Microstructure and Mechanical Properties Evolution in HfNbTaTiZr Refractory High‐Entropy Alloy During Cold Rolling

The effect of cold rolling on the structure and mechanical properties of the HfNbTaTiZr refractory high‐entropy alloy with a single body‐centered cubic (BCC) phase structure is studied. The microhardness evolution during cold rolling to the thickness strain ε_th = 80% shows three distinct stages: an increase till ε_th ≈ 15%, a plato in the interval ≈15–40%, and again some increase at ε_th ≥ 40%. This behavior is found to be associated with an increase in dislocation density at the first stage, the formation of kink bands at the second stage, and the development of shear bands with fine lamellar internal substructure at the third stage. After cold rolling to 80%, the alloy demonstrates the yield strength of 1220 MPa, peak strength 1320 MPa, and elongation to fracture 3.4%. A short steady‐state flow stage is observed on the engineering stress–strain curve that can also be associated with kinking.