Influence of Heat Treatment on the Mechanical and Thermomechanical Characteristics of a Ti₅₀Pd₃₀Ni₂₀ Alloy with High-Temperature Shape Memory Effect

Abstract—The influence of annealing at 600°C on the mechanical and thermomechanical characteristics of a Ti₅₀Pd₃₀Ni₂₀ alloy with high-temperature shape memory effect (SME) is studied. The best strength (σ_u = 1030 ± 140 MPa) and plastic (ε0max">ε${\text{ε}}_0^{max}$ = 11.5 ± 6.0%, δ_res = 6 ± 4%) characteristics have been obtained after annealing at 600°C. The maximum thermally recoverable strain (ε_SME = 4.3%) and the maximum degree of shape recovery (η_SME = 67%) are achieved after annealing at 600°C after preliminary induced tensile deformation at temperatures t_d =235–230°C and a strain rate ε˙">ε$\dot{\text{ε}}$ ≈ 2.8 × 10^–3 s^–1; in this case, the reverse martensitic transformation temperatures characterizing the main shape recovery are A_sSME = 220°C and A_fSME = 249°C. Taking into account the studies carried out before, we found that the martensitic transformation temperatures increase almost linearly and, conversely, the SME and the degrees of shape recovery decrease as the titanium nickelide is alloyed with palladium in the content range from 30 to 50 at %. Linear regression equations are derived. The results obtained are used for designing safety devices of, e.g., crosscutting and pushing types.