Mechanical behavior and thermal activation analysis of HfNbTaTiZr body-centered cubic high-entropy alloy during tensile deformation at 77 K

Abstract

Plastic deformation of HfNbTaTiZr body-centered cubic high-entropy alloy (BCC -HEA) was investigated at 77 K. Tensile stress-strain curves showed strong temperature dependence of yield strength. Characteristics of dislocation slip at 77 K was analyzed using slip traces which confirmed active slip on {112} planes. The apparent activation volume ( V * ) suggested thermally activated kink/kink-pair nucleation at 77 K ( V * ~7 b 3 ). V * values of BCC -HEA and pure Nb were nearly same at 77 K. Low-temperature plasticity of the BCC -HEA showed characteristics of pure BCC metals, suggesting chemical-complexity of HEAs may not alter the Peierls potential of a /2 < 111 > screw dislocations.

Plastic deformation of solid-solution strengthened Hf-Nb-Ta-Ti-Zr body-centered cubic medium/high-entropy alloys

“…Finally, the V * values of the HfTaTiZr alloy ranged 33 ~31 b 3 . In our previous article [11] , a similar range of the V * values (31 ~29 b 3 ) was observed in the HfNbTaTiZr alloy. The V * values of the alloys in the present study were mostly strain independent, which is due to low strain hardening rate of these alloys.…”

“…The evaluated V * indicated thermally-activated dislocation glide by overcoming the Peierls-Nabarro stress barrier as the ratecontrolling mechanism. It is noteworthy that the V * values of all the alloys were well above the range of kink/kink-pair nucleation, V * < 10 b 3 [11] . That is, independent of the alloy composition or tensile strength, the V * values indicated no relevant transition from the Peierls-type to kink nucleation mechanism.…”

Influence of Temperature and Plastic Strain on Deformation Mechanisms and Kink Band Formation in Homogenized HfNbTaTiZr

“…Recently, kink bands have been found in a HfNbTaTiZr multi-principal element alloy after coldrolling at RT [8]. This high entropy alloy (HEA) has attracted great interest as a candidate for novel structural applications [9] due to its outstanding combination of strength and ductility over a wide range of temperatures [10,11]. HEAs are expected to form single-phase solid solutions [12].…”