Effect of Ta addition on NiTiZr high-temperature shape memory alloy across multiple scales: a combined experimental–computational study

Abstract

This work investigates the effect of Ta addition in NiTiZr high-temperature shape memory alloy (HTSMA) in terms of phase transformation, mechanical and functional performance. The experimental observations were supported using a computational approach that includes atomistic simulations and Machine learning (ML). Additionally, phenomenological theory was employed to check the compatibility of B2 and B19’ phase with and without Ta in the lattice, enabling a multi-scale understanding of the alloy behaviour. The addition of Ta promotes B2 phase stabilization, reducing martensite stability and forming BCC α-Ta phases due to the limited solubility of Ta in the matrix, thereby enhancing compressive strength and formability up to 5at% Ta and raised the Ms to 170.03 °C, whereas above 5 at%, the alloys undergo coarsening of α-Ta phases causing weakening in the alloy under Ashby-Orowan criteria. The shape recovery behaviour of 5 at% Ta content in NiTiZr-Ta alloy was observed to be better due to the evolution of eutectic-like α-Ta phase arrangement causes better damping. The DFT-based density of states reveals electronic stability of the B2 phase and improved geometric compatibility between the B2 and B19’ phase after Ta alloying, which is further supported by SHAP-based feature importance analysis. This enables the study of alloy behaviour in a multi-scale perspective from electronic features to mechanical/functional properties of NiTiZr-Ta alloy. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2026.