Nanostructured NbMoTaW high entropy alloy thin films: High strength and enhanced fracture toughness

doi:10.1016/j.scriptamat.2019.04.011

Scripta Materialia

Volume 168, 15 July 2019, Pages 51-55

https://doi.org/10.1016/j.scriptamat.2019.04.011 Get rights and content

Abstract

Nanocrystalline NbMoTaW high entropy alloys (HEAs) have attracted significant attention due to their superior mechanical properties at elevated temperatures. However, the fracture behavior of nanocrystalline HEAs is still unknown. In this study, the fracture behavior of thin HEA films was investigated using micro-cantilever bending. The nanocrystalline films demonstrated critical stress intensities of ~3 MPa√m, which is significantly higher than previous single- and bi-crystalline values. This work demonstrates the capability of ion beam assisted deposition to strengthen nanocrystalline thin films with only minor losses in toughness.

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Acknowledgements

The authors would like to thank C. Zaubitzer (ScopeM, ETH Zurich) for his help in the sample preparation using FIB, K. Kunze (ScopeM, ETH Zurich) for his help in EBSD characterization, and Z.Q. Que (PSI, Villigen) and J. Ast (Empa, Thun) for the fruitful discussion.

Disclosure statement

No potential conflict of interest was reported by the authors.

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Molecular dynamics (MD) simulations are performed to investigate the nanoscale tribology behavior of Ti-based FeCoNiTi High-entropy alloy (HEA) coating through nanoscratching. Three coating interface models, (001)_HEA||(0001)_Ti, (001)_HEA||(11 $\overline{2}$ 0)_Ti, and (001)_HEA||(1 $\overline{1}$ 00)_Ti, are selected to explore the effects cutting depth (D) and cutting velocity (V) of abrasive particles during the nanoscratching process. The results show that the Ti-based HEA coating with the interface (001)_HEA||(0001)_Ti has the smallest coefficient of friction (COF) making it most suitable as the coating interface. The increase in V resulted in the increase of the frictional force influenced by the Other structure composed of disordered atoms. Due to the existence of multiple phase structures in the limited area of the coating, dislocation nucleation is difficult and disordered atoms are formed. This is different from the strengthening caused by dislocation accumulation in the scratching region. The HEA coating plays an effective role in protecting the pure Ti substrate. With the protection of HEA coating, dislocation slip and deformation twinning were not observed in the pure Ti substrate. However, dislocation slip are the main plastic deformation mechanisms of uncoated pure Ti. These findings provide a theoretical reference for upgrading the wear resistance of pure Ti with HEA coating and expands the area of application of pure Ti.

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Nanostructured NbMoTaW high entropy alloy thin films: High strength and enhanced fracture toughness

Abstract

Graphical abstract

Section snippets

Acknowledgements

Disclosure statement

Intermetallics

Intermetallics

Intermetallics

Scr. Mater.

Int. J. Fatigue

Acta Mater.

Curr. Opin. Solid State Mater. Sci.

Acta Mater.

Acta Mater.

Acta Mater.

Acta Mater.

Acta Mater.

Thin Solid Films

J. Mech. Phys. Solids

Acta Mater.