Effect of grinding and annealing on the structure of Ni-Mn-In alloy

The use of heat pumps based on solid-state phase transformation is promising for heating and cooling systems, in particular for miniaturisation purpose. The evolution of martensitic to austenitic transformation in magnetocaloric Ni50Mn34.5In15.5 has been studied using temperature dependent powder and Laue neutron diffraction. In the framework of (3+1)-dimensional superspace theory, the martensite displays an incommensurate 6M modulated structure of superspace group I2/m(00g) with a modulation wave vector depending on the sample preparation: q*=0.11 A-1 for single crystal and q*=0.33 A-1 for powders in the raw state. We attribute this difference to residual stress /defects introduced by the powder processing from single crystal state. In this experiment we plan to measure powder of Ni50Mn34.5In15.5 in the raw state and annealed at 800°C in the lab. to check the effect on peak broadenings in austenite (room T) and martensite (100K) and possibly measure its modulation vector.