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<p>The (B<sub>4</sub>C + Al<sub>2</sub>O<sub>3</sub>)/Al composite, incorporating in-situ amorphous Al<sub>2</sub>O<sub>3</sub> (am-Al<sub>2</sub>O<sub>3</sub>) formed by the oxidation of aluminum powder, exhibits exceptionally high-temperature mechanical properties, positioning it as a highly promising structural-functional neutron-absorbing material for dry storage of spent nuclear fuel. However, welding this composite has remained challenging due to the inherent strength-degrading am-Al<sub>2</sub>O<sub>3</sub> → <i>γ</i>-Al<sub>2</sub>O<sub>3</sub> phase transformation and the severely restricted process window during friction stir welding (FSW). To overcome this, this study innovatively proposes a stabilization pre-treatment (550&#xa0;°C/8&#xa0;h) prior to FSW. This treatment promotes a controlled, partial am-Al<sub>2</sub>O<sub>3</sub> → <i>γ</i>-Al<sub>2</sub>O<sub>3</sub> transformation in the base material (BM), crucially reducing deformation resistance during welding while retaining sufficient BM strength. The reduced resistance broadens the viable FSW parameter space, enabling high-quality joints at a practical rotation rate (500&#xa0;r/min) and increased welding speeds (up to 150&#xa0;mm/min). Consequently, the resulting joints exhibit superior mechanical properties, achieving strength efficiencies of 93.2&#xa0;pct at room temperature and 80&#xa0;pct at 350&#xa0;°C—notably exceeding the maximum strength reported in prior studies—while simultaneously demonstrating significantly enhanced tensile elongation. The enhanced performance stems from grain refinement and optimized Al<sub>2</sub>O<sub>3</sub> distribution, thereby minimizing microstructural inhomogeneity and strength gradients.</p>

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Microstructure and Mechanical Properties of Friction Stir Welded Joints in Stabilization-Treated (B4C + Al2O3)/Al Composite Sheets

  • 期刊论文

  • 发表日期：

    2026年3月12日

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  • B. M. Shi,
  • T. Y. Yang,
  • B. B. Wang,
  • X. Lei,
  • Y. N. Zan,
  • Q. Z. Wang,
  • P. Xue,
  • B. L. Xiao,
  • Z. Y. Ma

摘要

The (B4C + Al2O3)/Al composite, incorporating in-situ amorphous Al2O3 (am-Al2O3) formed by the oxidation of aluminum powder, exhibits exceptionally high-temperature mechanical properties, positioning it as a highly promising structural-functional neutron-absorbing material for dry storage of spent nuclear fuel. However, welding this composite has remained challenging due to the inherent strength-degrading am-Al2O3 → γ-Al2O3 phase transformation and the severely restricted process window during friction stir welding (FSW). To overcome this, this study innovatively proposes a stabilization pre-treatment (550 °C/8 h) prior to FSW. This treatment promotes a controlled, partial am-Al2O3 → γ-Al2O3 transformation in the base material (BM), crucially reducing deformation resistance during welding while retaining sufficient BM strength. The reduced resistance broadens the viable FSW parameter space, enabling high-quality joints at a practical rotation rate (500 r/min) and increased welding speeds (up to 150 mm/min). Consequently, the resulting joints exhibit superior mechanical properties, achieving strength efficiencies of 93.2 pct at room temperature and 80 pct at 350 °C—notably exceeding the maximum strength reported in prior studies—while simultaneously demonstrating significantly enhanced tensile elongation. The enhanced performance stems from grain refinement and optimized Al2O3 distribution, thereby minimizing microstructural inhomogeneity and strength gradients.