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Nanomaterials
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Nanostructural Processing Effects in Shape Memory Alloys
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Special Issue "Nanostructural Processing Effects in Shape Memory Alloys"

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanofabrication and Nanomanufacturing".

Deadline for manuscript submissions: 20 January 2024 | Viewed by 5807

Special Issue Editor

Prof. Dr. Leandru-Gheorghe Bujoreanu

E-Mail Website
Guest Editor
Faculty of Materials Science and Engineering, “Gheorghe Asachi” Technical University of Iasi, Blvd. Dimitrie Mangeron 71 A, Iasi, Romania
Interests: shape memory alloys; microstructure; thermal analysis; mechanical testing

Special Issue Information

Dear Colleagues,

Precipitation hardening is the oldest nanotechnology. Since its first description, the international scientific community became aware of the crucial role that matter arrangement at nanostructural scale plays in understanding particular material characteristics such as shape memory phenomena. Moreover, various nanostructuring techniques have since been developed which enable the tailoring of material properties. Thus, the role of coherent precipitates in matrix strengthening against permanent deformation has been intensely studied with the aim of enhancing reverse martensitic transformation in shape memory alloys (SMAs). On the other hand, severe plastic deformation has been increasingly used as a nanoprocessing technique to produce new SMAs with superior mechanical properties, while twin boundary management successfully caused marked increases of shape recovery strains. Additionally, although larger oligocrystalline grains have recently been identified as desired structures for facilitating larger superelastic strains, no superelasticity would be obtained without matrix hardening by coherent nanoprecipitation.

This Special Issue aims to group, into a single volume, original articles concerning topics related but not limited to the role of nanostructuring, coherent nanoprecipitation, grain and twin boundary engineering, and so on, in the properties of shape memory alloys. We also welcome the submission of articles discussing the requirement to obtain large rather than small crystalline grains in order to enhance shape memory properties.

Prof. Dr. Leandru-Gheorghe Bujoreanu
Guest Editor

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. Nanomaterials is an international peer-reviewed open access semimonthly 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 2900 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
  • martensitic transformation
  • nanoprecipitates
  • thermomechanical processing
  • nanostructuring
  • chemical composition
  • coherence
  • back stress
  • thermoelasticity
  • superelasticity

Published Papers (6 papers)

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Research

14 pages, 9755 KiB  
Article
Thermal Stability of Cu-Al-Ni Shape Memory Alloy Thin Films Obtained by Nanometer Multilayer Deposition
by
Jose F. Gómez-Cortés
,
María L. Nó
,
Andrey Chuvilin
,
Isabel Ruiz-Larrea
and
Jose M. San Juan
Nanomaterials 2023, 13(18), 2605; https://doi.org/10.3390/nano13182605 - 21 Sep 2023
Viewed by 540
Abstract
Cu-Al-Ni is a high-temperature shape memory alloy (HTSMA) with exceptional thermomechanical properties, making it an ideal active material for engineering new technologies able to operate at temperatures up to 200 °C. Recent studies revealed that these alloys exhibit a robust superelastic behavior at [...] Read more.
Cu-Al-Ni is a high-temperature shape memory alloy (HTSMA) with exceptional thermomechanical properties, making it an ideal active material for engineering new technologies able to operate at temperatures up to 200 °C. Recent studies revealed that these alloys exhibit a robust superelastic behavior at the nanometer scale, making them excellent candidates for developing a new generation of micro-/nano-electromechanical systems (MEMS/NEMS). The very large-scale integration (VLSI) technologies used in microelectronics are based on thin films. In the present work, 1 μm thickness thin films of 84.1Cu-12.4 Al-3.5Ni (wt.%) were obtained by solid-state diffusion from a multilayer system deposited on SiNx (200 nm)/Si substrates by e-beam evaporation. With the aim of evaluating the thermal stability of such HTSMA thin films, heating experiments were performed in situ inside the transmission electron microscope to identify the temperature at which the material was decomposed by precipitation. Their microstructure, compositional analysis, and phase identification were characterized by scanning and transmission electron microscopy equipped with energy dispersive X-ray spectrometers. The nucleation and growth of two stable phases, Cu-Al-rich alpha phase and Ni-Al-rich intermetallic, were identified during in situ heating TEM experiments between 280 and 450 °C. These findings show that the used production method produces an HTSMA with high thermal stability and paves the road for developing high-temperature MEMS/NEMS using shape memory and superelastic technologies. Full article
(This article belongs to the Special Issue Nanostructural Processing Effects in Shape Memory Alloys)
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16 pages, 7339 KiB  
Article
Heat Treatment and Dynamic Mechanical Analysis Strain Sweep Effects on the Phase Structure and Morphology of an Fe-28Mn-6Si-5Cr Shape Memory Alloy
by
Mihai Popa
,
Florin Popa
,
Bogdan Pricop
,
Nicanor Cimpoeșu
,
Nicoleta-Monica Lohan
,
Gabriel Kicsi
,
Bogdan Istrate
and
Leandru-Gheorghe Bujoreanu
Nanomaterials 2023, 13(7), 1250; https://doi.org/10.3390/nano13071250 - 01 Apr 2023
Viewed by 761
Abstract
Fe-Mn-Si-based shape memory alloys (SMAs) have been extensively investigated since 1982 for various useful properties that enhance the development of different applications such as anti-seismic dampers for very tall buildings, pipe joints, or rail fasteners. In particular, the Fe-28Mn-6Si-5Cr (mass. %) alloy has [...] Read more.
Fe-Mn-Si-based shape memory alloys (SMAs) have been extensively investigated since 1982 for various useful properties that enhance the development of different applications such as anti-seismic dampers for very tall buildings, pipe joints, or rail fasteners. In particular, the Fe-28Mn-6Si-5Cr (mass. %) alloy has been mainly used in vibration mitigation or self-adjustable axial displacement applications. Dynamic mechanical analysis (DMA), performed by strain sweeps (SS), enables the monitoring of the evolution of storage modulus and internal friction variations with increasing strain amplitudes at different constant frequencies and temperatures. Thus, applying dynamic bending with various frequencies and amplitudes that actually represents an isothermal mechanical treatment. In the present paper, an Fe-28Mn-6 Si-5Cr (mass. %) SMA was cast by ingot metallurgy, hot-rolled, and water quenched in order to obtain thermally induced martensite and avoid the occurrence of cooling cracks. The influence of the holding time, between 2 and 10 h, at 1050 °C and the effects of DMA-SS performed at three different frequencies were analyzed by a differential scanning calorimetry, an X-ray diffraction, and a scanning electron and atomic force microscopy. The effects of the holding time and mechanical treatment on the structure and morphology of martensite plates were corroborated with the results of the thermal analysis. Full article
(This article belongs to the Special Issue Nanostructural Processing Effects in Shape Memory Alloys)
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18 pages, 6223 KiB  
Article
Actuating Bimorph Microstructures with Magnetron-Sputtered Ti-Ni-Cu Shape Memory Alloy Films
by
Vlad Bolocan
,
Dragos Valsan
,
Aurel Ercuta
and
Corneliu-Marius Craciunescu
Nanomaterials 2022, 12(23), 4207; https://doi.org/10.3390/nano12234207 - 26 Nov 2022
Cited by 1 | Viewed by 864
Abstract
The generation of microactuation using narrow thermal hysteresis Ti-Ni-Cu shape-memory alloy films deposited on non-metallic substrates as the active element is studied based on a model previously developed for Ni-Ti/Si bimorphs. To this end, the compositional range in which the B2 (monoclinic) → [...] Read more.
The generation of microactuation using narrow thermal hysteresis Ti-Ni-Cu shape-memory alloy films deposited on non-metallic substrates as the active element is studied based on a model previously developed for Ni-Ti/Si bimorphs. To this end, the compositional range in which the B2 (monoclinic) → B19 (orthorhombic) martensitic phase transformation occurs was considered, and films were deposited by magnetron sputtering on heated Si and Kapton substrates. Ultra-fine grains were observed for the 550 °C deposition temperature. The selected composition was close to Ti50Ni35Cu15, so the narrowing of the thermal hysteresis is not associated with a significant reduction in shape recovery capability. The microstructure and composition of the target materials and as-deposited films used in our experiments were characterized by X-ray diffraction and scanning electron microscopy, whereas the temperature dependence of the volume fraction of the martensite phase was derived using differential scanning calorimetry records for the target materials and from the temperature dependence of the electrical resistance data for the films. An original model was used to predict the actuation of cantilever-type bimorphs with Kapton and Si substrates. Full article
(This article belongs to the Special Issue Nanostructural Processing Effects in Shape Memory Alloys)
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13 pages, 3468 KiB  
Article
Processing Effects on the Martensitic Transformation and Related Properties in the Ni55Fe18Nd2Ga25 Ferromagnetic Shape Memory Alloy
by
Mihaela Sofronie
,
Bogdan Popescu
,
Monica Enculescu
,
Mugurel Tolea
and
Felicia Tolea
Nanomaterials 2022, 12(20), 3667; https://doi.org/10.3390/nano12203667 - 19 Oct 2022
Cited by 1 | Viewed by 887
Abstract
The influence of processing on the martensitic transformation and related magnetic properties of the Ni55Fe18Nd2Ga25 ferromagnetic shape memory alloy, as bulk and ribbons prepared by the melt spinning method and subjected to different thermal treatments, is [...] Read more.
The influence of processing on the martensitic transformation and related magnetic properties of the Ni55Fe18Nd2Ga25 ferromagnetic shape memory alloy, as bulk and ribbons prepared by the melt spinning method and subjected to different thermal treatments, is investigated. Structural, calorimetric, and magnetic characterizations are performed. Thermal treatment at 1173 K induces a decrease in both the Curie and the martensitic transformation temperatures, while a treatment at 673 K produces the structural ordering of the ribbons, hence an increase in TC. A maximum value of the magnetic entropy variation of −5.41 J/kgK was recorded at 310 K for the as quenched ribbons. The evaluation of the magnetoresistive effect shows a remarkable value of −13.5% at 275 K on the bulk sample, which is much higher than in the ribbons. Full article
(This article belongs to the Special Issue Nanostructural Processing Effects in Shape Memory Alloys)
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11 pages, 4142 KiB  
Article
On the Possible Cause of Sudden Storage Modulus Increase during the Heating of PM FeMnSiCrNi SMAs
by
Bogdan Pricop
,
Marian Grigoraș
,
Firuța Borza
,
Burak Özkal
and
Leandru-Gheorghe Bujoreanu
Nanomaterials 2022, 12(14), 2342; https://doi.org/10.3390/nano12142342 - 08 Jul 2022
Viewed by 783
Abstract
A sudden increase in storage modulus (ΔE′) was repeatedly recorded during the heating of powder metallurgy (PM) 66Fe-14Mn-6Si-9Cr-5Ni (mass. %) shape memory alloy specimens subjected to dynamic mechanical analysis (DMA), under constant applied strain amplitude and frequency. This instability, exceeding 12 [...] Read more.
A sudden increase in storage modulus (ΔE′) was repeatedly recorded during the heating of powder metallurgy (PM) 66Fe-14Mn-6Si-9Cr-5Ni (mass. %) shape memory alloy specimens subjected to dynamic mechanical analysis (DMA), under constant applied strain amplitude and frequency. This instability, exceeding 12 GPa, was associated with the reverse martensitic transformation of α′-body centered cubic (bcc) martensite to γ-face centered cubic (fcc) austenite, overlapped on a magnetic transition. This transition, observed by thermomagnetic measurements (T-MAG), was associated with the temporary spontaneous alignment of magnetic spins, which lasted until thermal movement became prevalent, during heating. ΔE′ was located around 250 °C on DMA thermograms and this temperature had the tendency to increase with the solution treatment temperature. On T-MAG diagrams, magnetization saturation temperature decreased from 405 °C to 52 °C with the increase in applied magnetic field from 20 Oe to 1 kOe and the increase in mechanically alloyed powder volume from 20% to 40%. On scanning electron micrographs, the presence of thermally induced α’-bcc martensite was emphasized together with the sub-bands that impede its stress-induced formation during DMA solicitation. On X-ray diffraction patterns of the solution-treated specimens, the presence of 22–82% α′-bcc martensite was identified, together with 8–55% retained austenite. It was assumed that the pre-existence of austenite together with α’-bcc martensite, in the microstructure of the solution-treated specimens, favored the magnetic transition, which destabilized the material and caused the storage modulus increase. The specimen comprising the largest amounts of austenite experienced the largest ΔE′. Full article
(This article belongs to the Special Issue Nanostructural Processing Effects in Shape Memory Alloys)
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19 pages, 3362 KiB  
Article
Structural-Functional Changes in a Ti50Ni45Cu5 Alloy Caused by Training Procedures Based on Free-Recovery and Work-Generating Shape Memory Effect
by
Mihai Popa
,
Nicoleta-Monica Lohan
,
Bogdan Pricop
,
Nicanor Cimpoeșu
,
Marieta Porcescu
,
Radu Ioachim Comăneci
,
Maria Cazacu
,
Firuța Borza
and
Leandru-Gheorghe Bujoreanu
Nanomaterials 2022, 12(12), 2088; https://doi.org/10.3390/nano12122088 - 17 Jun 2022
Cited by 3 | Viewed by 1385
Abstract
Active elements made of Ti50Ni45Cu5 shape memory alloy (SMA) were martensitic at room temperature (RT) after hot rolling with instant water quenching. These pristine specimens were subjected to two thermomechanical training procedures consisting of (i) free recovery shape [...] Read more.
Active elements made of Ti50Ni45Cu5 shape memory alloy (SMA) were martensitic at room temperature (RT) after hot rolling with instant water quenching. These pristine specimens were subjected to two thermomechanical training procedures consisting of (i) free recovery shape memory effect (FR-SME) and (ii) work generating shape memory effect (WG-SME) under constant stress as well as dynamic bending and RT static tensile testing (TENS). The structural-functional changes, caused by the two training procedures as well as TENS were investigated by various experimental techniques, including differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X-ray diffraction (XRD), and atomic force microscopy (AFM). Fragments cut from the active regions of trained specimens or from the elongated gauges of TENS specimens were analyzed by DSC, XRD, and AFM. The DSC thermograms revealed the shift in critical transformation temperatures and a diminution in specific absorbed enthalpy as an effect of training cycles. The DMA thermograms of pristine specimens emphasized a change of storage modulus variation during heating after the application of isothermal dynamical bending at RT. The XRD patterns and AMF micrographs disclosed the different evolution of martensite plate variants as an effect of FR-SME cycling and of being elongated upon convex surfaces or compressed upon concave surfaces of bent specimens. For illustrative reasons, the evolution of unit cell parameters of B19′ martensite, as a function of the number of cycles of FR-SME training, upon concave regions was discussed. AFM micrographs emphasized wider and shallower martensite plates on the convex region as compared to the concave one. With increasing the number of FR-SME training cycles, plates’ heights decreased by 84–87%. The results suggest that FR-SME training caused marked decreases in martensite plate dimensions, which engendered a decrease in specific absorbed enthalpy during martensite reversion. Full article
(This article belongs to the Special Issue Nanostructural Processing Effects in Shape Memory Alloys)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Analysis of the degradation behavior of FeMnSi-Cu SMAs from macro to nano-scale
Authors: Ana-Maria Roman1; Ramona Cimpoesu1; Iban Amenabar2; Bogdan Pricop1; Monica Lohan1; Mihai Marius Cazacu3; Leandru Gheorghe Bujoreanu1; Iuliana Cocean4; Catalin Panaghie1; Georgeta Zegan5; Nicanor Cimpoeșu1
Affiliation: 1Faculty of Materials Science and Engineering, “Gheorghe Asachi” Technical University of Iași, Blvd. Dimitrie Mangeron 71A, 700050 Iași, Romania. 2CIC NanoGUNE BRTA, Donostia San Sebastian 20018, Spain 3Physics department, “Gheorghe Asachi” Technical University of Iași, Blvd. Dimitrie Mangeron 71A, 700050 Iași, Romania. 4Alexandru Ioan Cuza Univ, Fac Phys, 11 Carol I Bld, Iasi 700506, Romania 5Grigore T Popa Univ Med & Pharm, Fac Dent Med, Iasi 700115, Romania
Abstract: A new functional bio-material based on Fe-30Mn-5Si-xCu (x=1, 1.5 and 2 wt%) was obtained through the levitation induction melting process and evaluated as a biodegradable material. Iron-based biodegradable materials are considered a proper solution for medium-period implantation materials that can degrade in the body after a specific time for a body organ to heal. Alloying with manganese and low percentages of silicon can functionalize the alloy to exhibit a shape memory effect (SME) and copper to modify the transformation temperature domain and improve the antiseptic effect of the alloy. This alloy belongs to the class of biodegradable materials and can be functionalized considering the SME for specific medical applications. For this study, the degradation characteristics were assessed in vitro, by immersion tests into simulated body fluid (SBF) solution at 37±1 °C, by means of mass loss, monitoring the pH variation in the solution, open circuit potential, linear and cyclic potentiometry (OCP; LP and CP), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourrier-transform infrared spedctorscopy (FTIR) and nano-FTIR. The as-cast materials were thermo-mechanically worked through hot-rolling to obtain laminated plates. The thermal characteristics of the smart material were determined through differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Atomic force microscopy (AFM) will be used to highlight nano and microstructural changes during hot-rolling process and DMA solicitations. The type of corrosion was generalized and for the first 3-5 days, a mass increase was observed on the basis of the compounds formed at the metallic material- electrolyte solution interface. The compounds formed on the surface were identified as mainly oxides that passed into the electrolyte solution. A degradation rate was calculated based on mass loss, surface area of the samples and immersion time. Mechanical dynamic behavior and dimensions of a lamella sample were evaluated after 30 days of immersion. Nano-compounds presence on the surface through atmospheric corrosion and after immersion in SBF were observed and evaluated with the Neaspec system using the nano-FTIR technique.

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