Crystal structures and textures in the hot-forged Ni-Mn-Ga shape memory alloys

Three ferromagnetic shape-memory alloys with the chemical compositions of Ni^sub 53^Mn^sub 25^Ga^sub 22^, Ni^sub 48^Mn^sub 30^Ga^sub 22^, and Ni^sub 48^Mn^sub 25^Ga^sub 22^Co^sub 5^ were prepared by the induction-melting and hot-forging process. The crystal structures were investigated by the neutro...

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Bibliographic Details
Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2006-05, Vol.37 (5), p.1397-1403
Main Authors: CONG, D. Y, WANG, Y. D, LIN PENG, R, ZETTERSTRÖM, P, ZHAO, X, LIAW, P. K, ZUO, L
Format: Article
Language:English
Subjects:
Alloys
Applied sciences
Construction materials
Crystal structure
Exact sciences and technology
Konstruktionsmaterial
Materials science
Metals. Metallurgy
Polycrystals
TECHNOLOGY
TEKNIKVETENSKAP
Teknisk materialvetenskap
Temperature effects
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Summary:Three ferromagnetic shape-memory alloys with the chemical compositions of Ni^sub 53^Mn^sub 25^Ga^sub 22^, Ni^sub 48^Mn^sub 30^Ga^sub 22^, and Ni^sub 48^Mn^sub 25^Ga^sub 22^Co^sub 5^ were prepared by the induction-melting and hot-forging process. The crystal structures were investigated by the neutron powder diffraction technique, showing that Ni^sub 53^Mn^sub 25^Ga^sub 22^ and Ni^sub 48^Mn^sub 25^Ga^sub 22^Co^sub 5^ have a tetragonal, I4/mmm martensitic structure at room temperature, while Ni^sub 48^Mn^sub 30^Ga^sub 22^ has a cubic, L2^sub 1^ austenitic structure at room temperature. The development of textures in the hot-forged samples shows the in-plane plastic flow anisotropy from the measured pole figures by means of the neutron diffraction technique. Significant texture changes were observed for the Ni^sub 48^Mn^sub 25^Ga^sub 22^Co^sub 5^ alloy after room temperature deformation, which is due to the deformation-induced rearrangements of martensitic variants. An excellent shape-memory effect (SME) with a recovery ratio of 74 pct was reported in this Ni^sub 48^Mn^sub 25^Ga^sub 22^Co^sub 5^ polycrystalline alloy after annealing above the martensitic transformation temperature, and the "shape-memory" influence also occurs in the distributions of grain orientations. [PUBLICATION ABSTRACT]
ISSN:1073-5623
1543-1940
1543-1940
DOI:10.1007/s11661-006-0084-0