However, achieving low mass and reliable performance at cryogenic temperatures remains challenging. A team of researchers, namely Yuxin Song, Shunsuke Sato, Sheng Xu and Inho Lee, have developed a newly developed shape-memory alloy specifically engineered to meet these demanding requirements.
Composed of aluminium and titanium with a chemical composition of Ti₇₅.₂₅Al₂₀Cr₄.₇₅, this alloy features a low density of 4.36 × 10³ kg/m³ and a high specific strength of 185 × 10³ Pa·m³/kg at room temperature. It also exhibits outstanding superelasticity. This property results from a reversible stress-induced phase transformation between an ordered body-centred cubic parent phase and an ordered orthorhombic martensite phase, enabling a recoverable strain greater than 7 per cent.
This remarkable functionality remains stable across a wide temperature range from deep cryogenic levels at 4.2 K to above room temperature thanks to the unconventional temperature dependence of the transformation stresses. Notably, below a specific threshold during cooling, the critical stress required for phase transformation decreases as the temperature drops. This inverse relationship is attributed to temperature-sensitive anomalous lattice instability in the parent phase.
