scholarly journals Effect of Heat Treatment on Phase Transformation of NiTi Shape Memory Alloy produced by Metal Injection Moulding

2021 ◽  
Vol 18 (1) ◽  
pp. 71
Author(s):  
Ros Atikah Abdul Kadir ◽  
Nur Atira Shariff ◽  
Muhammad Hussain Ismail
Keyword(s):  
Heat Treatment ◽  
Phase Transformation ◽  
Shape Memory ◽  
Injection Moulding ◽  
Niti Alloy ◽  
Impurity Content ◽  
Metal Injection Molding ◽  
Niti Shape Memory Alloy ◽  
Secondary Phases ◽  
Heat Treated

The NiTi alloy is widely known for its unique properties which are pseudoelastic and shape memory effect. These two unique properties are suitable for biomedical applications such as an implant, biomedical suture etc. Various methods are available to produce NiTI like Metal Injection Molding (MIM), Vacuum Arc Melting (VAM), additive manufacturing (AM), etc. The most common method is MIM where the specimen undergoes the process of mixing, injection moulding, debinding and sintering. Commonly after sintering process, the specimen is inhomogeneous due to the formation of secondary phases and impurity content. These impurities content can be reduced by applying heat treatment which improves the microstructure of NiTi. The objective of the study is to investigate the effect of heat treatment on the microstructure and phase transformation of NiTi. In this study, samples were fabricated with each 50.0at% and 50.8at% of NiTi composition by using MIM. An annealing heat treatment of 430˚oC was applied to the heat-treated samples for increasing the yield strength of NiTi. All heat-treated samples were subjected to Differential Scanning Calorimetry (DSC) test for analysing the phase transformation; X-Ray Diffraction (XRD) test for identifying the existence of any secondary phases; and Scanning Electron Microscopy (SEM) test for observing the change in the microstructure. The results indicated that upon heating through the annealing process, the secondary phase of martensite which is known as NiTi (B19’) diffused and formed the austenite phase of NiTi (B2). Results from the DSC and SEM analyses showed that the formation of B2 is dominant after the heat treatment process.

SHAPE MEMORY INVESTIGATION OF SMART CAMAR LOGO USING NITI ALLOY WIRE

2015 ◽  
Vol 76 (3) ◽  
Author(s):  
Muhammad Safwan Shuhaimi ◽  
Nubailah Abd. Hamid ◽  
Rosliza Razali ◽  
Muhammad Hussain Ismail
Keyword(s):  
Phase Transformation ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Niti Alloy ◽  
Niti Shape Memory Alloy ◽  
Shape Effect ◽  
Niti Wire ◽  
The Wire ◽  
Reversible Phase

This project is investigates of NiTi shape memory alloy for simple smart application. The shape memory effect (SME) is attributed from the reversible phase transformation when subjected to stress and temperature. In this study, a small model of CAMAR logo was designed to mimic the shape memory effect. Three samples of wire were investigated; (i) Austenitic NiTi (ii) Martensitic NiTi and (iii) commercial plain carbon steel. The reversible austenite to martensite transformation of the NiTi wire was investigated by a differential scanning calorimetry (DSC) at temperatures ranging from -50 and 200oC. The wire was shaped into CAMAR logo using a mould and then heated at 500°C for 30 minutes in a high temperature furnace. To observe the shape effect recovery, the wire was straighten and reheated in warm water at different temperatures. Results showed that the austenitic wire exhibited complete shape memory recovery after heated at temperature approximately 35°C and  80°C. For the martensitic wire, complete recovery was only observed when the water temperature was ~ 80°C and no recovery was observed at ~30°C. This recovery effect was significantly influenced by the reversible phase transformation temperatures (PTTs) which attributed from the Austenite finish (Af) temperature.

scholarly journals Functionalization of the NiTi Shape Memory Alloy Surface by HAp/SiO2/Ag Hybrid Coatings Formed on SiO2-TiO2 Glass Interlayer

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1648 ◽  
Author(s):  
Karolina Dudek ◽  
Mateusz Dulski ◽  
Bożena Łosiewicz
Keyword(s):  
Heat Treatment ◽  
Shape Memory ◽  
Electrochemical Impedance ◽  
Niti Alloy ◽  
Composite Coatings ◽  
Energy Dispersive Spectrometer ◽  
Weight Ratio ◽  
Hybrid Coatings ◽  
Niti Shape Memory Alloy ◽  
Niti Shape Memory Alloys

The surface modification of NiTi shape memory alloys is a method for increasing their multi-functionalities. In our solution, hydroxyapatite powder was mixed with a chemically synthesized silicon dioxide/silver (nSiO2/Ag) nanocomposite in a different weight ratio between components (1:1, 5:1, and 10:1) and then electrophoretically deposited on the surface of the NiTi alloy, under various time and voltage conditions. Subsequently, uniform layers were subjected to heat treatment at 700 °C for 2 h in an argon atmosphere to improve the strength of their adhesion to the NiTi substrate. A change in linear dimensions of the co-deposited materials during the sintering process was also analyzed. After the heat treatment, XRD, Raman, and Scanning Electron Microscopy (SEM) + Energy Dispersive Spectrometer (EDS) studies revealed the formation of completely new composite coatings, which consisted of rutile and TiO2-SiO2 glass with silver oxide and HAp particles that were embedded into such coatings. It was found that spalling characterized the 1:1 ratio coating, while the others were crack-free, well-adhered, and capable of deformation to 3.5%. Coatings with a higher concentration of nanocomposite were rougher. Electrochemical impedance spectroscopy (EIS) tests in Ringer’s solution revealed the capacitive behavior of the material with high corrosion resistance. The kinetics and susceptibility to pitting corrosion was the highest for the NiTi electrode that was coated with a 5:1 ratio HAp/nSiO2/Ag hybrid coating.

The Effect of Chemical Composition on Microstructure and Transformation Behavior of NiTi Shape Memory Alloy Prepared by Vacuum Arc Melting

2008 ◽  
Vol 1 ◽  
pp. 91-97
Author(s):  
Mandana Bornapour ◽  
Y. Motemanni ◽  
Mahmoud Nili-Ahmadabadi ◽  
S. Raygan
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Niti Alloy ◽  
Martensite Phase ◽  
Vacuum Arc ◽  
Niti Shape Memory Alloy ◽  
Arc Melting ◽  
Vacuum Arc Melting ◽  
Niti Shape Memory Alloys

NiTi shape memory alloys are a group of materials which have a lot of applications especially in aerospace industries and medical equipments because of their excellent properties. Shape memory effect (SME), pseudo-elasticity (PE), high corrosion resistance and biocompatibility is special properties of these alloys which lead to their extensive applications. The superior behavior of NiTi alloy is due to thermoelastic martensitic phase transformation. In the present paper, two NiTi shape memory alloys were prepared by non-consumable vacuum arc melting technique in copper water cooled crucible. One of them had commercial elements and the other had high purity elements. Metallographic investigation, chemical analysis, XRD and DSC were carried out on two alloys. Metallographic observation and XRD shows that structure at ambient temperature consists of austenite phase besides Ti2Ni, Ni3Ti intermetallic compounds and martensite phase. Transformation investigation determines that the impurity such as iron in commercial alloy causes two stage phase transformation B2→R→B19′.

Study on Measurement of Group Velocity of Lamb Waves in Shape Memory Alloy Sheets

2014 ◽  
Vol 1065-1069 ◽  
pp. 2021-2024
Author(s):  
Kai Sheng Wang ◽  
Wei Chun Zhang
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Group Velocity ◽  
Lamb Waves ◽  
Niti Alloy ◽  
Effective Means ◽  
Niti Shape Memory Alloy ◽  
Time Frequency ◽  
Different Temperatures

This paper describes the nondestructive evaluation of microstructure using laser-excited Lamb waves to detect the phase transformation in NiTi shape memory alloy sheets. Lamb waves were applied in the NiTi sheet using a pulse laser beam. Piezoelectricity transducers were used to receive the Lamb waves, the group velocities of which were measured using a time-frequency analysis method at different temperatures. Results show that a marked variation in the group velocity occurs during the phase transformation in the NiTi alloy. The dependence of group velocity on temperature provides a effective means of inspecting microstructure transformation in NiTi alloys.

Influence of Heat Treatment Parameters on the Functional Behavior and Corrosion Performance of a Shape Memory Wire Actuator

2020 ◽  
Vol 986 ◽  
pp. 55-60 ◽  
Author(s):  
Gorkem Muttalip Simsek ◽  
Guney Guven Yapici
Keyword(s):  
Heat Treatment ◽  
Shape Memory ◽  
Corrosion Behavior ◽  
Niti Alloy ◽  
Treatment Temperature ◽  
Sustained Load ◽  
Functional Behavior ◽  
Heat Treated ◽  
Heat Treatment Regimes ◽  
The Impact

In the present study, the effect of heat treatment parameters on the functional response, corrosion behavior and microstructural evolution of NiTi shape memory alloys were investigated. Various heat treatment regimes were utilized to study the impact of temperature and duration on the actuation behavior of wire samples under bending. Results clarified that austenite transformation temperatures As and Af increased at higher treatment temperatures. Cyclic response in the range of 0 to 15 degrees indicated that the actuation force exhibits an inverse relation with the treatment temperature. Higher treatment durations below 500°C elevated both the hardness and the sustained load. Bending force levels above 1500gf were achieved after a 90 min treatment at 400°C, whereas that over 500°C brought about a noticeable drop in strength. Investigations on the corrosion behavior of NiTi alloy was utilized in the simulated body fluid revealing that the sample heat treated at 400°C for 90 min showed the highest corrosion resistance.

INFLUENCES OF HEAT TREATMENT ON TRANSFORMATION BEHAVIORS OF NEAR-EQUIATOMIC POROUS NITI SHAPE MEMORY ALLOY

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2410-2416
Author(s):  
H. C. JIANG ◽  
Y. CHEN ◽  
S. W. LIU ◽  
L. J. RONG
Keyword(s):  
Heat Treatment ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Niti Alloy ◽  
Niti Shape Memory Alloy ◽  
Scanning Calorimetry ◽  
Pore Characteristics ◽  
Transformation Temperatures ◽  
Porous Niti ◽  
High Temperature Synthesis

The pore characteristics and pore size distribution of porous near-equiatomic NiTi shape memory alloy fabricated by self-propagating high-temperature synthesis (SHS) are described in detail. The effects of different heat treatments on the transformation of porous NiTi alloy were investigated by differential scanning calorimetry (DSC), x-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicate that heat treatment had strong influences on the transformation temperatures and latent heats of transformation. When the porous alloy was annealed at 648K and 748K for 3.6ks, two steps transformation including R transformation occurred during cooling and heating and the R transformation temperatures are lower than B 2↔ B 19' transformation temperatures. However, no transformation was detected within the experimental temperature range if the porous alloy was solution treated at 1133K for 2.4ks. This novel phenomenon was the results of extensive Ti2Ni intermetallic compound precipitation. The transformation temperatures of porous NiTi alloy after annealing at 1323K for 3.6ks were much lower than those of the untreated alloy.

Effect of Cu on Structural and FF-Behavior of NiTi Shape Memory Alloy

2010 ◽  
Vol 442 ◽  
pp. 301-308
Author(s):  
S. Rani ◽  
M.S. Awan ◽  
I.N. Qureshi ◽  
F. Yasmin ◽  
M. Farooque
Keyword(s):  
Phase Transformation ◽  
Electron Microscope ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Cold Working ◽  
Niti Alloy ◽  
Fatigue Behavior ◽  
Optical Microscope ◽  
Niti Shape Memory Alloy ◽  
Transformation Temperatures

The functional fatigue behavior of Ti50Ni30Cu20 (at. %) shape memory alloy was investigated after subjecting to cold working and heat-treatment. Copper addition modified the phase transformation behavior with the introduction of B19-phase in the binary NiTi alloy. It was observed that aging after annealing and thermal cycling (-60 to 100)°C significantly effect the transformation temperatures. Observations in optical microscope and scanning electron microscope reveal inhomogeneity in the composition in the form of coarse Cu+Ti-rich precipitates. Investigations under transmission electron microscope showed growth of internally twined martensitic plates in solution treated sample. The phase transformation temperatures were determined with differential scanning calorimeter. The transformation temperatures were shifted towards lower side. Dislocations introduced during cold working and fine precipitation after aging, may be responsible for this change in the transformation characteristics of the material.

scholarly journals Effect of Heat Treatment on Repetitively Scanned SLM NiTi Shape Memory Alloy

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 77 ◽  
Author(s):  
Zhong Khoo ◽  
Jia An ◽  
Chee Chua ◽  
Yu Shen ◽  
Che Kuo ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Shape Memory ◽  
Transformation Strain ◽  
Niti Shape Memory Alloy ◽  
New Approach ◽  
Post Process ◽  
Heat Treated ◽  
High Transformation ◽  
Compositional Control ◽  
Complex Nickel

Selective Laser Melting (SLM) has been implemented to address the difficulties in manufacturing complex nickel titanium (NiTi) structures. However, the SLM production of NiTi is much more challenging than the fabrication of conventional metals. Other than the need to have a high density that leads to excellent mechanical properties, strict chemical compositional control is required as well for the SLM NiTi parts to exhibit desirable phase transformation characteristics. In addition, acquiring a high transformation strain from the produced specimens is another challenging task. In the prior research, a new approach—repetitive scanning—was implemented to achieve these objectives. The repetitively scanned samples demonstrated an average of 4.61% transformation strain when subjected to the tensile test. Nevertheless, there is still room for improvement as the conventionally-produced NiTi can exhibit a transformation strain of about 6%. Hence, post-process heat treatment was introduced to improve the shape memory properties of the samples. The results showed an improvement when the samples were heat treated at a temperature of 400 °C for a period of 5 min. The enhancement in the shape memory behavior of the repetitively scanned samples was mainly attributed to the formation of fine Ni4Ti3 metastable precipitates.

The Influence of Hafnium Content, Cold Work, and Heat Treatment on the R-Phase Transformation of Niti Based Shape Memory Alloys

1996 ◽  
Vol 459 ◽  
Author(s):  
Chen Zhang ◽  
Paul E. Thoma ◽  
Ralph H. Zee
Keyword(s):  
Heat Treatment ◽  
Differential Scanning Calorimetry ◽  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Cold Work ◽  
Niti Shape Memory Alloy ◽  
Scanning Calorimetry ◽  
Complex Manner

ABSTRACTThe R-phase transformation of a Ti-rich NiTi shape memory alloy (SMA) and two ternary SMAs having the compositions Ni49Ti51-XHfx with lat% and 3at% Hf, has been investigated. The influence of cold work (CW) and heat treatment (HT) on the R-phase transformation is analyzed thermally using Differential Scanning Calorimetry (DSC). Results show that the R-phase transformation depends on the SMA composition as well as the CW and HT conditions in a complex manner. For example, the formation of R-phase upon cooling from austenite (A) is increasingly suppressed with the substitution of Hf for Ti. For the ternary SMA with 3at% Hf, the A→R and R→A transformations are observed only at relatively large amounts of CW (above approximately 40%) and at a high HT temperature (450°C). DSC results also show that for the Ti-rich NiTi and the ternary SMA containing lat% Hf, the A→R and R→A transformation temperatures (TTs) are insensitive to cold work at a HT temperature of 450°C. However, at a lower HT temperature of 350°C, the TTs are found to decrease with increasing CW. For a given CW, the A→R and R→A transformations decrease with decreasing HT temperature and the effect is greatest at high CW (>50%) conditions. An effort is made to identify the factors responsible for the observed behavior in the R-phase transformation.

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