Strain glass state in Ni_50.3Ti_29.7Hf₂₀ high-temperature shape memory alloy

NiTiHf alloy is one of the most promising candidates for high-temperature shape-memory actuators. Although the phase transition behavior of NiTiHf is well understood, there are still new revelations. Here, we for the first time report the strain glass state in a NiTiHf alloy. Our results demonstrate that the H-phase precursor generated during rapid cooling suppresses the normal martensitic phase transition of NiTiHf, leading to the strain glass state. Moreover, we successfully controlled the strain glass transition via changing the cooling rate. These new findings make the NiTiHf system promising for high-temperature superelastic materials.