Grain size effects on NiTi shape memory alloy fatigue crack growth

Abstract

Fatigue cracking in polycrystalline NiTi was investigated using a multiscale experimental framework for average grain sizes (GS) from 10 nm to 1500 nm for the first time. Macroscopic fatigue crack growth rates, measured by optical digital image correlation (DIC), were connected to microscopic crack opening and closing displacements, measured by scanning electron microscope DIC (SEM-DIC) using a high-precision external SEM scan controller. Among all grain sizes, the 1500 nm GS sample exhibited the slowest crack growth rate at the macroscale, and the largest crack opening level (stress intensity at first crack opening) and minimum crack opening displacements at the microscale. Smaller GS samples (10, 18, 42, and 80 nm) exhibited non-monotonic trends in their fatigue performance, yet the correlation was strong between macroscale and microscale behaviors for each GS. The samples that exhibited the fastest crack growth rates (42 and 80 nm GS) showed a small crack opening level and the largest crack opening displacements. The irregular trends in fatigue performance across the nanocrystalline GS samples were consistent with non-monotonic values in elastic modulus reported previously, both of which may be related to the presence of residual martensite only evident in the small GS samples (10 and 18 nm).

BibTeX

@article{2018_lepage_grain_size_niti_fcg,
  title     = {Grain size effects on NiTi shape memory alloy fatigue crack growth},
  author    = {LePage W and Ahadi A and Lenthe WC and Sun QP and Pollock T and Shaw JA and Daly SH},
  journal   = {Journal of Materials Research},
  volume    = {33},
  pages     = {91-107},
  year      = {2018},
  doi       = {10.1557/jmr.2017.395},
}

Vancouver

LePage W, Ahadi A, Lenthe WC, Sun QP, Pollock T, Shaw JA, et al. Grain size effects on NiTi shape memory alloy fatigue crack growth. J. Mater. Res. 2018;33:91-107. doi:10.1557/jmr.2017.395

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This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature's AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1557/jmr.2017.395