Elastocaloric behavior of NiTi and NiTiHfPd shape memory alloys

This study presents a comparative experimental investigation of the elastocaloric (EC) behavior of a quaternary NiTiHfPd shape memory alloy (SMA) and a conventional binary NiTi under uniaxial compressive loading. Near-adiabatic temperature changes (ΔT) arising from stress-induced martensitic transformations were measured using high-speed, non-contact infrared thermography across a systematic range of applied strain levels (up to 7 %) and strain rates (0.0007–0.30 s⁻¹). Binary NiTi exhibited a more uniform temperature distribution and achieved a slightly higher average ΔT, while NiTiHfPd demonstrated superior peak cooling performance, attaining a maximum ΔT of −16.80 °C at 7 % strain and a strain rate of 0.30 s⁻¹, with lower energy dissipation (ΔW). The influence of applied strain and strain rate on ΔT, hysteresis loss (ΔW), and the coefficient of performance (COP) was systematically evaluated and quantitatively compared between the two alloys. Results indicate that NiTiHfPd’s reduced hysteresis and strong peak cooling performance offer distinct advantages for applications requiring high stress tolerance and rapid, localized cooling.