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<p>The 6061-T6 aluminum alloy is widely used in structural components under cyclic loading. This study investigates the low-cycle fatigue (LCF) behavior of this alloy through strain-controlled experiments combined with a multiscale crystal plasticity finite element (CPFE) framework. The fatigue crack nucleation life constituted a nearly consistent fraction of total life over the investigated strain amplitudes. A thermally activated slip-based model incorporating dislocation density as an internal state variable was implemented by backward Euler discretization and accurately reproduced experimental hysteresis loops. The CPFE simulations show that increasing strain amplitudes accelerates dislocation accumulation, with pile-ups preferentially occurring in regions of high grain boundary density. Orientation-dependent grain responses generate stress gradients and strain incompatibilities that promote crack initiation, while the peak accumulated equivalent plastic strain consistently localizes near grain boundaries. An extreme value statistical approach using the accumulated equivalent plastic strain as the fatigue indicator parameter (FIP) successfully predicts fatigue lives in agreement with experimental data. The simulations including brittle iron-rich intermetallic particles further reveal that particle-matrix property mismatch induces strong interfacial stress concentrations, where dislocation pile-ups trigger localized plasticity and preferential crack initiation. These multiscale simulations provide valuable insights for the structural integrity assessment and microstructure-informed design of fatigue-resistant aluminum alloys.</p>

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Crystal plasticity modeling of low-cycle fatigue in 6061-T6 aluminum alloy

  • 期刊论文

  • 发表日期：

    2026年6月3日

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  • Junsong Hu,
  • Ruijie Deng,
  • Pan Wang

摘要

The 6061-T6 aluminum alloy is widely used in structural components under cyclic loading. This study investigates the low-cycle fatigue (LCF) behavior of this alloy through strain-controlled experiments combined with a multiscale crystal plasticity finite element (CPFE) framework. The fatigue crack nucleation life constituted a nearly consistent fraction of total life over the investigated strain amplitudes. A thermally activated slip-based model incorporating dislocation density as an internal state variable was implemented by backward Euler discretization and accurately reproduced experimental hysteresis loops. The CPFE simulations show that increasing strain amplitudes accelerates dislocation accumulation, with pile-ups preferentially occurring in regions of high grain boundary density. Orientation-dependent grain responses generate stress gradients and strain incompatibilities that promote crack initiation, while the peak accumulated equivalent plastic strain consistently localizes near grain boundaries. An extreme value statistical approach using the accumulated equivalent plastic strain as the fatigue indicator parameter (FIP) successfully predicts fatigue lives in agreement with experimental data. The simulations including brittle iron-rich intermetallic particles further reveal that particle-matrix property mismatch induces strong interfacial stress concentrations, where dislocation pile-ups trigger localized plasticity and preferential crack initiation. These multiscale simulations provide valuable insights for the structural integrity assessment and microstructure-informed design of fatigue-resistant aluminum alloys.