Abstract: The martensitic transformation of CuAlNi single crystals is measured by DSC (differential scanning calorimeter). An isothermal single interface DO3→2H transformation arises when the specimen is quenched at a slow rate, but 2H→DO3 transformation always proceeds with multiple interfaces due to the existence of stored elastic energy inside martensite. The elastic energy is essentially stored on the martensitic interfaces and results in As→Mf, which brings a separate spectrum of heat flow on the measured curve. The size of stored elastic energy affects the hysteresis