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Fundamental Science and Applications of Highly Functional Alloys
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Fundamental Science and Applications of Highly Functional Alloys

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Advanced Materials Characterization".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 9819

Special Issue Editor

Prof. Dr. Takuo Sakon

E-Mail Website
Guest Editor
Department of Mechanical and Systems Engineering, Faculty of Science and Technology, Ryukoku University, Seta-Ooemachi Yokotani 1-5, Otsu, Shiga 520-2194, Japan
Interests: magnetism; shape memory alloys; magnetic actuators
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In the recent industry, high functional alloy materials with plural functionality are demanded. These characteristics are toughness, high ductility, super-elasticity, low thermal expansion, high durability, etc. As for materials that are used for actuators, oscillators, or transducers, further magnetic mechanical functionality is pursued in magnetic shape memory alloys. Articles about the recent progress of superalloys, invar alloys, shape memory alloy and other alloys that have high functionality are collected in this Special Issue. It is important to investigate a physical origin to expose the mechanisms of these characteristics, scientifically, to give further functionality to these materials. With applied technology, the articles of basic science using experimental theoretical considerations are raised.

Superally is a basically face-centered cubic austenitic alloy (fcc austenite). It possesses the characteristics of high mechanical strength, good surface stability, resistance to corrosion or oxidation, and excellent resistance to thermal creep deformation.

Invar alloy is an alloy notable for its uniquely low coefficient of thermal expansion. It is famous as FeNi36 (64FeNi), Inovco (Fe–33Ni–4.5Co), and FeNiCo alloys. The thermal expansion coefficient is less than 1 ppm/K. The coefficient is much smaller than that of normal metal, which is around 10 ppm/K. It is used on the part of the intense temperature change. The applications of Invar alloys are precision instruments such as clocks, seismic creep gauges, valves in engines of motorcars, antimagnetic watches, and large molds.

Shape memory alloys (SMA) have attracted a great deal of attention due to their attractive properties for applications, as well as their basic science of deformation and transformation in terms of structural and magnetic behaviors. A number of applications of shape memory alloys were achieved after Ti–Ni alloy was discovered in 1963 and developed extensively. SMA possesses super elasticity, 10–30 times superior than that of ordinary metal. Recently, ferromagnetic shape memory alloys (FSMA), Ni-Mn-Ga Ni-Mn-In, Ni-Mn-Sn and Ni-Mn-Sb Heusler alloy systems have been studied as candidates for highly-functional materials. These alloys are promising as SMA with a magnetic field-induced shape memory effect and as magnetocaloric effects.

This issue will be comprised articles reporting new and progressive research results, as well as reviews of particular classes of fundamental science of the alloys and their applied applications.

Prof. Dr. Takuo Sakon
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. Materials 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 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

  • Superalloy
  • Invar alloy
  • Shape memory alloy
  • Super-elasticity
  • Dynamic functionality
  • Magnetic functionality
  • Thermal functionality
  • Half metallic alloy
  • Strength
  • Ductility
  • Metal fatigue

Published Papers (3 papers)

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Research

13 pages, 1389 KiB  
Article
Magnetoresistance and Thermal Transformation Arrest in Pd2Mn1.4Sn0.6 Heusler Alloys
by Xiao Xu, Hironari Okada, Yusuke Chieda, Naoki Aizawa, Daiki Takase, Hironori Nishihara, Takuo Sakon, Kwangsik Han, Tatsuya Ito, Yoshiya Adachi, Takumi Kihara, Ryosuke Kainuma and Takeshi Kanomata
Materials 2019, 12(14), 2308; https://doi.org/10.3390/ma12142308 - 19 Jul 2019
Cited by 5 | Viewed by 2825
Abstract
The magnetization, electric resistivity, and magnetoresistance properties of Pd 2 Mn 1 . 4 Sn 0 . 6 Heusler alloys were investigated. The Curie temperature of the parent phase, martensitic transformation temperatures, and magnetic field dependence of the martensitic transformation temperatures were determined. [...] Read more.
The magnetization, electric resistivity, and magnetoresistance properties of Pd 2 Mn 1 . 4 Sn 0 . 6 Heusler alloys were investigated. The Curie temperature of the parent phase, martensitic transformation temperatures, and magnetic field dependence of the martensitic transformation temperatures were determined. The magnetoresistance was investigated from 10 to 290 K, revealing both intrinsic and extrinsic magnetoresistance properties for this alloy. A maximum of about − 3 . 5 % of intrinsic magnetoresistance under 90 kOe and of about − 30 % of extrinsic magnetoresistance under 180 kOe were obtained. Moreover, the thermal transformation arrest phenomenon was confirmed in the Pd 2 Mn 1 . 4 Sn 0 . 6 alloy, and an abnormal heating-induced martensitic transformation (HIMT) behavior was observed. Full article
(This article belongs to the Special Issue Fundamental Science and Applications of Highly Functional Alloys)
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12 pages, 1576 KiB  
Article
Investigation of the Itinerant Electron Ferromagnetism of Ni2+xMnGa1−x and Co2VGa Heusler Alloys
by Takuo Sakon, Yuhi Hayashi, Akihito Fukuya, Dexin Li, Fuminori Honda, Rie Y. Umetsu, Xiao Xu, Gendo Oomi, Takeshi Kanomata and Tetsujiro Eto
Materials 2019, 12(4), 575; https://doi.org/10.3390/ma12040575 - 14 Feb 2019
Cited by 8 | Viewed by 3431
Abstract
Experimental investigations into the field dependence of magnetization and temperature dependences of magnetic susceptibility in Ni2+xMnGa1−x (x = 0.00, 0.02, 0.04) and Co2VGa Heusler alloy ferromagnets were performed following the spin fluctuation theory of itinerant [...] Read more.
Experimental investigations into the field dependence of magnetization and temperature dependences of magnetic susceptibility in Ni2+xMnGa1−x (x = 0.00, 0.02, 0.04) and Co2VGa Heusler alloy ferromagnets were performed following the spin fluctuation theory of itinerant ferromagnetism, called as “Takahashi theory”. We investigated the magnetic field dependence of magnetization at the Curie temperature TC, which is the critical temperature of the ferromagnetic–paramagnetic transition, and also at T = 5 K, which concerns the ground state of the ferromagnetic state. The field dependence of the magnetization was analyzed by means of the H vs. M5 dependence, and the field dependence of the ground state at 5 K was investigated by means of an Arrott plot (H/M vs. M2) according to the Takahashi theory. As for Ni2+xMnGa1−x, the spin fluctuation parameter in k-space (momentum space, TA) and that in energy space (T0) obtained at TC and 5 K were almost the same. On the contrary, as for Co2VGa, the H vs. M5 dependence was not shown at TC. We obtained TA and T0 by means of an Arrott plot at 5 K. We created a generalized Rhodes–Wohlfarth plot of peff/pS versus TC/T0 for the other ferromagnets. The plot indicated that the relationship between peff/pS and T0/TC followed Takahashi’s theory. We also discussed the spontaneous magnetic moment at the ground state, pS, which was obtained by an Arrott plot at 5 K and the high temperature magnetic moment, pC, at the paramagnetic phase. As for the localized ferromagnet, the pC/pS was 1. As for weak ferromagnets, the pC/pS was larger than 1. In contrast, the pC/pS was smaller than 1 by many Heusler alloys. This is a unique property of Heusler ferromagnets. Half-metallic ferromagnets of Co2VGa and Co2MnGa were in accordance with the generalized Rhodes–Wohlfarth plot with a km around 1.4. The magnetic properties of the itinerant electron of these two alloys appeared in the majority bands and was confirmed by Takahashi’s theory. Full article
(This article belongs to the Special Issue Fundamental Science and Applications of Highly Functional Alloys)
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13 pages, 2156 KiB  
Article
Forced Magnetostrictions and Magnetizations of Ni2+xMnGa1−x at Its Curie Temperature
by Takuo Sakon, Yuhi Hayashi, Dexin Li, Fuminori Honda, Gendo Oomi, Yasuo Narumi, Masayuki Hagiwara, Takeshi Kanomata and Tetsujiro Eto
Materials 2018, 11(11), 2115; https://doi.org/10.3390/ma11112115 - 28 Oct 2018
Cited by 8 | Viewed by 2836
Abstract
Experimental investigations into the field dependence of magnetization and the relationship between magnetization and magnetostriction in Ni2+xMnGa1−x (x = 0.00, 0.02, 0.04) alloy ferromagnets were performed following the self-consistent renormalization (SCR) spin fluctuation theory of itinerant ferromagnetism. [...] Read more.
Experimental investigations into the field dependence of magnetization and the relationship between magnetization and magnetostriction in Ni2+xMnGa1−x (x = 0.00, 0.02, 0.04) alloy ferromagnets were performed following the self-consistent renormalization (SCR) spin fluctuation theory of itinerant ferromagnetism. In this study, we investigated the magnetization of and magnetostriction on Ni2+xMnGa1−x (x = 0.02, 0.04) to check whether these relations held when the ratio of Ni to Ga and, the valence electron concentration per atom, e/a were varied. When the ratio of Ni to Ga was varied, e/a increased with increasing x. The magnetization results for x = 0.02 (e/a = 7.535) and 0.04 (e/a = 7.570) suggest that the critical index δ of H ∝ Mδ is around 5.0 at the Curie temperature TC, which is the critical temperature of the ferromagnetic–paramagnetic transition. This result confirms Takahashi’s spin fluctuation theory and the experimental results of Ni2MnGa. The spontaneous magnetization pS slightly decreased with increasing x. For x = 0.00, the spin fluctuation parameter in k-space (momentum space; TA) and that in energy space (T0) were obtained. The relationship between peff/pS and TC/T0 can also be explained by Takahashi’s theory, where peff indicates the effective magnetic moments. We created a generalized Rhodes-Wohlfarth plot of peff/pS versus TC/T0 for other ferromagnets. The plot indicates that the relationship between peff/pS and T0/TC follows Takahashi’s theory. We also measured the magnetostriction for Ni2+xMnGa1−x (x = 0.02, 0.04). As a result, at TC, the plot of the magnetostriction (ΔL/L) versus M4 shows proportionality and crosses the origin. These magnetization and magnetostriction results were analyzed in terms of Takahashi’s SCR spin fluctuation theory. We investigated the magnetostriction at the premartensite phase, which is the precursor state to the martensitic transition. In Ni2MnGa system alloys, the maximum value of magnetostriction is almost proportional to the e/a. Full article
(This article belongs to the Special Issue Fundamental Science and Applications of Highly Functional Alloys)
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