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<p>This study investigates the effects of two-step heat treatment—solution treatment followed by aging—on the microstructural evolution and mechanical properties of a novel <i>β</i>–<i>γ</i> TiAl alloy with coexisting <i>β</i> and <i>α</i> single-phase regions. The results indicate that solution treatment within the <i>α</i> + <i>γ</i> two-phase region, followed by aging, leads to the formation of a fully lamellar microstructure with two distinct lamellar spacings—coarse and fine—within colony sizes of approximately 70&#xa0;<i>μ</i>m. The coarse and fine spacings measure about 50 and 500&#xa0;nm, respectively. When solution treatment is conducted in the <i>α</i> single-phase region, a fully lamellar structure with only fine spacing is obtained after aging, exhibiting larger colony sizes of around 120&#xa0;<i>μ</i>m. The microstructure featuring a single lamellar spacing demonstrates the poorest tensile and creep properties due to its coarse colony size. In contrast, the dual-scale lamellar structure significantly enhances both tensile and creep performance. This improvement is attributed to the refined colony size, the ability of coarse lamellae to accommodate more dislocations and twins, and the strengthening effect provided by the fine lamellae. When the heat treatment process is set to 1240&#xa0;°C/30&#xa0;min/AC (air cooling) + 850&#xa0;°C/3&#xa0;h/FC (furnace cooling), the alloy exhibits a 22.8 pct increase in room-temperature tensile strength, a 30.6 pct improvement at 800&#xa0;°C, and a 25.7 pct enhancement at 850&#xa0;°C compared to the as-forged condition. Furthermore, the creep life increases by 91.7 pct under 800&#xa0;°C/300&#xa0;MPa and by 83.8 pct under 800&#xa0;°C/200&#xa0;MPa.</p>

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Strength-Ductility Mechanisms and Creep Properties of the Thin/Thick Full Lamellar Structure in a Novel β–γ TiAl Alloy

  • 期刊论文

  • 发表日期：

    2026年3月17日

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  • Zhixin Zhang,
  • Junjie Hao,
  • Songtao Chang,
  • Guodong Li,
  • Hailong Zhang,
  • Lei Wang,
  • Xin Wang,
  • Qiang Wang,
  • Yanwei Li,
  • Xiaobing Li,
  • Kui Liu,
  • Jian Wang

摘要

This study investigates the effects of two-step heat treatment—solution treatment followed by aging—on the microstructural evolution and mechanical properties of a novel β–γ TiAl alloy with coexisting β and α single-phase regions. The results indicate that solution treatment within the α + γ two-phase region, followed by aging, leads to the formation of a fully lamellar microstructure with two distinct lamellar spacings—coarse and fine—within colony sizes of approximately 70 μm. The coarse and fine spacings measure about 50 and 500 nm, respectively. When solution treatment is conducted in the α single-phase region, a fully lamellar structure with only fine spacing is obtained after aging, exhibiting larger colony sizes of around 120 μm. The microstructure featuring a single lamellar spacing demonstrates the poorest tensile and creep properties due to its coarse colony size. In contrast, the dual-scale lamellar structure significantly enhances both tensile and creep performance. This improvement is attributed to the refined colony size, the ability of coarse lamellae to accommodate more dislocations and twins, and the strengthening effect provided by the fine lamellae. When the heat treatment process is set to 1240 °C/30 min/AC (air cooling) + 850 °C/3 h/FC (furnace cooling), the alloy exhibits a 22.8 pct increase in room-temperature tensile strength, a 30.6 pct improvement at 800 °C, and a 25.7 pct enhancement at 850 °C compared to the as-forged condition. Furthermore, the creep life increases by 91.7 pct under 800 °C/300 MPa and by 83.8 pct under 800 °C/200 MPa.