Eleanor Mak^1*, Binglun Yin^1*, William Curtin^1*

1 Laboratory for Multiscale Mechanics Modeling, Institute of Mechanical Engineering, École polytechnique fédérale de Lausanne (EPFL), Lausanne CH-1015, Switzerland

* Corresponding authors emails: eleanor.mak@epfl.ch, binglun.yin@epfl.ch, william.curtin@epfl.ch

DOI10.24435/materialscloud:s4-mm [version v1]

Publication date: Oct 26, 2021

How to cite this record

Eleanor Mak, Binglun Yin, William Curtin, A ductility criterion for bcc high entropy alloys, Materials Cloud Archive 2021.168 (2021), doi: 10.24435/materialscloud:s4-mm.

Description

A current goal driving alloy development is the identification of alloy compositions for high temperature applications but with the additional requirement of sufficient ductility at ambient temperatures. Multicomponent, single-phase, polycrystalline High Entropy Alloys (HEAs) have recently emerged as a new class of metal alloys, and some refractory bcc HEAs composed mainly of Nb, V, Ta, Cr, Mo, and/or W show excellent strength retention up to very high temperatures but low ductility at room temperature (RT). Here, it is postulated that the macroscopic ductility in bcc elements and alloys is determined by the intrinsic competition between brittle cleavage and ductile dislocation emission mechanisms at an atomistically sharp crack. The stress intensities K_Ic for cleavage and K_Ie for emission are evaluated within Linear Elastic Fracture Mechanics and validated by atomistic simulations on model alloys. A RT ductility criterion based on K_Ie/K_Ic for critical crack orientations is proposed based on the elemental metals and is then applied to HEAs. Agreement with experimental trends in ductility vs. composition across a range of existing HEAs is demonstrated. The analysis is then extended across large composition spaces of the Mo-Nb-Ta-V-W and Mo-Nb-Ti alloy families, identifying new compositions with the potential for RT ductility.

Materials Cloud sections using this data

Files

File name	Size	Description
bcc1.tar.gz MD5md5:46730efe17748474410af53a8ceb2caa	59.4 MiB	This dataset contains assorted input files to perform Nudged Elastic Band calculations of crack cleavage and emission in LAMMPS (e.g. initial and final atomic configurations of 2d and 3d cracks) and calculate material parameters to make predictions of crack behavior.
contents.txt MD5md5:6a6d79f437230c35954e1a5407b4dbe1	441 Bytes	Brief description of the contents of bcc1.tar.gz

License

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External references

Keywords

fracture bcc high entropy alloys intrinsic ductility SNSF