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.

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.

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.

Material and Process Development of Thin Film Shape Memory Alloy for MEMS Actuator

2015 ◽  
Author(s):  
Cory R. Knick ◽  
Christopher J. Morris
Keyword(s):  
Thin Film ◽  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Phase Change ◽  
Shape Memory ◽  
Microelectromechanical Systems ◽  
Austenite Phase ◽  
Niti Shape Memory Alloy ◽  
Scanning Calorimetry ◽  
Release Process

In this work we discuss the design and fabrication of a cantilever that may be actuated by utilizing the martensite to austenite phase transformation of a sputtered thin film of equiatomic NiTi shape memory alloy (SMA). The cantilever devices were fabricated on a silicon wafer using standard micro fabrication techniques, and may therefore be applicable to microelectromechanical systems (MEMS) switch or actuator applications. This paper details the development of a co-sputtering process to yield a SMA film with controllable composition of Ni50Ti50 and transformation temperature around 60° C. Shape memory effects were characterized using Differential Scanning Calorimetry (DSC), for which we demonstrated martensite-austenite phase change at 57° C for 1–3 um films, annealed at 600° C. We used wafer stress versus temperature measurements as additional confirmation for the repeatable measurement of reversible phase transformation peaking at 73° C upon heating. Up to 62 MPa was available for actuation during the thermally induced phase change. After exploring multiple approaches to a frontside wafer release process, we were successful in patterning and fabricating 10 um wide freestanding Ni50Ti50 cantilevers.

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.

Influence of Thermomechanical Treatment on Transformation Temperatures of Cu-Al-Ni Shape Memory Alloys

2008 ◽  
Vol 59 ◽  
pp. 92-100
Author(s):  
Ana Cris R. Veloso ◽  
Rodinei Medeiros Gomes ◽  
Dagoberto Brandao Santos ◽  
I.C.E.G. Lima ◽  
Severino Jackson Guedes de Lima ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Differential Scanning Calorimetry ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Thermomechanical Treatment ◽  
Hot Rolling ◽  
Rolling Process ◽  
Induction Melting ◽  
Scanning Calorimetry ◽  
Transformation Temperatures

In this study Cu-13.8Al alloys with 3.0% and 4.0% (wt%) of nickel were obtained by induction melting. The effect of homogenization heat treatment and hot rolling on the transformation temperatures of these alloys was investigated by differential scanning calorimetry. It was observed that the transformation temperatures increase with long homogenization times, and also by hot rolling, and this displacement is smaller for alloys with 4.0% of nickel. In both alloys in the quenched state, the reversion reaction is characterized by the appearance of multiple peaks attributed to the presence of martensites 2H and 18R. The influence of the rolling process must be associated with the loss of Ni and Al during the process.

Mechanical and Phase Transformation Behavior of Plastically Strained NiTi-based Shape Memory Alloys

2008 ◽  
Vol 1097 ◽  
Author(s):  
Peng Yu ◽  
Qizhen Li
Keyword(s):  
Differential Scanning Calorimetry ◽  
Plastic Deformation ◽  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Compression Test ◽  
Compression Tests ◽  
Transformation Behavior ◽  
Scanning Calorimetry ◽  
Final Fracture

AbstractThis paper examines the effect of plastic deformation on the strength and transformation heat and temperatures of the superelastic Nitinol samples. Two types of compression tests and differential scanning calorimetry tests were conducted. The first type of compression test deformed the samples to final fracture, and the second type included two loading –unloading cycles with or without plastic deformation. The mechanically tested samples were analyzed using differential scanning calorimetry.

scholarly journals The influence of heat treatment on microstructure and phase transformation Temperatures of Cu-Al-Ni shape memory alloy

2019 ◽  
Vol 68 (3-4) ◽  
pp. 111-118 ◽  
Author(s):  
Ivana Ivanić ◽  
Mirko Gojić ◽  
Borut Kosec ◽  
Tamara Holjevac Grgurić ◽  
Stjepan Kožuh
Keyword(s):  
Heat Treatment ◽  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Microstructural Analysis ◽  
Solution Annealing ◽  
Scanning Calorimetry ◽  
Transformation Temperatures ◽  
Casting Technique ◽  
Before And After

This paper presents the results of thermal and microstructural analysis of Cu-Al-Ni shape memory alloy before and after heat treatment. After casting, a bar of Cu-12.8 Al-4.1 Ni (wt.%) alloy, obtained by the vertical continuous casting technique, was subjected to a certain heat treatment procedure. Solution annealing was performed at 850 °C for 60 min, followed by water quenching. Tempering was then performed at four different temperatures (150 °C, 200 °C, 250 °C and 300 °C). The microstructural results were obtained by optical and scanning electron microscopy. Thermodynamic calculation of ternary Cu-Al-Ni system under equilibrium was performed using Thermo-Calc 5 software. Phase transformation temperatures were determined by differential scanning calorimetry (DSC). The DSC results show the highest values of transformation temperatures in as-cast state. After solution annealing and tempering, the transformation temperatures show lower values with exceptional stability of Ms temperature (martensite start temperature).

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