Study on mechanical and hot deformation behavior of (TiZrHf)50Ni30Cu14Co6 high-entropy shape memory alloy

High-entropy shape memory alloys (HESMAs) exhibit exceptional properties and extensive application prospects. However, research regarding their hot working performance and hot deformation behavior remains relatively scarce. We fabricated a (TiZrHf) 50 Ni 30 Cu 14 Co 6 (at.%) alloy and systematically explored its phase transformation behavior, room-temperature mechanical properties, and high-temperature oxidation resistance. Finally, we focused on analyzing its hot working behavior. Electron backscatter diffraction (EBSD) characterization revealed that the as-cast alloy is predominantly composed of the B19' phase with a minor fraction of the B2 phase. Differential scanning calorimetry (DSC) measurements determined the martensitic transformation start temperature ( M s ) to be 450.79 K, with a thermal hysteresis loop (Δ T ) of merely 61.48 K. Room-temperature compression tests yielded a compressive strength ( σ f ) of 2142.39 MPa and a plastic strain ( ε p ) of 17.31 % for the alloy. Cyclic loading experiments demonstrated a recovery strain ( ε r ) of 9.49 % and a superelastic recovery ( ε SE ) of 2.14 % at a compressive pre-strain ( ε pr ) of 15 %, manifesting distinct superelasticity. In high-temperature oxidation tests, X-ray photoelectron spectroscopy (XPS) analysis confirmed that after 48 h of exposure at 873 K, a composite oxide layer primarily consisting of Hf-Cu-Co oxides was formed on the alloy surface, which effectively impeded further oxidation. The Arrhenius constitutive model based on the Zener-Hollomon parameter can precisely predict the hot deformation behavior. Analysis of the hot working map at a strain of 0.6 determined the optimal hot working parameters within the range of 987–1043 K and 5 × 10 −2 to 5 × 10 −1 s −1 .