Special Issue "Latest Developments in Magnesium Technology—Alloying, Processing, Microstructure, Deformation Mechanism and Mechanical Properties"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: 31 December 2017

Special Issue Editors

Guest Editor
Dr. Alok Singh

Research Center for Strategic Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan
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Interests: microstructure; magnesium alloys; transmission electron microscopy; quasicrystal; phase transformation
Guest Editor
Prof. Dr. Sean R. Agnew

Department of Materials Science, University of Virginia, Charlottesville, Virginia, USA
Website | E-Mail
Interests: magnesium alloy processing–structure–property relationships; low symmetry metal deformation; plasticity; in-situ neutron diffraction

Special Issue Information

Dear Colleagues,

Research on magnesium alloys has made great progress in the past 20 years, as demonstrated by significant improvements in their collective properties: Strength, ductility, formability, and even corrosion resistance. These improvements have come about through the development of new alloys and new processing strategies. Alloy design strategies involving second phase precipitates have varied widely, from duplex microstructures involving long period stacking ordered (LSPO) intermetallic compounds, to ultrafine grained alloys with grain boundaries pinned by icosahedral quasicrystalline particles, all the way to microalloying strategies designed to enhance the number density of ultrafine precipitates and Guinier-Preston (GP) zones. Solid solution alloying effects of elements like Y and Li continue to be of great interest, for enhancement of ductility and even corrosion resistance. In addition, there have been major developments in understanding the deformation behavior that involves the activation of multiple slip systems and stacking faults, as well as mechanical twinning. Various experimental and simulation techniques and modelling have been applied to understand these phenomena. New processing techniques have been applied to obtain fine grain size and manipulate texture in order to control strength and ductility. New alloys have been developed such as Mg–Zn–Ca, which are promising for bio-applications, when combined with processing techniques to obtain the desired mechanical properties, and dilute Mg–Al–Ca–Mn alloys that exhibit excellent strength and ductility combinations after high-speed extrusion and aging. Thus, tremendous progress has been made by developing an understanding the role of various alloying elements and the basics of deformation mechanisms. This Special Issue aims to present the current status of development in these and related areas, and to present these perspectives in a single volume. We welcome and look forward to your latest contributions to these areas of investigation.

Dr. Alok Singh
Prof. Dr. Sean R. Agnew
Guest Editors

Manuscript Submission Information

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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 1000 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

  • Magnesium alloys
  • Processing (thixomolding, die casting, strip casting, DC casting, rolling and extrusion)
  • Microstructure evolution
  • Microalloying and precipitation
  • Duplex alloys involving intermetallic compounds
  • Deformation mechanisms—slip, stacking faults, and twinning
  • Constitutive modelling
  • Mechanical properties
  • Biomaterials
  • Corrosion

Published Papers (7 papers)

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Research

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Open AccessArticle Amplitude Dependent Internal Friction in a Mg-Al-Zn Alloy Studied after Thermal and Mechanical Treatment
Metals 2017, 7(10), 433; doi:10.3390/met7100433
Received: 11 July 2017 / Revised: 3 October 2017 / Accepted: 12 October 2017 / Published: 17 October 2017
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Abstract
The amplitude-dependent internal friction of continuously-cast and rolled AZ31 magnesium alloy was measured in this study. Samples were annealed and quenched step by step; immediately after the treatment, the amplitude dependence of the logarithmic decrement was measured. Changes in the microstructure due to
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The amplitude-dependent internal friction of continuously-cast and rolled AZ31 magnesium alloy was measured in this study. Samples were annealed and quenched step by step; immediately after the treatment, the amplitude dependence of the logarithmic decrement was measured. Changes in the microstructure due to thermomechanical treatment were reflected in changes in the damping. Internal friction is influenced by the dislocation substructure and its modification due to solute atoms migration, microplastic deformation, and twins’ formation. Internal friction in the rolled sheets is affected by the rolling texture. Full article
Open AccessArticle Effect of Y Addition on the Semi-Solid Microstructure Evolution and the Coarsening Kinetics of SIMA AZ80 Magnesium Alloy
Metals 2017, 7(10), 416; doi:10.3390/met7100416
Received: 18 July 2017 / Revised: 21 August 2017 / Accepted: 3 October 2017 / Published: 6 October 2017
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Abstract
Semi-solid feedstock of AZ80 magnesium alloy modified by trace rare-earth Y element (0, 0.2, 0.4, 0.8 wt. %) was fabricated by strain-induced melting activation (SIMA) in the form of extrusion and partial remelting. The effect of Y addition on the microstructure evolution of
[...] Read more.
Semi-solid feedstock of AZ80 magnesium alloy modified by trace rare-earth Y element (0, 0.2, 0.4, 0.8 wt. %) was fabricated by strain-induced melting activation (SIMA) in the form of extrusion and partial remelting. The effect of Y addition on the microstructure evolution of the extruded and isothermally heat treated alloy was observed by using an optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and quantitative analysis. The results show that the Y addition can refine the microstructure and make the β-Mg17Al12 phases agglomerate. During the subsequent isothermal treatment at 570 °C, the average solid grain size, shape factor and liquid fractions increased with the prolonged soaking time. The smaller spheroidal solid grains and larger shape factor were obtained in the semi-solid microstructure due to Y addition. The coalescence and Ostwald ripening mechanism operated the coarsening process of solid grains simultaneously. The coarsening rate constants of AZ80M1 (0.2 wt. % Y addition) of 164.22 μm3 s−1 was approximately four times less than the un-modified AZ80 alloy of 689.44 μm3 s−1. In contrast, the desirable semi-solid structure featured, with fine and well globular solid grains, an appropriate liquid fraction, and shape factor was achieved in AZ80M1 alloy treated at 570 °C for 20–30 min. Full article
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Open AccessFeature PaperArticle High Temperature Strength and Hot Working Technology for As-Cast Mg–1Zn–1Ca (ZX11) Alloy
Metals 2017, 7(10), 405; doi:10.3390/met7100405
Received: 18 August 2017 / Revised: 14 September 2017 / Accepted: 20 September 2017 / Published: 1 October 2017
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Abstract
Cast Mg–1Zn–1Ca alloy (ZX11) has been tested to evaluate its compressive strength between 25 °C and 250 °C, and workability in the range of 260–500 °C. The ultimate compressive strength of this alloy is about 30% higher than that of creep-resistant alloy Mg–3Sn–2Ca
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Cast Mg–1Zn–1Ca alloy (ZX11) has been tested to evaluate its compressive strength between 25 °C and 250 °C, and workability in the range of 260–500 °C. The ultimate compressive strength of this alloy is about 30% higher than that of creep-resistant alloy Mg–3Sn–2Ca (TX32) between 25 °C and 200 °C, and exhibits a plateau between 100 °C and 175 °C, similar to TX32. This is attributed to Mg2Ca particles present at grain boundaries that reduce their sliding. The processing map, developed between 260 and 420 °C in the strain rate limits of 0.0003 s−1 to 1 s−1, exhibited two domains in the ranges: (1) 280–330 °C and 0.0003–0.01 s−1 and (2) 330–400 °C and 0.0003–0.1 s−1. In these domains, dynamic recrystallization occurs, with basal slip dominating in the first domain and prismatic slip in the second, while the recovery mechanism being climb of edge dislocations in both. The activation energy estimated using standard kinetic rate equation is 191 kJ/mol, which is higher than the value for lattice self-diffusion in magnesium indicating that a large back stress is created by the presence of Ca2Mg6Zn3 intermetallic particles in the matrix. It is recommended that the alloy be best processed at 380 °C and 0.1 s−1 at which prismatic slip is favored due to Zn addition. At higher strain rates, the alloy exhibits flow instability and adiabatic shear band formation at <340 °C while flow localization and cracking at grain boundaries occurs at temperatures >400 °C. Full article
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Open AccessArticle Preparation, Microstructure Evolutions, and Mechanical Property of an Ultra-Fine Grained Mg-10Gd-4Y-1.5Zn-0.5Zr Alloy
Metals 2017, 7(10), 398; doi:10.3390/met7100398
Received: 30 August 2017 / Revised: 14 September 2017 / Accepted: 25 September 2017 / Published: 28 September 2017
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Abstract
In this work, the microstructural evolutions and mechanical properties of an as-cast Mg-10Gd-4Y-1.5Zn-0.5Zr (wt %) alloy during successive multi-pass equal channel angular pressing (ECAP) were systematically investigated by X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, and compression test. The obtained results show
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In this work, the microstructural evolutions and mechanical properties of an as-cast Mg-10Gd-4Y-1.5Zn-0.5Zr (wt %) alloy during successive multi-pass equal channel angular pressing (ECAP) were systematically investigated by X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, and compression test. The obtained results show that the microstructure of as-cast alloy consists of α-Mg grains, Mg3Gd island phase, few Y-rich particles, and lamellar 14H LPSO (long period stacking ordered) phase located at the grain boundaries. During ECAP, the Mg3Gd-type phase is crushed and refined gradually. However, the refined Mg3Gd particles are not distributed uniformly in the matrix, but still aggregated at the interdendritic area. The 14H phase becomes kinked during the early passes of ECAP and then broken at the kinking bands with more severe deformation. Dynamic recrystallization of α-Mg is activated during ECAP, and their average diameter decreases to around 1 μm, which is stabilized in spite of increasing ECAP passes. Moreover, nano-scale γ′ phases were dynamically precipitated in 16p ECAP alloy. Compression tests indicate that 16p ECAP alloy exhibits excellent mechanical property with compressive strength of 548 MPa and fracture strain of 19.1%. The significant improvement for both strength and ductility of deformed alloy could be ascribed to dynamic recrystallization (DRX) grains, refined Mg3Gd-type and 14H particles, and dynamically precipitated γ′ plates. Full article
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Open AccessArticle Stress Corrosion Cracking Behavior of Fine-Grained AZ61 Magnesium Alloys Processed by Equal-Channel Angular Pressing
Metals 2017, 7(9), 343; doi:10.3390/met7090343
Received: 21 July 2017 / Revised: 25 August 2017 / Accepted: 25 August 2017 / Published: 4 September 2017
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Abstract
The effect of equal-channel angular pressing (ECAP) on stress corrosion cracking (SCC) behavior of a cast AZ61 Mg alloy was investigated in distilled water (DW) using the slow strain rate tensile test (SSRT) at a strain rate of 1 × 10−6 s
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The effect of equal-channel angular pressing (ECAP) on stress corrosion cracking (SCC) behavior of a cast AZ61 Mg alloy was investigated in distilled water (DW) using the slow strain rate tensile test (SSRT) at a strain rate of 1 × 10−6 s−1. The fine-grained alloy after ECAP showed a greater SCC susceptibility but a higher ultimate tensile strength, compared with the as-cast counterpart. The results were attributed to refined grains, high-density dislocations and increased proportion of high-angle grain boundaries induced by severe plastic deformation, as well as isolated fine β-phase particles transiting from net-like β-phase. Full article
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Open AccessFeature PaperArticle Cumulative Effect of Strength Enhancer—Lanthanum and Ductility Enhancer—Cerium on Mechanical Response of Magnesium
Metals 2017, 7(7), 241; doi:10.3390/met7070241
Received: 2 June 2017 / Revised: 22 June 2017 / Accepted: 26 June 2017 / Published: 29 June 2017
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Abstract
In the present work, the cumulative effect of strength enhancer Lanthanum (La) and ductility enhancer Cerium (Ce) on the mechanical response of pure Mg was investigated. A ternary Mg-4La-0.4Ce alloy was developed using a disintegrated melt deposition method followed by hot extrusion. The
[...] Read more.
In the present work, the cumulative effect of strength enhancer Lanthanum (La) and ductility enhancer Cerium (Ce) on the mechanical response of pure Mg was investigated. A ternary Mg-4La-0.4Ce alloy was developed using a disintegrated melt deposition method followed by hot extrusion. The mechanical characterization revealed that the ternary alloy exhibited superior hardness and tensile and compressive strengths when compared to Mg and Mg-0.4Ce binary alloy, thereby validating the role of La as a strength enhancer. Furthermore, the ductility of the chosen alloy was also enhanced as compared to Mg and other La rich Mg alloys, indicating that the ductility enhancement is primarily due to Ce. The microstructural characterization revealed that the cumulative addition of La and Ce refined the grain size and led to the formation of a large volume of secondary phases which affected the mechanical properties. The effect of fine grains and the presence of secondary phases on the deformation behavior of the alloy were conclusively ascertained with the aid of deformation and fracture studies. Full article
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Review

Jump to: Research

Open AccessReview A Critical Review of Mg-Based Hydrogen Storage Materials Processed by Equal Channel Angular Pressing
Metals 2017, 7(9), 324; doi:10.3390/met7090324
Received: 16 July 2017 / Revised: 9 August 2017 / Accepted: 18 August 2017 / Published: 23 August 2017
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Abstract
As a kind of cost-efficient hydrogen storage materials with high hydrogen capacity and light weight, Mg-based alloys have attracted much attention. This review introduces an effective technique in producing bulk ultrafine-grained (UFG) Mg alloys and promoting its hydrogen storage property, namely, equal-channel angular
[...] Read more.
As a kind of cost-efficient hydrogen storage materials with high hydrogen capacity and light weight, Mg-based alloys have attracted much attention. This review introduces an effective technique in producing bulk ultrafine-grained (UFG) Mg alloys and promoting its hydrogen storage property, namely, equal-channel angular pressing (ECAP). This paper briefly describes the technical principle of ECAP and reviews the research progress on hydrogen storage properties of ECAP-processed Mg alloys. Special attention is given to their hydrogen storage behaviors including hydrogen storage dynamics, capacity, and cycling stability. Finally, it analyzes the factors that affect the hydrogen storage properties of ECAP-processed Mg alloys, such as the grain sizes, lattice defects, catalysts, and textures introduced by ECAP process. Full article
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