2024/5A06 Al/Al Composite Tubes through Heterogeneous Grain Structures

  • 期刊论文

  • 发表日期：

    2026年7月22日

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  • Qilun Li,
  • Jisen Qiao,
  • Anqi Zhao,
  • Yijia Li

摘要

High-quality Al/Al bimetallic composite tubes were fabricated in this study using 2024 and 5A06 aluminum alloys as feedstock through cylindrical billet assembly followed by indirect isothermal extrusion. Macroscopic observations confirmed that the composite tubes exhibited uniform wall thickness, smooth defect-free surfaces, and strong interfacial bonding along the extrusion direction, with the stable extrusion region accounting for more than 70% of the total length. Microstructural characterization revealed a pronounced grain structure asymmetry between the two alloys: the outer 2024 layer retained elongated banded sub-structured grains due to its high solute content and multiscale second-phase particles, which suppressed recrystallization, while the inner 5A06 layer developed a bimodal grain structure composed of fine dynamically recrystallized grains and coarse residual grains, resulting from heterogeneous strain partitioning and its high dynamic recrystallization sensitivity. Mechanical testing demonstrated that the composite tube achieved a significant improvement in elongation with minimal strength loss in the as-extruded state. After T6 heat treatment, it exhibited an ultimate tensile strength of 420 MPa with an elongation of 13.6%, outperforming most previously reported Al/Al bimetallic composites. Based on interfacial microstructural analysis, the effects of microstructural evolution during T6 treatment on mechanical performance were clarified.