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<p>SmCo<sub>7</sub> phase with a TbCu<sub>7</sub>-type structure is a promising candidate for high-performance high-temperature permanent magnets due to its high magnetocrystalline anisotropy and high saturation magnetization, but its metastability at room temperature limits practical applications. This work systematically investigates the effect of Ti substitution on phase structure and magnetic properties of SmCo<sub>7-x</sub>Ti<sub>x</sub> (<i>x</i> = 0–0.6) ribbons prepared by melt spinning and subsequent heat treatment. Results show that increasing Ti content suppresses the precipitation of SmCo<sub>5</sub> phase and promotes stabilization of TbCu<sub>7</sub>-type SmCo<sub>7</sub> phase in SmCo<sub>7-x</sub>Ti<sub>x</sub> as-cast alloys, and when <i>x</i> ≥ 0.45, SmCo<sub>11</sub>Ti and Sm<sub>2</sub>Co<sub>7</sub> phases precipitate. After melt spinning at 40&#xa0;m/s, all the SmCo<sub>7-x</sub>Ti<sub>x</sub> melt-spun ribbons exhibit a single TbCu<sub>7</sub>-type structure. The intrinsic coercivity (<i>H</i><sub>cj</sub>) first increases and then decreases with Ti content, reaching a maximum of 4.32 kOe at <i>x</i> = 0.45, while the magnetization (<i>σ</i><sub>2T</sub>) decreases monotonically. In the wheel speed range of 20–40&#xa0;m/s, increasing wheel speed refines grains and enhances intergranular exchange coupling, leading to a significant increase in the remanence ratio, which compensates for the decrease in <i>σ</i><sub>2T</sub> and results in an upward trend of remanence. After annealing below 700&#xa0;°C, ribbons retain the single-phase structure, but coercivity decreases continuously with temperature; at 800&#xa0;°C, TbCu<sub>7</sub>-type SmCo<sub>7</sub> phase decomposes into Sm<sub>2</sub>Co<sub>17</sub> and α-Co phases, causing severe deterioration of hard magnetic properties. The variation of remanence under different wheel speeds and annealing temperatures is governed by competition between the remanence ratio and <i>σ</i><sub>2T</sub>. The optimal comprehensive magnetic properties are achieved at <i>x</i> = 0.45 and a wheel speed of 40&#xa0;m/s. This study reveals the synergistic stabilization mechanism of TbCu<sub>7</sub>-type SmCo<sub>7</sub> phase by Ti substitution and melt spinning, and clarifies the remanence regulation by competition between remanence ratio and <i>σ</i><sub>2T</sub>, providing a basis for composition design of high-performance nanocrystalline permanent magnets.</p>

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Effect of Ti substitution on phase structure and magnetic properties of TbCu7-type SmCo7-xTix melt-spun ribbons

  • 期刊论文

  • 发表日期：

    2026年7月14日

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  • Xiang Liu,
  • Dekang Chen,
  • Ao Wang,
  • QingRong Yao,
  • Jiang Wang

摘要

SmCo7 phase with a TbCu7-type structure is a promising candidate for high-performance high-temperature permanent magnets due to its high magnetocrystalline anisotropy and high saturation magnetization, but its metastability at room temperature limits practical applications. This work systematically investigates the effect of Ti substitution on phase structure and magnetic properties of SmCo7-xTix (x = 0–0.6) ribbons prepared by melt spinning and subsequent heat treatment. Results show that increasing Ti content suppresses the precipitation of SmCo5 phase and promotes stabilization of TbCu7-type SmCo7 phase in SmCo7-xTix as-cast alloys, and when x ≥ 0.45, SmCo11Ti and Sm2Co7 phases precipitate. After melt spinning at 40 m/s, all the SmCo7-xTix melt-spun ribbons exhibit a single TbCu7-type structure. The intrinsic coercivity (Hcj) first increases and then decreases with Ti content, reaching a maximum of 4.32 kOe at x = 0.45, while the magnetization (σ2T) decreases monotonically. In the wheel speed range of 20–40 m/s, increasing wheel speed refines grains and enhances intergranular exchange coupling, leading to a significant increase in the remanence ratio, which compensates for the decrease in σ2T and results in an upward trend of remanence. After annealing below 700 °C, ribbons retain the single-phase structure, but coercivity decreases continuously with temperature; at 800 °C, TbCu7-type SmCo7 phase decomposes into Sm2Co17 and α-Co phases, causing severe deterioration of hard magnetic properties. The variation of remanence under different wheel speeds and annealing temperatures is governed by competition between the remanence ratio and σ2T. The optimal comprehensive magnetic properties are achieved at x = 0.45 and a wheel speed of 40 m/s. This study reveals the synergistic stabilization mechanism of TbCu7-type SmCo7 phase by Ti substitution and melt spinning, and clarifies the remanence regulation by competition between remanence ratio and σ2T, providing a basis for composition design of high-performance nanocrystalline permanent magnets.