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Special Issue "Fundamental Science and Applications of Highly Functional Alloys"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: 28 March 2019

Special Issue Editor

Guest Editor
Prof. Dr. Takuo Sakon

Department of Mechanical and Systems Engineering, Faculty of Science and Technology, Ryukoku University, Seta-Ooemachi Yokotani 1-5, Otsu, 520-2194 Shiga, Japan
Website | E-Mail
Interests: magnetism; shape memory alloys; magnetic actuators

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 papers will be 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 1800 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 (1 paper)

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Research

Open AccessArticle Forced Magnetostrictions and Magnetizations of Ni2+xMnGa1−x at Its Curie Temperature
Materials 2018, 11(11), 2115; https://doi.org/10.3390/ma11112115
Received: 16 September 2018 / Revised: 21 October 2018 / Accepted: 25 October 2018 / Published: 28 October 2018
PDF Full-text (2156 KB) | HTML Full-text | XML Full-text
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.
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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 HMδ 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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