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<p>High-Be Cu-Be alloys exhibit dendritic segregation and brittle β/γ phases, which complicate processing and applications. This study investigates the influence of cooling path on eutectoid transformation, microstructure, and mechanical properties in Cu-2.8Be and Cu-3.8Be alloys. A two-step homogenization treatment effectively eliminates segregation and suppresses the formation of harmful acicular phases. Diffusion-kinetic and thermodynamic analyses demonstrate that both the initial temperature and cooling rate determine eutectoid morphology and extent. Crystallographic and Eshelby-based analyses reveal that the β → γ transformation involves an isotropic contraction of ∼3.9%, producing much lower strain energy than the anisotropic β → α transformation (∼28.5% expansion and ∼9.2% contraction), thus explaining the preferential nucleation of γ. Rapid cooling promotes incomplete eutectoid decomposition along grain boundaries, forming fine α/γ lamellae with interlamellar spacing down to ∼7 nm. Lattice strain analysis confirms considerable distortions at α/γ interfaces (<i>ε</i><Stack> <sub><i>xx</i></sub> <sup>α</sup> </Stack> = 0.0167, <i>ε</i><Stack> <sub><i>xx</i></sub> <sup>γ</sup> </Stack> = 0.0095). The mechanical incompatibility and high internal strain at these interfaces cause stress concentration and crack initiation. This work establishes a process-micro-structure-property-mechanism framework essential for controlling the performance of high-Be Cu-Be alloys.</p>

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Eutectoid transformation in Cu-Be alloys tuned by cooling pathways: from crystallography to mechanical properties

  • 期刊论文

  • 发表日期：

    2026年2月26日

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  • Xiaoyu Jiang,
  • Qiuhua Guo,
  • Yanbin Jiang,
  • Daibo Zhu,
  • Meng Wang,
  • Wei Chen,
  • Zhou Li

摘要

High-Be Cu-Be alloys exhibit dendritic segregation and brittle β/γ phases, which complicate processing and applications. This study investigates the influence of cooling path on eutectoid transformation, microstructure, and mechanical properties in Cu-2.8Be and Cu-3.8Be alloys. A two-step homogenization treatment effectively eliminates segregation and suppresses the formation of harmful acicular phases. Diffusion-kinetic and thermodynamic analyses demonstrate that both the initial temperature and cooling rate determine eutectoid morphology and extent. Crystallographic and Eshelby-based analyses reveal that the β → γ transformation involves an isotropic contraction of ∼3.9%, producing much lower strain energy than the anisotropic β → α transformation (∼28.5% expansion and ∼9.2% contraction), thus explaining the preferential nucleation of γ. Rapid cooling promotes incomplete eutectoid decomposition along grain boundaries, forming fine α/γ lamellae with interlamellar spacing down to ∼7 nm. Lattice strain analysis confirms considerable distortions at α/γ interfaces (ε xx α = 0.0167, ε xx γ = 0.0095). The mechanical incompatibility and high internal strain at these interfaces cause stress concentration and crack initiation. This work establishes a process-micro-structure-property-mechanism framework essential for controlling the performance of high-Be Cu-Be alloys.