Strength enhancement of high entropy alloy HfNbTaTiZr by severe plastic deformation

• Published in: Journal of alloys and compounds 2018-11, Vol.768, p.924-937
• Main Authors: Čížek, J., Haušild, P., Cieslar, M., Melikhova, O., Vlasák, T., Janeček, M., Král, R., Harcuba, P., Lukáč, F., Zýka, J., Málek, J., Moon, J., Kim, H.S.
• Format: Article
• Language: English
• Subjects: Alloys; Crystal defects; Ductility; Entropy; Grain refinement; High entropy alloy; High entropy alloys; High strength alloys; Lattice vacancies; Mechanical properties; Plastic deformation; Positron annihilation spectroscopy; Severe plastic deformation; Solid solutions; Spectrum allocation; Strain; Ultrafine grained structure; Ultrafines
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2018.07.319

Refractory metal high entropy alloy HfNbTaTiZr with ultrafine grained structure and grain size of ≈80 nm was processed by high pressure torsion. The development of microstructure, lattice defects and mechanical properties with increasing strain was examined. Grain refinement of HfNbTaTiZr alloy deformed up to the equivalent strain e ≈ 50 resulted in a significant enhancement of strength while keeping sufficient ductility. However, further straining e > 100 led to a decrease of strength and the loss of ductility due to the decomposition of solid solution facilitated by vacancies introduced by severe plastic deformation. [Display omitted] •High entropy alloy HfNbTaTiZr was nanostructured by high pressure torsion.•Grain size of 80 nm was achieved by deformation to the equivalent strain e = 5.•Structure refinement resulted in remarkable enhancement of strength of the alloy.•Ductility remains sufficient for good workability.•Further deformation to very high strains resulted in loss of strength.