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<p>The growing application of wire arc additive manufactured (WAAMed) TC11 alloy in critical aerospace structures has spurred interest in its fatigue mechanisms and cyclic behavior, yet understanding of heat treatment effects remains limited. This study investigates how heat treatments influence the low-cycle fatigue response and life span of WAAMed TC11, with focus on the role of phase composition and microstructural stability. Results show that vertically oriented 550-AC (550&#xa0;°C/4&#xa0;h/air cooling) samples exhibit lower cyclic stress–strain levels than horizontal ones, revealing significant anisotropy. This arises from higher misorientation angles along elongated columnar α grain boundaries (<i>α</i><sub>GB</sub>s) in vertical samples, which impede slip bands interaction, reduce dislocation accumulation, and delay cyclic softening. In contrast, other heat treatments show negligible orientation dependence due to less pronounced α<sub>GB</sub> misorientation. During stable deformation, the 1020-AA (1020&#xa0;°C/2&#xa0;h/AC + 550&#xa0;°C/4&#xa0;h/AC) samples exhibit early cyclic softening due to fine lamellar structures acting as dislocation sinks, resulting in the poorest fatigue resistance and highest crack growth rate. Conversely, 550-AC samples show superior crack initiation resistance and minimal crack growth, attributed to a microstructure dominated by ~ 95% lamellar α<sub>P</sub> and high-misorientation boundaries. The optimal condition is 970-AA (970&#xa0;°C/2&#xa0;h/AC + 550&#xa0;°C/4&#xa0;h/AC), which yields a balanced assemblage of 24.2% crab-like <i>α</i><sub>P</sub>, 11.3% globularized <i>α</i> (<i>α</i><sub>G</sub>), and 64.5% secondary <i>α</i> (<i>α</i><sub>S</sub>). Despite slight softening induced by <i>α</i><sub>G</sub>, the refined <i>α</i><sub>S</sub> network enhances strain homogenization and crack deflection, achieving excellent strength, ductility, and fatigue performance. These results underscore the importance of microstructure-driven, application-specific heat treatment design for enhancing the reliability of additively manufactured aerospace components.</p>

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Effect of Heat Treatment on Low-Cycle Fatigue Behavior of Wire Arc Additive Manufactured TC11 Titanium Alloy

  • 期刊论文

  • 发表日期：

    2025年12月22日

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  • Yong Xie,
  • Qingjun Zhou,
  • Peng Dong,
  • Mengcheng Gong,
  • Chunbo Li

摘要

The growing application of wire arc additive manufactured (WAAMed) TC11 alloy in critical aerospace structures has spurred interest in its fatigue mechanisms and cyclic behavior, yet understanding of heat treatment effects remains limited. This study investigates how heat treatments influence the low-cycle fatigue response and life span of WAAMed TC11, with focus on the role of phase composition and microstructural stability. Results show that vertically oriented 550-AC (550 °C/4 h/air cooling) samples exhibit lower cyclic stress–strain levels than horizontal ones, revealing significant anisotropy. This arises from higher misorientation angles along elongated columnar α grain boundaries (αGBs) in vertical samples, which impede slip bands interaction, reduce dislocation accumulation, and delay cyclic softening. In contrast, other heat treatments show negligible orientation dependence due to less pronounced αGB misorientation. During stable deformation, the 1020-AA (1020 °C/2 h/AC + 550 °C/4 h/AC) samples exhibit early cyclic softening due to fine lamellar structures acting as dislocation sinks, resulting in the poorest fatigue resistance and highest crack growth rate. Conversely, 550-AC samples show superior crack initiation resistance and minimal crack growth, attributed to a microstructure dominated by ~ 95% lamellar αP and high-misorientation boundaries. The optimal condition is 970-AA (970 °C/2 h/AC + 550 °C/4 h/AC), which yields a balanced assemblage of 24.2% crab-like αP, 11.3% globularized α (αG), and 64.5% secondary α (αS). Despite slight softening induced by αG, the refined αS network enhances strain homogenization and crack deflection, achieving excellent strength, ductility, and fatigue performance. These results underscore the importance of microstructure-driven, application-specific heat treatment design for enhancing the reliability of additively manufactured aerospace components.