Effect of Aging Treatment on Phase Transformation of a Pseudoelastic NiTi Alloy

2014 ◽  
Vol 936 ◽  
pp. 1216-1223 ◽  
Author(s):  
Palloma Viera Muterlle ◽  
Eduard Benavides Villamarin ◽  
Paulo Herrera ◽  
Edson Paulo da Silva
Keyword(s):  
Phase Transformation ◽  
Shape Memory ◽  
Room Temperature ◽  
Niti Alloy ◽  
Aging Treatment ◽  
Single Step ◽  
Treatment Temperature ◽  
Scanning Calorimetry ◽  
Transformation Temperatures ◽  
X Ray

The pseudoelasticity (PE) and shape memory effect (SME) are the two main behaviors presented by the shape memory alloys (SMA's) and are associated respectively to mechanical and thermally induced martensitic transformations. The aim of this work is to investigate the effects of heat treatment temperature on the microstructure properties and phase transformation temperatures of a NiTi alloy with 57 w.t. % Ni. The X-ray diffraction (XRD) was carried out to obtain the phases present. The phase transformation temperatures were measured by differential scanning calorimetry (DSC). The alloy chemical composition and hardness were obtained by X-ray fluorescence (XRF), hardness (HRC) and microhardness (HV) tests, respectively. The analysis were performed in the state as received and after aging treatment at different temperatures between 350 °C and 600°C. The samples as received contained a fully austenitic microstructure at room temperature and the DSC analysis showed the presence of a phase transformation in multiple steps (B19'-R-B2). After aging at 350 °C the R phase was observed at room temperature with the austenite. With the aging treatment at 600 °C the R phase was solubilized and the alloy phase transformation occurred in a single step, ie, direct transformation from austenite to martensite and vice versa. The transformation temperatures Af, As, Ms and Mf changed with the aging treatment temperatures.

Cold Bending a Ni-Ti Shape Memory Alloy Wire

2015 ◽  
Vol 661 ◽  
pp. 98-104 ◽  
Author(s):  
Kuang-Jau Fann ◽  
Pao Min Huang
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Room Temperature ◽  
Aging Treatment ◽  
Treatment Temperature ◽  
Bending Test ◽  
Solution Treatment Temperature

Because of being in possession of shape memory effect and superelasticity, Ni-Ti shape memory alloys have earned more intense gaze on the next generation applications. Conventionally, Ni-Ti shape memory alloys are manufactured by hot forming and constraint aging, which need a capital-intensive investment. To have a cost benefit getting rid of plenty of die sets, this study is aimed to form Ni-Ti shape memory alloys at room temperature and to age them at elevated temperature without any die sets. In this study, starting with solution treatments at various temperatures, which served as annealing process, Ni-rich Ni-Ti shape memory alloy wires were bent by V-shaped punches in different curvatures at room temperature. Subsequently, the wires were aged at different temperatures to have shape memory effect. As a result, springback was found after withdrawing the bending punch and further after the aging treatment as well. A higher solution treatment temperature or a smaller bending radius leads to a smaller springback, while a higher aging treatment temperature made a larger springback. This springback may be compensated by bending the wires in further larger curvatures to keep the shape accuracy as designed. To explore the shape memory effect, a reverse bending test was performed. It shows that all bent wires after aging had a shape recovery rate above 96.3% on average.

scholarly journals Nanocrystal, phase transformation and microstructure of Ni50Ti50 shape memory alloy

2018 ◽  
Vol 24 (02) ◽  
pp. 22-25
Author(s):  
Dovchinvanchig M ◽  
Chunwang Zhao
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
One Step ◽  
Niti Matrix ◽  
Electronic Microscope

The nanocrystal, phase transformation and microstructure behavior of Ni50Ti50 shape memory alloy was investigated by scanning electronic microscope, X-ray diffraction and differential scanning calorimetry. The results showed that the microstructure of Ni-Ti binary alloy consists of the NiTi2 phase and the NiTi matrix phase. One-step phase transformation was observed alloy.

High-energy synchrotron X-ray diffraction measurements of simple bending of pseudoelastic NiTi shape memory alloy wires

2016 ◽  
Vol 31 (2) ◽  
pp. 104-109 ◽  
Author(s):  
Baozhuo Zhang ◽  
Marcus L. Young
Keyword(s):  
Phase Transformation ◽  
Shape Memory ◽  
High Energy ◽  
Bend Angle ◽  
Niti Shape Memory Alloy ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Mechanical Bending ◽  
Xrd Patterns

Many technological applications of austenitic shape memory alloys (SMAs) involve cyclical mechanical loading and unloading in order to take advantage of pseudoelasticity. In this paper, we investigated the effect of mechanical bending of pseudoelastic NiTi SMA wires using high-energy synchrotron radiation X-ray diffraction (SR-XRD). Differential scanning calorimetry was performed to identify the phase transformation temperatures. Scanning electron microscopy images show that micro-cracks in compressive regions of the wire propagate with increasing bend angle, while tensile regions tend not to exhibit crack propagation. SR-XRD patterns were analyzed to study the phase transformation and investigate micromechanical properties. By observing the various diffraction peaks such as the austenite (200) and the martensite (${\bar 1}12$), (${\bar 1}03$), (${\bar 1}11$), and (101) planes, intensities and residual strain values exhibit strong anisotropy, depending upon whether the sample is in compression or tension during bending.

Microstructure, Phase Stability, Mechanical Properties, and Shape Memory Characteristics of Ni-Fe-AI-B Alloys

1991 ◽  
Vol 246 ◽  
Author(s):  
E. P. George ◽  
C. T. Liu ◽  
C. J. Sparks ◽  
Ming-Yuan Kao ◽  
J. A. Horton ◽  
...  
Keyword(s):  
Shape Memory ◽  
Room Temperature ◽  
Cold Work ◽  
Second Phase ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Transformation Temperatures ◽  
Plate Morphology ◽  
Hot Rolled ◽  
Memory Characteristics

AbstractConventionally cast and hot-rolled Ni-Fe-AI-B alloys containing 4-20 at.% Fe, 23.9- 31.5 at.% Al, and 300 wppm B were investigated in this study. After oil quenching from 1300°C, all the alloys—except SMA-15 (27A1-14Fe)—have at least a two-phase microstructure, one phase of which is martensite with the characteristic plate morphology, and the other a globular second phase distributed throughout the microstructure. The amount of second phase generally increases with increasing Fe content. Alloys containing less than 14% Fe were found to be quite brittle at room temperature, indicating that a ductile second phase is at least partly responsible for the improved room-temperature ductility in the high-Fe alloys. The best tensile ductility (12%) was obtained in SMA-17 (23.9AI-20Fe) which was shown by X-ray diffraction to consist of 40% (mostly disordered) fcc [(Ni,Fe)3 (AI,Fe)] + 30% (partly ordered) bct martensite + 30% B2. Differential scanning calorimetry showed that the transformation temperatures for this alloy were MP = 65°C and AP = 95°C. Room-temperature tensile strains of 2-3% could be almost completely recovered in SMA-17 by heating for 3 min. at 600°C with the load removed. Upon subsequent cycling (i.e., strain-anneal cycling), the amount of strain recovery increased dramatically from 70% in the first cycle to nearly 100% after 4-5 cycles, indicating that cold work may help in improving the shape memory characteristics of this alloy. SMA-15 was found to have significantly higher transformation temperatures (Mp = 143°C and Ap = 170°C) than SMA-17; however, it is relatively brittle compared to SMA-17.

Adjusting Microstructure and Magnetic Properties of Ni-Mn-In Metamagnetic Shape Memory Alloys by Addition of Gd

2012 ◽  
Vol 535-537 ◽  
pp. 959-963
Author(s):  
Li Na Bai ◽  
Gui Xing Zheng ◽  
Jing Xin ◽  
Jian Jun Zhang
Keyword(s):  
Magnetic Field ◽  
Differential Scanning Calorimetry ◽  
Magnetic Properties ◽  
Shape Memory ◽  
Room Temperature ◽  
Vibrating Sample Magnetometry ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Microstructure And Magnetic Properties

The influences of Gd concentration on martensitic transformation and magnetic properties of NiMnIn alloys were investigated by differential scanning calorimetry (DSC) , vibrating sample magnetometry (VSM), X-ray diffraction (XRD) and etc. It shows that addition of Gd enhances martensite transition temperature and that X-ray diffraction analysis of experimental alloys is revealed which the mixture is martensite and austenite at room temperature. These alloys show promise as a metamagnetic shape memory alloy with magnetic-field-induced shape memory effect.

The Influence of γ-Irradiation on the Structure and Properties of the Cu-11.5 wt. % Al-4 wt. % Ni Shape Memory Alloys

2013 ◽  
Vol 845 ◽  
pp. 128-132
Author(s):  
Safaa N. Saud ◽  
Esah Hamzah ◽  
T. Abubakar ◽  
Azadeh Refaei ◽  
Raheleh Hosseinian
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Structural Properties ◽  
Room Temperature ◽  
Structure And Properties ◽  
Γ Irradiation ◽  
Transformation Temperatures ◽  
Enthalpy And Entropy ◽  
Complex Influence

This study investigated the influence of 60Co-γ-irradiation on the structure and properties of Cu-Al-Ni shape memory alloys. The phase transformation temperatures were evaluated by differential scanning calorimeter (DSC). It was found that the γ-irradiation had a complex influence on the phase transformation parameters of Cu-Al-Ni SMAs. However, the transformation temperatures were shifted and a new curve was obtained after exposure to different irradiation doses. The thermodynamic parameters such as enthalpy and entropy tended to increase/decrease depending on the amount of the exposure. The structural properties of the exposed samples were studied by using optical microscopy and hardness measurements at room temperature. It was also found that the structural-properties of the Cu-Al-Ni SMAs were completely affected by the amount of the applied γ-irradiation dose.

PHASE TRANSFORMATION AND MICROSTRUCTURE BEHAVIOUR OF CU-AL-NI SHAPE MEMORY ALLOYS INCORPORATED WITH COBALT ADDITION

2015 ◽  
Vol 74 (10) ◽  
Author(s):  
Y. C. Wee ◽  
T. Abubakar ◽  
E. Hamzah ◽  
Safaa N. Saud
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Phase Transformation ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Transformation Temperatures ◽  
X Ray ◽  
Co Addition ◽  
Cobalt Addition ◽  
Scanning Electron

The effect of Co addition on phase transformation temperatures and microstructures of Cu-Al-Ni SMA were investigated via differential scanning calorimetry, field emission scanning electron microscopy corresponding with energy dispersive spectroscopy and x-ray diffraction. The results revealed that the β1’ and γ1’ phases’ morphology and orientation were varied after the addition of Co along with the presence of intermetallic compounds known as γ2. This phase was indicated using the EDS and XRD is related to the intermetallic compound of Al75Co22Ni3. In addition, the phase transformation temperatures tend to increase with the addition of Co and this enhancement is mainly attributed to the variation of phase morphology and the existence of γ2 precipitates. 

Effect of the Cooling Time in Annealing at 350°C on the Phase Transformation Temperatures of a Ni55Ti45 wt. Alloy

2015 ◽  
Vol 1120-1121 ◽  
pp. 958-961
Author(s):  
Tadeu Castro da Silva ◽  
Daniel Monteiro Rosa ◽  
Edson Paulo da Silva
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Cooling Time ◽  
Phase Transformation Temperature ◽  
Thermal Treatments ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Transformation Temperatures

When submitted to annealing thermal treatments Shape Memory Alloys have their phase transformation temperatures effected. The aim of the present work is to investigate the effects of cooling time in the phase transformation temperatures of Ni55Ti45in w.t. % alloy annealed at 350°C. Samples of this alloy were maintained at 350°C for one hour and then cooled in the same furnace for 10 minutes, 1 hour and 24 hours. The phase transformation temperatures were measured by means of Differential Scanning Calorimetry (DSC) at cooling and heating rates of 20°C/min. The results show that the annealing at 350°C changed the phase transformation up to 54%. For 10 minutes cooling time the Mftemperature increase from 15,65°C to 24,1°C. For the others cooling times the phase transformation temperature did not change significantly. Therefore, the cooling time for the annealing at 350°C did not effect the phase transformation temperatures of the Ni45Ti55in wt % shape memory alloy.

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.

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