CC BY
8
Chelyabinsk Physical and Mathematical Journal. 2022. Т. 7, вып. 3. С. 384-389.
УДК 621.391+621.396 DOI: 10.47475/2500-0101-2022-17312
THERMOMECHANICAL PROPERTIES
AND THE EFFECT OF HEAT TREATMENT
ON THE PHASE TRANSFORMATION
OF A SEMI-FINISHED Ni49.9Ti501 ALLOY MICROWIRES
WITH SHAPE MEMORY EFFECT
FOR ELASTOCALORIC APPLICATIONS
D.D. Kuznetsov1", G.A. Shandryuk2b, V.S. Kalashnikov1c, V.V. Koledov1d, V.G. Shavrov1e, V.A. Andreev34/, A.V. Nesolenov1'9, M.S. Bybik1h
1 Kotelnikov Institute of Radio-Engineering and Electronics of RAS, Moscow, Russia
2 Topchiev Institute of Petrochemical Synthesis of RAS, Moscow, Russia
3 "Matek-Sma Ltd.", Moscow, Russia
4Baikov Institute of Metallurgy and Materials Science of RAS, Moscow, Russia "[email protected], [email protected], [email protected], [email protected], [email protected], f [email protected], 9 [email protected], [email protected]
Recently shape memory microwires have attracted the attention as a promising solidstate functional material for elastocaloric heat pumps and refrigerators. In this work we study the martensitic transition in NiTi microwires versus degree of annealing. The optimal combination of the amorphous and nano crystalline phases in the structure of the shape memory microwires provides the maximal strength and reliability together with pronounced elastocaloric properties, which is crucial for a long haul elastocaloric heat pump application. The 100 / thick microwire was subjected to long-term tests and have demonstrated a reversible deformation 2-3 % under load up to 675 MPa. The wire retained its mechanical stability up to 900 MPa.
Keywords: phase transformation, microwire, differential scanning calorimetry, thermomechanical analysis, shape memory effect, NiTi alloy, elastocaloric effect.
Introduction
In recent years, in connection with the widespread use of shape memory alloys (SMA) in medicine, instrument making, technology of micro- and nanoelectromechanical systems (MEMS and NEMS), the growing attention has been paid to increasing their reliability and functionality by optimizing the conditions for their production [1-4]. TiNi alloy has become a very interesting material for creating solid-state refrigerating machines due to the strong elastocaloric effect (ECE), which manifests itself during the martensitic transformation, when the high-temperature cubic ordered phase B2 (austenite) transforms under external stress into a low-temperature monoclinic phase-disordered B19' (martensite) or/and the orthorhombic R phase (also martensite) [5; 6]. Recently the microwires and melt spun ribbons are proved to demonstrate a potential
The work was supported by Russian Science Foundation, grant no. 22-19-00783.
for energy systems, due to very high specific power of the ECE based solid state working body — up tp 150 W/g [7]. The materials with SME and ECE need to satisfy special demands for the application in the technology of the solid-state refrigeration, including the high strength, high functional properties and the long term stability of the functional properties [8; 9]. The present work is devoted to the study of the effect of heat treatment on the martensitic phase transformation in a semi-finished product of microwire from №49.9Ti50.i at.% alloy, produced by "Matek-Sma Ltd.", and the determination of thermomechanical properties and reliability during long-term mechanical tests.
1. Samples and Methods
A rod made of Ni49.9Ti50.1 at.% alloy with a diameter of 5 mm was subjected to warm forging (up to 450°), it was subjected to warm (450-300° to 0.5 mm) and cold (at 20° up to 0.1 mm) drawing (see more details in [10]). To determine the thermomechanical properties, the setup described in [9] was used. The experimental method is based on the stretching of a 20 mm long microwire sample made of an SME alloy under a constant load at a variable temperature. So, the specified installation allows measuring deformation in the range of 0-90% in the temperature range -130 ^ 300° ± 1.5% and the applied mechanical stress 0-2000 MPa ±4-5% with a wire diameter of up to 100 ^m [11].
Differential scanning calorimetry (DSC) was carried out by METTLER TOLEDO DSC3+ in temperature range from -80° to 200° for samples after annealing at 250, 450 and 550° for 7 minutes and at 600° for 20 minutes.
2. Results and Discussion
The typical DSC data are illustrated in the fig. 1. The thermograms of the sample without heat treatment (fig. 1 (a)) and after annealing at 250° for 7 minutes has insignificant differences. The peaks of martensitic transition are weakly expressed and the interval of martensitic transformation is very wide, which indicates a large fraction of the volume of the amorphous phase. Typical transformation temperatures: Ms = 73° and Mf = 20° (for the R phase), As = 10° and Af = 150° (B2 phase) and MRi9s = -19° and MR19f = -40°, the value of the latent heat of transformation for the austenitic transformation qA = 10.73 J/g, qR = 5.00 J/g, qR19 = 6.21 J/g in both cases.
Fig. 1. DSC results for Ni49.9Ti50.1 wire after annealing at 600° for 20 min (a); 450°, 7 min (b);
without annealing (c)
An increase in the annealing temperature led to the appearance of a large fraction of a defect-free crystal structure, as a result of which we see two large peaks on the
thermogram upon cooling the sample, a general narrowing of the PT temperature range and a shift in the start and end points of the temperature; annealing at 450° for 7 minutes: Ms = 47°, Mf = 40°, As = 47°, Af = 64°, MR19s = -2°, MR19f = -11° and for 550° for 7 minutes: Ms = 35°, Mf = 21°, As = 45°, Af = 58°, MR19s = 15°,
MR19f = 3° •
The thermogram of the sample after annealing at 600° for 20 minutes has a qualitatively new appearance. It shows that such heat treatment has led to the narrow temperature range and complete transformation occurs without the formation of R
martensite: As = 47°, Af = 64°, MR19s = 34°, M
R19f
23°
The functional properties of as drawn microwire was tested for loading and temperature cycling during a continuous experiment which have lasted for more them 200 000 seconds (see fig. 2 (a, b)). The microwire sample retained its mechanical stability up to 900 MPa. Pronounced reversible deformation 2-3% was observed for the stress up to 675 MPa.
Fig. 2. Long-term thermomechanical testing of the №49.9Ti5o.i microwire for elastocaloric application: (a) the temperature dependence of the deformation of microwire under the external stress from 25 to 675 MPa; (b) the time dependence of the applied external stress, strain and temperature during long-term thermomechanical testing of the microwire
Conclusion
We can conclude, that microwires of Ti-Ni shape memory alloy are very stable and can survive long time during continuous periodic stresses, retaining not only the mechanical stability, but also the martensitic transition and the consequent ECE. Present day request to highly reliable solid-state materials with ECE, which is encouraged by the idea to a practical implementation of the heat pumps and refrigerators with the efficiency close to the ideal Carnot cycle may find a solution through the creation of the new class of the nanostructural materials. The promising candidate are microwires with an optimal thermal treatment combining the high strength and reliability with a stable martensitic transition and functional properties as ECE and SME. Further technological works should open the way to the practical design of the next generation heat pumps and refrigerators.
References
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Article received 30.05.2022.
Corrections received 20.08.2022.
Челябинский физико-математический журнал. 2022. Т. 7, вып. 3. С. 384-389.
DOI: 10.47475/2500-0101-2022-17312
ТЕРМОМЕХАНИЧЕСКИЕ СВОЙСТВА И ВЛИЯНИЕ ТЕРМИЧЕСКОЙ ОБРАБОТКИ НА ФАЗОВОЕ ПРЕВРАЩЕНИЕ ПОЛУФАБРИКАТА МИКРОПРОВОЛОКИ ИЗ СПЛАВА Ni49.9Ti5a1 С ЭФФЕКТОМ ПАМЯТИ ФОРМЫ ДЛЯ ЭЛАСТОКАЛОРИЧЕСКИХ ПРИМЕНЕНИЙ
Д. Д. Кузнецов1'0,, Г. А. Шандрюк2'Ь, В. С. Калашников1'0, В. В. Коледов1'd, В. Г. Шавров1'e, В. А. Андреев3'4'1, А. В. Несоленов1'9, М. С. Быбик1'к
1 Институт радиотехники и электроники им. В. А. Котельникова РАН, Москва, Россия 2Институт нефтехимического синтеза им. А. В. Топчиева РАН, Москва, Россия 3ООО «Промышленный центр МАТЭК-СПФ», Москва, Россия 4Институт металлургии и материаловедения им. А. А. Байкова, Москва, Россия [email protected], Ь[email protected], [email protected], [email protected], [email protected], f [email protected], [email protected], [email protected]
В последнее время микропроволоки с памятью формы привлекли внимание как перспективный твердотельный функциональный материал для эластокалорических тепловых насосов и холодильников. В этой работе мы изучаем мартенситный переход в микропроводах NiTi в зависимости от степени отжига. Оптимальное сочетание аморфной и нанокристаллической фаз в структуре микропроводов с памятью формы обеспечивает максимальную прочность и надёжность в сочетании с выраженными эластокалорическими свойствами, что имеет решающее значение для длительного применения эластокалорических тепловых насосов. Микропроволока толщиной 100 мкм была подвергнута длительным испытаниям и продемонстрировала обратимую деформацию на 2-3 % при нагрузке до 675 МПа. Проволока сохраняла свою механическую стабильность до 900 МПа.
Ключевые слова: фазовое превращение, микропроволока, дифференциальная сканирующая калориметрия, термомеханический анализ, эффект памяти формы, сплав NiTi, эластока-лорический эффект.
Поступила в редакцию 30.05.2022. После переработки 20.08.2022.
Сведения об авторах Кузнецов Дмитрий Дмитриевич, младший научный сотрудник лаборатории магнитных явлений в микроэлектронике, Институт радиотехники и электроники им. В. А. Котельникова РАН, Москва, Россия; e-mail: [email protected]. Ш^андрюк Георгий Александрович, старший научный сотрудник лаборатории № 21 «Модификации полимеров» им. Н.А.Платэ, Институт нефтехимического синтеза им. А. В. Топчиева РАН, Москва, Россия; e-mail: [email protected].
Калашников Владимир Сергеевич, младший научный сотрудник лаборатории магнитных явлений в микроэлектронике, Институт радиотехники и электроники им. В. А. Котельникова РАН, Москва, Россия; e-mail: [email protected].
Работа поддержана Российским научным фондом, грант 22-19-00783.
Коледов Виктор Викторович, доктор физико-математических наук, ведущий научный сотрудник лаборатории магнитных явлений в микроэлектронике, Институт радиотехники и электроники им. В. А. Котельникова РАН, Москва, Россия; e-mail: [email protected].
Ш^авров Владимир Григорьевич, доктор физико-математических наук, профессор, заведующий лабораторией магнитных явлений в микроэлектронике, Институт радиотехники и электроники им. В. А. Котельникова РАН, Москва, Россия; e-mail: [email protected].
Андреев Владимир Александрович, сотрудник компании ООО «Промышленный центр МАТЭК-СПФ»; Институт металлургии и материаловедения им. А. А. Байкова РАН, Москва, Россия; e-mail: [email protected].
Несоленов Антон Викторович, аспирант лаборатории магнитных явлений в микроэлектронике, Институт радиотехники и электроники им. В. А. Котельникова РАН, Москва, Россия; e-mail: [email protected]
Быбик Мария Сергеевна, инженер лаборатории магнитных явлений в микроэлектронике, Институт радиотехники и электроники им. В. А. Котельникова РАН, Москва, Россия; e-mail: [email protected].
