scholarly journals Continuous Heating Dissolution and Continuous Cooling Precipitation Diagrams of a Nickel-Titanium Shape Memory Alloy

2021 ◽  
Author(s):  
Christian Rowolt ◽  
Benjamin Milkereit ◽  
Jette Broer ◽  
Armin Springer ◽  
Olaf Kessler
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Martensite Transformation ◽  
Continuous Heating ◽  
Solution Annealing ◽  
Scanning Calorimetry ◽  
Transformation Temperatures ◽  
Niti Alloys ◽  
Continuous Cooling ◽  
Precipitation Processes

AbstractBinary NiTi alloys are the most common shape memory alloys in medical applications, combining good mechanical properties and high biocompatibility. In NiTi alloys, the shape memory effect is caused by the transformation of an austenite phase to a martensite phase and the reverse process. Transformation temperatures are strongly influenced by the exact chemical composition of the NiTi phase and the presence of precipitates in the microstructure induced by thermo-mechanical treatment, especially solution annealing and ageing. Isothermal time–temperature precipitation diagrams can be found in the literature. Cooling is frequently not considered, as water quenching is typically assumed to be sufficient. To the best of our knowledge, continuous heating dissolution (CHD) and continuous cooling precipitation (CCP) diagrams do not exist. Differential scanning calorimetry (DSC) is a common method to analyse the austenite/martensite transformation in shape memory alloys, but it has not yet been used to analyse precipitation processes during continuous temperature changes. We have enabled DSC to analyse dissolution and precipitation processes in situ during heating as well as during cooling from the solution annealing temperature. Results are presented as CHD and CCP diagrams, including information from microstructure analysis and the associated changes in the austenite/martensite transformation temperatures.

Effect of the Loading History on Shape Memory Alloy Transformation Temperatures

2008 ◽  
Vol 59 ◽  
pp. 57-62 ◽  
Author(s):  
Gabriella Faiella ◽  
Vincenza Antonucci ◽  
Michele Giordano ◽  
Federica Daghia ◽  
Erasmo Viola
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Constitutive Models ◽  
Complex Loading ◽  
Loading History ◽  
Scanning Calorimetry ◽  
Stress Strain ◽  
Transformation Temperatures ◽  
Composite Systems ◽  
First Results

Due to the complex microstructure and phase transformations taking place in Shape Memory Alloys (SMA), the behaviour and properties of these materials are deeply influenced by their loading history in terms of stress, strain and temperature. Indeed, a thorough understanding of the effects of the loading history on SMA properties is fundamental for a correct modelling and design of SMA applications, in particular in the case of complex loading. An example are shape memory alloys embedded in composite systems, in which stress, strain and temperature vary simultaneously depending upon the properties of the SMA and composite. This work presents the first results of an experimental investigation on the effects of the loading history on SMA transformation temperatures. Nitinol wires of untrained material were considered. Specimens consisting of Martensite and R-phase were subjected to different loading histories, keeping in turn stress, strain or temperature at a constant value. Transformation temperatures at zero stress of these samples were measured via Differential Scanning Calorimetry. Contrarily to most constitutive models assumptions, the DSC results highlight a dependence of the transformation temperatures on the loading history, influencing in particular the Martensite to Austenite phase transformation.

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.

scholarly journals Influence of alloying elements on the thermal behavior of NiTi shape memory alloys

2021 ◽  
Vol 342 ◽  
pp. 06007
Author(s):  
Nicoleta-Monica Lohan ◽  
Çtefan-Lucian Toma ◽  
Mihai Popa ◽  
Alin Marian Cazac ◽  
Bogdan Pricop
Keyword(s):  
Shape Memory Alloys ◽  
Thermal Behavior ◽  
Shape Memory ◽  
Alloying Elements ◽  
Alloying Element ◽  
Scanning Calorimetry ◽  
Automotive Manufacturing ◽  
Niti Alloys ◽  
The Third ◽  
Niti Shape Memory Alloys

NiTi based shape memory alloys are one of the most intensely studied alloys from its class. Therefore, diverse commercial applications have been developed due to certain properties such as: shape memory effect, superelasticity and corrosion resistance. Currently, the main applications of NiTi alloys are automotive manufacturing and aerospace actuators, biomedical devices or pipe couplings. In recent years, NiTi shape memory alloys have been alloyed with a third element in order to improve the above-mentioned properties. In order to investigate the influence of the alloying elements on the thermal behavior of NiTi alloys, the addition of the third alloying element (Ta and Nb) is under investigation in the present study. The thermal behavior of the three alloys (NiTi, NiTiNb and NiTiTa) was studied by differential scanning calorimetry. Following the experiments, it was observed that the addition of the third alloying element influences the critical transformation temperatures.

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).

scholarly journals Effect of Ni-Content on the Transformation Temperatures in NiTi-20 at. % Zr High Temperature Shape Memory Alloys

Metals ◽  
2017 ◽  
Vol 7 (11) ◽  
pp. 511 ◽  
Author(s):  
Matthew Carl ◽  
Jesse Smith ◽  
Brian Van Doren ◽  
Marcus Young
Keyword(s):  
High Temperature ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Transformation Temperatures ◽  
Ni Content

scholarly journals Microstructure and Phase Transformation Analysis of Ni50−xTi50Lax Shape Memory Alloys

Crystals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 345 ◽  
Author(s):  
Weiya Li ◽  
Chunwang Zhao
Keyword(s):  
Phase Transformation ◽  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Martensite Transformation ◽  
Transformation Behavior ◽  
Ni Content ◽  
Start Temperature

The microstructure and martensitic transformation behavior of Ni50−xTi50Lax (x = 0.1, 0.3, 0.5, 0.7) shape memory alloys were investigated experimentally. Results show that the microstructure of Ni50−xTi50Lax alloys consists of a near-equiatomic TiNi matrix, LaNi precipitates, and Ti2Ni precipitates. With increasing La content, the amounts of LaNi and Ti2Ni precipitates demonstrate an increasing tendency. The martensitic transformation start temperature increases gradually with increasing La content. The Ni content is mainly responsible for the change in martensite transformation behavior in Ni50−xTi50Lax alloys.

scholarly journals Effects of Impurities Content (Oxygen, Carbon, Nitrogen) on Microstructure and Phase Transformation Temperatures of Near Equiatomic TiNi Shape Memory Alloys

1997 ◽  
Vol 07 (C5) ◽  
pp. C5-143-C5-148 ◽  
Author(s):  
P. Olier ◽  
F. Barcelo ◽  
J. L. Bechade ◽  
J. C. Brachet ◽  
E. Lefevre ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Transformation Temperatures
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