Structure and Phase Stability of NiMnGa Ferromagnetic Shape Memory Alloys by Experimental and Ab Initio Techniques

Abstract:

This paper summarizes some of our recent results on crystal structure, microstructure, orientation relationship between martensitic variants and crystallographic features of martensitic transformation in Ni-Mn-Ga FSMAs. It was shown that Ni53Mn25Ga22 has a tetragonal I4/mmm martensitic structure at room temperature. The neighboring martensitic variants in Ni53Mn25Ga22 have a compound twinning relationship with the twinning elements K1={112}, K2={11-2}, η1=<11-1>, η2=<111>, P={1-10} and s=0.379. The ratio of the relative amounts of twins within the same initial austenite grain is ~1.70. The main orientation relationship between austenite and martensite is Kurdjumov-Sachs (K-S) relationship. Based on the crystallographic phenomenological theory, the calculated habit plane is {0.690 -0.102 0.716}A (5.95° from {101}A), and the magnitude, direction and shear angle of the macroscopic transformation shear are 0.121, <-0.709 0.105 0.698>A (6.04° from <-101>A) and 6.88°, respectively.

• Periodical: Materials Science Forum (Volumes 638-642)
• Pages: 2040-2045
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.638-642.2040
• Online since: January 2010
• Authors: Claude Esling, Dao Yong Cong, Jing Bai, Yu Dong Zhang, Jean Marc Raulot, Xiang Zhao, Liang Zuo
• Keywords: Ab Initio Calculation, Crystal Structure, Ferromagnetic Shape Memory Alloys (FSMAs), Orientation Relationship, Phase Transformation

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