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<p>Geometrically necessary dislocations (GNDs) and back stress serve as critical microscopic determinants for the microstructural hardening and plastic flow capacity of alloys. This study characterizes the micromechanical response of a Ti-43.5Al-4Nb-1Mo-0.1B (TNM) alloy by employing crystal plasticity finite element (CPFE) simulations integrated with electron backscatter diffraction (EBSD) for crystal orientation mapping. A novel crystal plasticity (CP) constitutive theory, grounded in GND and back stress evolution, is proposed. By integrating experimental findings with simulation results, the analysis elucidates the effects of GNDs and back stress induced by varying strain rates on the mechanical properties of the TNM alloy during nanoindentation. The load-depth curves from both experiments and simulations exhibit strong consistency, confirming that nanoindentation effectively validates constitutive parameters for TiAl alloys. Furthermore, this study systematically examines surface pile-up, cumulative shear strain distribution, the indentation size effect (ISE), and GND evolution in γ and α<sub>2</sub> phase single crystals across multiple strain rates. Findings indicate that strain rate modulates the synergistic effects of GNDs and back stress, resulting in distinct plastic deformation behaviors for the γ and α<sub>2</sub> phases. GNDs activated by higher strain rates facilitate dislocation movement and enhance deformation resistance by reinforcing the internal stress field, thereby promoting GND density accumulation. Ultimately, this process triggers a significant ISE, increasing material hardness and strain hardening. This research provides a micromechanical explanation for the modulation of TiAl alloy properties through strain rate variations and offers theoretical support for performance optimization.</p> Graphical Abstract <p></p>

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Effect of Strain Rate on the Nanoindentation Behavior of TiAl Alloys Based on Crystal Plasticity Finite Element Method

  • 期刊论文

  • 发表日期：

    2026年4月7日

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  • Chenyang Han,
  • Haiyan Li,
  • Linghao Zeng,
  • Ruicheng Feng,
  • Wenshuai Niu,
  • Hui Cao,
  • Baocheng Zhou

摘要

Geometrically necessary dislocations (GNDs) and back stress serve as critical microscopic determinants for the microstructural hardening and plastic flow capacity of alloys. This study characterizes the micromechanical response of a Ti-43.5Al-4Nb-1Mo-0.1B (TNM) alloy by employing crystal plasticity finite element (CPFE) simulations integrated with electron backscatter diffraction (EBSD) for crystal orientation mapping. A novel crystal plasticity (CP) constitutive theory, grounded in GND and back stress evolution, is proposed. By integrating experimental findings with simulation results, the analysis elucidates the effects of GNDs and back stress induced by varying strain rates on the mechanical properties of the TNM alloy during nanoindentation. The load-depth curves from both experiments and simulations exhibit strong consistency, confirming that nanoindentation effectively validates constitutive parameters for TiAl alloys. Furthermore, this study systematically examines surface pile-up, cumulative shear strain distribution, the indentation size effect (ISE), and GND evolution in γ and α2 phase single crystals across multiple strain rates. Findings indicate that strain rate modulates the synergistic effects of GNDs and back stress, resulting in distinct plastic deformation behaviors for the γ and α2 phases. GNDs activated by higher strain rates facilitate dislocation movement and enhance deformation resistance by reinforcing the internal stress field, thereby promoting GND density accumulation. Ultimately, this process triggers a significant ISE, increasing material hardness and strain hardening. This research provides a micromechanical explanation for the modulation of TiAl alloy properties through strain rate variations and offers theoretical support for performance optimization.

Graphical Abstract