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Thermomagnetization measurements of Co51.5Cr26.5Ga11Si11 under magnetic fields of 0.5, 10, 40, and 70 kOe at low temperature and under 500 Oe at high temperature. Note that at low temperatures the phase with stronger magnetism is the parent (L) phase. and , which are the reverse martensitic transformation (LT) starting temperature and the forward martensitic transformation (LT) finishing temperature, were obtained by extrapolation. At high temperatures, another martensitic transformation (HT) is observed. The forward martensitic transformation (HT) starting temperature and the reverse martensitic transformation (HT) finishing temperature are indicated. The upper pictures show the cooling-induced shape memory effect as well as the normal SME observed by the same sample. A bent sample (b) can recover its original shape by both cooling by liquid nitrogen (a) and by the heating with a flame (c). Refer to supplementary Video 1 (Ref. 12 ) for the full process.
In situ transmission electron microscope micrographs of Co51.5Cr26.5Ga11Si11 and their corresponding selected-area diffraction patterns. (a) Parent (L) phase at 77 K formed by the abnormal martensitic transformation (LT) at low temperature. (b) Martensite phase at 419 K. (c) Parent (H) phase at 831 K is also shown, which is formed bythe normal martensitic transformation (HT) at high temperature. Corresponding schematic figures of the crystal structures are also illustrated.
(a) Compression tests for Co51Cr27Ga11Si11 single crystal sample, the crystal orientation parallel to the loading axis is marked in the inverse pole figure. A large hysteresis can be observed and almost perfect superelasticity is obtained. The martensitic transformation starting stress ( ) and the reverse martensitic transformation finishing stress ( ) are indicated in the figure. (b) The equilibrium stress is assumed to be and the temperature dependences of , , and are summarized. The inverse temperature dependence of superelastic stress (ITDSS) is confirmed.
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