Orientation-Resolved Nanoindentation of Single Crystal Ti-15Mo: Inverted Elastic Anisotropy and Yield-Onset Behavior Beyond Simple CRSS Predictions
Abstract
Ti-15Mo (wt%) is a well-established β-stabilized alloy whose mechanical response is strongly governed by phase stability and deformation mechanisms that operate at the single-grain scale. Because these intragranular mechanisms are intrinsically anisotropic, understanding the orientation dependence of the elastic and plastic response is critical to the texture-engineered processing of wrought components. Here, we quantify the nanomechanical anisotropy of single-crystal Ti-15Mo by combining EBSD with nanoindentation to correlate hardness, indentation modulus, strain rate sensitivity, and indentation yield response with the crystallographic surface normal near ⟨111⟩,⟨124⟩,⟨011⟩,⟨023⟩, and ⟨013⟩ directions. While the modulus anisotropy is small (~10%), contrary to the prediction for a cubic crystal with A>1, orientations near ⟨111⟩ exhibit the lowest moduli. Yield onset is likewise softest near ⟨111⟩ and spans 41%, while hardness spans only 6.6% and follows neither the modulus nor the yield ordering. The alloy also exhibits yield behavior not captured by the simple CRSS/Schmid-factor models evaluated here. Strain-rate-jump tests yield V*=18-31b3, consistent with kink-pair-nucleation-controlled plasticity; based on V*, the orientations separate into two groups suggestive of glide-dominated versus twin/transformation-participating response. We reveal an inversion of the elastic anisotropy expected for a homogeneous cubic β-phase and an orientation-dependent yield-onset response that is not reproduced by the simple Schmid-factor models examined here. Retained athermal ω is proposed as the contributor because β→ω collapse occurs on {111}β planes and may provide anelastic compliance through the reversible ω→β transformation.
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BibTeX
@misc{abebe2026orientationresolved,
title = {{Orientation-Resolved Nanoindentation of Single Crystal Ti-15Mo: Inverted Elastic Anisotropy and Yield-Onset Behavior Beyond Simple CRSS Predictions}},
author = {Kidus Abebe and David Gaetano and Aurelia Moriyama-Gurish and Jana Šmilauerová and Yanfei Gao and Udo D. Schwarz and Amit Datye},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.18181},
eprint = {2610.18181},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.18181},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Orientation-Resolved Nanoindentation of Single Crystal Ti-15Mo: Inverted Elastic Anisotropy and Yield-Onset Behavior Beyond Simple CRSS Predictions
AU - Kidus Abebe
AU - David Gaetano
AU - Aurelia Moriyama-Gurish
AU - Jana Šmilauerová
AU - Yanfei Gao
AU - Udo D. Schwarz
AU - Amit Datye
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.18181
UR - https://arxiv.org/abs/2610.18181
AB - Ti-15Mo (wt%) is a well-established β-stabilized alloy whose mechanical response is strongly governed by phase stability and deformation mechanisms that operate at the single-grain scale. Because these intragranular mechanisms are intrinsically anisotropic, understanding the orientation dependence of the elastic and plastic response is critical to the texture-engineered processing of wrought components. Here, we quantify the nanomechanical anisotropy of single-crystal Ti-15Mo by combining EBSD with nanoindentation to correlate hardness, indentation modulus, strain rate sensitivity, and indentation yield response with the crystallographic surface normal near ⟨111⟩,⟨124⟩,⟨011⟩,⟨023⟩, and ⟨013⟩ directions. While the modulus anisotropy is small (~10%), contrary to the prediction for a cubic crystal with A>1, orientations near ⟨111⟩ exhibit the lowest moduli. Yield onset is likewise softest near ⟨111⟩ and spans 41%, while hardness spans only 6.6% and follows neither the modulus nor the yield ordering. The alloy also exhibits yield behavior not captured by the simple CRSS/Schmid-factor models evaluated here. Strain-rate-jump tests yield V*=18-31b^3, consistent with kink-pair-nucleation-controlled plasticity; based on V*, the orientations separate into two groups suggestive of glide-dominated versus twin/transformation-participating response. We reveal an inversion of the elastic anisotropy expected for a homogeneous cubic β-phase and an orientation-dependent yield-onset response that is not reproduced by the simple Schmid-factor models examined here. Retained athermal ω is proposed as the contributor because β→ω collapse occurs on {111}_β planes and may provide anelastic compliance through the reversible ω→β transformation.
ER -