In recent years, a new cooling phenomenon (elastic calorific value effect) that utilizes heat transfer associated with superelasticity has been attracting attention as a technology that replaces the conventional cooling method using Freon gas.The elastic calorific value effect is the effect of heat generation and endothermic heat corresponding to the difference in entropy before and after transformation in the transformation in which the crystal structure and magnetic structure change according to the application and unloading of stress. If a shape memory alloy having superelastic properties that "returns to its original shape when its force is removed even if it is greatly deformed" is deformed in an adiabatic environment, cooling using this effect becomes possible.

　However, in general, the lower the temperature of a material, the harder it becomes and the more it loses its elasticity.Therefore, at low temperatures, frictional heat is generated during deformation, and it has been difficult to obtain an excellent cooling effect even with an elastic heat quantity effect.

　In response, this research group has developed a Cn-Al-Mn alloy that can expand and contract by about 4.2% up to an extremely low temperature range of up to 7K.This time, when the elastic calorific value effect obtained when the superelastic alloy was expanded and contracted was evaluated, it was found that the cooling effect could be obtained up to 22K.Since the minimum temperature at which the elastic calorific value effect was exhibited in the superelastic alloys reported so far was 210K, the applicable temperature range was actually expanded to the low temperature side by 188K.

　With this result, it is expected that superelastic alloys will be applied as actuators and cooling units in the cryogenic region, and in the fields of superconductivity, liquefied gas, and space engineering.

Paper information:[NPG Asia Materials] Cryogenic superelasticity with large elastocaloric effect