Achieving Giant Magnetically Induced Reorientation of Martensitic Variants in Magnetic Shape-Memory Ni-Mn-Ga Films by Microstructure Engineering

2015 ◽  
Vol 27 (32) ◽  
pp. 4760-4766 ◽  
Author(s):  
Paolo Ranzieri ◽  
Marco Campanini ◽  
Simone Fabbrici ◽  
Lucia Nasi ◽  
Francesca Casoli ◽  
...  
Keyword(s):  
Shape Memory ◽  
Magnetic Shape Memory ◽  
Martensitic Variants

Application of EBSD to the Crystallographic Investigation on Ni-Mn-Ga Alloys

2012 ◽  
Vol 706-709 ◽  
pp. 1879-1884 ◽  
Author(s):  
Zong Bin Li ◽  
Yu Dong Zhang ◽  
Claude Esling ◽  
Hao Yang ◽  
Ji Jie Wang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Shape Memory ◽  
Shape Change ◽  
Memory Performance ◽  
Crystallographic Investigation ◽  
Orientation Relationships ◽  
Magnetic Shape Memory ◽  
Ferromagnetic Shape Memory Alloys ◽  
Electron Backscattered Diffraction ◽  
Martensitic Variants

For off-stoichiometric Ni2MnGa ferromagnetic shape memory alloys, a large shape change could be induced through the rearrangement of martensitic variants under an external magnetic field. Insight into the orientation relationships of martensitic variants and the characteristics of variant boundaries is thus essential for understanding the magnetic shape memory performance. In this paper, a thorough crystallographic investigation was made on the incommensurate 7M modulated martensite in one polycrystalline Ni50Mn30Ga20alloy by means of X-ray diffraction and SEM electron backscattered diffraction (EBSD). Locally, there are four differently-oriented martensitic variants, being twin related to one another. The twin interface planes are coherent and they are in coincidence with the respective twinning planes (K1). A primary exploration was performed to improve the microstructure by repeated magnetic field training during phase transition. The present investigation could offer useful guidance to develop specific technique for microstructure optimization.

Improvements to the Kiefer and Lagoudas Model for Prediction of the Magneto-Mechanical Behavior of Magnetic Shape Memory Alloys

2011 ◽  
Author(s):  
Alex Waldauer ◽  
Heidi P. Feigenbaum ◽  
Nickolaus M. Bruno ◽  
Constantin Ciocanel
Keyword(s):  
Magnetic Field ◽  
Shape Memory Alloys ◽  
Mechanical Behavior ◽  
Shape Memory ◽  
Inelastic Strain ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys ◽  
Demagnetizing Field ◽  
Thermodynamic Basis ◽  
Martensitic Variants

Magnetic shape memory alloys (MSMAs) are a class of materials that exhibit large, recoverable inelastic strain. After cooling from austenite to martensite, MSMAs have a tetragonal crystalline structure with three possible orientations called variants. These variants can rotate as a result of applied stress or applied magnetic field and the resulting inelastic strain can be as high as 10% [1]. To effectively use MSMAs in any potential application, a model that can accurately predict the magneto-mechanical behavior of the MSMA is required. Kiefer and Lagoudas developed a thermodynamic basis for modeling MSMAs and then apply it in the case where two of the three martensitic variants exist [2]. The improvements to the Kiefer and Lagoudas model proposed in this paper include a different analysis of the demagnetizing effect and an inclusion of the resulting axial demagnetizing field.

Effects of Annealing on Microstructure and Martensitic Transition of Ni-Mn-Co-In Ferromagnetic Shape Memory Alloys

2011 ◽  
Vol 674 ◽  
pp. 171-175
Author(s):  
Katarzyna Bałdys ◽  
Grzegorz Dercz ◽  
Łukasz Madej
Keyword(s):  
Electron Microscopy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Smart Materials ◽  
Martensitic Transition ◽  
Magnetic Shape Memory ◽  
Ferromagnetic Shape Memory Alloys ◽  
Initial State ◽  
X Ray ◽  
Ferromagnetic Shape Memory

The ferromagnetic shape memory alloys (FSMA) are relatively the brand new smart materials group. The most interesting issue connected with FSMA is magnetic shape memory, which gives a possibility to achieve relatively high strain (over 8%) caused by magnetic field. In this paper the effect of annealing on the microstructure and martensitic transition on Ni-Mn-Co-In ferromagnetic shape memory alloy has been studied. The alloy was prepared by melting of 99,98% pure Ni, 99,98% pure Mn, 99,98% pure Co, 99,99% pure In. The chemical composition, its homogeneity and the alloy microstructure were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The phase composition was also studied by X-ray analysis. The transformation course and characteristic temperatures were determined by the use of differential scanning calorimetry (DSC) and magnetic balance techniques. The results show that Tc of the annealed sample was found to decrease with increasing the annealing temperature. The Ms and Af increases with increasing annealing temperatures and showed best results in 1173K. The studied alloy exhibits a martensitic transformation from a L21 austenite to a martensite phase with a 7-layer (14M) and 5-layer (10M) modulated structure. The lattice constants of the L21 (a0) structure determined by TEM and X-ray analysis in this alloy were a0=0,4866. The TEM observation exhibit that the studied alloy in initial state has bigger accumulations of 10M and 14M structures as opposed from the annealed state.

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