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Most Cited Journal of Magnesium and Alloys Articles

The most cited articles published since 2015, extracted from Scopus.

Magnesium casting technology for structural applications

Volume 1, Issue 1, March 2013, Pages 2-22
Alan A. Luo | Alan A. Luo

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. This paper summarizes the melting and casting processes for magnesium alloys. It also reviews the historical development of magnesium castings and their structural uses in the western world since 1921 when Dow began producing magnesium pistons. Magnesium casting technology was well developed during and after World War II, both in gravity sand and permanent mold casting as well as high-pressure die casting, for aerospace, defense and automotive applications. In the last 20 years, most of the development has been focused on thin-wall die casting applications in the automotive industry, taking advantages of the excellent castability of modern magnesium alloys. Recently, the continued expansion of magnesium casting applications into automotive, defense, aerospace, electronics and power tools has led to the diversification of casting processes into vacuum die casting, low-pressure die casting, squeeze casting, lost foam casting, ablation casting as well as semi-solid casting. This paper will also review the historical, current and potential structural use of magnesium with a focus on automotive applications. The technical challenges of magnesium structural applications are also discussed. Increasing worldwide energy demand, environment protection and government regulations will stimulate more applications of lightweight magnesium castings in the next few decades. The development of use of Integrated Computational Materials Engineering (ICME) tools will accelerate the applications of magnesium castings in structural applications.

Advances in Mg corrosion and research suggestions

Volume 1, Issue 3, September 2013, Pages 177-200
Andrej Atrens | Guang Ling Song | Guang Ling Song | Fuyong Cao | Zhiming Shi | Patrick K. Bowen

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. Recent research is summarised with an emphasis on the use of Mg alloys for biodegradable medical applications. Mg melt purification using Zr has been shown to provide the opportunity to produce ultra-high-purity Mg alloys, which could lead to stainless Mg. Nor's solution may be a good starting model for the study of Mg for biodegradable medical implant applications. A systematic laboratory investigation is needed to elucidate the details of how the corrosion behaviour is controlled by the various constituents of the body fluids. In the evaluation of the Mg corrosion mechanism there is a critical lack of understanding of (i) the amount of hydrogen dissolved in the Mg metal during corrosion, and during anodic polarisation, and (ii) the size film-free area where corrosion occurs, and how to measure this area. In the evaluation of the apparent valence of Mg using an applied anodic current density, for reliable values, it is important to apply a sufficiently large applied current density. The available data are consistent with the slightly modified uni-positive Mg+ion mechanism, which maintains that (i) the surface of Mg is covered by a partially protective film, and the film-free area increases as the potential becomes more positive (i.e. a catalytic activation process), (ii) corrosion occurs preferentially at breaks in the partial protective film, (iii) corrosion at the breaks in the partially protective film involves the uni-positive Mg ion, (iv) undermining of particles occurs when Mg is severely dissolved, and (v) there may be some self-corrosion not covered by these four processes, which may be associated with crevice-like features on a severely corroded surface or hydride dissolution at relatively negative potentials. Self-corrosion might also be possible under condition of essentially uniform corrosion. Mg+has not been experimentally observed. Its existence is postulated as an extremely-short lifetime intermediate in the reaction sequence between metallic Mg and the equilibrium ion Mg++. There has been no direct experimental examination of this sequence, and a key challenge remains to devise an experimental approach to study the details of this reaction sequence and the intermediate steps. The apparent valence of Mg continues to be a critical question. If defendable values of effective valence for Mg less than 1.0 were measured, this would indicate that some phenomena contribute to these low values that are not currently accounted for in the uni-positive Mg+corrosion mechanism. The most likely candidate would be self-corrosion.

Effect of graphene nanoplatelets (GNPs) addition on strength and ductility of magnesium-titanium alloys

Volume 1, Issue 3, September 2013, Pages 242-248
Muhammad Rashad | Muhammad Rashad | Fusheng Pan | Fusheng Pan | Fusheng Pan | Aitao Tang | Aitao Tang | Yun Lu | Muhammad Asif | Shahid Hussain | Jia She | Jia She | Jun Gou | Jun Gou | Jianjun Mao | Jianjun Mao

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. Effect of graphene nanoplatelets (GNPs) addition on mechanical properties of magnesium-10wt%Titanium (Mg-10Ti) alloy is investigated in current work. The Mg-(10Ti + 0.18GNPs) composite was synthesized using the semi powder metallurgy method followed by hot extrusion. Microstructural characterization results revealed the uniform distribution of reinforcement (Ti + GNPs) particles in the matrix, therefore (Ti + GNPs) particles act as an effective reinforcing filler to prevent the deformation. Room temperature tensile results showed that the addition of Ti + GNPs to monolithic Mg lead to increase in 0.2% yield strength (0.2% YS), ultimate tensile strength (UTS), and failure strain. Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) and X-Ray Diffraction (XRD) were used to investigate the surface morphology, elemental dispersion and phase analysis, respectively.

Design of lightweight magnesium car body structure under crash and vibration constraints

Volume 2, Issue 2, June 2014, Pages 99-108
Morteza Kiani | Imtiaz Gandikota | Masoud Rais-Rohani | Masoud Rais-Rohani | Keiichi Motoyama

© 2014 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. Car body design in view of structural performance and lightweighting is a challenging task due to all the performance targets that must be satisfied such as vehicle safety and ride quality. In this paper, material replacement along with multidisciplinary design optimization strategy is proposed to develop a lightweight car body structure that satisfies the crash and vibration criteria while minimizing weight. Through finite element simulations, full frontal, offset frontal, and side crashes of a full car model are evaluated for peak acceleration, intrusion distance, and the internal energy absorbed by the structural parts. In addition, the first three fundamental natural frequencies are combined with the crash metrics to form the design constraints. The wall thicknesses of twenty-two parts are considered as the design variables. Latin Hypercube Sampling is used to sample the design space, while Radial Basis Function methodology is used to develop surrogate models for the selected crash responses at multiple sites as well as the first three fundamental natural frequencies. A nonlinear surrogate-based optimization problem is formulated for mass minimization under crash and vibration constraints. Using Sequential Quadratic Programming, the design optimization problem is solved with the results verified by finite element simulations. The performance of the optimum design with magnesium parts shows significant weight reduction and better performance compared to the baseline design.

Enhanced strength and ductility of Mg-Gd-Y-Zr alloys by secondary extrusion

Volume 1, Issue 1, March 2013, Pages 54-63
X. Li | W. Qi | K. Zheng | N. Zhou

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The Mg-12Gd-3Y-0.6Zr (GW123, wt.%) alloy was prepared by cast, and thermo-mechanically treated by single and secondary hot extrusion techniques. The microstructure, texture and mechanical properties of the extruded alloy were investigated. The results show that in different treated conditions the microstructure is mainly composed of α-Mg solid solution and second phases of Mg3Y3Gd2and Mg5(GdY) precipitates. The best mechanical properties are achieved in the secondary extruded alloy after ageing, with the ultimate tensile strength (UTS), tensile yield strength (TYS) and elongation (e{open}) being 446 MPa, 350 MPa and 10.2% at room temperature. A weak texture aligned with 〈101-0〉||ED (extrusion direction) component and spread from 〈101-0〉 to 〈112-0〉 poles was obtained in secondary extrusion, which is caused by the occurrence of dynamic recrystallization (DRX) in shear bands for texture randomization. The fracture modes in extruded GW123 alloy are mixed pattern of transgranular and intergranular fracture, as well as cleavage fracture. The strengthening mechanisms were quantitatively analysed from the different aspects using the measured microstructural parameters. The grain boundaries and solid solution strengthening were the main contributors to the high tensile strength of the GW123 alloy.

Effects of trace Gd concentration on texture and mechanical properties of hot-rolled Mg-2Zn-xGd sheets

Volume 1, Issue 1, March 2013, Pages 23-30
Hong Yan | Rongshi Chen | Nan Zheng | Jun Luo | Shigeharu Kamado | Enhou Han

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The effects of Gd concentration (0.1, 0.3, 0.7 wt%) on the microstructure, texture and mechanical properties of rolled and annealed Mg-2Zn-xGd sheets have been investigated aiming to develop low cost and high ductile Mg-Zn-Gd sheets. Dynamic recrystallization, static recrystallization and grain growth during hot rolling process and annealing process were delayed with increase of Gd concentration, leading to fine grain microstructure. The rolled 0.1 wt% Gd sheet showed strong basal texture which remained stable after annealing process and exhibited medium elongation of about 25%. In contrast, the rolled 0.3 wt% Gd sheet had weak basal texture which transformed to non-basal texture with double peaks tilted about ±48° to the transverse direction due to the static recrystallization during annealing process. Consequently, the annealed sheets exhibited higher elongation of 40% along the rolling direction and 50% along the transverse direction due to the existence of non-basal texture. It is suggested that the minimum effective concentration for texture randomization in the Mg-2Zn-xGd alloy is about 0.3 wt%.

Role of multi-microalloying by rare earth elements in ductilization of magnesium alloys

Volume 2, Issue 1, March 2014, Pages 1-7
Yuanding Huang | Weimin Gan | Karl Ulrich Kainer | Norbert Hort

© 2014 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The present work investigates the influences of microalloying with rare earths on the mechanical properties of magnesium alloys. The amount of each rare earth element is controlled below 0.4 wt.% in order not to increase the cost of alloy largely. The synergic effects from the multi-microalloying with rare earths on the mechanical properties are explored. The obtained results show that the as-cast magnesium alloys multi-microalloying with rare earths possesses a quite high ductility with a tensile strain up to 25-30% at room temperature. Moreover, these alloys exhibit much better corrosion resistance than AZ31 alloy. The preliminary in situ neutron diffractions on the deformation of these alloys indicate that the multi-microalloying with rare earths seems to be beneficial for the activation of more slip systems. The deformation becomes more homogeneous and the resultant textures after deformation are weakened.

The effect of addition of Nd and Ce on the microstructure and mechanical properties of ZM21 Mg alloy

Volume 1, Issue 1, March 2013, Pages 94-100
Binjiang Lv | Jian Peng | Jian Peng | Yi Peng | Aitao Tang

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The microstructures and mechanical properties of Mg-2.0Zn-1.0Mn (ZM21) alloys with certain amount of Ce and Nd additions were investigated, and the influence mechanism of Ce and Nd on the microstructures and mechanical properties of extruded alloys was discussed. The results indicated that the addition of Nd and Ce can refine the grains in ZM21 alloy, for which the distribution density of second phase particle played a major role to hinder the growth of dynamic recrystallization (DRX) grain in alloys by adding a content of 0.4 wt.% Ce and Nd. The average grain size of ZM21 alloy with the additions of 0.4 wt.% Nd and Ce reached 6 ± 3 μm and 13 ± 2 μm, respectively. Adding Ce and Nd to ZM21 alloy, the changes of mechanical properties were mainly attributed to a reduction in basal texture intensity, refinement grain size as well as the dispersion density and distribution position of fine second phase particles. Furthermore, by addition of Ce and Nd to ZM21 alloy, the non-basal plane slip system could be activated which decreased the basal texture intensity.

Investigation of a novel self-sealing pore micro-arc oxidation film on AM60 magnesium alloy

Volume 1, Issue 1, March 2013, Pages 82-87
Yingwei Song | Kaihui Dong | Dayong Shan | En Hou Han

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. Micro-arc oxidation (MAO) is one of the promising methods to improve the corrosion resistance of magnesium alloys. However, there are plenty of micro-pores in the traditional MAO films, deteriorating their protection property. A novel self-sealing pore MAO film was developed in this paper. The morphologies and chemical composition of the film were detected by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The corrosion behavior was investigated by electrochemical and salt spray tests. The possible film formation and corrosion mechanisms were proposed. The self-sealing pore film presents a blue appearance. Most of the micro-pores in the surface of the film are sealed during the film formation process. The chemical composition of the film mainly contains Mg, O, Ti, F and P. The self-sealing pore film exhibits better corrosion resistance compared with the traditional silicate film. Especially, the self-sealing pore film keeps intact after salt spray test for 2000 h, which can be attributed to its high compactness.

The role of Al2Y in grain refinement in Mg-Al-Y alloy system

Volume 1, Issue 2, June 2013, Pages 115-121
H. W. Chang | D. Qiu | J. A. Taylor | M. A. Easton | M. X. Zhang

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. A series of Mg-10(Al + Y) alloys with various weight ratios of Al to Y were cast to investigate the role of Al2Y in grain refinement in Mg-Al-Y ternary system. Thermal analysis combined with microstructural and EDX analysis was used to determine the phase transformation temperatures during solidification process. Experimental results show that when the Al content is below 4 wt%, a peritectic reaction, L + Al2Y → α-Mg, occurs after the intermetallic Al2Y forms directly from the melt as a pro-peritectic phase. Once the Al content is above 4 wt%, an eutectic reaction occurs at a lower temperature. The presence of the pro-peritectic phase can lead to nucleation of α-Mg directly through a peritectic reaction although grain refining efficiency is also closely related to the active particle size. In the case where solidification does not involve a peritectic reaction, the growth restriction factor, quantitatively the Q-value, governs the grain refining efficiency. Higher Q-value corresponds to finer grains.

A comparative corrosion behavior of Mg, AZ31 and AZ91 alloys in 3.5% NaCl solution

Volume 3, Issue 2, June 2015, Pages 142-148
I. B. Singh | M. Singh | S. Das

© 2015 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The corrosion behavior of Mg, AZ31 and AZ91 has been evaluated in 3.5% NaCl solution using weight loss, electrochemical polarization and impedance measurements. Corrosion rate derived from the weight losses demonstrated the occurrence of steeply fast corrosion reaction on AZ91 alloy after three hours of immersion, indicating the start of galvanic corrosion. An increase of corrosion rate with immersion time was also observed for AZ31 but with lesser extent than AZ91 alloy. Whereas Mg metals showed a decrease of corrosion rate with immersion time, suggesting the formation of a protective layer on their surfaces. In contrast, the corrosion current density (Icorr) derived from the Tafel plots, exhibited their corrosion resistances in order of Mg > AZ91 > AZ31. Electrochemical charge transfer resistance (Rct) and double layer capacitance measured by electrochemical impedance spectroscopy (EIS), are well in accordance with the measured Icorr.EIS measurements with time and microstructural examination of the corroded and uncorroded samples are helpful in elucidation of results measured by electrochemical polarization.

Dynamic precipitation during multi-axial forging of an Mg-7Gd-5Y-1Nd-0.5Zr alloy

Volume 1, Issue 1, March 2013, Pages 47-53
Ting Li | Kui Zhang | Xinggang Li | Zhiwei Du | Yongjun Li | Minglong Ma | Guoliang Shi

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The dynamic precipitation behavior during multi-axial forging in an Mg-7Gd-5Y-1Nd-0.5Zr alloy has been investigated and compared with that in static precipitation treatment. The results indicated that dynamic precipitation does occur during multi-axial forging. The dynamic precipitate can be deduced as β phase with face-centered cubic crystal structure (a = 2.22 nm). Most of the β precipitates locate at the dynamic recrystallization grain boundaries. The morphology and orientation relationship is different from that of the β phase formed in the static precipitation treated alloys, although the crystal structure is the same. The precipitation temperature of β phase during MAF is higher than that in the static precipitation treatment.

Influence of incorporating Si3N4particles into the oxide layer produced by plasma electrolytic oxidation on AM50 Mg alloy on coating morphology and corrosion properties

Volume 1, Issue 4, December 2013, Pages 267-274
Xiaopeng Lu | Carsten Blawert | Nico Scharnagl | Karl Ulrich Kainer

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The influence of incorporating different sizes of Si3N4particles on the microstructure and corrosion properties of a phosphate-based plasma electrolytic oxidation (PEO) coating on AM50 magnesium alloy was investigated. The experiments for this study were performed in alkaline electrolytes containing 1 g/L KOH, 10 g/L Na3PO4with and without three different sized of Si3N4particles. The corrosion properties of PEO coatings were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 0.5 wt.% NaCl solution. Microstructure observations by SEM showed that the surface morphology and composition of the PEO coating were affected greatly by particle addition. Si3N4particles can still be found without decomposition in the final coating due to their high melting point.

Corrosion behavior of Mg-Gd-Zn based alloys in aqueous NaCl solution

Volume 2, Issue 3, September 2014, Pages 245-256
A. Srinivasan | A. Srinivasan | C. Blawert | Y. Huang | C. L. Mendis | K. U. Kainer | N. Hort

© 2014 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The corrosion behavior of Mg-10Gd-xZn (x = 2, 6 wt.%) alloys in 0.5 wt.% NaCl solution was investigated. Microstructures of both the alloys consisted of (Mg,Zn)3Gd phase and lamellar long period stacking ordered (LPSO) phase. The morphology of the second phase at the grain boundary differed in both alloys: it was a continuous network structure in Mg-10Gd-6Zn, whereas it was relatively discrete in Mg-10Gd-2Zn. The dendrites were finer in size and highly branched in Mg-10Gd-6Zn. The corrosion results indicated that the increase in Zn content increased the corrosion rate in Mg-10Gd-xZn alloys. Micro-galvanic corrosion occurred near the grain boundary in both alloys initially as the grain boundary phase was stable and acted as a cathode, however, filiform corrosion dominated in the later stage, which was facilitated by the LPSO phase in the matrix. Severe micro-galvanic corrosion occurred in Mg-10Gd-6Zn due to the higher volume of second phase. The stability of the second phase at the grain boundary was altered and dissolved after the long immersion times. Probably the NaCl solution chemically reacted with the grain boundary phase and de-stabilized it during the long immersion times, and was removed by the chromic acid used for the corrosion product removal.

Formability of AZ31 Mg alloy sheets within medium temperatures

Volume 1, Issue 4, December 2013, Pages 312-317
Lei Wang | Qi Qiao | Yang Liu | Xiu Song

© 2014 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The stretching tests of the commercial AZ31 Mg alloy were conducted at 130 °C, 170 °C, 210 °C, at the forming speeds of 10 mm/min and 50 mm/min, respectively. The formability of AZ31 sheets at high temperature was evaluated by forming limit diagrams (FLD). The fracture morphologies were analyzed using a scanning electron microscope. The results show that the FLD of AZ31 Mg alloy is affected by the forming temperature, in another word, the formability increases with the increasing of the forming temperature. That may be because the non-basal slip system starts to move by thermal activation at high forming temperature. It is also demonstrated that the formability of the AZ31 Mg alloy is on the decline with the increasing of the forming speed. The slipping performs thoroughly to release the stress during the deformation if the forming speed decreases. In addition, the higher the forming temperature is, the more obvious the effect of the forming speed is. The forming temperature is the main dominating factor on the formability of AZ31 Mg alloy.

Microstructures and mechanical properties of friction stir processed Mg-2.0Nd-0.3Zn-1.0Zr magnesium alloy

Volume 1, Issue 2, June 2013, Pages 122-127
F. Y. Zheng | Y. J. Wu | L. M. Peng | L. M. Peng | X. W. Li | P. H. Fu | W. J. Ding | W. J. Ding

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The effect of Friction stir process (FSP) parameters on the microstructure and mechanical properties of an extruded Mg-2.0Nd-0.3Zn-1.0Zr (wt.%) alloy was investigated in this paper. The alloy was friction stir processed with different passes: single-pass, three-pass and five-pass, under a tool rotation rate of 800 rpm and a traverse speed of 200 mm min-1. FSP results in remarkable grain refinement of the extruded alloy (average grain size ~3.8 μm as 3 passes) and almost complete dissolution of the Mg12Nd phase in the matrix. With the increase of pass, the average grain size in the stir zone (SZ) is decreased firstly and then increases. The Vikers hardness of SZs in all FSPed samples is higher than that of the parent material (PM). Tensile tests at room-temperature show that the tensile strengths of the stir zones along the FSP advancing direction are slightly lower than those of PM. However, the elongations are remarkably improved from 13.0% for PM to 24.5% for SZ FSPed with three-passes. These improved tensile properties are attributed to the microstructure refinement, dynamic recrystallization and dissolution of the Mg12Nd phase.

The effect of Equal Channel Angular Pressing process on the microstructure of AZ31 Mg alloy strip shaped specimens

Volume 1, Issue 2, June 2013, Pages 145-149
S. M. Arab | A. Akbarzadeh

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. Equal Channel Angular Pressing (ECAP) is one of the most applicable Sever Plastic Deformation (SPD) processes which leads to strength and ductility improvement through the grain refining and development of a suitable texture. In this study, after designing and manufacturing a suitable die, 4 pass ECAP process at route C is done on strip shaped specimens of AZ31 magnesium alloy in order to achieve desirable microstructural and mechanical properties. Microstructure then got studied through the optical microscopy. Results show that mean grain size is decreased and grain size distribution got close to normal distribution state by increasing the pass number. However, the grain size is reduced by increasing of ECAP temperature.

Effect of equal channel angular pressing on AZ31 wrought magnesium alloys

Volume 1, Issue 4, December 2013, Pages 336-340
Avvari Muralidhar | S. Narendranath | H. Shivananda Nayaka

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. AZ31 wrought magnesium alloys are light weight materials which play an important role in order to reduces the environmental burdens in modern society because of its high strength to weight ratio, corrosion resistance, and stiffness and machinability. Applications of this material are mainly in structural component i.e., in constructions, automobile, aerospace, electronics and marine industries. In the present work, the microstructure characterization of the AZ31 alloys up to four ECAP passes at temperature of 573 K was observed for route Bc. Average grain size of the material was reduced from 31.8 μm to 8 μm after four ECAP passes. Mechanical properties of the alloy improved with increase in number of ECAP passes. Moreover, X-ray diffraction analysis was carried out for as received and ECAP processed material.

Microstructure and mechanical behavior of the Mg-Mn-Ce magnesium alloy sheets

Volume 2, Issue 1, March 2014, Pages 8-12
Qingshan Yang | Qingshan Yang | Bin Jiang | Bin Jiang | Xin Li | Hanwu Dong | Hanwu Dong | Wenjun Liu | Wenjun Liu | Fusheng Pan | Fusheng Pan

© 2014 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The microstructural evolution and mechanical behavior of Mg-Mn-Ce magnesium alloy were investigated in the present study. Mg alloy was prepared with metal model casting method and subsequently hot extruded at 703 K with the reduction ratio of 101:1. The grains were dynamically recrystallized after the extrusion process. Moreover, the (0002) pole figure of Mg-Mn-Ce alloy developed a splitting of pronounced basal texture. The mechanical properties were different due to different angles between c-axis and loading direction (0°, 45° and 90°) in the tensile tests. This significantly induces an asymmetry in the yield behavior. The Mg-Mn-Ce alloy exhibits a classical dimple structure as a result of slip accumulation and ductile tear.

Plasma electrolytic oxidation of magnesium and its alloys: Mechanism, properties and applications

Volume 5, Issue 1, March 2017, Pages 74-132
Gh Barati Darband | M. Aliofkhazraei | P. Hamghalam | N. Valizade

© 2017 Plasma Electrolyte Oxidation (PEO) process has increasingly been employed to improve magnesium surface properties by fabrication of an MgO-based coating. Originating from conventional anodizing procedures, this high-voltage process produces an adhesive ceramic film on the surface. The present article provides a comprehensive review around mechanisms of PEO coatings fabrication and their different properties. Due to complexity of PEO coatings formation, a complete explanation regarding fabrication mechanisms of PEO coatings has not yet been proposed; however, the most important advancements in the field of fabrication mechanisms of PEO coatings were gathered in this work. Mechanisms of PEO coatings fabrication on magnesium were reviewed considering voltage–time plots, optical spectrometry, acoustic emission spectrometry and electronic properties of the ceramic film. Afterwards, the coatings properties, affecting parameters and improvement strategies were discussed. In addition, corrosion resistance of coatings, important factors in corrosion resistance and methods for corrosion resistance improvement were considered. Tribological properties (important factors and improvement methods) of coatings were also studied. Since magnesium and its alloys are broadly used in biological applications, the biological properties of PEO coatings, important factors in their biological performance and existing methods for improvement of coatings were explained. Addition of ceramic based nanoparticles and formation of nanocomposite coatings may considerably influence properties of plasma electrolyte oxidation coatings. Nanocomposite coatings properties and nanoparticles adsorption mechanisms were included in a separate sector. Another method to improve coatings properties is formation of hybrid coatings on PEO coatings which was discussed in the end.

Multi-response optimization of process parameters in friction stir welded AM20 magnesium alloy by Taguchi grey relational analysis

Volume 3, Issue 1, March 2015, Pages 36-46
Prakash Kumar Sahu | Sukhomay Pal

© 2015 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. The purpose of this paper is to optimize the process parameter to get the better mechanical properties of friction stir welded AM20 magnesium alloy using Taguchi Grey relational analysis (GRA). The considered process parameters are welding speed, tool rotation speed, shoulder diameter and plunging depth. The experiments were carried out by using Taguchi's L18 factorial design of experiment. The processes parameters were optimized and ranked the parameters based on the GRA. The percentage influence of each process parameter on the weld quality was also quantified. A validation experimental run was conducted using optimal process condition, which was obtained from the analysis, to show the improvement in mechanical properties of the joint. This study also shows the feasibility of the GRA with Taguchi technique for improvement in welding quality of magnesium alloy.

Effect of Zr modification on solidification behavior and mechanical properties of Mg-Y-RE (WE54) alloy

Volume 1, Issue 4, December 2013, Pages 346-351
Jilin Li | Rongshi Chen | Yuequn Ma | Wei Ke

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. Magnesium alloys containing rare earth elements (RE) have received considerable attention in recent years due to their high mechanical strength and good heat-resisting performance. Among them, Mg-5%Y-4%RE (WE54) magnesium alloy is a high strength sand casting magnesium alloy for use at temperatures up to 300 °C, which is of great interest to engineers in the aerospace industry. In the present work, the solidification behavior of Zr-containing WE54 alloy and Zr-free alloy was investigated by computer-aided cooling curve analysis (CA-CCA) technique. And the solidification microstructure and mechanical properties of them were also investigated comparatively. It is found from the cooling curves and as-cast microstructure of WE54 alloy that the nucleation temperature of α-Mg in WE54 alloy increases after Zr addition, and the as-cast microstructure of the alloy is significantly refined by Zr. While the phase constitution of WE54 alloy is not changed after Zr addition. These phenomena indicate that Zr acts as heterogeneous nuclei during the solidification of WE54 alloy. Due to refined microstructure, the mechanical properties of Zr-containing WE54 alloy is much higher than Zr-free WE54 alloy.

Effect of homogenization treatment on microstructure evolution and the distributions of RE and Zr elements in various Mg-Li-RE-Zr alloys

Volume 1, Issue 2, June 2013, Pages 139-144
Lei Bao | Qichi Le | Zhiqiang Zhang | Jianzhong Cui | Qinxue Li

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. Mg-3Li-0.4Zr alloys containing RE elements (Gd, La, Nd) (Mg-3Li-RE-0.4Zr alloys) are investigated to reveal the influence of homogenization treatment on microstructures and distributions of RE, Zr elements. It is found that 300 °C × 24 h homogenization treatment shows better improvement on the microstructure including the refinement of grain size, the dispersion of cellular dendrite and low melting point particles. Before treatment, La and Nd segregate effectively at grain boundary and Zr segregates in the form of precipitates. Homogenization treatment induces the reduction of RE segregation. However, the segregation of Zr in precipitates cannot be abated due to the relatively low diffusion rate compared with RE elements.

Microstructure and mechanical properties of a high ductility Mg-Zn-Mn-Ce magnesium alloy

Volume 1, Issue 4, December 2013, Pages 283-291
Lei Gao | Hong Yan | Jun Luo | Alan A. Luo | Rongshi Chen

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. A high-ductility ZME200 (Mg-2.3Zn-0.4Mn-0.2Ce.11All compositions in wt.% except otherwise stated.) alloy was newly developed for vehicle closure and structure applications, based on an earlier ZE20 (Mg-2.0Zn-0.2Ce) alloy for extrusion applications. Previous study indicates that the hot deformation behavior of as-cast ZME200 alloy varies with processing parameters, namely temperature and strain rate. In this follow-up study, a conventional rolling process was optimized to obtain magnesium sheets with a very fine grain structure and high ductility. The microstructure, mechanical properties, and corrosion resistances of ZME200 alloy were investigated, and compared with those of commercial AZ31 magnesium alloy. It was demonstrated that the ZME200 alloy sheet exhibits extraordinarily higher ductility (36% in tensile elongation), much superior stretch formability (an Erichsen value of 9.5), lower anisotropy, comparable strength and corrosion resistance to AZ31 alloy. The unique RD-TD double split texture with remarkably reduced intensity and grain refinement gives rise to the significantly improved ductility and formability at room-temperature.

First-principles calculations of structural, elastic and electronic properties of AB2type intermetallics in Mg-Zn-Ca-Cu alloy

Volume 1, Issue 3, September 2013, Pages 256-262
Pingli Mao | Bo Yu | Zheng Liu | Feng Wang | Yang Ju

© 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University. Electronic structure and elastic properties of MgCu2, Mg2Ca and MgZn2phases were investigated by means of first-principles calculations from CASTEP program based on density functional theory (DFT). The calculated lattice parameters were in good agreement with the experimental and literature values. The calculated heats of formation and cohesive energies shown that MgCu2has the strongest alloying ability and structural stability. The elastic constants of MgCu2, Mg2Ca and MgZn2phases were calculated, the bulk moduli, shear moduli, Young's moduli and Poisson's ratio were derived. The calculated results shown that MgCu2, Mg2Ca and MgZn2are all ductile phases. Among the three phases, MgCu2has the strongest stiffness and the plasticity of MgZn2phase is the best. The density of states (DOS), Mulliken electron occupation number and charge density difference of MgCu2, Mg2Ca and MgZn2phases were discussed to analyze the mechanism of structural stability and mechanical properties.

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