Plastic deformation properties of Zr–Nb–Ti–Ta–Hf high-entropy alloys

Abstract

We have investigated the plastic deformation properties of single-phase Zr–Nb–Ti–Ta–Hf high-entropy alloys from room temperature (RT) up to 300 °C. Uniaxial deformation tests at a constant strain rate of 10⁻⁴s⁻¹ were performed, including incremental tests such as stress relaxations, strain-rate changes, and temperature changes in order to determine the thermodynamic activation parameters of the deformation process. The microstructure of deformed samples was characterized by transmission electron microscopy. The strength of the investigated Zr–Nb–Ti–Ta–Hf phase is not as high as the values frequently reported for high-entropy alloys in other systems. At RT we measure a flow stress of about 850 °C. We find an activation enthalpy of about 1 eV and a stress dependent activation volume between 0.5 and 2 nm³. The measurement of the activation parameters at higher temperatures is affected by structural changes evolving in the material during plastic deformation.

Keywords:

• high-entropy alloys
• dislocations
• plasticity

Acknowledgements

The authors thank Prof. Walter Steurer for communication of the single-phase composition of the presently investigated HEA, Marc Heggen for valuable discussions, Eva-Maria Würtz for sample preparation and characterization, and Maximilian Kruth for the preparation of TEM specimens.

Disclosure statement

No potential conflict of interest was reported by the authors.