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.

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.

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.

The Structure and Mechanical Properties of Plastically Consolidated Al-Ni Alloy

2016 ◽  
Vol 682 ◽  
pp. 245-251 ◽  
Author(s):  
Grzegorz Włoch ◽  
Tomasz Skrzekut ◽  
Jakub Sobota ◽  
Antoni Woźnicki ◽  
Justyna Cisoń
Keyword(s):  
Mechanical Properties ◽  
Vickers Hardness ◽  
Tensile Tests ◽  
Mechanical Analysis ◽  
Intermetallic Phases ◽  
Scanning Calorimetry ◽  
Porosity Formation ◽  
X Ray ◽  
Ni Alloy ◽  
Thermal Stability Of

Mixed and preliminarily consolidated powders of aluminium and nickel (90 mass % Al and 10 mass % Ni) were hot extruded. As results the rod, 8 mm in diameter, was obtained. As-extruded material was subjected to the microstructural investigations using scanning electron microscopy (SEM/EDS) and X-ray analysis (XRD). The differential scanning calorimetry (DSC) and thermo-mechanical analysis (TMA) were also performed. The mechanical properties of as extruded material were determined by the tensile test and Vickers hardness measurements. In order to evaluate the thermal stability of PM alloy, samples were annealed at the temperature of 475 and 550 °C. After annealing Vickers hardness measurements and tensile tests were carried out. The plastic consolidation of powders during extrusion was found to be very effective, because no pores or voids were observed in the examined material. The detailed microstructural investigations and XRD analyses did not reveal the presence of the intermetallic phases in the as-extruded material. During annealing, the Al3Ni intermetallic compound was formed as the result of chemical reaction between the alloy components. The hardness of the alloy after annealing at the temperature of 475°C was found to be comparable to the hardness in as-extruded state. Annealing of the material at the temperature of 550°C results in hardness decreasing by about 50%, as the consequence of porosity formation and Al3Ni cracking.

Tensile and Creep Properties of the Refractory Nb Base In-Situ Composite

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1608-1614
Author(s):  
Jin Hak Kim ◽  
Tatsuo Tabaru ◽  
Hisatoshi Hirai
Keyword(s):  
Fracture Surface ◽  
Tensile Tests ◽  
Constant Load ◽  
Tensile Creep ◽  
Tensile Fracture ◽  
Creep Tests ◽  
Tensile Fracture Surface ◽  
In Situ Composite ◽  
Temperature Ranges

Niobium-base in-situ composite Nb-18Si-5Mo-5Hf-2C (in mol%) was prepared and heat-treated at 2070 K for 20 hour. The uni-axile tensile tests at high temperature ranges and the constant load tensile creep tests at 1570 K were performed. The specimen tensile-tested at 1470 K exhibited the excellent UTS of 450 MPa, and the brittle to ductile transition temperature is between 1470 and 1670 K. The specimens creep tested showed good creep strength; the stress exponent is about 5. The tensile fracture surface of the in-situ composite is complex and attributed to cleavage of the Nb 5 Si 3, Nb ss / Nb 5 Si 3 interface separation, ductile rupture of the Nb ss and correlations of these. On the otherhand, the fracture surface of creep tested consists of intergranular above 150 MPa and transgranular below 120 MPa with severely deformed Nb ss .

Influence of Deformation Speed on Fatigue and Tensile Properties of a Ti-Ni-Cu Shape Memory Alloy

1999 ◽  
Vol 604 ◽  
Author(s):  
Y Kishi ◽  
Z. Yajima ◽  
K Shimizu ◽  
M. Asai
Keyword(s):  
Fatigue Life ◽  
Martensitic Transformation ◽  
Shape Memory ◽  
Tensile Properties ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Tensile Fracture ◽  
Scanning Calorimetry ◽  
Sinusoidal Waveform ◽  
Deformation Speed

AbstractThe mechanical fatigue life and tensile property of a Ti-41at.%Ni-8.5at.%Cu alloy, which was solution-treated after some thermo-mechanical treatments, were investigated at 370±1 K as a function of deformation speed. The tensile properties were also investigated at 295±1 K as a function of deformation speed. The B2→B19 martensitic transformation start temperature, Ms, of the alloy was determined to be 338 K by a differential scanning calorimetry, while that of the as-rolled alloy could not be determined. Two types of fatigue tests were carried out by using plate-shaped specimens of 3.5 mm width and 1.5 mm thickness with sinusoidal waveform stresses of 20 Hz and 0.5 Hz frequencies being applied respectively. The fatigue life obtained from the 20 Hz tests was superior to that from the 0.5 Hz tests, the former being about 2 times longer than the latter at the same stress level. Tensile tests were performed at three tensilem speeds of 8.3 × 106, 8.3 × 10−5 and 8.3 × 10−3 m/s. In all the stress - strain curves obtained, an apparent yielding was observed after the liner elastic deformation. The apparent yielding is due to the occurrence of martensitic transformation. The critical stress for inducing martensite and tensile fracture stress increased with increasing tensile speed. Therefore, it is clear that fatigue and tensile properties of Ti-Ni-Cu shape memory alloys are strongly affected by not only test temperature but also deformation speed.

scholarly journals Characterization Techniques of a Shape Memory Nickel Titanium Alloy

Proceedings ◽  
2020 ◽  
Vol 38 (1) ◽  
pp. 15
Author(s):  
Andrade ◽  
Soares ◽  
Nobrega ◽  
Hilário ◽  
Santos
Keyword(s):  
Differential Scanning Calorimetry ◽  
Titanium Alloy ◽  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Tensile Tests ◽  
Metallic Alloys ◽  
Nickel Titanium ◽  
Metallographic Analysis ◽  
Scanning Calorimetry

This paper presents a characterization processes study of metallic alloys, more specifically the shape memory alloys (SMA) composed by Nickel and Titanium (NiTinol). Two different wire suppliers were studied, starting with metallographic analysis until observe the contours of the grain wires. Differential scanning calorimetry (DSC) test was also performed to obtain phase transformation temperatures of the NiTinol alloys. Finally, after several tensile tests, some results were obtained for stresses, strains, elasticity modules and maximum rupture deformation.

scholarly journals Microstructure and Thermomechanical Characterization of Fe-28Mn-6Si-5Cr Shape Memory Alloy

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 649
Author(s):  
Antonio Collazo ◽  
Raúl Figueroa ◽  
Carmen Mariño-Martínez ◽  
Carmen Pérez
Keyword(s):  
Shape Memory ◽  
Thermal Activation ◽  
Tensile Tests ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Potential Applications ◽  
Ε Martensite ◽  
Microscopy Techniques ◽  
Activation Cycle

Iron-based shape memory alloys (SMAs) have been widely studied during the last years, producing new formulations with potential applications in civil engineering. In the present paper, the microstructure and the thermomechanical behavior of the Fe-28Mn-6Si-5Cr memory alloy has been investigated. At room temperature, the presence of ε-martensite and γ-austenite was confirmed using optical and electron microscopy techniques. The martensitic transformation temperatures (As, Af, Ms, and Mf) were determined by differential scanning calorimetry, together with an X-ray diffraction technique. The use of these techniques also confirmed that this transformation is not totally reversible, depending on the strain degree and the number of thermal cycles. From the kinetics study of the ε → γ transformation, the isoconversion curves (transformation degree versus time) were built, which provided the information required to optimize the thermal activation cycle. Tensile tests were performed to characterize the mechanical properties of the studied alloy. These kinds of tests were also performed to assess the shape memory effect, getting a recovery stress of 140 MPa, after a 7.6% pre-strain and a thermal activation up to 160 °C.

Influence of Heat Treatment on Martensitic Transformations in Copper-Based Alloys with Shape Memory Effect

2016 ◽  
Vol 869 ◽  
pp. 474-478
Author(s):  
Luiz Carlos Sekitani da Silva ◽  
Cezar Henrique Gonzalez ◽  
Carlos Augusto do Nascimento Oliveira ◽  
Karla Carolina Alves da Silva
Keyword(s):  
Heat Treatment ◽  
Shape Memory ◽  
Thermal Hysteresis ◽  
Martensitic Transformations ◽  
Scanning Calorimetry ◽  
Critical Temperatures ◽  
Heat Treated Sample ◽  
Heat Treated ◽  
Treated Sample ◽  
Shape Memory Effects

In the present work the copper base alloys with shape memory effects were characterized. The alloys were subjected to three different heat treatments that promoted changes in characteristics of thermoelastic martensitic transformation (transformation temperatures, thermal hysteresis and enthalpies of transformation). The alloys have their microstructures characterized by optical and scanning electron microscopy. Microhardness tests were performed. Differential scanning calorimetry (DSC) was used to evaluate the transformation critical temperatures of alloy and the transformation enthalpies for each heat treated sample. Thermoelastic properties have changed for each heat treatment. In the micrographs of the heat-treated samples was possible to observe the microstructure of the martensitic phase characteristic. They show the presence of martensite platelets (needles) self-accommodation.

scholarly journals Mechanical and Microstructural Characterization of Ultrasonic Welded NiTiCu Shape Memory Alloy Wires to Silver-Coated Copper Ferrules

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1936
Author(s):  
Toni Sprigode ◽  
Andreas Gester ◽  
Guntram Wagner ◽  
Thomas Mäder ◽  
Björn Senf ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Spot Welding ◽  
Base Material ◽  
Welding Process ◽  
Microstructural Characterization ◽  
Tensile Tests ◽  
Ultrasonic Welding ◽  
Transition Temperatures ◽  
Scanning Calorimetry

The aim of this study was to investigate the mechanical behavior, and the microstructure of NiTiCu shape memory alloy wires joined with silver-coated copper ferrules via ultrasonic spot welding. Therefore, the electrical resistance was measured during tensile testing, and the joints were analyzed by scanning electron microscopy. Energy-dispersive X-ray spectroscopy has determined the compounds of the developed welding zones. Furthermore, the influence of the ultrasonic welding on the transition temperatures of the NiTiCu wires was examined via differential scanning calorimetry. Tensile tests have shown that the ultimate tensile strengths of the joints reached almost 100% of that of the base material. An additional heat treatment rebuilt the typical shape memory alloy behavior after the ultrasonic welding process detwinned the martensitic wires. In addition, the B19′ structure of the welding zone and the ultrasonic spot-welding process did not affect the transition temperatures of the shape memory alloy.

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