Microstructure and solidification behavior of Ni-Mn-Ga magnetic shape memory alloys

Jian Chen; Michael A. Gharghouri; Calvin V. Hyatt

doi:10.1117/12.540752

21 July 2004 Microstructure and solidification behavior of Ni-Mn-Ga magnetic shape memory alloys

Jian Chen, Michael A. Gharghouri, Calvin V. Hyatt

Proceedings Volume 5387, Smart Structures and Materials 2004: Active Materials: Behavior and Mechanics; (2004) https://doi.org/10.1117/12.540752
Event: Smart Structures and Materials, 2004, San Diego, CA, United States

Abstract

In order to understand the solidification behavior of Ni-Mn-Ga alloys, ingots with different compositions were prepared by arc melting. Two series of compositions were investigated: Ni_100-2xMn_xGa_x (15≤x ≤30) and Ni₅₀Mn_50-yGa_y (0≤y≤50). The microstructures obtained were observed and the compositions of the phases occurring in the ingots were identified by energy dispersive spectroscopy in the scanning electron microscope. Based on these observations, three solidification paths were identified: direct solidification of γ-Ni from the liquid, direct solidification of β-NiMnGa from the liquid, and solidification of β-NiMnGa phase via a peritectic reaction. It was found that the γ-Ni liquidus surface covers a large area of the ternary phase diagram. The γ-Ni liquidus boundary is located between Ni₅₀Mn₂₅Ga₂₅ and Ni₄₅Mn_27.5Ga_27.5 in the equal Mn and Ga alloy series, and between Ni₅₀Mn₅Ga₄₅ and Ni₅₀Mn₁₀Ga₄₀ in the 50 at.% Ni alloy series. The alloys with compositions close to the stoichiometric Ni2MnGa composition that show the magnetic shape memory effect are all covered by the γ-Ni liquidus surface. The β-NiMnGa liquidus surface covers the remaining alloy compositions.

Citation Download Citation

Jian Chen, Michael A. Gharghouri, and Calvin V. Hyatt "Microstructure and solidification behavior of Ni-Mn-Ga magnetic shape memory alloys", Proc. SPIE 5387, Smart Structures and Materials 2004: Active Materials: Behavior and Mechanics, (21 July 2004); https://doi.org/10.1117/12.540752

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