Thermal stability of Ni₅₄Mn₂₅Ga_20.9Gd _0.1 high-temperature shape memory alloy with large reversible strain

The thermal stability of polycrystalline Ni₅₄Mn ₂₅Ga_20.9Gd_0.1 high-temperature shape memory alloy was systematically investigated by the combination of X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and compression tests. The results show that the non-modulated tetragonal martensite of structure and type I(111)_M twin of substructure was unchanged even after 2000 thermal cycles, and some dislocation structures were formed in martensite of thermal-cycled alloy. The martensitic transformation temperatures after different thermal cycles have no difference, and the shape memory effect decreased from 7.5% to 7.4% due to formation of dislocation structures. The excellent thermal stability was ascribed to the single-phase and well self-accommodated martensitic twins.