Strength enhancement of high entropy alloy HfNbTaTiZr by severe plastic deformation

Abstract

Refractory metal high entropy alloy HfNbTaTiZr with ultrafine grained structure and grain size of approximate to 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 approximate to 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. (C) 2018 Elsevier B.V. All rights reserved.