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Metals
Special Issues
Progress in and Prospects of Shape Memory Alloys
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Progress in and Prospects of Shape Memory Alloys

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metallic Functional Materials".

Deadline for manuscript submissions: closed (31 October 2023) | Viewed by 3892

Special Issue Editors

Dr. Elena P. Ryklina

E-Mail Website
Guest Editor
Metal Forming Department, National University of Science & Technology (MISIS), Moscow, Russia
Interests: shape memory alloys; titanium nickelide; thermomechanical treatment (TMT); severe plastic deformation (SPD); ageing; microstructure; martensitic transformations; structural heredity; mechanical and functional characteristics and their reproducibility; medical and technical applications
Special Issues, Collections and Topics in MDPI journals
Dr. Kristina Polyakova

E-Mail Website
Guest Editor
Metal Forming Department, National University of Science & Technology (MISIS), Moscow, Russia
Interests: shape memory alloys; titanium nickelide; thermomechanical treatment (TMT); structure; ageing; phase transformations; mechanical and functional characteristics; medical applications

Special Issue Information

Dear Colleagues,

Among the wide variety of functional materials, shape memory alloys remain mostly attractive for use due to their unique shape recovery characteristics and mechanical properties. The scope of their application is extremely wide and ranges from intelligent devices for space technologies to medical implants.

The content of this Special Issue covers the host of improvements made in recent years concerning the main stages of SMAs development: discussions are welcome on topics from manufacturing and structural studies to designing and applying intelligent devices with desired sets of functional properties.

The specific interest of this Issue covers innovative characterization, diagnostics, testing approaches and investigation of novel phenomena in SMAs, including the structural and textural heredity of SMAs and their role in control of martensitic transformation as well as functional and mechanical characteristic, non-typical Elinvar effect, critical grain size for stress-induced martensitic transformation etc.

Besides this, we would like to draw the attention of scholars to the problems of reproducibility. This issue remains very prevalent owing to the providing of the final set of SMAs properties is determined by a great deal of various factors: strain–temperature training modes including tension, compression, bending, torsion; form and scale factors, surface state etc.

Academics are invited to submit both reviews and articles on any topic relevant to this Special Issue.

Dr. Elena P. Ryklina
Dr. Kristina Polyakova
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • shape memory alloys
  • microstructure
  • martensitic transformations
  • mechanical and functional behavior
  • structural and textural heredity
  • manufacturing methods
  • heat and thermomechanical treatment
  • external action
  • surface treatment
  • reproducibility
  • modeling
  • applications

Published Papers (4 papers)

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Research

12 pages, 3906 KiB  
Article
Effects of Severe Plastic Deformation and Subsequent Annealing on Microstructures of a Ni50.6Ti49.4 Shape Memory Alloy
by Jintao Zhang, Shibo Wang, Peng Hu, Yu Zhang, Hua Ding and Yi Huang
Metals 2024, 14(2), 184; https://doi.org/10.3390/met14020184 - 2 Feb 2024
Viewed by 930
Abstract
High-pressure torsion (HPT) was applied to the Ni50.6Ti49.4 (at. %) alloy ingot up to 1/4, 2, 16, 32 and 48 turns under a pressure of 6.0 GPa. The samples were examined by X-ray diffraction (XRD), transmission electron microscope (TEM) and microhardness measurement. The [...] Read more.
High-pressure torsion (HPT) was applied to the Ni50.6Ti49.4 (at. %) alloy ingot up to 1/4, 2, 16, 32 and 48 turns under a pressure of 6.0 GPa. The samples were examined by X-ray diffraction (XRD), transmission electron microscope (TEM) and microhardness measurement. The results indicate that martensitic transformation and formation of amorphous phase occurred during the HPT process. As the HPT turns increased, more amorphous phase formed. The fraction of amorphization was analyzed based on the X-ray results. The microhardness increased with the HPT turns, which may be related to strain-induced martensite transformation, formation of the amorphous phase, increased dislocation densities and grain refinement. Differential scanning calorimetry (DSC) test revealed that shape memory alloys can be produced by HPT and post-HPT annealing from a NiTi ingot. Full article
(This article belongs to the Special Issue Progress in and Prospects of Shape Memory Alloys)
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17 pages, 51448 KiB  
Article
Effect of Isochronous Annealings on the Microstructure and Mechanical Properties of the Ti49.8Ni50.2 (at.%) Alloy after abc Pressing at 573 K
by Aleksandr Lotkov, Victor Grishkov, Roman Laptev, Dorzhima Zhapova, Natalia Girsova and Angelina Gusarenko
Metals 2023, 13(10), 1632; https://doi.org/10.3390/met13101632 - 22 Sep 2023
Viewed by 833
Abstract
The regularities and features of the evolution of the grain–subgrain structure, phase composition and mechanical properties in Ti49.8Ni50.2 (at.%), depending on the temperature of isochronous annealings at 573–973 K are herein studied. The state of the Ti49.8Ni50.2 [...] Read more.
The regularities and features of the evolution of the grain–subgrain structure, phase composition and mechanical properties in Ti49.8Ni50.2 (at.%), depending on the temperature of isochronous annealings at 573–973 K are herein studied. The state of the Ti49.8Ni50.2 (at.%) alloy samples after abc pressing at T = 573 K with the given true strain e = 9.55 was taken as the initial state. It is shown that the grain–subgrain structure of the samples after annealing for 1 h in the temperature range of 573–673 K changes slightly. In samples annealed at 673 K, regions with the microband structure similar to the microstructure of a fast-frozen turbulent liquid flow were found. It has been established that during annealing at 773 K the beginning of an active recrystallization process is realized; the size of grains does not exceed the submicrocrystalline scale (~200 nm). At 873 K, the recrystallization process occurs in the entire volume of the samples; the grains with an average size of 2 ± 0.5 µm are almost equiaxed. The microstructure of the samples after annealing at 973 K (with average grain sizes of 5 ± 0.5 µm) is qualitatively similar to the microstructure of the samples after annealing at 873 K. It was found that the phase composition of the samples as a result of isochronous annealing at 573–973 K changes from R and B19’ immediately after abc pressing to a three-phase state: B2, R and B19’ phases. It is shown that the highest values of yield stress σy, ultimate tensile strength σUTS (1043 MPa and 1232 MPa, correspondingly) and low ductility (the deformation to fracture εf = 48%) are observed in the initial samples. Increasing the temperature of post-deformation annealing and, correspondingly, the development of recrystallization, led to a decrease in σy, σUTS and an increase in εf to the values of these characteristics in the coarse-grained samples (σy = 400 MPa, σUTS = 920 MPa and εf = 90%). Full article
(This article belongs to the Special Issue Progress in and Prospects of Shape Memory Alloys)
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14 pages, 5160 KiB  
Article
On Structural Sensitivity of Young’s Modulus of Ni-Rich Ti-Ni Alloy
by Elena Ryklina, Semen Murygin, Victor Komarov, Kristina Polyakova, Natalia Resnina and Vladimir Andreev
Metals 2023, 13(8), 1428; https://doi.org/10.3390/met13081428 - 9 Aug 2023
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Abstract
When developing bone implants, Young’s modulus is one of the primary characteristics of the material that should be considered. This study focuses on regulating the modulus of Ti-50.8 at.% Ni alloy by varying the grain/subgrain size as well as the initial structure using [...] Read more.
When developing bone implants, Young’s modulus is one of the primary characteristics of the material that should be considered. This study focuses on regulating the modulus of Ti-50.8 at.% Ni alloy by varying the grain/subgrain size as well as the initial structure using subsequent aging at 430 °C for 10 h. After post-deformation annealing (PDA), the temperature dependence of Young’s modulus exhibits a pronounced V-shaped character with a minimum at the onset temperature of the forward martensitic transformation, Ms, regardless of the structure. The grain/subgrain size of B2-austenite strongly affects the modulus magnitude. This effect is ambiguous for a material with a grain size range of 0.13–3 µm and depends on the test temperature. The effect of aging on the modulus reduction depends on the initial structure; it is most pronounced in an alloy with a relatively coarse grain size of 9 µm and brings a decrease of 3.8 times at a temperature of 37 °C. Aging of the initially recrystallized Ni-rich NiTi alloy makes it possible to obtain a вone-like elastic modulus of E = 12–13 GPa at an operating temperature of 37 °C. An ultrafine-grained substructure exhibits the same Young’s modulus values in the low temperature range from −100 to 25 °C. Full article
(This article belongs to the Special Issue Progress in and Prospects of Shape Memory Alloys)
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13 pages, 16027 KiB  
Article
Influence of Current Density upon Hydrogenation on the Shape Memory Effect of Binary TiNi Alloy Single Crystals
by Irina V. Kireeva, Yuriy I. Chumlyakov, Liya P. Yakovleva and Anna V. Vyrodova
Metals 2023, 13(8), 1412; https://doi.org/10.3390/met13081412 - 7 Aug 2023
Viewed by 812
Abstract
Some results concerning the hydrogen effect at electrolytic saturation at a current density of j = 1500 and 3500 A/m2 for 3 h at room temperature on the temperature dependence of the yield stress σ0.1(T) and the shape [...] Read more.
Some results concerning the hydrogen effect at electrolytic saturation at a current density of j = 1500 and 3500 A/m2 for 3 h at room temperature on the temperature dependence of the yield stress σ0.1(T) and the shape memory effect (SME) under tension of the [011]-oriented Ti-50.55%Ni (at.%) alloy single crystals are presented. It was shown that hydrogen is in a solid solution and forms particles of titanium hydride TiH2 after hydrogenation at j = 1500 and 3500 A/m2, respectively. Both hydrogen in the solid solution and TiH2 particles led to a decrease in the Ms temperature of the onset of the forward martensitic transformation (MT) upon cooling and the Md temperature (Md is the temperature at which the stresses for the onset of the stress-induced MT are equal to the stresses for the onset of plastic flow of the high-temperature B2 phase), and increased the yield stress σ0.1 of the B2 phase at the Md temperature compared to hydrogen-free crystals. It was found that the SME under stress depends on the tensile stress level and current density. The maximum SME εSME = 10 ± 0.2% at σex = 200 MPa and εSME = 10.5 ± 0.2% at σex = 300 MPa was observed in the hydrogen-free crystals and after hydrogenation at j = 1500 A/m2, respectively, which exceeded the theoretical value of lattice deformation ε0 = 8.95% for the B2-B19′ MT in [011] orientation under tension. At j = 1500 A/m2, the physical reason for the excess of the SME of the theoretical ε0 value was due to the increase in the plasticity of B19′ martensite upon hydrogenation. At j = 3500 A/m2, εSME = 8.0 ± 0.2%, and it was less than ε0 = 8.95% for B2-B19′ MT in [011] orientation under tension. The decrease in SME after hydrogenation at j = 3500 A/m2 was associated with the interaction of two types of B19′-martensite: oriented under stress and non-oriented, formed near TiH2 particles. It was shown that the redistribution of hydrogen in the bulk of the crystals during long-term holding for 168 h at 263 K after hydrogenation at j = 1500 A/m2 increases the SME relative to crystals without long-term holding: 3.5 times at 50 MPa and 1.8 times at 100–150 MPa. After long-term holding, εSME = 9.5 ± 0.2% at 150 MPa, which exceeds the theoretical value ε0 = 8.95% for B2-B19′ MT in [011] orientation under tension. Full article
(This article belongs to the Special Issue Progress in and Prospects of Shape Memory Alloys)
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