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<p>High-entropy alloys have shown great application prospects in the field of high-temperature brazing due to their excellent properties. However, due to their excessively high melting temperature and poor metallurgical compatibility, achieving high-temperature, highly reliable connections between ceramic matrix composites and refractory alloys still faces significant challenges. This study proposes a semi-solid brazing strategy, which uses CoCrFeNiCu<sub>x</sub> high-entropy alloy filler to connect C/C-SiC composites with TZM (titanium-zirconium-molybdenum alloy). This filler exhibits a dual endothermic melting behavior, forming an adjustable semi-solid window, which not only ensures sufficient fluidity but also suppresses excessive interfacial reactions. During the brazing process, the Cu-rich liquid phase promotes the formation of the initial interface. On the alloy side, the face-centered cubic (FCC) phase replaces the Cu liquid phase, generating a continuous µ-Co<sub>7</sub>Mo<sub>6</sub> layer. On the composite material side, the elements dissolved in the Cu-rich liquid phase react with the composite material to form the M₇C₃ reaction layer, while Cu reacts with the SiC matrix to form the decomposition zone. As the temperature and holding time increase, the reaction intensity increases, and the M<sub>7</sub>C<sub>3</sub> reaction layer and decomposition zone thicken. The optimized joint (1180&#xa0;°C, 15&#xa0;min) achieved a high shear strength of 40.2&#xa0;MPa and maintained its integrity at 800&#xa0;°C, demonstrating an anomalous strengthening effect due to stress relaxation. The finite element simulation results indicate that joint fracture primarily occurs at the Cu(s, s)/M<sub>7</sub>C<sub>3</sub> boundary and is mainly influenced by the normal stress (S<sub>22</sub>), consistent with experimental observations. This study provides a mechanistic framework for the relationship between the evolution of semi-solid HEA phases, interface design, and strength retention, and offers new ideas for the development of connection technologies between ceramic matrix composites and refractory alloys.</p>

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Semi-solid brazing via CoCrFeNiCux high-entropy alloy fillers: interfacial microstructure, mechanical properties, and joining mechanism of C/C-SiC composites and TZM alloy

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月2日

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  • Wenlong Zhou,
  • Wei Fu,
  • Yanxing Wang,
  • Zuorui Gao,
  • Shengpeng Hu,
  • Xiaoguo Song,
  • Hyoung Seop Kim,
  • Jicai Feng

摘要

High-entropy alloys have shown great application prospects in the field of high-temperature brazing due to their excellent properties. However, due to their excessively high melting temperature and poor metallurgical compatibility, achieving high-temperature, highly reliable connections between ceramic matrix composites and refractory alloys still faces significant challenges. This study proposes a semi-solid brazing strategy, which uses CoCrFeNiCux high-entropy alloy filler to connect C/C-SiC composites with TZM (titanium-zirconium-molybdenum alloy). This filler exhibits a dual endothermic melting behavior, forming an adjustable semi-solid window, which not only ensures sufficient fluidity but also suppresses excessive interfacial reactions. During the brazing process, the Cu-rich liquid phase promotes the formation of the initial interface. On the alloy side, the face-centered cubic (FCC) phase replaces the Cu liquid phase, generating a continuous µ-Co7Mo6 layer. On the composite material side, the elements dissolved in the Cu-rich liquid phase react with the composite material to form the M₇C₃ reaction layer, while Cu reacts with the SiC matrix to form the decomposition zone. As the temperature and holding time increase, the reaction intensity increases, and the M7C3 reaction layer and decomposition zone thicken. The optimized joint (1180 °C, 15 min) achieved a high shear strength of 40.2 MPa and maintained its integrity at 800 °C, demonstrating an anomalous strengthening effect due to stress relaxation. The finite element simulation results indicate that joint fracture primarily occurs at the Cu(s, s)/M7C3 boundary and is mainly influenced by the normal stress (S22), consistent with experimental observations. This study provides a mechanistic framework for the relationship between the evolution of semi-solid HEA phases, interface design, and strength retention, and offers new ideas for the development of connection technologies between ceramic matrix composites and refractory alloys.