Deformation Behavior of Functionally Graded Ti-Ni Shape Memory Alloys

2007 ◽  
Vol 544-545 ◽  
pp. 211-214 ◽  
Author(s):  
Tae Hyun Nam ◽  
Hyun Gon Kim ◽  
Ju Young Choi ◽  
Jung Moo Lee ◽  
Suk Bong Kang ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Thermal Cycling ◽  
Shape Memory ◽  
Yield Stress ◽  
Deformation Behavior ◽  
Annealing Temperature ◽  
Tensile Tests ◽  
Constant Load ◽  
Functionally Graded ◽  
Ni Alloy

Deformation behavior of temperature gradient anneal(TGA) treated Ti-50.0Ni(at%) alloys were investigated by means of thermal cycling tests under constant load and tensile tests. TGA treated Ti-Ni alloy wires showed a sequential deformation behavior along the length of the specimen since the stress required for the B2-B19’ transformation increased with decreasing annealing temperature. Considerably large residual elongation(about 0.4 %) occurred in the TGA treated Ti-Ni alloy under the applied stress of 80 MPa, which is ascribed to the fact that yield stress of the sample annealed at 823 K is lower than the stress required for the B2-B19’ transformation of the sample annealed at 658 K.

Functionally Graded Ti-Ni Shape Memory Alloys

2007 ◽  
Vol 539-543 ◽  
pp. 3169-3172 ◽  
Author(s):  
Tae Hyun Nam ◽  
Cheol Am Yu ◽  
Yun Jung Lee ◽  
Yinong Liu
Keyword(s):  
Temperature Gradient ◽  
Shape Memory ◽  
Tensile Tests ◽  
Constant Load ◽  
Functionally Graded ◽  
Scanning Calorimetry ◽  
Treated Sample ◽  
Ni Alloy ◽  
Temperature Ranges ◽  
Cold Worked

Shape memory characteristics and superelasticity of an temperature gradient annealing(TGA) treated equiatomic Ti-Ni alloy have been investigated by means of differential scanning calorimetry(DSC), thermal cycling tests under constant load and tensile tests. By annealing 25% cold worked alloy under the temperature gradient from 658 K to 466 K, 7 K variation in TR*and 19 K variation in Ms* were obtained along the length of sample(150mm). Temperature dependence of transformation elongation(dε/dT) of TGA treated Ti-Ni alloy wires was in the range of 0.05 %/K and 0.01 %/K depending on annealing temperature ranges. The dε/dT obtained from TGA treated sample under the temperature gradient from 658 K to 466 K was 0.03 %/K. TGA treated alloy showed the clear superelastic recovery.

Shape Memory Effect and Superelasticity of an Equiatomic Ti-Ni Alloy with Surface Sulfide Layers

2006 ◽  
Vol 510-511 ◽  
pp. 262-265
Author(s):  
Tae Hyun Nam ◽  
Shin Goo Hur ◽  
Jae Hwa Lee ◽  
Gyu Bong Cho
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Martensitic Transformation ◽  
Shape Memory ◽  
Tensile Tests ◽  
Constant Load ◽  
Ni Alloy ◽  
Memory Characteristics ◽  
Scanning Electron ◽  
Start Temperature

Shape memory characteristics and superelasticity of an equiatomic Ti-Ni alloy with surface sulfide layers were investigated by means of thermal cycling tests under constant load, tensile tests, and scanning electron microscopy. Martensitic transformation start temperature (Ms) increased by sulfidation, which is ascribed to a compressive stress imposed by surface sulfide layers. Surface sulfide layers were found to make transformation elongation be small when their thickness was less than 5 ㎛. This is ascribed to the fact that the surface sulfide layers were not detached from substrates and constrained martensitic transformation. When thickness of the surface sulfide layers was 35 ㎛, transformation elongation was not affected by them because they were detached during transformation. Superelastic recovery decreased by the sulfide layers when their thickness was about 5 ㎛, while it did not change when the thickness was about 35 ㎛.

EFFECT OF ANNEALING ON SHAPE MEMORY CHARACTERISTICS OF Ti-50.85at.%Ni ALLOY

2008 ◽  
Vol 01 (03) ◽  
pp. 209-213 ◽  
Author(s):  
J. I. KIM ◽  
T. H. NAM ◽  
Y. J. LEE ◽  
S. MIYAZAKI
Keyword(s):  
Shape Memory ◽  
Transformation Temperature ◽  
Annealing Temperature ◽  
Tensile Tests ◽  
Phase Transformation Temperature ◽  
Martensitic Transformation Temperature ◽  
Ni Alloy ◽  
The Matrix ◽  
Cold Worked ◽  
Memory Characteristics

In order to clarify the effect of annealing on the shape memory behavior of Ti -50.85at.% Ni alloy, the deformation and transformation behavior were investigated using tensile tests and differential scanning calorimeter (DSC). The martensitic transformation temperature increases with increasing annealing temperature until it reach as a maximum, and then decreases with further increasing annealing temperature. This can be rationalized by interaction between the distribution of Ti 3 Ni 4 precipitates and recovery of cold-worked structure. The R-phase transformation temperature increases with increasing annealing temperature until reaching a maximum, and then decreases with a further increase of annealing temperature. This is attributed to the change of Ni content in the matrix caused by precipitation of Ti 3 Ni 4. The critical stress for slip decreases rapidly with increasing annealing temperature, influenced by interaction between the distribution of Ti 3 Ni 4 precipitates and recovery of cold-worked structure.

Deformation behavior of shape memory TiNi alloy crystals

1984 ◽  
Vol 18 (4) ◽  
pp. 363-366 ◽  
Author(s):  
T. Saburi ◽  
M. Yoshida ◽  
S. Nenno
Keyword(s):  
Shape Memory ◽  
Deformation Behavior ◽  
Ni Alloy

Martensitic Transformation and Mechanical Properties of Fe-added Au-Cu-Al Shape Memory Alloy with Various Heat Treatment Conditions

2014 ◽  
Vol 1760 ◽  
Author(s):  
Akira Umise ◽  
Masaki Tahara ◽  
Kenji Goto ◽  
Tomonari Inamura ◽  
Hideki Hosoda
Keyword(s):  
Heat Treatment ◽  
Cold Rolling ◽  
Shape Memory ◽  
Yield Stress ◽  
Mechanical Treatment ◽  
Tensile Tests ◽  
Treatment Temperature ◽  
Shape Memory Properties ◽  
Cold Rolled ◽  
Thermo Mechanical Treatment

ABSTRACTIn order to improve shape memory properties of Au-Cu-Al based shape memory alloys, the possibility to utilize thermo-mechanical treatment was investigated in this study, and effects of heat-treatment temperature on microstructure, martensitic transformation and mechanical properties of cold-rolled Au-30Cu-18Al-2Fe (AuCuAlFe) alloy were clarified by X-ray diffraction analysis (XRD, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and tensile tests at room temperature (RT). Here, Fe addition to AuCuAl improves ductility. Cold rolling with the thickness reduction of 30% was successfully carried out in AuCuAlFe at RT. An exothermic heat was observed in DSC at temperature from 402K, suggesting that recovery started at 402K. Besides, the transformation temperature hysteresis increased by the cold-rolling. The alloy was completely recrystallized after the heat treatment at 573K for 3.6ks. Tensile tests revealed that the yield stress was raised by cold rolling and largely by the subsequent heat treatment at 433K, which corresponded to the recovery start temperature by DSC. The yield stress decreased with increasing heat treatment temperature over 453K, probably due to recrystallization. AuCuAlFe cold-rolled and subsequent heat-treated at 573K exhibited the lowest yield stress as well as stress-plateau region, indicating that the thermo-mechanical treatment is effective to improve shape memory properties of Au-Cu-Al based alloys.

scholarly journals The Investigation of Mechanical and Functional Properties and Microstructural Features of Coarse-Grained SME Ti49.0Ni51.0 Alloy during Multiple Martensitic Transformations and Annealing

2021 ◽  
Vol 346 ◽  
pp. 02011
Author(s):  
Anna Churakova ◽  
Elina Kayumova ◽  
Dmitry Gunderov
Keyword(s):  
Grain Size ◽  
Thermal Cycling ◽  
Yield Stress ◽  
Martensitic Transformations ◽  
Tensile Tests ◽  
Mechanical Tests ◽  
Coarse Grained ◽  
Initial State ◽  
Subsequent Aging ◽  
Mechanical Tensile

The paper was investigated the effect of preliminary multiple martensitic transformations on the microstructure and mechanical and functional stability during subsequent annealing in the range of aging temperatures of the Ti49.051.0 alloy in the coarse-grained state. The structure in the initial state has an austenitic structure with a grain size of 30 ± 5 μm; after TC, the structure is martensite with a grain size of 30 ± 5 μm. According to the results of mechanical tensile tests, thermal cycling leads to an increase in the yield stress, which is associated with the generation and accumulation of dislocations. An increase in the number of cycles to n = 100 led to a slight decrease in the yield stress, which may be due to the saturation effect during thermal cycling. Subsequent aging at T=400 °C after thermal cycling showed that the yield stress increases. At the same time, the results of mechanical tests showed that, in general, the preliminary TC (n = 100) with subsequent aging contributes to an increase in the yield strength and strength. The structure revealed after thermal cycling and subsequent low-temperature annealing confirms the precipitation of aging strengthening particles Ti3Ni4.

Influence of Thermal Cycling on Dilatation and Electrical Resistance of Ti - 49.8 at. %Ni Alloy after Hot Rolling

2010 ◽  
Vol 667-669 ◽  
pp. 985-990 ◽  
Author(s):  
R.I. Babicheva ◽  
I.Z. Sharipov ◽  
K.J. Mulyukov
Keyword(s):  
Thermal Cycling ◽  
Shape Memory ◽  
Phase Transformations ◽  
Shape Memory Effect ◽  
Hot Rolling ◽  
Electrical Resistance ◽  
Recoverable Strain ◽  
Ni Alloy ◽  
B2 Phase ◽  
Subsequent Stabilization

The effect of thermal cycling of the Ti - 49.8 at. % Ni alloy deformed by rolling at 500 оС on dilatation of the material was investigated. It was shown that R → B2 and B19' → B2 phase transformations take place during heating due to retaining of R-phase at the lowest temperature of cycling. The evolution and subsequent stabilization of two-way shape memory effect (TWSME) upon thermal cycling are caused by decreasing of the residual B19'- martensitic phase formed during rolling. It was revealed that recoverable strain of the alloy doesn’t exceed 0.8 % even after forty cycles.

Deformation Behavior of Functionally Graded Ti-Ni Shape Memory Alloys

2007 ◽  
pp. 211-214
Author(s):  
Tae Hyun Nam ◽  
Hyun Gon Kim ◽  
Ju Young Choi ◽  
Jung Moo Lee ◽  
Suk Bong Kang ◽  
...  
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Deformation Behavior ◽  
Functionally Graded
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