scholarly journals Phase Transformations, Microstructure and Shape Memory Effect of NiTiAg Alloy with Different Atomic Percentages (at. % Ag) Manufactured by Casting Method

2021 ◽  
Vol 39 (4A) ◽  
pp. 543-551
Author(s):  
Saja M. Hussein ◽  
Khansaa D. Salman ◽  
Ahmed A. Hussein
Keyword(s):  
Shape Memory ◽  
Phase Transformations ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Martensite Phase ◽  
Austenite Phase ◽  
Vacuum Arc ◽  
Casting Method ◽  
Vacuum Arc Remelting ◽  
Niti Matrix

In this paper, shape memory alloys (SMAs) (NiTi-based) have been manufactured by casting with a different atomic percentage of a silver element (0, 1, 2 and 3 at. % Ag) using a Vacuum Arc Remelting (VAR) furnace. The silver element is added to the binary alloys due to its excellent properties such as (anti-corrosion, anti-bacterial and high electrical conductivity), which make these alloys using in wider applications. These alloys with different atomic percentages (Ni55Ti45Ag0, Ni55Ti44Ag1, Ni55Ti43Ag2 and Ni55Ti42Ag3) have been manufactured. The successful manufacturing process has been achieved and proved via examinations and tests. The FESEM microscopic examinations show that the silver element has been distributed uniformly and homogeneously in the NiTi matrix. Moreover, the emergence of austenite phase, martensite phase and little amount impurities. Regarding the XRD examination, showed that there is an increase in the number of peaks of Ag phase with an increase in the atomic percentage of the silver element, as well to emergence of phase (Ti2Ni) upon heating, phase (Ti 002) upon cooling, and phase (Ni4Ti3) is not desired. The starting and finishing of the phase transformations have been determined for all samples by the DSC test. The Shape Memory Effect (SME) for the alloy (Ni50Ti42Ag3) is measured to be about 89.99%.

The Concept of Physical Metric in the Thermomechanical Modeling of Phase Transformations With Emphasis on Shape Memory Alloy Materials

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Vassilis P. Panoskaltsis ◽  
Lazaros C. Polymenakos ◽  
Dimitris Soldatos
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Phase Transformations ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Material Model ◽  
Internal Variable ◽  
Theoretical Interest ◽  
Numerical Examples ◽  
Thermomechanical Modeling

In this work we derive a new version of generalized plasticity, suitable to describe phase transformations. In particular, we present a general multi surface formulation of the theory which is capable of describing the multiple and interacting loading mechanisms, which occur during phase transformations. The formulation relies crucially on the consideration of the intrinsic material (“physical”) metric as a primary internal variable and does not invoke any decomposition of the kinematical quantities into elastic and inelastic (transformation induced) parts. The new theory, besides its theoretical interest, is also important for application purposes such as the description and the prediction of the response of shape memory alloy materials. This is shown in the simplest possible setting by the introduction of a material model. The ability of the model in simulating several patterns of the experimentally observed behavior of these materials such as the pseudoelastic phenomenon and the shape memory effect is assessed by representative numerical examples.

Phase Transitions and Microstructural Processes in Shape Memory Alloys

2013 ◽  
Vol 762 ◽  
pp. 483-486 ◽  
Author(s):  
Osman Adiguzel
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Structural Changes ◽  
Lattice Structure ◽  
Austenite Phase ◽  
Temperature Phase ◽  
Martensitic Transition ◽  
Microscopic Scale

Shape memory alloys exhibit a peculiar property, shape memory effect that is the result from the structural changes in microscopic scale. These alloys return to previously defined shapes when they are subjected to variation of temperature after deformation of the low temperature phase. Shape-memory effect is based on martensitic transformation, with which the material changes its internal crystalline structure. The ordered structure or super lattice structure is essential for the shape memory effect of the material. Copper based alloys exhibit this property in the β-phase field, which possesses the simple bcc-structure at high temperature austenite phase. As the temperature is lowered, austenite phase undergoes martensitic transition following two ordering reactions, and microstructural changes in microscopic scale govern this transition. In the present work, Cu alloys were investigated by transmission electron microscope, TEM, and x-ray diffraction techniques.

Solid State Transformations and Equilibrium Crystal Structures of an Au-Cu Alloy with Shape Memory Effect

2012 ◽  
Vol 730-732 ◽  
pp. 859-864 ◽  
Author(s):  
Georgina Miranda ◽  
F.S. Silva ◽  
Delfim Soares
Keyword(s):  
High Temperature ◽  
Solid State ◽  
Shape Memory ◽  
Phase Transformations ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Equilibrium Phase ◽  
Lattice Parameters ◽  
Solid State Transformation ◽  
Heating And Cooling

Au-50%Cu (at. %) alloy presents the shape memory effect (SME), which is dependent of the solid state transformation that happens during heating, after the introduction of an internal stress in the quenched state. The solid state phase transformation temperatures were determined by means of Differential Thermal Analysis (DTA), both in heating and cooling cycles. With the obtained DTA results, a sequence of high temperature X-ray diffraction (XRD) experiments were made, in order to confirm the presence of the solid state phase transformations and to determine their stable crystal structure and lattice parameters. These XRD results were compared with those obtained from the literature. The displacements of the lattice parameters were determined, for each equilibrium phase, for measurements at room temperature and at high temperature. The characteristics of the quenched samples were also studied in order to determine the phase transformations that are responsible for the shape memory effect in this alloy.

scholarly journals NiMn-Based Metamagnetic Shape Memory Alloys

2009 ◽  
Vol 635 ◽  
pp. 23-31 ◽  
Author(s):  
Ryosuke Kainuma ◽  
K. Ito ◽  
W. Ito ◽  
R.Y. Umetsu ◽  
T. Kanomata ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Powder Metallurgy ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Parent Phase ◽  
Martensite Phase ◽  
Ternary Alloys ◽  
Plasma Sintering ◽  
Spark Plasma

The magnetic properties of the parent and martensite phases of the Ni2Mn1+xSn1-x and Ni2Mn1+xIn1-x ternary alloys and the magnetic field-induced shape memory effect obtained in NiCoMnIn alloys are reviewed, and our recent work on powder metallurgy performed for NiCoMnSn alloys is also introduced. The concentration dependence of the total magnetic moment for the parent phase in the NiMnSn alloys is very different from that in the NiMnIn alloys, and the magnetic properties of the martensite phase with low magnetization in both NiMnSn and NiMnIn alloys has been confirmed by Mössbauer examination as being paramagnetic, but not antiferromagnetic. The ductility of NiCoMnSn alloys is drastically improved by powder metallurgy using the spark plasma sintering technique, and a certain degree of metamagnetic shape memory effect has been confirmed.

The structure–phase transformations and mechanical properties of the shape memory effect alloys based on the system Cu–Al–Ni

2017 ◽  
Vol 4 (3) ◽  
pp. 4758-4762 ◽  
Author(s):  
Alexey E. Svirid ◽  
Vladimir G. Pushin ◽  
Natalia N. Kuranova ◽  
Alexandr V. Luk'yanov ◽  
ArtemV. Pushin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shape Memory ◽  
Phase Transformations ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Structure Phase

Phase transformations and shape memory effect in copper-aluminium-manganese alloys

1988 ◽  
Vol 22 (6) ◽  
pp. 821-825 ◽  
Author(s):  
J.J. Counioux ◽  
J.L. Macqueron ◽  
M. Robin ◽  
J.M. Scarabello
Keyword(s):  
Shape Memory ◽  
Phase Transformations ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Manganese Alloys

scholarly journals Martensite Phase Causing Two Way Shape Memory Effect in Cu-13.7Al-4.0Ni (mass%) Alloy Single Crystals

1991 ◽  
Vol 32 (2) ◽  
pp. 128-134 ◽  
Author(s):  
Hidekazu Sakamoto ◽  
Koichi Sugimoto ◽  
Yasuhiko Nakamura ◽  
Akira Tanaka ◽  
Ken’ichi Shimizu
Keyword(s):  
Shape Memory ◽  
Single Crystals ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Martensite Phase

Fabrication and Characterization of Nanoscale Shape Memory Alloy MEMS Actuators

2020 ◽  
Author(s):  
Cory R. Knick
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Martensite Phase ◽  
Radius Of Curvature ◽  
Curvature Radius ◽  
Thermal Actuators ◽  
Mems Actuators ◽  
Out Of Plane

The miniaturization of engineering devices has created interest in new actuation methods capable of large displacements and high frequency responses. Shape memory alloy (SMA) thin films have exhibited one of the highest power densities of any material used in these actuation schemes and can thermally recovery strains of up to 10%. Homogenous SMA films can experience reversible shape memory effect, but without some sort of physical biasing mechanism, the effect is only one-way. SMA films mated in a multi-layer stack have the appealing feature of an intrinsic two-way shape memory effect (SME). In this work, we developed a near-equiatomic NiTi magnetron co-sputtering process and characterized shape memory effects. We mated these SMA films in several “bimorph” configurations to induce out of plane curvature in the low-temperature Martensite phase. We quantify the curvature radius vs. temperature on MEMS device structures to elucidate a relationship between residual stress, recovery stress, radius of curvature, and degree of unfolding. We fabricated and tested laser-irradiated and joule heated SMA MEMS actuators to enable rapid actuation of NiTi MEMS devices, demonstrating some of the lowest powers (5–15 mW) and operating frequencies (1–3 kHz) ever reported for SMA or other thermal actuators.

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