Martensitic transformation and shape memory effect in Ni54.75Mn13.25Fe7Ga25 ferromagnetic shape memory alloy

Effect of chemical composition was investigated on martensitic transformation temperatures, Curie temperature, magnetization and microstructures for Ni-(Mn, Fe, Co)-Ga and Cu-Mn-Ga systems. In the Ni-(Mn, Fe, Co)-Ga alloys, which is a modification of Ni-Mn-Ga systems, the Af and TC over 400 K were achieved. Cu-Mn-Ga alloy exhibited shape memory effect at temperatures above 373 K and had TC over 400 K. Furthermore, Cu-Mn-Ga exhibits good ductility even in polycrystalline condition unlike the case of Ni-Mn-Ga. Effect of addition of the fourth element to improve the magnetic property is under investigation.

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Martensitic Transformation Behavior and Shape Memory Effect of an Aged Ni-rich Ti-Ni-Hf High Temperature Shape Memory Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.138.399 ◽

2008 ◽

Vol 138 ◽

pp. 399-406 ◽

Cited By ~ 3

Author(s):

Xiang Long Meng ◽

Yu Dong Fu ◽

Wei Cai ◽

J.X. Zhang ◽

Qing Fen Li ◽

...

Keyword(s):

High Temperature ◽

Martensitic Transformation ◽

Shape Memory Alloy ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Aging Temperature ◽

Transformation Behavior ◽

Transformation Temperatures ◽

Solution Treated

The martensitic transformation behavior and shape memory effect (SME) have been investigated in a Ni-rich Ti29.6Ni50.4Hf20 high temperature shape memory alloy (SMA) in the present study. After aging, the transformation temperatures of Ti29.6Ni50.4Hf20 alloy increase obviously due to the precipitation of (Ti,Hf)3Ni4 particles. And the transformation sequence changes from one-step to two-step. When the experimental alloy is aged at different temperatures for 2h, the transformation temperatures increase rapidly with increasing the aging temperature and then change slightly with further increasing the aging temperature. Most of the martensite variants preferentially oriented in the aged Ti29.6Ni50.4Hf20 alloy. The aged Ti29.6Ni50.4Hf20 alloy shows the better thermal stability of transformation temperatures than the solution-treated one because the precipitates depress the introduction of defects during thermal cycling. In addition, the proper aged Ti29.6Ni50.4Hf20 alloy also shows the larger SME than the solution-treated one since the precipitates strengthen the matrix strongly.

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Martensitic Transformation and Shape Memory Effect of Ni53.25Mn21.75Ga25 Ferromagnetic Shape Memory Alloy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.476-478.1504 ◽

2012 ◽

Vol 476-478 ◽

pp. 1504-1507

Author(s):

Hai Bo Wang ◽

Shang Shen Feng ◽

Pei Yang Cai ◽

Yan Qiu Huo

Keyword(s):

Magnetic Field ◽

Martensitic Transformation ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Parent Phase ◽

Transformation Strain ◽

Scanning Calorimetry ◽

Reversible Transformation ◽

Ferromagnetic Shape Memory

The martensitic transformation, crystalline structure, microstructure and shape memory effect of the Ni53.25Mn21.75Ga25 (at.%) alloy are investigated by means of Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD), Transmission Electron Microscope (TEM) and the standard metal strain gauge technique. The XRD results showed that the Ni53.25Mn21.75Ga25 alloy is composed of cubic parent phase at room temperature. TEM observation proved that the typical twin martensite is tetragonal structure and tweed-like contrast which is typical image for the parent phase. A large reversible transformation strain, about 0.54%, is obtained in this undeformed polycrystalline alloy due to martensitic transformation and its reverse transformation. This transformation strain is also increased to 0.65% by the external magnetic field. It is believed that the effect of the magnetic field on the preferential orientation of martensitic variants increases the transformation strain.

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