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: closed (31 December 2017) | Viewed by 57141

Special Issue Editors

Research Center for Strategic Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan
Interests: microstructure; magnesium alloys; transmission electron microscopy; quasicrystal; phase transformation

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Guest Editor
Department of Materials Science, University of Virginia, Charlottesville, WV, USA
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

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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

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Published Papers (11 papers)

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Research

Jump to: Review

15 pages, 11940 KiB  
Article
Effect of Solidification Cooling Rate on Microstructure and Mechanical Properties of an Extruded Mg-Zn-Y Alloy
by Alok Singh, Yoshiaki Osawa, Hidetoshi Somekawa and Toshiji Mukai
Metals 2018, 8(5), 337; https://doi.org/10.3390/met8050337 - 10 May 2018
Cited by 5 | Viewed by 4050
Abstract
The Effect of the solidification conditions and subsequent extrusion of a Mg-3.0Zn-0.5Y (at. %) alloy containing quasicrystalline icosahedral (i-) phase was studied. Solidification was carried out by three methods using a chill casting mold, a conventional steel mold and a water-cooled [...] Read more.
The Effect of the solidification conditions and subsequent extrusion of a Mg-3.0Zn-0.5Y (at. %) alloy containing quasicrystalline icosahedral (i-) phase was studied. Solidification was carried out by three methods using a chill casting mold, a conventional steel mold and a water-cooled mold. Subsequently, castings were extruded in the temperature range of 235–270 C at an extrusion ratio of 25:1. The solidification molds showed different characteristics. The water-cooled mold was most effective in cooling through the walls, but least effective at the center of the mold. The conventional cast mold was the most effective in cooling at the mold center. All the castings had an interdendritic eutectic structure of the i-phase, and a supersaturation of the matrix in zinc. As a result, all the extrusions had similar grain size close to 1 μ m and very fine nano-size precipitation. Yield strengths in tension were in the range of 376 and 404 MPa, and from 300 to 330 MPa in compression. All elongations to fracture were about 13%. It is concluded that supersaturation of the matrix during solidification is the main factor, resulting in the dynamic precipitation of very fine precipitates and fine grain size during extrusion. Full article
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15 pages, 5777 KiB  
Article
Processing Effects on the Formability of Magnesium Alloy Sheets
by Jan Bohlen, Guadalupe Cano, Daria Drozdenko, Patrik Dobron, Karl Ulrich Kainer, Sven Gall, Sören Müller and Dietmar Letzig
Metals 2018, 8(2), 147; https://doi.org/10.3390/met8020147 - 23 Feb 2018
Cited by 23 | Viewed by 5334
Abstract
As a generalized semi-finished product, the use of magnesium sheets requires addressing two major aspects of their processing: their microstructure and texture control, which are both essential for the forming behavior of such sheets during their forming to parts. Further, the processing of [...] Read more.
As a generalized semi-finished product, the use of magnesium sheets requires addressing two major aspects of their processing: their microstructure and texture control, which are both essential for the forming behavior of such sheets during their forming to parts. Further, the processing of such sheets is complex, and therefore expensive, and requires simplification. In this work, magnesium alloys AZ31, ZE10, and ME21 are investigated in the form of conventionally rolled sheets, as well as in the form of extruded sheets. Their microstructural and textural development are correlated to their mechanical and forming properties. During extrusion, strong textures develop that hinder stretch-forming operations, even in rare earth-containing alloys. Chemical composition and process parameters have a significant impact on the texture development, and enable the design of sheet materials with weak textures and potentially enhanced formability. Full article
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15 pages, 4969 KiB  
Article
Comprehensive Characterisation of a Newly Developed Mg–Dy–Al–Zn–Zr Alloy Structure
by Lenka Kunčická and Radim Kocich
Metals 2018, 8(1), 73; https://doi.org/10.3390/met8010073 - 19 Jan 2018
Cited by 20 | Viewed by 3618
Abstract
This is a report on the structure phases and precipitates in a newly developed Mg–10Dy–3Al–1Zn–0.2Zr alloy. Specimens from the cast alloy were heat treated at temperatures of 480 °C, 520 °C and 560 °C, all for 8 and 16 h, and subsequently quenched. [...] Read more.
This is a report on the structure phases and precipitates in a newly developed Mg–10Dy–3Al–1Zn–0.2Zr alloy. Specimens from the cast alloy were heat treated at temperatures of 480 °C, 520 °C and 560 °C, all for 8 and 16 h, and subsequently quenched. The structures were then analysed using scanning and transmission electron microscopy, while the mechanical properties were investigated using microhardness measurements. The results showed the different temperatures, as well as times, influence both the chemical composition and morphology of the precipitated phases. The occurrence of the β-phase changed with increasing temperature and time from grain boundary segregations through fine elongated particles to coarse plate-like precipitates. Polygon-shaped Dy-rich precipitates were observed in all the samples; however, their size decreased and their distribution homogenised with increasing annealing temperature and time. The samples annealed at 520 °C and 560 °C exhibited the presence of lamellar 18R-type long period stacking ordered (LPSO) phases. Microhardness measurements were in accordance with results of the microscopic analyses; although the values varied between 60 and 65 HV for all the material states, the most uniform distribution was observed for the 560 °C/8-h sample, which featured the finest precipitates and LPSO phases. Full article
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6765 KiB  
Article
Amplitude Dependent Internal Friction in a Mg-Al-Zn Alloy Studied after Thermal and Mechanical Treatment
by Zuzanka Trojanová, Pavel Lukáč, Ján Džugan and Kristýna Halmešová
Metals 2017, 7(10), 433; https://doi.org/10.3390/met7100433 - 17 Oct 2017
Cited by 6 | Viewed by 4368
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 [...] Read more.
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
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3417 KiB  
Article
Effect of Y Addition on the Semi-Solid Microstructure Evolution and the Coarsening Kinetics of SIMA AZ80 Magnesium Alloy
by Qi Tang, Hao Sun, Mingyang Zhou and Gaofeng Quan
Metals 2017, 7(10), 416; https://doi.org/10.3390/met7100416 - 6 Oct 2017
Cited by 14 | Viewed by 4904
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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12798 KiB  
Article
High Temperature Strength and Hot Working Technology for As-Cast Mg–1Zn–1Ca (ZX11) Alloy
by Kamineni Pitcheswara Rao, Kalidass Suresh, Yellapregada Venkata Rama Krishna Prasad, Chalasani Dharmendra, Norbert Hort and Hajo Dieringa
Metals 2017, 7(10), 405; https://doi.org/10.3390/met7100405 - 1 Oct 2017
Cited by 10 | Viewed by 5955
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 [...] Read more.
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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19307 KiB  
Article
Preparation, Microstructure Evolutions, and Mechanical Property of an Ultra-Fine Grained Mg-10Gd-4Y-1.5Zn-0.5Zr Alloy
by Huan Liu, Jia Ju, Jing Bai, Jiapeng Sun, Dan Song, Jingli Yan, Jinghua Jiang and Aibin Ma
Metals 2017, 7(10), 398; https://doi.org/10.3390/met7100398 - 28 Sep 2017
Cited by 27 | Viewed by 4633
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 [...] Read more.
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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4429 KiB  
Article
Stress Corrosion Cracking Behavior of Fine-Grained AZ61 Magnesium Alloys Processed by Equal-Channel Angular Pressing
by Qiuyuan Xie, Aibin Ma, Jinghua Jiang, Zhaojun Cheng, Dan Song, Yuchun Yuan and Huan Liu
Metals 2017, 7(9), 343; https://doi.org/10.3390/met7090343 - 4 Sep 2017
Cited by 14 | Viewed by 4535
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 [...] Read more.
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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9517 KiB  
Article
Cumulative Effect of Strength Enhancer—Lanthanum and Ductility Enhancer—Cerium on Mechanical Response of Magnesium
by Wei Yang, Sravya Tekumalla and Manoj Gupta
Metals 2017, 7(7), 241; https://doi.org/10.3390/met7070241 - 29 Jun 2017
Cited by 14 | Viewed by 5055
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

2697 KiB  
Review
A Review: Effect of Friction Stir Welding on Microstructure and Mechanical Properties of Magnesium Alloys
by Yajie Li, Fengming Qin, Cuirong Liu and Zhisheng Wu
Metals 2017, 7(12), 524; https://doi.org/10.3390/met7120524 - 25 Nov 2017
Cited by 37 | Viewed by 7040
Abstract
Friction stir welding (FSW) is well recognized as a very practical technology for joining magnesium alloys. Although, a large amount of progress have been made on the FSW of magnesium alloys, it should be emphasized that many challenges still remain in joining magnesium [...] Read more.
Friction stir welding (FSW) is well recognized as a very practical technology for joining magnesium alloys. Although, a large amount of progress have been made on the FSW of magnesium alloys, it should be emphasized that many challenges still remain in joining magnesium using FSW. In this article, we briefly review the background of friction stir welding of magnesium alloys, and then focus on the effects of the friction stir welding on the macrostructure, microstructure evolution, texture distribution, and the mechanical properties of the welding joints. The macro-defects in welds and their relationship to the welding parameters such as welding speed, rotation speed, and axial force were also discussed. The review concluded with some suggested methods improvement and future challenges related to FSW of magnesium alloys. The purpose of the present review paper is to fully understand the relationships between the microstructure and the properties, and then establish a global, state-of-the-art FSW of magnesium alloys. Full article
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8597 KiB  
Review
A Critical Review of Mg-Based Hydrogen Storage Materials Processed by Equal Channel Angular Pressing
by Lisha Wang, Jinghua Jiang, Aibin Ma, Yuhua Li and Dan Song
Metals 2017, 7(9), 324; https://doi.org/10.3390/met7090324 - 23 Aug 2017
Cited by 45 | Viewed by 6250
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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