Neutron diffraction study on crystal structure and phase transformation in Ni-Mn-Ga ferromagnetic shape memory alloys

authorCount :6
Crystal structure and phase transformation behaviors in two Ni-Mn-Ga ferromagnetic shape memory alloys (FSMAs) with compositions of Ni48Mn30Ga22 and Ni53Mn25Ga22 (at. %) as a function of temperature were investigated by in situ neutron diffraction experiments. Neutron diffraction technique proves to be highly efficient in characterizing structural transformation in Ni-Mn-Ga FSMAs, which consist of nearby elements in the periodic table. Our neutron results show that Ni48Mn30Ga22 has a cubic, L-21 Heusler structure from 373 to 293 K. Its crystal structure changes into a seven-layered orthorhombic martensitic structure when cooled to 243 K, and no further transformation is observed upon cooling to 19 K. Neutron diffraction results also show that Ni53Mn25Ga22 has a tetragonal 14/mmm martensitic structure from 20 to 403 K. A pre-transformation around room temperature is observed from an abrupt jump in unit-cell volume of Ni53Mn25Ga22, which corresponds with an endothermic peak detected in a heated DSC curve.

Wang, Y. D. (författare)
Xu, J. Z. (författare)
Zuo, L. (författare)
Zetterstroem, P.Stockholms universitet,Avdelningen för strukturkemi (författare)
Delaplane, R.Uppsala universitet,Neutronforskningslaboratoriet i Studsvik (författare)
Stockholms universitetAvdelningen för strukturkemi (creator_code:org_t)

Ingår i:Powder Diffraction: Cambridge University Press (CUP)22:4, s. 307-3110885-71561945-7413

Av författaren/redakt...: Cong, D. Y.; Wang, Y. D.; Xu, J. Z.; Zuo, L.; Zetterstroem, P.; Delaplane, R.

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