scholarly journals Influence of the Texture and Strain on the Behaviour of Ni53.6Mn27.1Ga19.3 and Ni54.2Mn29.4Ga16.4 Shape Memory Alloys

2013 ◽  
Vol 2013 ◽  
pp. 1-8
Author(s):  
Alexandra Rudajevova ◽  
Jiří Pospíšil
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Longitudinal Axis ◽  
Internal Stresses ◽  
Sample Treatment ◽  
Round Cross Section ◽  
Columnar Grains ◽  
Shape Memory Effects ◽  
Round Cross ◽  
Martensitic Variants

Polycrystalline samples of Ni53.6Mn27.1Ga19.3 and Ni54.2Mn29.4Ga16.4 shape memory alloys were investigated using dilatometry. The longitudinal axes of the samples were perpendicular to the columnar grains. Both alloys showed positive shape memory effects. The martensitic phase transformation occurred without hysteresis in both alloys with transformation temperatures of 174°C for the Ni53.6Mn27.1Ga19.3 alloy and 253°C for the Ni54.2Mn29.4Ga16.4 alloy. The dilatation characteristics for both alloys were determined in three perpendicular directions. The strain associated with the internal stress at the interface between the two martensitic structures and the two grains affected the dilatation characteristics in the y and z directions (perpendicular to the longitudinal axis of the sample). The microstructure was determined for all the directions investigated. To investigate the mechanical history, a round cross-section of the Ni54.2Mn29.4Ga16.4 sample was machined using a milling machine along the longitudinal axis so that both sides of the sample were symmetrical. This sample treatment changed the dilatation characteristics of the martensite and austenite. The study and analysis of the dilatation characteristics of the thermal cycle showed the relaxation of internal stresses and the reorientation of the martensitic variants.

The electron beam freeform fabrication of NiTi shape memory alloys. Part I: Microstructure and physical–chemical behavior

2020 ◽  
pp. 146442072097505
Author(s):  
RPM Guimarães ◽  
F Pixner ◽  
G Trimmel ◽  
J Hobisch ◽  
T Rath ◽  
...  
Keyword(s):  
Electron Beam ◽  
Additive Manufacturing ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Nickel Titanium ◽  
Freeform Fabrication ◽  
Austenitic Transformation ◽  
Columnar Grains ◽  
One Step ◽  
Niti Shape Memory Alloys

Nickel–titanium alloys are the most widely used shape memory alloys due to their outstanding shape memory effect and superelasticity. Additive manufacturing has recently emerged in the fabrication of shape memory alloy but despite substantial advances in powder-based techniques, less attention has been focused on wire-based additive manufacturing. This work reports on the preliminary results for the process-related microstructural and phase transformation changes of Ni-rich nickel–titanium alloy additively manufactured by wire-based electron beam freeform fabrication. To study the feasibility of the process, a simple 10-layer stack structure was successfully built and characterized, exhibiting columnar grains and achieving one-step reversible martensitic–austenitic transformation, thus showing the potential of this additive manufacturing technique for processing shape memory alloys.

A brief review of shape memory effects and fabrication processes of NiTi shape memory alloys

2020 ◽  
Vol 33 ◽  
pp. 5552-5556 ◽  
Author(s):  
Swadhin Kumar Patel ◽  
Biswajit Swain ◽  
Rakesh Roshan ◽  
Niroj K. Sahu ◽  
A. Behera
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Memory Effects ◽  
Shape Memory Effects ◽  
Niti Shape Memory Alloys

scholarly journals Mechanism of the Improvement of Shape Memory Effects in NbC Containing Fe-Mn-Si-Based Shape Memory Alloys

2007 ◽  
Vol 48 (4) ◽  
pp. 869-877 ◽  
Author(s):  
K. Ogawa ◽  
T. Sawaguchi ◽  
T. Kikuchi ◽  
S. Kajiwara
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Memory Effects ◽  
Shape Memory Effects

scholarly journals Asymptotic Self-Similarity of Minimizers and Local Bounds in a Model of Shape-Memory Alloys

2021 ◽  
Author(s):  
Sergio Conti ◽  
Johannes Diermeier ◽  
Melanie Koser ◽  
Barbara Zwicknagl
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Volume Fraction ◽  
Self Similarity ◽  
Various Boundary Conditions ◽  
Energy Bounds ◽  
Small Volume Fraction ◽  
The One ◽  
Arbitrary Volume ◽  
Martensitic Variants

AbstractWe prove that microstructures in shape-memory alloys have a self-similar refinement pattern close to austenite-martensite interfaces, working within the scalar Kohn-Müller model. The latter is based on nonlinear elasticity and includes a singular perturbation representing the energy of the interfaces between martensitic variants. Our results include the case of low-hysteresis materials in which one variant has a small volume fraction. Precisely, we prove asymptotic self-similarity in the sense of strong convergence of blow-ups around points at the austenite-martensite interface. Key ingredients in the proof are pointwise estimates and local energy bounds. This generalizes previous results by one of us to various boundary conditions, arbitrary rectangular domains, and arbitrary volume fractions of the martensitic variants, including the regime in which the energy scales as $\varepsilon ^{2/3}$ ε 2 / 3 as well as the one where the energy scales as $\varepsilon ^{1/2}$ ε 1 / 2 .

scholarly journals SMA Wire Characterization for 3D Steerable Active Devices

2018 ◽  
Author(s):  
Saeed Karimi ◽  
Bardia Konh ◽  
Hashem Ashrafiuon
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Smart Materials ◽  
Loading Condition ◽  
Memory Effects ◽  
Medical Applications ◽  
Temperature Changes ◽  
Active Devices ◽  
Shape Memory Effects ◽  
Biomedical Fields

Shape Memory Alloys (SMAs) are a unique class of smart materials that recover their deformed shapes, caused by a loading condition, through temperature changes [1]. SMAs are employed in a variety of areas including aerospace, automotive, and biomedical fields. Their Pseudoelastic characteristics, shape memory effects, and biocompatibility make them particularly suitable for medical applications.

scholarly journals Influence of Structural Defects on the Properties of Metamagnetic Shape Memory Alloys

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1131
Author(s):  
J. I. Pérez-Landazábal ◽  
V. Sánchez-Alarcos ◽  
V. Recarte ◽  
O. A. Lambri ◽  
F. G. Bonifacich ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Entropy Change ◽  
High Energy ◽  
Milling Process ◽  
Structural Defects ◽  
Internal Stresses ◽  
Spin Glass Behavior ◽  
Deformed State

The production of μ-particles of Metamagnetic Shape Memory Alloys by crushing and subsequent ball milling process has been analyzed. The high energy involved in the milling process induces large internal stresses and high density of defects with a strong influence on the martensitic transformation; the interphase creation and its movement during the martensitic transformation produces frictional contributions to the entropy change (exothermic process) both during forward and reverse transformation. The frictional contribution increases with the milling time as a consequence of the interaction between defects and interphases. The influence of the frictional terms on the magnetocaloric effect has been evidenced. Besides, the presence of antiphase boundaries linked to superdislocations helps to understand the spin-glass behavior at low temperatures in martensite. Finally, the particles in the deformed state were introduced in a photosensitive polymer. The mechanical damping associated to the Martensitic Transformation (MT) of the particles is clearly distinguished in the produced composite, which could be interesting for the development of magnetically-tunable mechanical dampers.

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