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Intermetallic Alloys: Fabrication, Properties and Applications 2017

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

Deadline for manuscript submissions: closed (30 May 2018) | Viewed by 32112

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Prof. Dr. Louisa Meshi

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Department of Materials Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105 POB 653, Israel
Interests: intermetallics; high-entropy alloys; light-weight alloys; electron crystallography; characterization; structure solution; X-ray diffraction; transmission electron microscopy
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Dear Colleagues,

Our world advances rapidly. New materials are needed to face novel applications. In the past, new materials were found mostly by applying a "trial and error" approach. The need for generalization and a quicker path towards discoveries pushed governments all over the world to sponsor the so-called "Materials Genome Initiative", i.e., an initiative to identify potential materials with unique properties through systematization of knowledge and the combination of theory and experiment. Thus, new theories and rules are being developed in order to predict the functional materials of tomorrow. Most of the research points to intermetallics. The class of intermetallics possesses an excellent combination of high strength, low density and good corrosion resistance, especially at higher temperatures and in severe environments. Some of intermetallides also exhibit interesting electric–magnetic properties (such as shape memory, thermo-electricity, magnetic ordering, superconductivity, and many others). However, these materials have some drawbacks, such as combination of high strength and poor ductility and lack of industrialized manufacturing and processing technologies. Many specialists all over the world address these drawbacks. Examples of such efforts are iron aluminides and titanium aluminides, which are prominent lightweight, creep- and oxidation-resistant materials, used today in aircraft engines, raising efficiency and reducing weight and CO2 and NOx emissions. Another difficulty encountered in the research of intermetallics is characterization. Potential applications usually require intermetallides to be embedded in more ductile metallic matrices. In such cases, intermetallics appear as small precipitates in multiphase alloys. Characterization of the atomic structure of such nano-sized precipitates is a challenge in of itself. The current Special Issue, "Intermetallic Alloys: Fabrication, Properties and Applications" invites researchers working in all the listed topics to publish their work. Both theoretical and experimental research, review articles, and novel results are welcome.

Prof. Dr. Louisa Meshi
Guest Editor

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Keywords

Intermetallics
Alluminides
TEM
SEM
XRD
Characterization
Crystal structure
Microstructure
Sintering
Cast
Wrought
Mechanical properties
Magnetic properties
Manufacturing
DFT
Phase diagram
Metallurgy
Light-weight alloys
Refractory

Published Papers (6 papers)

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Research

33 pages, 14949 KiB

Open AccessArticle

Elasto-Plastic Mechanical Properties and Failure Mechanism of Innovative Ti-(SiC_f/Al₃Ti) Laminated Composites for Sphere-Plane Contact at the Early Stage of Penetration Process

by Jingchuan Liu, Lan Zhang, Fengchun Jiang, Mengqi Zhang, Liquan Wang and Feihong Yun

Materials 2018, 11(7), 1152; https://doi.org/10.3390/ma11071152 - 06 Jul 2018

Cited by 13 | Viewed by 4460

Abstract

A novel silicon carbide (SiC) continuous ceramic fiber-reinforced (CCFR) Ti/Al₃Ti Metal-Intermetallic-Laminate (MIL) composite was fabricated. A high-efficiency semi-analytical model was proposed based on the numerical equivalent inclusion method (NEIM) for analyzing the small-strain elasto-plastic contact in the early stage of the penetration process. The microstructure and interface features were characterized by the scanning electron microscopy (SEM). Quasi-static compression tests were performed to determine the contact response and validate the proposed model. A group of in-depth parametric studies were carried out to quantify the influence of the microstructure. The comparison between results under the sphere-plane and plane-plane contact load indicates that, under the first sphere-plane, the compressive strength and failure strain are both lower and the SiC reinforcement effect on strength is very clear while the effect on ductility is not clear. The maximum plastic strain concentration (MPSC) in the Al₃Ti layer is closest to the upper boundary of the central SiC fiber and then extends along the depth direction as the load increases, which are also the locations where cracks may initiate and extend. Moreover, the CCFR-MIL composite shows better mechanical properties when the center distance between adjacent SiC fibers is four times the fiber diameter and the volume fraction of Ti is 40%. Full article

(This article belongs to the Special Issue Intermetallic Alloys: Fabrication, Properties and Applications 2017)

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12 pages, 15148 KiB

Open AccessFeature PaperArticle

Improved Formability of Mg-AZ80 Alloy under a High Strain Rate in Expanding-Ring Experiments

by Shmuel Samuha, Eyal Kahana, Oren Sadot and Roni Z. Shneck

Materials 2018, 11(2), 329; https://doi.org/10.3390/ma11020329 - 24 Feb 2018

Cited by 7 | Viewed by 3873

Abstract

Magnesium alloys offer a favored alternative to steels and aluminum alloys due to their low density and relatively high specific strength. Their application potentials are, however, impeded by poor formability at room temperature. In the current work, improved formability for the commercial magnesium AZ80 alloy was attained through the application of the high-rate electro-magnetic forming (EMF) technique. With the EMF system, elongation of 0.2 was achieved while only 0.11 is obtained through quasistatic loading. Systematic microstructural and textural investigations prior, during and post deformation under high strain-rate experiments were carried out using electron back-scattered diffraction (EBSD) and other microscopic techniques. The analysis indicates that enhanced elongation is achieved as a result of the combination of deformation, comprising basal and non-basal slip systems, twinning and dynamic recrystallization. An adopted EMF-forming technique is tested which results in enhanced elongation without failure and a higher degree of dynamically annealed microstructure. Full article

(This article belongs to the Special Issue Intermetallic Alloys: Fabrication, Properties and Applications 2017)

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10 pages, 7920 KiB

Open AccessArticle

Radiation Resistance of the U(Al, Si)₃ Alloy: Ion-Induced Disordering

by Louisa Meshi, Gili Yaniv, Pavel Horak, Jiri Vacik, Natalia Mykytenko, Gennady Rafailov, Itzchak Dahan, David Fuks and Arik Kiv

Materials 2018, 11(2), 228; https://doi.org/10.3390/ma11020228 - 02 Feb 2018

Cited by 6 | Viewed by 3853

Abstract

During the exploitation of nuclear reactors, various U-Al based ternary intermetallides are formed in the fuel-cladding interaction layer. Structure and physical properties of these intermetallides determine the radiation resistance of cladding and, ultimately, the reliability and lifetime of the nuclear reactor. In current research, U(Al, Si)₃ composition was studied as a potential constituent of an interaction layer. Phase content of the alloy of an interest was ordered U(Al, Si)₃, structure of which was reported earlier, and pure Al (constituting less than 20 vol % of the alloy). This alloy was investigated prior and after the irradiation performed by Ar ions at 30 keV. The irradiation was performed on the transmission electron microscopy (TEM, JEOL, Japan) samples, characterized before and after the irradiation process. Irradiation induced disorder accompanied by stress relief. Furthermore, it was found that there is a dose threshold for disordering of the crystalline matter in the irradiated region. Irradiation at doses equal or higher than this threshold resulted in almost solely disordered phase. Using the program “Stopping and Range of Ions in Matter” (SRIM), the parameters of penetration of Ar ions into the irradiated samples were estimated. Based on these estimations, the dose threshold for ion-induced disordering of the studied material was assessed. Full article

(This article belongs to the Special Issue Intermetallic Alloys: Fabrication, Properties and Applications 2017)

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9 pages, 4873 KiB

Open AccessArticle

Characterization of an Additive Manufactured TiAl Alloy—Steel Joint Produced by Electron Beam Welding

by Gloria Basile, Giorgio Baudana, Giulio Marchese, Massimo Lorusso, Mariangela Lombardi, Daniele Ugues, Paolo Fino and Sara Biamino

Materials 2018, 11(1), 149; https://doi.org/10.3390/ma11010149 - 17 Jan 2018

Cited by 17 | Viewed by 4906

Abstract

In this work, the characterization of the assembly of a steel shaft into a γ-TiAl part for turbocharger application, obtained using Electron Beam Welding (EBW) technology with a Ni-based filler, was carried out. The Ti-48Al-2Nb-0.7Cr-0.3Si (at %) alloy part was produced by Electron Beam Melting (EBM). This additive manufacturing technology allows the production of a lightweight part with complex shapes. The replacement of Nickel-based superalloys with TiAl alloys in turbocharger automotive applications will lead to an improvement of the engine performance and a substantial reduction in fuel consumption and emission. The welding process allows a promising joint to be obtained, not affecting the TiAl microstructure. Nevertheless, it causes the formation of diffusive layers between the Ni-based filler and both steel and TiAl, with the latter side being characterized by a very complex microstructure, which was fully characterized in this paper by means of Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, and nanoindentation. The diffusive interface has a thickness of about 6 µm, and it is composed of several layers. Specifically, from the TiAl alloy side, we find a layer of Ti₃Al followed by Al₃NiTi₂ and AlNi₂Ti. Subsequently Ni becomes more predominant, with a first layer characterized by abundant carbide/boride precipitation, and a second layer characterized by Si-enrichment. Then, the chemical composition of the Ni-based filler is gradually reached. Full article

(This article belongs to the Special Issue Intermetallic Alloys: Fabrication, Properties and Applications 2017)

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11004 KiB

Open AccessArticle

Largest Magnetic Moments in the Half-Heusler Alloys XCrZ (X = Li, K, Rb, Cs; Z = S, Se, Te): A First-Principles Study

by Xiaotian Wang, Zhenxiang Cheng and Guodong Liu

Materials 2017, 10(9), 1078; https://doi.org/10.3390/ma10091078 - 14 Sep 2017

Cited by 44 | Viewed by 7897

Abstract

A recent theoretical work indicates that intermetallic materials LiMnZ (Z = N, P) with a half-Heusler structure exhibit half-metallic (HM) behaviors at their strained lattice constants, and the magnetic moments of these alloys are expected to reach as high as 5 μ_B per formula unit. (Damewood et al. Phys. Rev. B 2015, 91, 064409). This work inspired us to find new Heusler-based half-metals with the largest magnetic moment. With the help of the first-principles calculation, we reveal that XCrZ (X = K, Rb, Cs; Z = S, Se, Te) alloys show a robust, half-metallic nature with a large magnetic moment of 5 μ_B at their equilibrium and strained lattice constants in their most stable phases, while the excellent HM nature of LiCrZ (Z = S, Se, Te) alloys can be observed in one of their metastable phases. Moreover, the effects of uniform strain in LiCrZ (Z = S, Se, Te) alloys in type II arrangement have also been discussed. Full article

(This article belongs to the Special Issue Intermetallic Alloys: Fabrication, Properties and Applications 2017)

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4110 KiB

Open AccessArticle

Accessing Colony Boundary Strengthening of Fully Lamellar TiAl Alloys via Micromechanical Modeling

by Jan Eike Schnabel and Swantje Bargmann

Materials 2017, 10(8), 896; https://doi.org/10.3390/ma10080896 - 03 Aug 2017

Cited by 12 | Viewed by 6494

Abstract

In this article, we present a strategy to decouple the relative influences of colony, domain and lamella boundary strengthening in fully lamellar titanium aluminide alloys, using a physics-based crystal plasticity modeling strategy. While lamella and domain boundary strengthening can be isolated in experiments using polysynthetically twinned crystals or mircomechanical testing, colony boundary strengthening can only be investigated in specimens in which all three strengthening mechanisms act simultaneously. Thus, isolating the colony boundary strengthening Hall–Petch coefficient

K_{C}

experimentally requires a sufficient number of specimens with different colony sizes

λ_{C}

but constant lamella thickness

λ_{L}

and domain size

λ_{D}

, difficult to produce even with sophisticated alloying techniques. The here presented crystal plasticity model enables identification of the colony boundary strengthening coefficient

K_{C}

as a function of lamella thickness

λ_{L}

. The constitutive description is based on the model of a polysynthetically twinned crystal which is adopted to a representative volume element of a fully lamellar microstructure. In order to capture the micro yield and subsequent micro hardening in weakly oriented colonies prior to macroscopic yield, the hardening relations of the adopted model are revised and calibrated against experiments with polysynthetically twinned crystals for plastic strains up to 15%. Full article

(This article belongs to the Special Issue Intermetallic Alloys: Fabrication, Properties and Applications 2017)

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