Acoustic emissions associated with stress-induced twin boundary mobility in Fe 7 Pd 3 ferromagnetic shape memory alloys

2017 ◽  
Vol 139 ◽  
pp. 162-165 ◽  
Author(s):  
A.J. Bischoff ◽  
S.G. Mayr
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Twin Boundary ◽  
Acoustic Emissions ◽  
Boundary Mobility ◽  
Ferromagnetic Shape Memory Alloys ◽  
Ferromagnetic Shape Memory

scholarly journals Acoustic Emissions during Structural Changes in Shape Memory Alloys

Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 58 ◽  
Author(s):  
Dezső Beke ◽  
Lajos Daróczi ◽  
László Tóth ◽  
Melinda Bolgár ◽  
Nora Samy ◽  
...  
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Structural Changes ◽  
Acoustic Emissions ◽  
Martensitic Transformations ◽  
Ferromagnetic Shape Memory Alloys ◽  
Time Correlations ◽  
Martensitic State ◽  
The Asymmetry ◽  
Ferromagnetic Shape Memory

Structural changes (martensitic transformation, rearrangements of martensitic variants) in shape memory alloys have an intermittent character that is accompanied by the emission of different (thermal, acoustic, and magnetic) noises, which are fingerprints of the driven criticality, resulting in a damped power-law behaviour. We will illustrate what kinds of important information can be obtained on the structural changes in shape memory alloys. It was established that the power exponents of distributions of acoustic emission (AE) parameters (energy, amplitude, etc.), belonging to martensitic transformations, show quite a universal character and depend only on the symmetry of the martensite. However, we have shown that the asymmetry of the transformation (the exponents are different for the forward and reverse transformations) results in as large differences as those due to the martensite symmetry. We will also demonstrate how the recently introduced AE clustering method can help to identify the different contributions responsible for the asymmetry. The usefulness of the investigations of time correlations between the subsequent events and correlations between acoustic and magnetic noise events in ferromagnetic shape memory alloys will be demonstrated too. Finally, examples of acoustic and magnetic emissions during variant rearrangements (superplastic or superelastic behaviour) in the martensitic state will be described.

Magnetic properties of ferromagnetic shape memory alloys Ni _{2-x} Cu _{x} MnGa

2005 ◽  
Vol 21 (3-4) ◽  
pp. 151-157 ◽  
Author(s):  
Takeshi Kanomata ◽  
Takuji Nozawa ◽  
Daisuke Kikuchi ◽  
Hironori Nishihara ◽  
Keiichi Koyama ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Ferromagnetic Shape Memory Alloys ◽  
Ferromagnetic Shape Memory

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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