Special Issue "Magnesium Technology"
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A special issue of Metals (ISSN 2075-4701).
Deadline for manuscript submissions: closed (31 May 2012)
Special Issue Editor
Guest Editor
Dr. Manoj Gupta
Materials Group, Department of Mechanical Engineering, NUS, 9 Engineering Drive 1, 117576 Singapore
Website: http://www.eng.nus.edu.sg/EResnews/0011/rd/rd_8.html
E-Mail: mpegm@nus.edu.sg
Phone: +65 6516 6358
Fax: +65 67791459
Interests: microwave processing; solidification processing; powder processing; light weight materials (aluminum and magnesium); composites/nanocomposites
Special Issue Information
Dear Colleagues,
Magnesium is the metal for the 21st century. Mg-alloys are being considered as one of the most versatile material choices amongst the structural materials that exhibit both energy efficiency and environmental benefits. Mg-based materials (alloys and composites) have enormous and unlimited potential to replace aluminium, steel and structural plastics in diverse industrial and commercial sectors such as automotive, aviation, defense, biomedical, sporting equipments, consumer electronics, etc. To support such huge demands, the need for the day is to improve manufacturing technologies, and R&D of new Mg-based materials with superior properties.
Recently, magnesium technology has taken a great leap towards catering to futuristic applications with the advent of high performance Mg-based materials such as Mg-nanocomposites and Mg-nanocrystalline/bulk amorphous materials (Mg-BMG), which are produced using unique processing methods. In these new materials, exceptional properties have been achieved that otherwise would have been unattainable in conventional alloys. Concerted research efforts are being made to understand their material characteristics under various loading/operating conditions using advanced characterization tools.
The aim of this Special Issue on ‘Magnesium Technology’ is to present the state-of-the-art research trends that highlight the advancement in Mg-materials processing, novel Mg-based materials development, insight into deformation processes using experimental investigations and theoretical simulation/modeling. Contributions related to advantage of Mg-materials in terms of recyclability/fuel/cost/energy savings and application specific research works are encouraged.
Dr. Manoj Gupta
Guest EditorSubmission
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. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as 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.
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Keywords
- Mg-Alloy Development
- Mg-based micro/nano composites, nano/quasi-crystalline/amorphous materials
- Processing Technology (solid/liquid-state processes, physical metallurgy, joining, machining)
- Microstructural evolution, physical, mechanical, thermal, chemical properties
- Deformation processes and mechanisms
- Numerical simulation and atomistic modeling
- Environmental (greenhouse gas emissions/recyclability/fuel/energy/cost savings)
- Applications (automotive, aviation, consumer electronics, sports, bio-medical, etc.)
Published Papers (11 papers)
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Received: 12 April 2012; in revised form: 25 May 2012 / Accepted: 29 May 2012 / Published: 7 June 2012
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Abstract: The microstructure, tensile properties, cyclic stress amplitude fatigue response and final fracture behavior of a magnesium alloy, denoted as AZ31, discontinuously reinforced with nano-particulates of aluminum oxide and micron size nickel particles is presented and discussed. The tensile properties, high cycle fatigue and final fracture behavior of the discontinuously reinforced magnesium alloy are compared with the unreinforced counterpart (AZ31). The elastic modulus and yield strength of the dual particle reinforced magnesium alloy is marginally higher than of the unreinforced counterpart. However, the tensile strength of the composite is lower than the monolithic counterpart. The ductility quantified by elongation to failure over 0.5 inch (12.7 mm) gage length of the test specimen showed minimal difference while the reduction in specimen cross-section area of the composite is higher than that of the monolithic counterpart. At the microscopic level, cyclic fatigue fractures of both the composite and the monolithic alloy clearly revealed features indicative of the occurrence of locally ductile and brittle mechanisms. Over the range of maximum stress and at two different load ratios the cyclic fatigue resistance of the magnesium alloy composite is superior to the monolithic counterpart. The mechanisms responsible for improved cyclic fatigue life and resultant fracture behavior of the composite microstructure are highlighted.
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Received: 14 May 2012; in revised form: 4 June 2012 / Accepted: 6 June 2012 / Published: 11 June 2012
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Abstract: In this work, a Mg-5Nb metal–metal composite was reinforced with nano SiC (SiCn) ceramic reinforcement of varying volume fractions, using the disintegrated melt deposition technique. The extruded Mg-5Nb-SiCn composites were characterized for their microstructure and mechanical properties. Based on the results obtained, it was observed that the volume fraction of nano-SiC reinforcement played an important role in determining the grain size and improving the mechanical properties. A comparison of properties with those of pure Mg and Mg-5Nb composite showed that while the improvement in hardness occurred at all volume fractions, a minimum volume fraction of ~0.27% SiCn was required to increase the tensile and compressive strengths. The observed mechanical response of the composites were investigated in terms of the effect of SiCn volume fraction, processing, distribution of metallic and ceramic reinforcements and the inherent properties of the matrix and reinforcements. The influences of these factors on the mechanical behavior of the composites are understood based on the structure–property relationship.
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Received: 27 May 2012; in revised form: 13 June 2012 / Accepted: 14 June 2012 / Published: 25 June 2012
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Abstract: The influence of transition metal oxide catalysts (ZrO2, CeO2, Fe3O4 and Nb2O5) on the hydrogen desorption kinetics of MgH2 was investigated using constant pressure thermodynamic driving forces in which the ratio of the equilibrium plateau pressure (pm) to the opposing plateau (pop) was the same in all the reactions studied. The results showed Nb2O5 to be vastly superior to other catalysts for improving the thermodynamics and kinetics of MgH2. The modeling studies showed reaction at the phase boundary to be likely process controlling the reaction rates of all the systems studied.
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Received: 1 June 2012; in revised form: 29 June 2012 / Accepted: 3 July 2012 / Published: 24 July 2012
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Abstract: Potential of widespread industrial applications of magnesium has been realized in recent years. A variety of magnesium alloy matrix composites are now being studied for mechanical properties. Since magnesium is the lightest structural metal, it can replace aluminum in existing applications for further weight savings. This review presents an overview of hollow particle filled magnesium matrix syntactic composite foams. Fly ash cenospheres are the most commonly used hollow particles for such applications. Fly ash cenospheres primarily have alumino-silicate composition and contain a large number of trace elements, which makes it challenging to study the interfacial reactions and microstructure in these composites. Microstructures of commonly studied AZ and ZC series magnesium alloys and their syntactic foams are discussed. Although only a few studies are available on these materials because of the nascent stage of this field, a comparison with similar aluminum matrix syntactic foams has provided insight into the properties and weight saving potential of magnesium matrix composites. Analysis shows that the magnesium matrix syntactic foams have higher yield strength at the same level of density compared to most other metal matrix syntactic foams. The comparison can guide future work and set goals that need to be achieved through materials selection and processing method development.
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Received: 30 May 2012; in revised form: 5 July 2012 / Accepted: 16 July 2012 / Published: 25 July 2012
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Abstract: Pd capped pure Mg thin film (50 nm thick) was prepared by magnetron sputtering and its hydrogenation at room temperature has been investigated. After exposure to 4% hydrogen gas diluted by argon, the Pd/Mg thin films show drastic optical changes from the metallic state to the transparent state within five seconds by hydrogenation. Transmission electron microscope observation reveals that this sample has an anomalous structure; Mg grain is surrounded by Pd. This structure may be the reason why Pd/Mg films can be hydrogenated so quickly at room temperature.
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Received: 26 April 2012; in revised form: 6 August 2012 / Accepted: 10 August 2012 / Published: 17 August 2012
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Abstract: In this study, metallic elements that have limited/negligible solubility in pure magnesium (Mg) were incorporated in Mg using the disintegrated melt deposition technique. The metallic elements added include: (i) micron sized titanium (Ti) particulates with negligible solubility; (ii) nano sized copper (Cu) particulates with limited solubility; and (iii) the combination of micro-Ti and nano-Cu. The combined metallic addition (Ti + Cu) was carried out with and without preprocessing by ball-milling. The microstructure and mechanical properties of the developed Mg-materials were investigated. Microstructure observation revealed grain refinement due to the individual and combined presence of hard metallic particulates. The mechanical properties evaluation revealed a significant improvement in microhardness, tensile and compressive strengths. Individual additions of Ti and Cu resulted in Mg-Ti composite and Mg-Cu alloy respectively, and their mechanical properties were influenced by the inherent properties of the particulates and the resulting second phases, if any. In the case of combined addition, the significant improvement in properties were observed in Mg-(Ti + Cu)BM composite containing ball milled (Ti + Cu) particulates, when compared to direct addition of Ti and Cu particulates. The change in particle morphology, formation of Ti3Cu intermetallic and good interfacial bonding with the matrix achieved due to preprocessing, contributed to its superior strength and ductility, in case of Mg-(Ti + Cu)BM composite. The best combination of hardness, tensile and compressive behavior was exhibited by Mg-(Ti + Cu)BM composite formulation.
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Received: 25 June 2012; in revised form: 27 July 2012 / Accepted: 6 August 2012 / Published: 23 August 2012
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Abstract: The hot deformation characteristics of AZ31 magnesium alloy rod extruded at temperatures of 300 °C, 350 °C and 450 °C have been studied in compression. The extruded material had a fiber texture with parallel to the extrusion axis. When extruded at 450 °C, the texture was less intense and the direction moved away from the extrusion axis. The processing maps for the material extruded at 300 °C and 350 °C are qualitatively similar to the material with near-random texture (cast-homogenized) and exhibited three dynamic recrystallization (DRX) domains. In domains #1 and #2, prismatic slip is the dominant process and DRX is controlled by lattice self-diffusion and grain boundary self-diffusion, respectively. In domain #3, pyramidal slip occurs extensively and DRX is controlled by cross-slip on pyramidal slip systems. The material extruded at 450 °C exhibited two domains similar to #1 and #2 above, which moved to higher temperatures, but domain #3 is absent. The results are interpreted in terms of the changes in fiber texture with extrusion temperature. Highly intense texture, as in the rod extruded at 350 °C, will enhance the occurrence of prismatic slip in domains #1 and #2 and promotes pyramidal slip at temperatures >450 °C (domain #3).
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Received: 28 May 2012; in revised form: 10 July 2012 / Accepted: 17 August 2012 / Published: 29 August 2012
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Abstract: In the present study, AZ41 and AZ51 alloys were fabricated using disintegrated melt deposition technique followed by hot extrusion. AZ41/Yttria and AZ51/Yttria composites were prepared using 0.6 wt% yttria nano particles in the alloys using the same fabrication technique. From the tensile test results, both strengths (yield and tensile) and ductility were improved in AZ51 when compared to AZ41. In comparison with its alloy counterparts, the yield and tensile strengths were enhanced while maintaining the same ductility in AZ41/Yttria composite, but comparable strengths with decreased ductility were observed in AZ51/Yttria composite. Under compressive loading, an improvement in strengths with similar ductility was observed in AZ51 when compared to AZ41. The best combination of strengths and ductility was observed in AZ51/Yttria composites from compression test results. The obtained mechanical properties are correlated with the microstructure observations.
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Received: 1 June 2012; in revised form: 14 August 2012 / Accepted: 15 August 2012 / Published: 31 August 2012
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Abstract: In this paper we review the latest developments in the use of severe plastic deformation (SPD) techniques for enhancement of hydrogen sorption properties of magnesium and magnesium alloys. Main focus will be on two techniques: Equal Channel Angular Pressing (ECAP) and Cold Rolling (CR). After a brief description of these two techniques we will discuss their effects on the texture and hydrogen sorption properties of magnesium alloys. In particular, the effect of the processing temperature in ECAP on texture will be demonstrated. We also show that ECAP and CR have produced different textures. Despite the scarcity of experimental results, the investigations up to now indicate that SPD techniques produce metal hydrides with enhanced hydrogen storage properties.
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Received: 2 July 2012; in revised form: 20 August 2012 / Accepted: 21 August 2012 / Published: 14 September 2012
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Abstract: Progress in systematic development of a thermodynamic database for Mg alloys with 21 components is reported. Models for multicomponent alloys are built in a methodical approach from quantitative descriptions of unary, binary and ternary subsystems. For a large number of ternary—and some higher—alloy systems, an evaluation of the modeling depth is made with concise reference to experimental work validating these thermodynamic descriptions. A special focus is on ternary intermetallic phase compositions. These comprise solutions of the third component in a binary compound as well as truly ternary solid solution phases, in addition to the simple ternary stoichiometric phases. Concise information on the stability ranges is given. That evaluation is extended to selected quaternary and even higher alloy systems. Thermodynamic descriptions of intermetallic solution phases guided by their crystal structure are also elaborated and the diversity of such unified phases is emphasized.
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Received: 22 June 2012; in revised form: 24 October 2012 / Accepted: 24 October 2012 / Published: 13 November 2012
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Abstract: This paper summarizes and reviews the findings of our research on AM60B magnesium alloy conducted in past 8 years. It essentially covers three categories: microstructural study, environmental effect, and fatigue crack growth rate of AM60B. The experimental and numerical studies on the influence of casting defects on this particular material’s properties are reviewed in the first part. It has been shown that the non-uniform solidification of the casting results in variations of the microstructure in different layers (skin and core) of the alloy which affects the mechanical properties in those regions. Moreover, the influence of microstructure on fatigue crack initiation and propagation response of the alloy is presented. The influence of several casting defects on the failure mechanism of the material are also numerically analyzed and discussed. The influence of elevated and cold temperatures on the fatigue response of the alloy is reviewed in the second part. Our findings show that the temperature does not have a significant effect on the number of cycles to failure. However, but at some stress level, this effect cannot be dismissed. The fatigue crack growth rate (FCGR) response of the alloy at a wide range of stress ratios is also investigated in the last part. The FCGR of the alloy showed a noticeable dependency on the stress ratio. A model is proposed for estimating the FCGR of the alloy, which could provide a good prediction of alloy’s FCGR over a wide range of negative and positive stress ratios. The integrity of the new model is also compared against other models. Finally, the influence of compressive loading on fatigue life of the specimens under constant and random amplitude cyclic loading is investigated experimentally.
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Last update: 3 January 2013
