Wide-temperature superelasticity in a dual-phase Nb-doped TiNiCuHf high entropy strain glass alloy

We report on a Nb-doped dual-phase high entropy strain glass alloy, Ti_(40-x/2)Ni_(40-x/2)Cu₁₀Hf₁₀Nb_x, specifically designed to demonstrate superelasticity in a wide-temperature range. The precipitation of Nb-rich β-Nb phase result in the increase of Ni-site/Ti-site atomic ratio in the matrix, which gives rise to the decrease of martensitic transformation with increasing Nb content (x). When x exceeds 12.5 %, the martensitic transformation is completely suppressed and it undergoes a strain glass transition. The enhanced austenite stability of strain glass alloy effectively decreases the lower temperature limit of superelasticity. Furthermore, the severe lattice distortion mechanically strengthened the above high entropy strain glass alloy, which increases the higher temperature limit of superelasticity. Thus, the Ti_32.5Ni_32.5Cu₁₀Hf₁₀Nb₁₅ strain glass alloy exhibits superelasticity across a wide temperature range from -125 °C to 50 °C with recoverable strain of 4 %. The designed TiNiCuHfNb high entropy strain glass alloys are promising for outer-space explorations with large temperature variations.