Cracking the case: fluctuations enhance ductility in refractory alloys
Abstract
Refractory body-centered cubic (BCC) alloys are attractive candidates for structural applications at extreme temperatures, yet combining room-temperature ductility with high-temperature strength remains the unsolved challenge. Ductility in crystals requires that dislocations emit from a sharp crack tip before brittle cleavage, but continuum theories that treat disordered alloys as chemically homogeneous incorrectly predict brittleness for many experimentally ductile alloys. Here we show that atomic-scale stress fluctuations in disordered alloys create an additional local stress intensity at the crack tip, enabling dislocation loop nucleation below the cleavage threshold. Accounting for these fluctuations yields a local ductility criterion where alloys deemed brittle by conventional fracture mechanics can be intrinsically ductile. Atomistic simulations with machine-learned interatomic potentials and an analytic fracture mechanics model correctly predict composition-driven brittle-to-ductile transitions in binary and ternary Mo-Nb-Ti alloys, in Nb-Ti alloys at 4 K, and in several commercial BCC alloys at room temperature. Guided by this criterion, we predict, fabricate, and test the Hf15Mo15Nb32Ti38 alloy, confirming its room-temperature ductility. This fluctuation-driven mechanism provides a quantitative basis for designing ductile multicomponent BCC alloys.
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BibTeX
@misc{liyanage2026cracking,
title = {{Cracking the case: fluctuations enhance ductility in refractory alloys}},
author = {Manura Liyanage and Julia Chmielewska and Tijmen Vermeij and Johann Michler and Christian Leinenbach and W. A. Curtin and Anirudh Raju Natarajan},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.13465},
eprint = {2609.13465},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.13465},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Cracking the case: fluctuations enhance ductility in refractory alloys
AU - Manura Liyanage
AU - Julia Chmielewska
AU - Tijmen Vermeij
AU - Johann Michler
AU - Christian Leinenbach
AU - W. A. Curtin
AU - Anirudh Raju Natarajan
PY - 2026
DA - 2026/09/11
PB - arXiv
DO - 10.48550/arxiv.2609.13465
UR - https://arxiv.org/abs/2609.13465
AB - Refractory body-centered cubic (BCC) alloys are attractive candidates for structural applications at extreme temperatures, yet combining room-temperature ductility with high-temperature strength remains the unsolved challenge. Ductility in crystals requires that dislocations emit from a sharp crack tip before brittle cleavage, but continuum theories that treat disordered alloys as chemically homogeneous incorrectly predict brittleness for many experimentally ductile alloys. Here we show that atomic-scale stress fluctuations in disordered alloys create an additional local stress intensity at the crack tip, enabling dislocation loop nucleation below the cleavage threshold. Accounting for these fluctuations yields a local ductility criterion where alloys deemed brittle by conventional fracture mechanics can be intrinsically ductile. Atomistic simulations with machine-learned interatomic potentials and an analytic fracture mechanics model correctly predict composition-driven brittle-to-ductile transitions in binary and ternary Mo-Nb-Ti alloys, in Nb-Ti alloys at 4 K, and in several commercial BCC alloys at room temperature. Guided by this criterion, we predict, fabricate, and test the Hf_15Mo_15Nb_32Ti_38 alloy, confirming its room-temperature ductility. This fluctuation-driven mechanism provides a quantitative basis for designing ductile multicomponent BCC alloys.
ER -