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1

Superplasticity in a ZK60 magnesium alloy at low temperatures  

SciTech Connect

High tensile ductilities associated with superplasticity occur when the grain size is small and typically less than {approximately}10 {micro}m. The conventional superplasticity in pseudo single phase alloys is observed at relatively low strain rate of <10{sup {minus}3} s{sup {minus}1} and at temperatures of {approximately}0.8T{sub m} where T{sub m} is the melting point of the material. Recently, several method have been developed for extreme grain refinement including mechanical alloying, crystallization from amorphous powders, and/or equal-channel-angular-extrusion. Experimental evidence suggests that a reduction in grain size will increase the strain rate and/or decrease the temperature for optimum superplastic flow. The purpose of this paper is to investigate superplastic deformation mechanism at lower temperatures. In this study, mechanical properties in a pseudo single phase magnesium alloy were examined at relatively low homologous temperatures of {approximately}0.5T{sub m}. Based on the constitutive equation for superplastic flow, deformation mechanism at low temperatures is discussed.

Watanabe, Hiroyuki; Mukai, Toshiji [Osaka Municipal Technical Research Inst. (Japan)] [Osaka Municipal Technical Research Inst. (Japan); Higashi, Kenji [Osaka Prefecture Univ., Sakai (Japan)] [Osaka Prefecture Univ., Sakai (Japan)

1999-01-22

2

Superplasticity in a ZK60 magnesium alloy at low temperatures  

Microsoft Academic Search

High tensile ductilities associated with superplasticity occur when the grain size is small and typically less than 10 μm. The conventional superplasticity in pseudo single phase alloys is observed at relatively low strain rate of <10⁻³ s⁻¹ and at temperatures of 0.8T{sub m} where T{sub m} is the melting point of the material. Recently, several method have been developed for

Hiroyuki Watanabe; Toshiji Mukai; Kenji Higashi

1999-01-01

3

Low temperature superplasticity of a fine-grained ZK60 magnesium alloy processed by equal-channel-angular extrusion  

Microsoft Academic Search

Fine-grained ZK60 magnesium alloy with the grain size of 1.4 ?m was processed by equal-channel-angular extrusion. The material exhibited low temperature superplasticity. The normalized plot suggested that the present material had equilibrium grain boundaries at the superplastic temperature in contrast to typical materials processed by severe plastic deformation.

Hiroyuki Watanabe; Toshiji Mukai; Koichi Ishikawa; Kenji Higashi

2002-01-01

4

Tensile properties of extruded ZK60RE alloys  

Microsoft Academic Search

ZK60RE alloys were made by melting ZK60 alloy and cerium-rich rare earth (RE) metal in an electric furnace. The content of RE is 0, 0.5, 1, 1.5, 2, 3 wt.% RE, respectively. The influence of RE on microstructure and tensile mechanical properties of ZK60 magnesium alloys was studied. The results showed that cerium-rich misch metal (MM) had an obvious effect

Chunjiang Ma; Manping Liu; Guohua Wu; Wenjiang Ding; Yanping Zhu

2003-01-01

5

The development of superplastic ductilities and microstructural homogeneity in a magnesium ZK60 alloy processed by ECAP  

Microsoft Academic Search

An extruded ZK60 magnesium alloy was processed by equal-channel angular pressing (ECAP) and then tested in tension at elevated temperatures. The results show the alloy is superplastic at a testing temperature of 473K with an optimum ductility of ?1310% when using an initial strain rate of 2.010?4s?1. The results demonstrate that optimum superplasticity is achieved at intermediate strain rates and

Roberto B. Figueiredo; Terence G. Langdon

2006-01-01

6

In vivo degradation and tissue compatibility of ZK60 magnesium alloy with micro-arc oxidation coating in a transcortical model.  

PubMed

Magnesium alloys were studied extensively as a class of biodegradable metallic materials for medical applications. In the present study, ZK60 magnesium alloy was considered as a candidate and the micro-arc oxidation (MAO) treatment was adopted in order to reduce the degradation rate of the alloy. The in vivo degradation behaviors and biological compatibilities of ZK60 alloys with and without MAO treatment were studied with a transcortical model in rabbits. The implant and the surrounding bone tissues were characterized by CT, SEM and histological methods at 2, 4 and 12 weeks after the implantation. The results demonstrated that both the bare and MAO-coated ZK60 alloys completely degraded within 12 weeks in this animal model. The MAO coating decreased the degradation rate of ZK60 alloy and enhanced the response of the surrounding tissues within the first 2 weeks. After then, an acceleration of the degradation of the MAO-coated ZK60 alloy was observed. It was found that the alloy could be degraded before the complete degradation of the MAO coating, leading to the local peeling off of the coating. An in vivo degradation mechanism of the MAO-coated ZK60 alloy was proposed based on the experimental results. The severe localized degradation caused by the peeling off of the MAO coating was the main reason for the acceleration of the degradation of the MAO-coated ZK60 alloy. PMID:23910291

Lin, Xiao; Tan, Lili; Wang, Qiang; Zhang, Guangdao; Zhang, Bingchun; Yang, Ke

2013-10-01

7

In vitro corrosion and cytocompatibility of ZK60 magnesium alloy coated with hydroxyapatite by a simple chemical conversion process for orthopedic applications.  

PubMed

Magnesium and its alloys--a new class of degradable metallic biomaterials-are being increasingly investigated as a promising alternative for medical implant and device applications due to their advantageous mechanical and biological properties. However, the high corrosion rate in physiological environments prevents the clinical application of Mg-based materials. Therefore, the objective of this study was to develop a hydroxyapatite (HA) coating on ZK60 magnesium alloy substrates to mediate the rapid degradation of Mg while improving its cytocompatibility for orthopedic applications. A simple chemical conversion process was applied to prepare HA coating on ZK60 magnesium alloy. Surface morphology, elemental compositions, and crystal structures were characterized using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction, respectively. The corrosion properties of samples were investigated by immersion test and electrochemical test. Murine fibroblast L-929 cells were harvested and cultured with coated and non-coated ZK60 samples to determine cytocompatibility. The degradation results suggested that the HA coatings decreased the degradation of ZK60 alloy. No significant deterioration in compression strength was observed for all the uncoated and coated samples after 2 and 4 weeks' immersion in simulated body fluid (SBF). Cytotoxicity test indicated that the coatings, especially HA coating, improved cytocompatibility of ZK60 alloy for L929 cells. PMID:24300096

Wang, Bing; Huang, Ping; Ou, Caiwen; Li, Kaikai; Yan, Biao; Lu, Wei

2013-01-01

8

Grain refinement of AZ31 and ZK60 Mg alloys towards superplasticity studies  

Microsoft Academic Search

Low temperature superplastic (SP) behavior (mechanical and deformation mechanisms) of two commercial Mg-based alloys (AZ31 and ZK60) was characterized. The two alloys were tested in the as extruded condition with initial grain size of 15 ?m (AZ31) and fine (2 ?m) and coarse (25 ?m) grains mixed randomly for the ZK60. Strain rate was activated in the range 10?51 s?1

A. Bussiba; A. Ben Artzy; A. Shtechman; S. Ifergan; M. Kupiec

2001-01-01

9

Deformation behavior and microstructure evolution of wrought magnesium alloys  

NASA Astrophysics Data System (ADS)

There are many researches on the deformation behavior of wrought magnesium alloys, such as AZ31, AZ80, AZ91, and ZK60 magnesium alloys at different temperatures and strain rates, but few of them focuses on the deformation behavior of AZ41M and ZK60M alloys, especially under the twin-roll casting (TRC) state. Meanwhile, the existing researches only focus on the grain refinement law of the magnesium alloys under deformation conditions, the deformation mechanism has not been revealed yet. The hot compression behavior of AZ41M and ZK60M magnesium alloys under the temperature and strain rate ranges of 250-400 C and 0.001-1 s-1 are studied by thermal simulation methods using Gleeble 1500 machine and virtual simulation using finite element analysis software. Simulation results show that sine hyperbolic law is the most suitable flow stress model for wider deformation conditions. The most reasonable selected deformation conditions of ZK60M alloy is 350 C/0.1 s-1 for TRC and 350 C/1 s-1 for conventional casting (CC), while AZ41M alloy is 300 C/0.01 s-1 for TRC and 350 C/0.1 s-1 for CC. Deformation behavior and dynamic recrystallization (DRX) mechanism of them are analyzed at the same deformation conditions. The microstructures of AZ41M and ZK60M alloys are observed at different deformed conditions by optical microscopy (OM) and electron back scatter diffraction (EBSD) and it reveals the flow behavior and deformation mechanism of them. Working harden and work soften contribute to the activation of basal, non-basal slip systems which promote DRX. The proposed research reveals the deformation behavior and mechanism of the AZ41M and ZK 60M magnesium alloys and concludes their optimized deformation parameters and processes and provides a theory basis for their manufacturing and application.

Wang, Shouren; Song, Linghui; Kang, Sukbong; Cho, Jaehyung; Wang, Yingzi

2013-05-01

10

Routes to develop fine-grained magnesium alloys and composites for high strain rate superplasticity  

SciTech Connect

Recent activities in the research of magnesium became higher in order to reduce the weight of components such as motor vehicles from the economical and ecological point of view. Superplastic properties of magnesium alloys and their composites were reviewed with a special emphasis on the achievement of high strain rate superplastic forming. The role of grain size on superplastic deformation mechanisms was particularly addressed. Commercial Mg-Al-Zn alloys and a ZK60-based composite are used as model materials to illustrate the underlining principles leading to the observation of high strain rate superplasticity. In this paper, experimental results from several processing routes, including thermomechanical processing, severe plastic deformation, and extrusion of machined chips and rapidly solidified powders, are presented. High strain rate superplasticity (HSRS) is demonstrated in ZK60-based composites.

Mukai, Toshiji; Watanabe, Hiroyuki; Nieh, T.G.; Higashi, Kenji

2000-07-01

11

Dynamic testing at high strain rates of an ultrafine-grained magnesium alloy processed by ECAP  

Microsoft Academic Search

A ZK60 magnesium alloy was processed by equal-channel angular pressing (ECAP) at 473K to produce a grain size of ?0.8?m and it was then tested under dynamic conditions at strain rates up to 4.0103s?1 using a split-Hopkinson bar. The stressstrain curves in dynamic testing exhibited upwards concave curvature suggesting the occurrence of twinning. Examination by transmission electron microscopy showed that

B. Li; S. Joshi; K. Azevedo; E. Ma; K. T. Ramesh; R. B. Figueiredo; T. G. Langdon

2009-01-01

12

Superplasticity in a powder metallurgy magnesium composite  

SciTech Connect

Metal-matrix composites (MMC) have great potential to be used in high-performance aerospace and automobile applications. It is important, therefore, to develop secondary processing for MMCs which can effectively produce complex engineering components directly from wrought products. Many studies now have been performed that demonstrate superplasticity can be developed in MMCs. Superplasticity has been reported in some Mg alloys, including ZK60, AZ31, AZ61, and Mg-Li alloys. But, none of these alloys showed superplasticity at high strain rates. Although HSRS has been extensively demonstrated in Al-base MMCs, both in PM and IM products, neither conventional superplasticity nor HSRS has yet been shown in any Mg-base composite. The purpose of this paper is to present, for the first time, the observation of HSRS in a 17 vol% SiC particulate-reinforced ZK60A magnesium composite (ZK60/SiC/17p).

Nieh, T.G.; Wadsworth, J. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States)

1995-04-15

13

Magnesium Alloys and their Applications  

NASA Astrophysics Data System (ADS)

In the recent years there has been a dramatic increase in research activity and also applications of magnesium alloys. The driving force is the growing demand by the automobile industry resulting from the pressure to reduce weight and hence to reduce the fuel consumption. The U.S. car industry incorporates the largest amount of magnesium at the present time. In Europe, Volkswagen had a history of using magnesium in the VW Beetle. Volkswagen, in common with other major car producers has initiated a major research and development programme for advanced magnesium materials. The main emphasis of this book is in the field of general physical metallurgy and alloy development refelcting the need to provide a wider range of alloys both casting and wrought alloys to meet the increasing demands of industry. Other topics are nevertheless well represented such as casting, recycling, joining, corrosion, and surface treatment.

Kainer, Karl U.

1999-04-01

14

Elastic Properties and Internal Friction of Two Magnesium Alloys at Elevated Temperatures  

SciTech Connect

The elastic properties and internal friction of two magnesium alloys were studied from 25 C to 450 C using Resonant Ultrasound Spectroscopy (RUS). The Young's moduli decrease with increasing temperature. At 200 C, a change in the temperature dependence of the elastic constants is observed. The internal friction increases significantly with increasing temperature above 200 C. The observed changes in the temperature dependence of the elastic constants and the internal friction are the result of anelastic relaxation by grain boundary sliding at elevated temperatures. Elastic properties govern the behavior of a materials subjected to stress over a region of strain where the material behaves elastically. The elastic properties, including the Young's modulus (E), shear modulus (G), bulk modulus (B), and Poisson's ratio (?), are of significant interest to many design and engineering applications. The choice of the most appropriate material for a particular application at elevated temperatures therefore requires knowledge of its elastic properties as a function of temperature. In addition, mechanical vibration can cause significant damage in the automotive, aerospace, and architectural industries and thus, the ability of a material to dissipate elastic strain energy in materials, known as damping or internal friction, is also important property. Internal friction can be the result of a wide range of physical mechanisms, and depends on the material, temperature, and frequency of the loading. When utilized effectively in engineering applications, the damping capacity of a material can remove undesirable noise and vibration as heat to the surroundings. The elastic properties of materials can be determined by static or dynamic methods. Resonant Ultrasound Spectroscopy (RUS), used in this study, is a unique and sophisticated non-destructive dynamic technique for determining the complete elastic tensor of a solid by measuring the resonant spectrum of mechanical resonance for a sample of known geometry, dimensions, and mass. In addition, RUS allows determination of internal friction, or damping, at different frequencies and temperatures. Polycrystalline pure magnesium (Mg) exhibits excellent high damping properties. However, the poor mechanical properties limit the applications of pure Mg. Although alloying can improve the mechanical properties of Mg, the damping properties are reduced with additions of alloying elements. Therefore, it becomes necessary to study and develop Mg-alloys with simultaneous high damping capacity and improved mechanical properties. Moreover, studies involving the high temperature dynamic elastic properties of Mg alloys are limited. In this study, the elastic properties and internal friction of two magnesium alloys were studied at elevated temperatures using RUS. The effect of alloy composition and grain size was investigated. The wrought magnesium alloys AZ31 and ZK60 were employed. Table 1 gives the nominal chemical compositions of these two alloys. The ZK60 alloy is a commercial extruded plate with a T5 temper, i.e. solution-treated at 535 C for two hours, quenched in hot water, and aged at 185 C for 24 hours. The AZ31 alloy is a commercial rolled plate with a H24 temper, i.e. strain hardened and partially annealed.

Freels, M.; Liaw, P. K.; Garlea, E.; Morrell, J. S.; Radiovic, M.

2011-06-01

15

Electrodeposition of magnesium and magnesium/aluminum alloys  

DOEpatents

Electrolytes and plating solutions for use in processes for electroplating and electroforming pure magnesium and alloys of aluminum and magnesium and also electrodeposition processes. An electrolyte of this invention is comprised of an alkali metal fluoride or a quaternary ammonium halide, dimethyl magnesium and/or diethyl magnesium, and triethyl aluminum and/or triisobutyl aluminum. An electrolyte may be dissolved in an aromatic hydrocarbon solvent to form a plating solution. The proportions of the component compounds in the electrolyte are varied to produce essentially pure magnesium or magnesium/aluminum alloys having varying selected compositions.

Mayer, Anton (Los Alamos, NM)

1988-01-01

16

Ordered Magnesium-Lithium alloys  

Microsoft Academic Search

Emerging technologies increasingly depend on the production of ultra-lightweight materials. Magnesium-lithium (MgLi) alloys are the lightest metallic alloys, having densities near that of plastics, and are strong enough to be used in a variety of high- performance applications. Although considerable work has been done on the MgLi system, little is known regarding potential ordered phases. An analysis of the system

Richard Taylor; Stefano Curtarolo; Gus Hart

2009-01-01

17

Corrosion in Magnesium and a Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Magnesium and a magnesium alloy (AZ91C) have been ion implanted over a range of ions energies (50 to 150 keV) and doses (1 x 10('16) to 2 x 10('17) ions/cm('2)) to modify the corrosion properties of the metals. The corrosion tests were done by anodic polarization in chloride -free and chloride-containing aqueous solutions of a borated -boric acid with a pH of 9.3. Anodic polarization measurements showed that some implantations could greatly reduce the corrosion current densities at all impressed voltages and also increased slightly the pitting potential, which indicated the onset of the chloride attack. These improvements in corrosion resistance were caused by boron implantations into both types of samples. However, iron implantations were found to improve only the magnesium alloy. To study the corrosion in more detail, Scanning Auger Microprobe Spectrometer (SAM), Scanning Electron Microscope (SEM) with an X-ray Energy Spectrometry (XES) attachment, and Transmission Electron Microscope (TEM) measurements were used to analyze samples before, after, and at various corrosion stages. In both the unimplanted pure magnesium and AZ91C samples, anodic polarization results revealed that there were three active corrosion stages (Stages A, C, and E) and two passivating stages (Stages B and D). Examination of Stages A and B in both types of samples showed that only a mild, generalized corrosion had occurred. In Stage C of the TD samples, a pitting breakdown in the initial oxide film was observed. In Stage C of the AZ91C samples, galvanic and intergranular attack around the Mg(,17)Al(,12) intermetallic islands and along the matrix grain boundaries was observed. Stage D of both samples showed the formation of a thick, passivating oxygen containing, probably Mg(OH)(,2) film. In Stage E, this film was broken down by pits, which formed due to the presence of the chloride ions in both types of samples. Stages A through D of the unimplanted samples were not seen in the boron or iron implanted samples. Instead one low current density passivating stage was formed, which was ultimately broken down by the chloride attack. It is believed that the implantation of boron modified the initial surface film to inhibit corrosion, whereas the iron implantation modified the intermetallic (Mg(,17)Al(,12)) islands to act as sacrificial anodes.

Akavipat, Sanay

18

Magnesium-lithium casting alloys  

NASA Technical Reports Server (NTRS)

The strength properties of magnesium-lithium alloys at room, low, and high temperatures are investigated. It is found that the alloys may have practical application at ambient temperatures up to 100 C, that negative temperatures have a favorable influence on the alloy strength, and that cyclic temperature variations have practically no effect on the strength characteristics. The influence of chemical coatings on corrosion resistance of the MgLi alloys is examined. Several facilities based on pressure casting machines, low-pressure casting machines, and magnetodynamic pumps were designed for producing MgLi alloy castings. Results were obtained for MgLi alloys reinforced with fibers having a volumetric content of 15%.

Latenko, V. P.; Silchenko, T. V.; Tikhonov, V. A.; Maltsev, V. P.; Korablin, V. P.

1974-01-01

19

Microstructure and orientation relationships of Mg alloy matrix composite reinforced with SiC whiskers and B 4C particles  

Microsoft Academic Search

The microstructure and orientation relationships of ZK60A magnesium alloy matrix composite reinforced with SiC whiskers and B4C particles have been studied by means of transmission electron microscopy and high-resolution electron microscopy. MgO nanocrystalline particles are formed at SiC\\/Mg interfaces with a cube-on-cube orientation relationship with SiC whiskers. MgB2 nanorods are formed near the B4C particles. Two types of orientation relationships

Y. X. Chen; D. X. Li

2007-01-01

20

Imparting passivity to vapor deposited magnesium alloys  

NASA Astrophysics Data System (ADS)

Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread implementation of magnesium alloys is currently hindered by their relatively poor corrosion resistance. The objective of this research dissertation is to develop a scientific basis for the creation of a corrosion resistant magnesium alloy. The corrosion resistance of magnesium alloys is affected by several interrelated factors. Among these are alloying, microstructure, impurities, galvanic corrosion effects, and service conditions, among others. Alloying and modification of the microstructure are primary approaches to controlling corrosion. Furthermore, nonequilibrium alloying of magnesium via physical vapor deposition allows for the formation of single-phase magnesium alloys with supersaturated concentrations of passivity-enhancing elements. The microstructure and surface morphology is also modifiable during physical vapor deposition through the variation of evaporation power, pressure, temperature, ion bombardment, and the source-to-substrate distance. Aluminum, titanium, yttrium, and zirconium were initially chosen as candidates likely to impart passivity on vapor deposited magnesium alloys. Prior to this research, alloys of this type have never before been produced, much less studied. All of these metals were observed to afford some degree of corrosion resistance to magnesium. Due to the especially promising results from nonequilibrium alloying of magnesium with yttrium and titanium, the ternary magnesium-yttrium-titanium system was investigated in depth. While all of the alloys are lustrous, surface morphology is observed under the scanning electron microscope. The corrosion rate of the nonequilibrium sputtered alloys, as determined by polarization resistance, is significantly reduced compared to the most corrosion resistant commercial magnesium alloys. The open circuit potentials of the sputter deposited alloys are significantly more noble compared to commercial, equilibrium phase magnesium alloys. Galvanic corrosion susceptibility has also been considerably reduced. Nonequilibrium magnesium-yttrium-titanium alloys have been shown to achieve passivity autonomously by alteration of the composition chemistry of the surface oxide/hydroxide layer. Self-healing properties are also evident, as corrosion propagation can be arrested after initial pitting of the material. A clear relationship exists between the corrosion resistance of sputter vapor deposited magnesium alloys and the amount of ion bombardment incurred by the alloy during deposition. Argon pressure, the distance between the source and the substrate, and alloy morphology play important roles in determining the ability of the alloy to develop a passive film. Thermal effects, both during and after alloy deposition, alter the stress state of the alloys, precipitation of second phases, and the mechanical stability of the passive film. An optimal thermal treatment has been developed in order to maximize the corrosion resistance of the magnesium-yttrium-titanium alloys. The significance of the results includes the acquisition of electrochemical data for these novel materials, as well as expanding the utilization of magnesium alloys by the improvement in their corrosion resistance. The magnesium alloys developed in this work are more corrosion resistant than any commercial magnesium alloy. Structural components comprised of these alloys would therefore exhibit unprecedented corrosion performance. Coatings of these alloys on magnesium components would provide a corrosion resistant yet galvanically-compatible coating. The broad impact of these contributions is that these new low-density, corrosion resistant magnesium alloys can be used to produce engine

Wolfe, Ryan C.

21

In vitro and in vivo corrosion measurements of magnesium alloys  

Microsoft Academic Search

The in vivo corrosion of magnesium alloys might provide a new mechanism which would allow degradable metal implants to be applied in musculo-skeletal surgery. This would particularly be true if magnesium alloys with controlled in vivo corrosion rates could be developed. Since the magnesium corrosion process depends on its corrosive environment, the corrosion rates of magnesium alloys under standard in

Frank Witte; Jens Fischer; Jens Nellesen; Horst-Artur Crostack; Volker Kaese; Alexander Pisch; Felix Beckmann; Henning Windhagen

2006-01-01

22

Degradation mechanism and surface modification of biomedical magnesium alloy.  

E-print Network

???The degradability of magnesium and magnesium alloys in a physiological environment makes them desirable biodegradable biomaterials in many applications. However, their fast degradation rates in (more)

Xin, Yunchang (???)

2010-01-01

23

Magnesium diffusion in several aluminum alloys  

NASA Astrophysics Data System (ADS)

Various surface quality defects or stains are sometimes observed on rolled aluminum. Two such defects, "white lacy" stain and "dirty" metal, appear to be caused by the formation of locally thicker films of hydrated aluminum and magnesium oxides, respectively. This paper examines the formation of these oxides, particularly MgO, on three aluminum alloys with varying bulk magnesium concentrations, namely 5052, 3004 and 3003, containing 2.64, 0.96 and 0.03% magnesium, respectively. Samples were prepared and heat treated in flowing air as a function of temperature and time. The surfaces were examined by Auger electron spectroscopy to determine the relative ratio of the magnesium and aluminum present on the oxide surfaces. Auger depth profiling was used to characterize the composition of the oxides. Surface morphologies, as observed by ultra-high resolution scanning electron microscopy, also were compared. Alloys containing higher bulk magnesium contents, i.e., 5052 and 3004, showed more magnesium diffusion and magnesium oxide formation on the sample surface. At high temperatures, the surface of 5052 tends to be almost totally MgO. Only limited magnesium diffusion and MgO formation was observed on the 3003 alloy.

Holub, K. J.; Matienzo, L. J.

24

REVIEW ARTICLE A review on magnesium alloys as biodegradable materials  

E-print Network

metal exhibits even poorer corrosion resistance in Cl­ containing physiologic environ- ment. Therefore, magnesium alloys could be developed as a new biodegradable metal, taking advantage of their fast corrosion. Keywords biomaterials, magnesium alloys, degradation, corrosion 1 Introduction Magnesium alloys, as a new

Zheng, Yufeng

25

Anticorrosive magnesium hydroxide coating on AZ31 magnesium alloy by hydrothermal method  

NASA Astrophysics Data System (ADS)

Magnesium alloys are potential biodegradable biomaterials in orthopedic surgery. However, the rapid degradation rate has limited their application in biomedical field. A great deal of studies have been done to improve the resistance of magnesium alloys. In this article, An anticorrosive magnesium hydroxide coating with a thickness of approximately 100?m was formed on an AZ31 magnesium alloy by hydrothermal method. The morphology of the coatings were observed by an optical microscope and SEM. And the samples were soaked in hank's solution (37C) to investigate the corrosion resistance. Magnesium alloy AZ31 with magnesium hydroxide coatings present superior corrosion resistance than untreated samples.

Zhu, Yanying; Wu, Guangming; Zhao, Qing; Zhang, Yun-Hong; Xing, Guangjian; Li, Donglin

2009-09-01

26

Impurity control and corrosion resistance of magnesium-aluminum alloy  

SciTech Connect

The corrosion resistance of magnesium alloys is very sensitive to the contents of impurity elements such as iron. In this study, a series of diecast AXJ530 magnesium alloy samples were prepared with additions of Mn and Fe. Through a comprehensive phase diagram calculation and corrosion evaluation, the mechanisms for the tolerance limit of Fe in magnesium alloy are discussed. This adds a new dimension to control the alloying impurity in terms of alloying composition design and casting conditions.

Liu, M. [GM China Lab] [GM China Lab; Song, GuangLing [ORNL] [ORNL

2013-01-01

27

Constitutive Modeling of Magnesium Alloy Sheets  

SciTech Connect

Magnesium alloy sheets have unique mechanical properties: high in-plane anisotropy/asymmetry of yield stress and hardening response, which have not been thoroughly studied. The unusual mechanical behavior of magnesium alloys has been understood by the limited symmetry crystal structure of h.c.p metals and thus by deformation twinning. In this paper, the phenomenological continuum plasticity models considering the unusual plastic behavior of magnesium alloy sheet were developed for a finite element analysis. A new hardening law based on two-surface model was developed to consider the general stress-strain response of metal sheets such as Bauschinger effect, transient behavior and the unusual asymmetry. Three deformation modes observed during the continuous tension/compression tests were mathematically formulated with simplified relations between the state of deformation and their histories. In terms of the anisotropy and asymmetry of the initial yield stress, the Drucker-Prager's pressure dependent yield surface was modified to include the anisotropy of magnesium alloys. Also, characterization procedures of material parameters for the constitutive equations were presented and finally the correlation of simulation with measurements was performed to validate the proposed theory.

Lee, M. G.; Piao, K.; Wagoner, R. H. [Department of Materials Science and Engineering, 2041 College Road, Ohio State University, Columbus, OH 43210 (United States); Lee, J. K. [Department of Mechanical Engineering, Scott Laboratory, 201 West 19th Avenue, Ohio State University, Columbus, OH 43210 (United States); Chung, K. [School of Materials Science and Engineering, Intelligent Textile System Research Center, Seoul National University, 56-1, Shinlim-Dong, Kwanak-Ku, Seoul 151-742 (Korea, Republic of); Kim, H. Y. [Division of Mechanical Engineering and Mechatronics, Kangwon National University, 192-1 Hyoja 2-Dong, Chunchon, Gangwon-Do, 200-701 (Korea, Republic of)

2007-05-17

28

Magnesium  

Microsoft Academic Search

Magnesium is the lightest of all metals used as the basis for constructional alloys. It is this property which entices automobile manufacturers to replace denser materials, not only steels, cast irons and copper base alloys but even aluminium alloys by magnesium based alloys. The requirement to reduce the weight of car components as a result in part of the introduction

B. L Mordike; T Ebert

2001-01-01

29

Precipitation, Recovery and Recrystallization Under Static and Dynamic Conditions for High Magnesium Aluminum-Magnesium Alloys.  

National Technical Information Service (NTIS)

Previous studies of the mechanical behavior of warm rolled high magnesium aluminum-magnesium alloys have shown that excellent tensile properties can be developed in these materials. Several questions raised in these previous efforts regarding recrystalliz...

C. W. Chesterman

1980-01-01

30

Superplastic deformation mechanism in powder metallurgy magnesium alloys and composites  

Microsoft Academic Search

The parametric dependencies for superplastic flow in powder metallurgy (PM) magnesium alloys and composites were characterized so as to elucidate the deformation mechanism. The mechanism was proposed to be slip accommodated grain boundary sliding. However, the PM alloys and composites were strengthened at low temperatures below ?550K. This was different from the case in ingot metallurgy (IM) magnesium alloys, that

H. Watanabe; T. Mukai; M. Mabuchi; K. Higashi

2001-01-01

31

Superplasticity of coarse-grained magnesium alloy  

Microsoft Academic Search

Superplasticity of coarse-grained magnesium alloy has been investigated. Elongation of 320% has been obtained at 773 K and a strain rate of 110?3 s?1. The grains were refined from initial 300 to 25 ?m when the stress reached its maximum. The grain size maintained about 2530 ?m dynamically in the proceeding deformation. Mechanical behavior and microstructures have also been studied.

Xin Wu; Yi Liu

2002-01-01

32

The Microstructure of Mechanically Alloyed Nanocrystalline Aluminium-Magnesium  

E-print Network

The Microstructure of Mechanically Alloyed Nanocrystalline Aluminium-Magnesium Jen Gubicza1 analysis. Magnesium gradually goes into solid solution during ball milling and after 3 h almost all. Experimental A series of aluminium-magnesium samples were prepared from high purity aluminium (99.9%) powder

Gubicza, Jenõ

33

Magnesium Alloy Stent Expansion Behavior Simulated by Finite Element Method  

E-print Network

. Magnesium alloy is brittle compared with stainless steel. This means it has less elongation than other stent the potential application and implanted behavior of the Magnesium alloy (MgSnMn) stent design and material tool used to design stent. The inner diameter of the stent is 1.5mm and the length is 7.0 mm, whereas

Zheng, Yufeng

34

Protective coatings on magnesium and its alloys a critical review  

Microsoft Academic Search

Magnesium and its alloys have excellent physical and mechanical properties for a number of applications. In particular its high strength:weight ratio makes it an ideal metal for automotive and aerospace applications, where weight reduction is of significant concern. Unfortunately, magnesium and its alloys are highly susceptible to corrosion, particularly in salt-spray conditions. This has limited its use in the automotive

J. E. Gray; B. Luan

2002-01-01

35

Tuning the Hydrogen Storage in Magnesium Alloys  

NASA Astrophysics Data System (ADS)

We investigate the hydrogen storage properties of promising magnesium alloys. MgH2 (7.6 wt % H) would be a very useful storage material if the (de)hydrogenation kinetics can be improved and the desorption temperature is markedly lowered. Using first principles calculations, we show that hydrides of Mg-transition metal (TM) alloys adopt a structure that promotes faster (de)hydrogenation kinetics, as is also observed in experiment [1]. Within the lightweight TMs, the most promising alloying element is titanium. Alloying Mg with Ti alone, however, is not sufficient to decrease the stability of the hydride phases, which is necessary to reduce the hydrogen desorption temperature [2]. We find that adding aluminium or silicon markedly destabilizes Mg-Ti hydrides and stabilizes Mg-Ti alloys. Finally, we show that controlling the structure of Mg-Ti-Al(Si) system by growing it as multilayers, has a beneficial influence on the thermodynamic properties and makes it a stronger candidate for hydrogen storage [3].[4pt] Ref: [1] S. Er et al., Phys. Rev. B, 79, 024105 (2009). [2] S. Er et al., J. Phys.: Condens. Matter, 22, 074208 (2010). [3] S. Er et al., J. Phys. Chem. Lett., 1, 1982 (2010).

Er, Suleyman; de Wijs, Gilles A.; Brocks, Geert

2011-03-01

36

On the precipitation of magnesium silicide in irradiated aluminum-magnesium alloys  

SciTech Connect

Thermal neutron irradiation of aluminium or its alloys causes the production of silicon by transmutation. In aluminium-magnesium alloys, the transmutation-produced silicon reacts with magnesium and forms small precipitates. The precipitation in irradiated Al-Mg alloys is similar to the early stage of aging in thermally treated Al-Mg-Si alloys. This study evidences the simultaneous generation of two crystallographically different precipitate types. On the basis of electron diffraction patterns, unit cell parameters are derived and compared with structures found in thermally aged alloys. One of the two precipitate types has an Mg{sub 2}Si composition, while the other is an Al-Si-Mg intermetallic compound with high aluminium and silicon but low magnesium content. The formation of magnesium poor precipitates is important since it indicates that the threshold neutron fluence for grain boundary precipitation of silicon may be much higher than estimated in the past.

Verwerft, M.

2000-03-14

37

General and localized corrosion of magnesium alloys: A critical review  

Microsoft Academic Search

Magnesium (Mg) alloys as well as experimental alloys are emerging as light structural materials for current, new, and innovative\\u000a applications. This paper describes the influence of the alloying elements and the different casting processes on the microstructure\\u000a and performance of these alloys and corrosion. It gives a comprehensible approach for the resistance of these alloys to general,\\u000a localized and metallurgically

Edward Ghali; Wolfgang Dietzel; Karl-Ulrich Kainer

2004-01-01

38

Potential automotive uses of wrought magnesium alloys  

SciTech Connect

Vehicle weight reduction is one of the major means available to improve automotive fuel efficiency. High-strength steels, aluminum (Al), and polymers are already being used to reduce weight significantly, but substantial additional reductions could be achieved by greater use of low-density magnesium (Mg) and its alloys. Mg alloys are currently used in relatively small quantities for auto parts, generally limited to die castings (e.g., housings). Argonne National Laboratory`s Center for Transportation Research has performed a study for the Lightweight Materials Program within DOE`s Office of Transportation Materials to evaluate the suitability of wrought Mg and its alloys to replace steel/aluminum for automotive structural and sheet applications. Mg sheet could be used in body nonstructural and semi-structural applications, while extrusions could be used in such structural applications as spaceframes. This study identifies high cost as the major barrier to greatly increased Mg use in autos. Two technical R and D areas, novel reduction technology and better hot-forming technology, could enable major cost reductions.

Gaines, L.; Cuenca, R.; Wu, S. [Argonne National Lab., IL (United States); Stodolsky, F. [Argonne National Lab., IL (United States)]|[Argonne National Lab., Washington, DC (United States)

1996-06-01

39

Ignition of Magnesium and Magnesium-Aluminum Alloy by Impinging Hot-Air Stream  

Microsoft Academic Search

An experimental study on the nonsteady ignition process of magnesium and 50-50 magnesium-aluminum alloy was made by using the stagnation region of an impinging hot air stream. The study has revealed that the ignition of magnesium was caused to occur through a four-stage surface oxidation process and finally through a homogeneous exothermic reaction in the gaseous phase. The ignition mechanism

TADAO TAKENO; SABURO YUASA

1980-01-01

40

In vitro mechanical integrity of hydroxyapatite coated magnesium alloy  

Microsoft Academic Search

The mechanical integrity of resorbable implants during service, especially in load bearing orthopaedic applications, is critical. The high degradation rate of resorbable magnesium and magnesium-based implants in body fluid may potentially cause premature in-service failure. In this study, a magnesium alloy (AZ91) was potentiostatically coated with hydroxyapatite at different cathodic voltages in an attempt to enhance the mechanical integrity. The

M. Bobby Kannan; Lynnley Orr

2011-01-01

41

Casting Porosity-Free Grain Refined Magnesium Alloys  

SciTech Connect

The objective of this project was to identify the root causes for micro-porosity in magnesium alloy castings and recommend remedies that can be implemented in production. The findings confirm the key role played by utilizing optimal gating and risering practices in minimizing porosity in magnesium castings.?

Schwam, David [Case Western Reserve University] [Case Western Reserve University

2013-08-12

42

Chrome-free surface treatments for magnesium alloy  

Microsoft Academic Search

Conversion coatings for magnesium have traditionally been based on immersion treatment in a solution containing hexavalent chromium compounds. However, the need for a replacement surface treatment has been strongly emphasized by the present environmental drive to eliminate hexavalent chromium. The development of permanganate bath chemical conversion coatings for magnesium alloys was studied, using mass gain measurements, measurements of corrosion potential,

H. Umehara; M. Takaya; S. Terauchi

2003-01-01

43

A review of laser welding techniques for magnesium alloys  

Microsoft Academic Search

Laser welding will be an important joining technique for magnesium alloys with their increasing applications in aerospace, aircraft, automotive, electronics and other industries. In this document the research and progress in laser welding of magnesium alloys are critically reviewed from different perspectives. To date, two types of industrial lasers, carbon dioxide (CO2) and neodymium-doped yttrium aluminum garnet (Nd:YAG), have been

X. Cao; M. Jahazi; J. P. Immarigeon; W. Wallace

2006-01-01

44

Column strength of magnesium alloy AM-57S  

NASA Technical Reports Server (NTRS)

Tests were made to determine the column strength of extruded magnesium alloy AM-57S. Column specimens were tested with round ends and with flat ends. It was found that the compressive properties should be used in computations for column strengths rather than the tensile properties because the compressive yield strength was approximately one-half the tensile yield strength. A formula for the column strength of magnesium alloy AM-57S is given.

Holt, M

1942-01-01

45

Corrosion fatigue of die-cast and extruded magnesium alloys  

Microsoft Academic Search

To study the fatigue life of die-cast and extruded AZ91D, AM50 and AZ31 magnesium alloys, corrosion fatigue tests were carried out using a rotating beam type fatigue machine. Corrosive environment (3.5% NaCl) significantly decreases fatigue life of alloys, especially for extruded alloys. The fatigue data at high stresses were analyzed using fitting equations. Extruded alloys show a higher sensitivity to

A Eliezer; E. M Gutman; E Abramov; Ya Unigovski

2001-01-01

46

Formability Analysis of Magnesium Alloy Sheet Bulging Using FE Simulation  

SciTech Connect

There is currently much focus on the application of magnesium alloys to automotive structural components. This has arisen due to the positive environmental aspects associated with use of magnesium alloys such as weight reduction and recycling potential. In recent years many researchers have focused on the application of various forming processes to magnesium alloys. Magnesium alloys would seem highly suitable for sheet forming due to high N and r values, however, in application their formability has been inferior to, for example, aluminium alloys. It has thus been concluded that, when dealing with magnesium alloys, it is difficult to predict formability based on material properties. In order to improve formability and forming accuracy when using Mg alloys it is necessary to build a database and inference system which could decide the optimal forming parameters for complex automotive components. Currently not enough data is available to build such a database due to the limited number of studies available in literature. In this study an experimental analysis of hemispherical bulge forming at elevated temperature was undertaken in order to evaluate formability and hence build a database for forming process design. A finite element model based on the experiment has been built and validated against the experimental results. A ductile failure criterion has been integrated with the FE model and is used to predict the onset of failure. This paper discusses the development and validation of the finite element model with the ductile failure criterion and presents results from the experimental tests and FE simulations.

Mac Donald, B. J.; Hunt, D. [School of Mechanical Engineering, Dublin City University, Dublin 9 (Ireland); Yoshihara, S. [Dept of Material and Environment Technology, Yamanashi University, Kofu, Yamanashi (Japan); Manabe, K. [Department of Mechanical Engineering, Tokyo Metropolitan University, Tokyo (Japan)

2007-05-17

47

Properties of boride-added powder metallurgy magnesium alloys  

NASA Astrophysics Data System (ADS)

Magnesium alloys with metallic borides, magnesium diboride (MgB2) or aluminum diboride (AlB2), were investigated regarding their mechanical properties, transverse rupture strength (TRS) and micro Vickers hardness (HV). The alloys were made from pure Mg, Al and B powders by mechanical alloying and hot pressing to have boride content of between 2.0 and 20 vol%. The alloy with AlB2 exhibited an obvious improvement of HV around a boride content of 6 vol% though the other alloy, with MgB2, did not. TRS showed moderate maxima around the same boride content region for the both alloys. X-ray diffraction measurements indicated an intermetallic compound, Mg17Al12, formed in the alloy with AlB2, which was consistent with its higher hardness.

Tanaka, Atsushi; Yoshimura, Syota; Fujima, Takuya; Takagi, Ken-ichi

2009-06-01

48

Adherent protective coatings plated on magnesium-lithium alloy  

NASA Technical Reports Server (NTRS)

Zinc is plated on a magnesium-lithium alloy by using a modification of the standard zinc-plate immersion bath. Further protection is given the alloy by applying a light plating of copper on the zinc plating. Other metals are plated on the copper by using conventional plating baths.

1965-01-01

49

Review of warm forming of aluminummagnesium alloys  

Microsoft Academic Search

Aluminummagnesium (AlMg) alloys (5000 series) are desirable for the automotive industry due to their excellent high-strength to weight ratio, corrosion resistance, and weldability. However, the formability and the surface quality of the final product of these alloys are not good if processing is performed at room temperature. Numerous studies have been conducted on these alloys to make their use possible

Serkan Toros; Fahrettin Ozturk; Ilyas Kacar

2008-01-01

50

Facile and fast fabrication of superhydrophobic surface on magnesium alloy  

NASA Astrophysics Data System (ADS)

Superhydrophobic surface has many special functions and is widely investigated by researchers. Magnesium alloy is one of the lightest metal materials among the practice metals. It plays an important role in automobile, airplane and digital product for reducing devices weight. But due to the low standard potential, magnesium alloy has a high chemical activity and easily be corroded. That seriously impedes the application of magnesium alloy. In the process of fabrication a superhydrophobic surface on magnesium alloy, there are two ineluctable problems that must be solved: (1) high chemical activity and (2) the chemical activity is inhomogeneous on surface. In this study, we solved those problems by using the two characters to gain a rough surface on magnesium alloy and obtained a superhydrophobic surface after following modification process. The results show that the as-prepared superhydrophobic surface has obvious anti-corrosion effect in typically corrosive solution and naturally humid air. The delay-icing and self-cleaning effects are also investigated. The presented method is low-cost, fast and has great potential value in large-scale industry production.

Wang, Zhongwei; Li, Qing; She, Zuxin; Chen, Funan; Li, Longqin; Zhang, Xiaoxu; Zhang, Peng

2013-04-01

51

Corrosion behavior of silicon nitride bonding silicon carbide in molten magnesium and AZ91 magnesium alloy  

Microsoft Academic Search

The corrosion behaviors of silicon nitride bonding silicon carbide (Si3N4\\/SiC) composites in molten magnesium and AZ91 magnesium alloy were investigated through immersion tests. The microstructure and the component of the surface layer of the composites were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The experimental results show that there were slight corrosion phenomena

Hukui Chen; Jianrui Liu; Weidong Huang

2006-01-01

52

Magnesium and its alloys applications in automotive industry  

Microsoft Academic Search

The objective of this study is to review and evaluate the applications of magnesium in the automotive industry that can significantly\\u000a contribute to greater fuel economy and environmental conservation. In the study, the current advantages, limitations, technological\\u000a barriers and future prospects of Mg alloys in the automotive industry are given. The usage of magnesium in automotive applications\\u000a is also assessed

Mustafa Kemal Kulekci

2008-01-01

53

Temperature Dependent Constitutive Modeling for Magnesium Alloy Sheet  

SciTech Connect

Magnesium alloys have been increasingly used in automotive and electronic industries because of their excellent strength to weight ratio and EMI shielding properties. However, magnesium alloys have low formability at room temperature due to their unique mechanical behavior (twinning and untwining), prompting for forming at an elevated temperature. In this study, a temperature dependent constitutive model for magnesium alloy (AZ31B) sheet is developed. A hardening law based on non linear kinematic hardening model is used to consider Bauschinger effect properly. Material parameters are determined from a series of uni-axial cyclic experiments (T-C-T or C-T-C) with the temperature ranging 150-250 deg. C. The influence of temperature on the constitutive equation is introduced by the material parameters assumed to be functions of temperature. Fitting process of the assumed model to measured data is presented and the results are compared.

Lee, Jong K. [Department of Mechanical Engineering, Korea Polytechnic University (Korea, Republic of); Lee, June K. [Department of Mechanical Engineering, Ohio State University (United States); Kim, Hyung S. [Department of Mechanical Design, Induk University (Korea, Republic of); Kim, Heon Y. [Division of Mechanical Engineering and Mechatronics, Kangwon National University (Korea, Republic of)

2010-06-15

54

Biodegradable Magnesium Alloys: A Review of Material Development and Applications  

PubMed Central

Magnesium based alloys possess a natural ability to biodegrade due to corrosion when placed within aqueous substances, which is promising for cardiovascular and orthopedic medical device applications. These materials can serve as a temporary scaffold when placed in vivo, which is desirable for treatments when temporary supportive structures are required to assist in the wound healing process. The nature of these materials to degrade is attributed to the high oxidative corrosion rates of magnesium. In this review, a summary is presented for magnesium material development, biocorrosion characteristics, as well as a biological translation for these results. PMID:22408600

Persaud-Sharma, Dharam; McGoron, Anthony

2012-01-01

55

Applications of Computer Simulation Methods in Plastic Forming Technologies for Magnesium Alloys  

Microsoft Academic Search

Applications of computer simulation methods in plastic forming of magnesium alloy parts are discussed. As magnesium alloys possess very poor plastic formability at room temperature, various methods have been tried to improve the formability, for example, suitable rolling process and annealing procedures should be found to produce qualified magnesium alloy sheets, which have the reduced anisotropy and improved formability. The

S. H. Zhang; W. T. Zheng; Y. L. Shang; X. Wu; G. Palumbo; L. Tricarico

2007-01-01

56

Simulation of Stresses during Casting of Binary Magnesium-Aluminum Alloys  

E-print Network

Simulation of Stresses during Casting of Binary Magnesium-Aluminum Alloys M.G. POKORNY, C.A. MONROE properties that are suitable for advanced stress modeling is even more limited for magnesium alloys. Recently of an AZ91 magnesium alloy in order to predict hot tears.[4] This study relied on crude estimates

Beckermann, Christoph

57

PHYSICAL REVIEW B 84, 084101 (2011) Guiding the experimental discovery of magnesium alloys  

E-print Network

PHYSICAL REVIEW B 84, 084101 (2011) Guiding the experimental discovery of magnesium alloys Richard 2011; published 19 August 2011) Magnesium alloys are among the lightest structural materials known and are of considerable technological interest. To develop superior magnesium alloys, experimentalists must have

Hart, Gus

58

The effect of cooling rate on thermophysical properties of magnesium alloys  

E-print Network

ARTICLES The effect of cooling rate on thermophysical properties of magnesium alloys M.N. Khan magnesium alloys (AZ91D, AM60B, and AE44) have been studied. Phase-transformation temperatures and enthalpy behavior of magnesium alloys, but the effect of cooling rate on phase-transformation temperatures

Medraj, Mamoun

59

Novel Magnesium Alloys Developed for Biomedical Application: A Review Nan Li, Yufeng Zheng*  

E-print Network

Novel Magnesium Alloys Developed for Biomedical Application: A Review Nan Li, Yufeng Zheng* State in the development of magnesium alloys both for industrial and biomedical applications. Industrial interest in magnesium alloys is based on strong demand of weight reduction of transportation vehicles for better fuel

Zheng, Yufeng

60

Influence of beryllium and rare earth additions on ignition-proof magnesium alloys  

Microsoft Academic Search

A kind of magnesium alloy which has excellent ignition-proof performance and approximate chemical composition with AZ91D alloy was obtained by beryllium and rare earth (RE) addition. A high content of beryllium in magnesium alloy could prevent the ignition of the magnesium, but it also makes the grain coarse and decreases the tensile properties. RE elements were added to refine the

Zeng Xiaoqin; Wang Qudong; Lu Yizhen; Zhu Yanping; Ding Wenjiang; Zhao Yunhu

2001-01-01

61

Research on Alloying Tecniques of Mischmetal in Die Casting Magnesium Alloy  

Microsoft Academic Search

An aim of the experiments is to study alloying techniques of dollop-like MM, as-cast and extruded Mg-MM master alloy in die casting AZ91D magnesium alloy at conventional cold chamber die casting temperature. The as-cast AZ91D-1.2wt%MM alloys were prepared and MM was added by different way at 720C. The results showed that the efficiency of alloying achieved less than 50% within

Yulei Xu; Kui Zhang; Xinggang Li; Kang Zhang; Jian Lei; Haibo Yuan

2009-01-01

62

Upsettability and forming limit of magnesium alloys at elevated temperatures  

NASA Astrophysics Data System (ADS)

In recent years, Magnesium (Mg) and its alloys have become a center of special interest in the automotive industry. Due to their high specific mechanical properties, they offer a significant weight saving potential in modern vehicle constructions. Most Mg alloys show very good machinability and processability, and even the most complicated die casting parts can be easily produced. In this study, Microstructure, Vickers hardness and tensile tests were examined and performed for each specimen to verify effects of forming conditions. Also to verify upsettability and forming limit of the specimen at room temperature and elevated temperature, upsetting experiments were performed. For comparison, experiments at elevated temperature were performed for various Mg alloy, such as AZ31, AZ91, and AM50. The experimental results were compared with those of CAE analysis to propose forming limit of Magnesium alloys.

Park, Heung Sik; Kim, Si Pom; Park, Young Chul; Park, Joon Hong; Baek, Seung Gul

2012-11-01

63

Electrochemical performance of magnesium alloy and its application on the sea water battery  

Microsoft Academic Search

The magnesium sea water battery belongs to a kind of reserved battery, which takes the active metal such as magnesium alloy as the anode based on the sea water as the electrolyte. Experiments of magnesium alloy sea water battery were carried out and its electrochemical performance was studied. Thin sheets of Mg-Al-Zn and Mg-Mn series of magnesium alloy were fabricated

Hongyang ZHAO; Pei BIAN; Dongying JU

2009-01-01

64

ABRASIVE WEAR OF ALUMINIUM-MAGNESIUM ALLOYS AT VARIOUS TEMPERATURES  

Microsoft Academic Search

The abrasive wear and hot'' hardness of alloys of aluminium and ; magnesium of various concentrations was investigated at various temperatures. ; Specimens, cast into a chill mold and subsequently annealed, were studied. They ; had the following concentrationsn: 0, 1, nesium, the remainder being technically ; pure aluminum. The following temperatures were selected for testing: specimen of ; 5

V. N. Kashcheyev; L. N. Voytsekhovksaya

1959-01-01

65

Warm incremental forming of magnesium alloy AZ31  

Microsoft Academic Search

Industrial application of magnesium alloy AZ31 is dramatically increasing due to the very competitive mechanical strength vs. weight ratio. On the other hand, AZ31 is very difficult to be formed at room temperature. In this study incremental forming of the above material is taken into account, with particular reference to formability limits. The role of the main process parameters on

G. Ambrogio; L. Filice; G. L. Manco

2008-01-01

66

Creep behavior of magnesium die-cast alloy ZA85  

Microsoft Academic Search

The compressive creep behavior of a magnesium die-cast alloy with 8 wt.% Zn and 5 wt.% Al was investigated. We argue that grain boundary sliding does not contribute to the deformation. Creep data and microstructural analysis strongly support dislocation creep, influenced by the formation and over-aging of precipitates, as the dominant mechanism.

M. Vogel; O. Kraft; E. Arzt

2003-01-01

67

Mechanical surface treatments on titanium, aluminum and magnesium alloys  

Microsoft Academic Search

Generally, mechanical surface treatments induce high dislocation densities in near-surface regions. Due to the local plastic deformation, residual stresses are developed and the surface topography is changed. These changes can have contradictory influences on the fatigue strength. Results on the influence of mechanical surface treatments on magnesium are presented in relation to the relatively well-studied titanium and aluminum alloys.

L Wagner

1999-01-01

68

Recycling of Magnesium Alloy Employing Refining and Solid Oxide Membrane (SOM) Electrolysis  

NASA Astrophysics Data System (ADS)

Pure magnesium was recycled from partially oxidized 50.5 wt pct Mg-Al scrap alloy and AZ91 Mg alloy (9 wt pct Al, 1 wt pct Zn). Refining experiments were performed using a eutectic mixture of MgF2-CaF2 molten salt (flux). During the experiments, potentiodynamic scans were performed to determine the electrorefining potentials for magnesium dissolution and magnesium bubble nucleation in the flux. The measured electrorefining potential for magnesium bubble nucleation increased over time as the magnesium content inside the magnesium alloy decreased. Potentiostatic holds and electrochemical impedance spectroscopy were employed to measure the electronic and ionic resistances of the flux. The electronic resistivity of the flux varied inversely with the magnesium solubility. Up to 100 pct of the magnesium was refined from the Mg-Al scrap alloy by dissolving magnesium and its oxide into the flux followed by argon-assisted evaporation of dissolved magnesium and subsequently condensing the magnesium vapor. Solid oxide membrane electrolysis was also employed in the system to enable additional magnesium recovery from magnesium oxide in the partially oxidized Mg-Al scrap. In an experiment employing AZ91 Mg alloy, only the refining step was carried out. The calculated refining yield of magnesium from the AZ91 alloy was near 100 pct.

Guan, Xiaofei; Zink, Peter A.; Pal, Uday B.; Powell, Adam C.

2013-04-01

69

Imparting passivity to vapor deposited magnesium alloys  

Microsoft Academic Search

Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread

Ryan C. Wolfe

2005-01-01

70

Improvement of hydrogen storage properties of magnesium alloys by cold rolling and forging  

NASA Astrophysics Data System (ADS)

In this talk we show that cold rolling (CR) could be used to enhance hydrogen sorption properties of magnesium and magnesium alloys. In particular, cold rolling could reduce the first hydrogenation time, the so-called activation. Pure magnesium, commercial AZ91D alloy, and an experimental creep resistant magnesium alloy MRI153 in the as-cast and die-cast states were investigated. We found that both MRI and AZ91 alloys present faster activation kinetic than pure magnesium. This could be explained by the texture, higher number of defects, and nanostructure in CR materials but also precipitates at the grain boundaries. The effect of filing was also investigated.

Huot, Jacques; Amira, Sofiene; Lang, Julien; Skryabina, Nataliya; Fruchart, Daniel

2014-08-01

71

Ordered magnesium-lithium alloys: First-principles predictions Richard H. Taylor  

E-print Network

Ordered magnesium-lithium alloys: First-principles predictions Richard H. Taylor Department 2010 Magnesium-lithium Mg-Li alloys are among the lightest structural materials. Although considerable Emerging technologies increasingly depend on the pro- duction of ultralight-weight materials. Magnesium

Hart, Gus

72

In vitro corrosion and biocompatibility of binary magnesium alloys Xuenan Gu a  

E-print Network

In vitro corrosion and biocompatibility of binary magnesium alloys Xuenan Gu a , Yufeng Zheng a 2 September 2008 Accepted 21 October 2008 Available online 9 November 2008 Keywords: Magnesium alloy Corrosion In vitro Cytotoxicity Hemocompatibility a b s t r a c t As bioabsorbable materials, magnesium

Zheng, Yufeng

73

Potential Magnesium Alloys for High Temperature Die Cast Automotive Applications: A Review  

Microsoft Academic Search

Magnesium, as a lightweight construction material, has rapidly grown its applications in the automotive industry since the early 1990s. To maximize the weight reduction of vehicles by lightweight magnesium alloys in the coming years, the use of newly developed high-temperature magnesium alloys is expected to increase significantly, particularly in the powertrain applications where the creep resistance is always required. This

Henry Hu; Alfred Yu; Naiyi Li; John E. Allison

2003-01-01

74

Formation of defect bands in high pressure die cast magnesium alloys  

Microsoft Academic Search

Die cast magnesium components are being increasingly used worldwide because of the excellent castability and properties that magnesium alloys offer. High pressure die casting of thin-walled components is particularly suitable because of the excellent flow characteristics of molten magnesium alloys. Typical automotive applications for thin-walled castings include components such as instrument panels, steering wheels, door frames and seat frames. These

A. K Dahle; S Sannes; D. H St. John; H Westengen

2001-01-01

75

In vitro degradation behavior and cytocompatibility of Mg-Zn-Zr alloys  

PubMed Central

Zinc and zirconium were selected as the alloying elements in biodegradable magnesium alloys, considering their strengthening effect and good biocompatibility. The degradation rate, hydrogen evolution, ion release, surface layer and in vitro cytotoxicity of two MgZnZr alloys, i.e. ZK30 and ZK60, and a WE-type alloy (MgYREZr) were investigated by means of long-term static immersion testing in Hanks solution, non-static immersion testing in Hanks solution and cell-material interaction analysis. It was found that, among these three magnesium alloys, ZK30 had the lowest degradation rate and the least hydrogen evolution. A magnesium calcium phosphate layer was formed on the surface of ZK30 sample during non-static immersion and its degradation caused minute changes in the ion concentrations and pH value of Hanks solution. In addition, the ZK30 alloy showed insignificant cytotoxicity against bone marrow stromal cells as compared with biocompatible hydroxyapatite (HA) and the WE-type alloy. After prolonged incubation for 7days, a stimulatory effect on cell proliferation was observed. The results of the present study suggested that ZK30 could be a promising material for biodegradable orthopedic implants and worth further investigation to evaluate its in vitro and in vivo degradation behavior. PMID:20532960

Huan, Z. G.; Leeflang, M. A.; Fratila-Apachitei, L. E.; Duszczyk, J.

2010-01-01

76

Study of Forming of Magnesium Alloy by Explosive Energy  

SciTech Connect

Magnesium alloy is an attractive next generation material due to its high specific strength with low weight. However, magnesium alloys has few slip lines with close-packed hexagonal lattice, and generally poor ductility at room temperature, therefore it is difficult to form this material by cold forging. It is well known that the speed of deformation of metallic materials rapidly changes at the high strain rate. For some metallic materials, it is reported that the ductility also increases at the high strain rate with this speed effect. In this study, a series of high speed impulsive compressive tests were carried. By using explosives for shock wave loading, the velocity in this experiment reached 100 m/s that can't be easily obtained in normal experiment. In this paper, the possibility of forming the AZ31 extrusion magnesium alloy using explosive-impulsive pressure is investigated. And improved ductility by the effect of high-rate deformation is observed with this alloy.

Ruan, Liqun; Hokamoto, Kazuyuki; Marumo, Yasuo [Kumamoto University Department of Mechanical Systems Engineering Graduate School of Science and Technology, Kurokami 2-39-1, Kumamoto-shi 860-8555 (Japan); Yahiro, Ititoku [Mitsui Engineering and Shipbuilding Co., Ltd. Nihonbasi 1-3-16, Toukyou 104-8439 (Japan)

2011-05-04

77

The Corrosion of Magnesium and of the Magnesium Aluminum Alloys Containing Manganese  

NASA Technical Reports Server (NTRS)

The extensive use of magnesium and its alloys in aircraft has been seriously handicapped by the uncertainties surrounding their resistance to corrosion. This problem has been given intense study by the American Magnesium Corporation and at the request of the Subcommittee on Materials for Aircraft of the National Advisory Committee for Aeronautics this report was prepared on the corrosion of magnesium. The tentative conclusions drawn from the experimental facts of this investigation are as follows: the overvoltage of pure magnesium is quite high. On immersion in salt water the metal corrodes with the liberation of hydrogen until the film of corrosion product lowers the potential to a critical value. When the potential reaches this value it no longer exceeds the theoretical hydrogen potential plus the overvoltage of the metal. Rapid corrosion consequently ceases. When aluminum is added, especially when in large amounts, the overvoltage is decreased and hydrogen plates out at a much lower potential than with pure magnesium. The addition of small amount of manganese raises the overvoltage back to practically that of pure metal, and the film is again negative.

Boyer, J A

1927-01-01

78

In vivo corrosion of four magnesium alloys and the associated bone response  

Microsoft Academic Search

Degrading metal alloys are a new class of implant materials suitable for bone surgery. The aim of this study was to investigate the degradation mechanism at the boneimplant interface of different degrading magnesium alloys in bone and to determine their effect on the surrounding bone. Sample rods of four different magnesium alloys and a degradable polymer as a control were

F. Witte; V. Kaese; H. Haferkamp; E. Switzer; A. Meyer-Lindenberg; C. J. Wirth; H. Windhagen

2005-01-01

79

Developing superplasticity in a magnesium AZ31 alloy by ECAP  

Microsoft Academic Search

The processing of a magnesium AZ31 alloy by equal-channel angular pressing refines the grain size to ~2.2?m, but annealing\\u000a for 30min at 673K coarsens the grains to ~6.0?m. Despite this microstructural instability, the alloy is superplastic when\\u000a pulled in tension at temperatures in the range of 623723K with elongations up to >1000% at strain rates at and below 10?4s?1. Experiments

Roberto B. Figueiredo; Terence G. Langdon

2008-01-01

80

Potential applications of wrought magnesium alloys for passenger vehicles  

SciTech Connect

Vehicle weight reduction is one of the major means available for improving automotive fuel efficiency. Although high-strength steels, aluminum (Al), and polymers are already being used to achieve significant weight reductions, substantial additional weight reductions could be achieved by increased use of magnesium (Mg) and its alloys, which have very low density. Magnesium alloys are currently used in relatively small quantities for auto parts; use is generally limited to die castings, such as housings. The Center for Transportation Research at Argonne National Laboratory has performed a study for the Lightweight Materials Program within DOE`s Office of Transportation Materials to evaluate the suitability of wrought Mg and its alloys to replace steel or aluminum for automotive structural and sheet applications. This study identifies technical and economic barriers to this replacement and suggests R&D areas to enable economical large-volume use. Detailed results of the study will be published at a later date. Magnesium sheet could be used in body nonstructural and semi-structural applications, while extrusions could be used in such structural applications as spaceframes. Currently, Mg sheet has found limited use in the aerospace industry, where costs are not a major concern. The major barrier to greatly increased automotive use is high cost; two technical R&D areas are identified that could enable major reductions in costs. These are novel reduction technology and better hot-forming technology, possibly operating at lower temperatures and involving superplastic behavior.

Gaines, L.; Cuenca, R.; Stodolsky, F.; Wu, S.

1995-12-31

81

Microstructure analysis of magnesium alloy melted by laser irradiation  

NASA Astrophysics Data System (ADS)

The effects of laser surface melting (LSM) on microstructure of magnesium alloy containing Al8.57%, Zn 0.68%, Mn0.15%, Ce0.52% were investigated. In the present work, a pulsed Nd:YAG laser was used to melt and rapidly solidify the surface of the magnesium alloy with the objective of changing microstructure and improving the corrosion resistance. The results indicate that laser-melted layer contains the finer dendrites and behaviors good resistance corrosion compared with the untreated layer. Furthermore, the absorption coefficient of the magnesium alloy has been estimated according to the numeral simulation of the thermal conditions. The formation process of fine microstructure in melted layers was investigated based on the experimental observation and the theoretical analysis. Some simulation results such as the re-solidification velocities are obtained. The phase constitutions of the melted layers determined by X-ray diffraction were ?-Mg 17Al 12 and ?-Mg as well as some phases unidentified.

Liu, S. Y.; Hu, J. D.; Yang, Y.; Guo, Z. X.; Wang, H. Y.

2005-12-01

82

The Influence of Aluminum Content of AZ61 and AZ80 Magnesium Alloys on Hot Cracking  

Microsoft Academic Search

This study aims to investigate how aluminum content in magnesium alloys AZ61 and AZ80 impacts the hot cracking susceptibility of magnesium alloys. Differences in aluminum content are known to influence the total crack length of hot cracking. Magnesium alloy AZ61's total crack length was the longest in one thermal cycle, while AZ80's total crack length increased as the number of

C. J. Huang; C. M. Cheng; C. P. Chou

2011-01-01

83

Mg-Zn-Y alloys with long-period stacking ordered structure: in vitro assessments of biodegradation behavior.  

PubMed

Using Dulbecco's modified eagle medium (DMEM) with 10% fetal bovine serum (FBS) as simulated body fluid, degradation behavior of Mg100-3x(Zn1Y2)x (1?x?3) alloy series with long period stacking order (LPSO) structures was investigated. As indicated, with increasing the volume fraction of LPSO phase, degradation rate of the alloys is accelerated. Further refining the grain size by microalloying with zirconium and warm extrusion has a significant effect to mitigate the degradation rate of the Mg97Zn1Y2 alloy. Time-dependent behavior during degradation of the magnesium alloys can be described using an exponential decay function of WR=exp(a+bt+ct(2)), where WR is normalized residual mass/volume of the alloy. A parameter named as degradation half-life period (t0.5) is suggested to quantitatively assess the degradation rate. For the localized-corrosion controlled alloys, the t0.5 parameter physically scales with electrochemical response ?E which is a range between corrosion potential (Ecorr) and pitting potential (Ept). In comparison with conventional engineering magnesium alloys such as the AZ31, WE43, ZK60 and ZX60 alloys, extruded Mg96.83Zn1Y2Zr0.17 alloy with LPSO structure exhibits a good combination of high mechanical strength, lower biodegradation rate and good biocompatibility. PMID:23910258

Zhao, Xu; Shi, Ling-ling; Xu, Jian

2013-10-01

84

Semi-solid Twin-roll Casting Process of Magnesium Alloy Sheets  

NASA Astrophysics Data System (ADS)

An experimental approach has been performed to ascertain the effectiveness of semi-solid strip casting using a horizontal twin roll caster. The demand for light-weight products with high strength has grown recently due to the rapid development of automobile and aircraft technology. One key to such development has been utilization of magnesium alloys, which can potentially reduce the total product weight. However, the problems of utilizing magnesium alloys are still mainly related to high manufacturing cost. One of the solutions to this problem is to develop magnesium casting-rolling technology in order to produce magnesium sheet products at competitive cost for commercial applications. In this experiment, magnesium alloy AZ31B was used to ascertain the effectiveness of semi-solid roll strip casting for producing magnesium alloy sheets. The temperature of the molten magnesium, and the roll speeds of the upper and lower rolls, (which could be changed independently), were varied to find an appropriate manufacturing condition. Rolling and heat treatment conditions were changed to examine which condition would be appropriate for producing wrought magnesium alloys with good formability. Microscopic observation of the crystals of the manufactured wrought magnesium alloys was performed. It has been found that a limiting drawing ratio of 2.7 was possible in a warm deep drawing test of the cast magnesium alloy sheets after being hot rolled.

Watari, H.; Davey, K.; Rasgado, M. T. Alonso; Haga, T.; Koga, N.

2004-06-01

85

Tension-Compression Asymmetry Under Superplastic Flow in Magnesium Alloys  

NASA Astrophysics Data System (ADS)

Superplastic magnesium alloys prepared by ingot metallurgy and powder metallurgy were processed and characterized. By performing uniaxial tension and compression tests of the extruded alloys along the longitudinal direction, it was found that both alloys were highly symmetric at low-strain rates within the superplastic regime. However, near the maximum strain rate within the superplastic regime, the symmetric flow disappeared. Specifically, the flow stress in early deformation under tension was slightly lower than that under compression, and the strain hardening under tension was higher than that under compression. The asymmetry was explained using the hypothesis that grain-boundary sliding under tension is easier than under compression. As indirect evidence for easier grain-boundary sliding under tension, it was shown that the coarsened intergranular precipitates tended to agglomerate on grain boundaries experiencing a tensile stress.

Watanabe, Hiroyuki; Fukusumi, Masao

2014-10-01

86

Creep processes in magnesium alloys and their composites  

NASA Astrophysics Data System (ADS)

A comparison is made between the creep characteristics of two squeeze-cast magnesium alloys (AZ 91 and QE 22) reinforced with 20 vol pct Al2O3 short fibers and the unreinforced AZ 91 and QE 22 matrix alloys. The results show the creep resistance of the reinforced materials is considerably improved by comparison with the unreinforced matrix alloys. It is suggested that creep strengthening in these short-fiber composites arises primarily from the existence of a threshold stress and the effect of load transfer. By testing samples to failure, it is demonstrated that the unreinforced and reinforced materials exhibit similar times to failure at the higher stress levels. A detailed microstructural investigation by transmission electron microscopy (TEM) reveals no substantial changes in matrix microstructure due to the presence of the reinforcement. This suggests that direct composite strengthening dominates over indirect effects.

Skleni?ka, V.; Pahutov, M.; Kucha?ov, K.; Svoboda, M.; Langdon, T. G.

2002-03-01

87

High-strain-rate nanoindentation behavior of fine-grained magnesium alloys  

E-print Network

The effects of temperature and alloying elements on deformation in the high-strain-rate regime were investigated by testing fine-grained magnesium alloys with an average grain size of 2 ? 3 ?m by a nanoindentation technique. ...

Somekawa, Hidetoshi

88

Sheet metal forming of magnesium wrought alloys formability and process technology  

Microsoft Academic Search

New developments at the Institute for Metal Forming and Metal Forming Machine Tools show that magnesium sheets possess excellent forming behavior, if the process is conducted at elevated temperatures. For the evaluation of mechanical properties relevant for forming of magnesium sheets, uniaxial tensile tests have been carried out at various temperatures and strain rates.Deep drawing tests with magnesium alloys AZ31B,

E. Doege; K. Drder

2001-01-01

89

Corrosion behavior of rapidly solidified magnesium-aluminium-zinc alloys  

SciTech Connect

Rapidly solidified magnesium alloys with 8 at%, 15 at%, and 20 at% Al and 1 at% and 3 at% Zn were fabricated by centrifugal atomization followed by hot extrusion. Microstructure of the alloys was composed of a fine-grain magnesium matrix (0.5 {micro}m) with {beta}-Mg{sub 17}Al{sub 12} precipitates. Electrochemical and weight-loss tests were performed in borate and ASTM D 1384 solution (chloride, carbonate, and sulfate). In both media, corrosion current f the alloys decreased with increases in aluminum or zinc content. In borate solution, a passivating plateau was observed from the corrosion potential (E{sub corr}) to E{sub corr} + 1,200 mV. Current density decreased with aluminum and zinc concentrations. Electrochemical behavior of the synthesized matrix and precipitates was characterized. Zinc increased E{sub corr} of the two phases, with a corresponding decrease of corrosion current. The same trend was noticed for aluminum but with a less dramatic effect. The corrosion mechanism was suggested result from galvanic coupling of the matrix and the second phase. The galvanic corrosion, however, was reduced strongly by passivation of the matrix as a result of the surrounding precipitates. The positive influence of rapid solidification (corrosion rate decreased 1 order of magnitude) was the creation of a fine, highly homogeneous microstructure through this fabrication process.

Daloz, D.; Michot, G. [Ecole des Mines, Nancy (France). Lab. de Metallurgie Physique et Science des Materiaux; Steinmetz, P. [Faculte des Sciences, Vandoeuvre les Nancy (France). Lab. de Chimie du Solide Mineral

1997-12-01

90

Construction of extrusion limit diagram for AZ31 magnesium alloy by FE simulation  

Microsoft Academic Search

The maximum speed at which magnesium can be extruded is considerably slower than that of many common aluminium extrusion alloys. This affects both the economies of production and the final mechanical behaviour. The present work quantifies the limiting extrusion speeds and ratios of magnesium alloy AZ31 as a function of billet temperature. This is done by combining hot compression test

R. Ye Lapovok; M. R Barnett; C. H. J Davies

2004-01-01

91

Study on the environmentally friendly anodizing of AZ91D magnesium alloy  

Microsoft Academic Search

A new anodizing process, based on an environmentally friendly electrolyte solution that contains none of chromate, phosphate or fluoride but can enhance the corrosion protection of magnesium alloy significantly, is investigated. Anodizing behaviors of magnesium and its alloys are influenced by many factors, including the constituents and concentrations of electrolyte solution, the nature of basis metal as well as applied

Yongjun Zhang; Chuanwei Yan; Fuhui Wang; Hanyi Lou; Chunan Cao

2002-01-01

92

Effects of process parameters on warm and electromagnetic hybrid forming of magnesium alloy sheets  

Microsoft Academic Search

As the lightest structural metal, magnesium (Mg) is attracting increasing interest from both the industrial and academic fields. Magnesium alloy parts are mainly processed by die casting due to their poor sheet formability at room temperature. Warm forming is a popular method of forming; Mg alloy sheets produced in this manner show excellent formability around 200400C. Electromagnetic forming (EMF) can

Zhenghua Meng; Shangyu Huang; Jianhua Hu; Wei Huang; Zhilin Xia

2011-01-01

93

SIMULATION OF STRESSES DURING CASTING OF BINARY MAGNESIUM-ALUMINUM ALLOYS M.G. Pokorny1  

E-print Network

heat treated or contained porosity (e.g., die cast specimens) must be excluded. Some studies have beenSIMULATION OF STRESSES DURING CASTING OF BINARY MAGNESIUM-ALUMINUM ALLOYS M.G. Pokorny1 , C, Geesthacht, Germany Keywords: Magnesium Alloys, Casting, Stress Simulation Abstract A visco

Beckermann, Christoph

94

Reliability of Laser Welding Process for ZE41A-T5 Magnesium Alloy Sand Castings  

E-print Network

) and tungsten inert gas (TIG) arc processes are the two main welding methods, especially for the repair, preheating is not recommended due to the energy waste. For the welding and repair of magnesium alloy castingsReliability of Laser Welding Process for ZE41A-T5 Magnesium Alloy Sand Castings Haider Al-Kazzaz1

Medraj, Mamoun

95

Modelling of Superplastic Forming of AZ31 Magnesium Alloy  

SciTech Connect

In this study the constitutive equation of the superplastic AZ31 magnesium-based alloy is modelled by the power law relationship between the stress, the strain and the strain-rate and an accurate procedure for determining the constants of the material is presented. Moreover, the problem of optimizing the pressure-time load curve of a free forming process is investigated and resolved by means of a pressure jump forming process. The experimental tests, carried out to support the finite-element modelling, have shown good agreement between the numerical results and the experimental data.

Giuliano, G. [University of Cassino, Department of Industrial Engineering, via Di Biasio 43, 03043 Cassino (Italy)

2011-01-17

96

FE simulation of magnesium alloy microstructure evolution in tension  

NASA Astrophysics Data System (ADS)

Finite element (FE) simulation of microstructure evolution was performed in the current work. The flow stress curve for FE simulation was obtained from tensile test which was carried out at room temperature. Samples were machined from a rolled sheet of AZ31B magnesium alloy. Simplified micro scale models were developed in order to study the influence of the round inclusion and twin-like inclusion on the material fracture behaviour. It was shown that fracture initiation point is dependent on the yield stress of the inclusion. Finally, polycrystalline model including ten grains of similar sizes was developed. The triple junction points were recognized as sites of fracture initiation.

Gzyl, Michal; Rosochowski, Andrzej

2013-12-01

97

CIRP Conference on Modeling of Machining Operations (CIRP CMMO) Constitutive Modelling of AZ31B-O Magnesium Alloy  

E-print Network

B-O Magnesium Alloy for Cryogenic Machining E. Girauda* , F. Rossib , G. Germaina , J.C. Outeirob disks of AZ31B-O magnesium alloy, using a special designed tool. In order to include the effects of Machining Operations" in the person of the Conference Chair Prof. Luca Settineri Keywords: Magnesium alloy

Paris-Sud XI, Université de

98

Laser Surface Engineering of Magnesium Alloys: A Review  

NASA Astrophysics Data System (ADS)

Magnesium (Mg) and its alloys are well known for their high specific strength and low density. However, widespread applications of Mg alloys in structural components are impeded by their insufficient wear and corrosion resistance. Various surface engineering approaches, including electrochemical processes (plating, conversion coatings, hydriding, and anodizing), gas-phase deposition (thermal spray, chemical vapor deposition, physical vapor deposition, diamond-like coatings, diffusion coatings, and ion implantation), and organic polymer coatings (painting and powder coating), have been used to improve the surface properties of Mg and its alloys. Recently, laser surface engineering approaches are attracting significant attention because of the wide range of possibilities in achieving the desired microstructural and compositional modifications through a range of laser-material interactions (surface melting, shock peening, and ablation). This article presents a review of various laser surface engineering approaches such as laser surface melting, laser surface alloying, laser surface cladding, laser composite surfacing, and laser shock peening used for surface modification of Mg alloys. The laser-material interactions, microstructural/compositional changes, and properties development (mostly corrosion and wear resistance) accompanied with each of these approaches are reviewed.

Singh, Ashish; Harimkar, Sandip P.

2012-06-01

99

Low temperature superplasticity in an AZ91 magnesium alloy processed by ECAE  

SciTech Connect

Magnesium alloys are especially suitable for use of the structural components in aerospace and outerspace applications due to their low density. In general, however, magnesium alloys have poor workability because of their h.c.p. structure. Therefore it is desirable to improve the poor workability, and superplastic forming is expected to be put into the processing in practical applications. In the present work, equal channel angular extrusion (ECAE), which allows one to attain high shear strain, has been conducted on an AZ91 magnesium alloy. The alloy processed by ECAE exhibited superplastic behavior at low temperatures of 448 and 473 K, which are about 0.5T{sub m}.

Mabuchi, M. [National Industrial Research Inst. of Nagoya (Japan)] [National Industrial Research Inst. of Nagoya (Japan); Iwasaki, H.; Yanase, K. [Himeji Inst. of Tech., Himeji, Hyogo (Japan)] [Himeji Inst. of Tech., Himeji, Hyogo (Japan); Higashi, K. [Osaka Prefecture Univ., Sakai, Osaka (Japan)] [Osaka Prefecture Univ., Sakai, Osaka (Japan)

1997-03-15

100

Formability study of magnesium alloy AZ31B  

NASA Astrophysics Data System (ADS)

The main aim of this paper is to study the formability of the AZ31B magnesium alloy at various temperature and strain rates. The tensile tests are performed to describe the rheological behavior of material, and the constitutive law is identified with Voce law [1], which contains a softening item. The law is proved effectiveness by fitting the equation with the experimental data. Nakazima experiments with hemispherical punch have been performed at CEMEF on a hydraulic testing machine. Six strain paths are selected by performing various sample geometries [2]. The AramisOptical strain measurement system has been used to obtain principle forming limit strain. The Forming Limit Diagram (FLD) is obtained by the critical point on the specimen surface at various temperatures. It is shown that the forming limit curve is higher at high temperature. Based on the Voce law model, finite element simulations of deep drawing test have been done with the commercial finite element code FORGE in order to investigate the feasibility of hot stamping process for AZ31. In the simulation, the punch load and the thickness distributions have been studied. Meanwhile, the cross-shaped cup deep drawing simulations have been conducted with the data provided in the conference Website. The similar conclusion are obtained that the formability of AZ31 improve at high temperature and the simulation is effective in hot stamping processing. The study results are helpful for the application of the stamping technology for the magnesium alloy sheet [3].

Liu, Z. G.; Lasne, P.; Massoni, E.

2011-08-01

101

Investigation of Deformation Dynamics in a Wrought Magnesium Alloy  

SciTech Connect

In the present research, the deformation dynamics and the effect of the deformation history on plastic deformation in a wrought magnesium alloy have been studied using real-time in-situ neutron diffraction measurements under a continuous loading condition and elastic-viscoplastic self-consistent (EVPSC) polycrystal modeling. The experimental results reveal that the pre-deformation delayed the activation of the tensile twinning during subsequent compression, mainly resulting from the residual strain. No apparent detwinning occurred during unloading and even in the elastic region during reverse loading. It is believed that the grain rotation played an important role in the elastic region during reverse loading. The EVPSC model, which has been recently updated by implementing the twinning and detwinning model, was employed to characterize the deformation mechanism during the strain-path changes. The simulation result predicts well the experimental observation from the real-time in-situ neutron diffraction measurements. The present study provides a deep insight of the nature of deformation mechanisms in a hexagonal close-packed structured polycrystalline wrought magnesium alloy, which might lead to a new era of deformation-mechanism research.

Wu, Wei [ORNL; Qiao, Hua [McMaster University; An, Ke [ORNL; Wu, Peidong [McMaster University; Liaw, Peter K [University of Tennessee, Knoxville (UTK)

2014-01-01

102

Effects of Zn-In-Sn elements on the electric properties of magnesium alloy anode materials.  

PubMed

A new magnesium alloy anode is based on an environmentally friendly electrode that contains none of mercury, lead and chromate, but it can enhance the electric properties of alloy significantly. Magnesium alloy adding eco-friendly elements Zn-In-Sn which was developed by orthogonal design were obtained by two casting methods. The effect of additive elements on performance of electrode material was studied. The effects of elements addition and casting method on electric properties and corrosive properties of Mg-Zn-In-Sn alloys were investigated by using electrochemical measurements, corrosive tests and observation of surface structure. The results show that Mg-Zn-In-Sn alloy anode has higher electromotive force and more stable work potential than that commercial magnesium alloy AZ91. It is suitable for anode material of magnesium battery for its small hydrogen evolution, less self-corrosion rate and easy to shed corrosive offspring off. PMID:25084604

Yu, Zhan; Ju, Dongying; Zhao, Hongyang; Hu, Xiaodong

2011-06-01

103

Influence of porosity on the fatigue limit of die cast magnesium and aluminium alloys  

Microsoft Academic Search

High cycle fatigue properties of high-pressure die-cast magnesium alloys AZ91 hp, AM60 hp, AE42 hp, AS21 hp and of similarly produced cast aluminium alloy AlSi9Cu3 have been investigated. Ultrasonic fatigue tests up to 109 cycles show mean fatigue limits of approx. 3850 MPa (magnesium alloys) and 75 MPa (AlSi9Cu3) in the tested casting condition. Fatigue cracks initiated at porosity in

H Mayer; M Papakyriacou; B Zettl; S. E Stanzl-Tschegg

2003-01-01

104

Fundamental studies of friction-stir welding (FSW) of magnesium alloys to 6061-T6 aluminum and FSW of dissimilar magnesium alloys  

Microsoft Academic Search

This study has primarily explored the specificities of the process used for the friction-stir welding (FSW) of the magnesium (Mg) alloys (both SSC and wrought) to themselves and to 6061-T6 aluminum (Al), as well as the microstructural analysis of the resultant welds in order to understand the fundamental mechanisms involved in the mixing of these metals. Dissimilar Mg alloy systems

Anand Chandrika Somasekharan

2005-01-01

105

MUTLI-OBJECTIVE OPTIMIZATION OF MICROSTRUCTURE IN WROUGHT MAGNESIUM ALLOYS  

SciTech Connect

The microstructural features that govern the mechanical properties of wrought magnesium alloys include grain size, crystallographic texture, and twinning. Several processes based on shear deformation have been developed that promote grain refinement, weakening of the basal texture, as well as the shift of the peak intensity away from the center of the basal pole figure - features that promote room temperature ductility in Mg alloys. At ORNL, we are currently exploring the concept of introducing nano-twins within sub-micron grains as a possible mechanism for simultaneously improving strength and ductility by exploiting a potential dislocation glide along the twin-matrix interface a mechanism that was originally proposed for face-centered cubic materials. Specifically, we have developed an integrated modeling and optimization framework in order to identify the combinations of grain size, texture and twin spacing that can maximize strength-ductility combinations. A micromechanical model that relates microstructure to material strength is coupled with a failure model that relates ductility to a critical shear strain and a critical hydrostatic stress. The micro-mechanical model is combined with an optimization tool based on genetic algorithm. A multi-objective optimization technique is used to explore the strength-ductility space in a systematic fashion and identify optimum combinations of the microstructural parameters that will simultaneously maximize the strength-ductility in the alloy.

Radhakrishnan, Balasubramaniam [ORNL] [ORNL; Gorti, Sarma B [ORNL] [ORNL; Simunovic, Srdjan [ORNL] [ORNL

2013-01-01

106

Biofunctionalized anti-corrosive silane coatings for magnesium alloys.  

PubMed

Biodegradable magnesium alloys are advantageous in various implant applications, as they reduce the risks associated with permanent metallic implants. However, a rapid corrosion rate is usually a hindrance in biomedical applications. Here we report a facile two step procedure to introduce multifunctional, anti-corrosive coatings on Mg alloys, such as AZ31. The first step involves treating the NaOH-activated Mg with bistriethoxysilylethane to immobilize a layer of densely crosslinked silane coating with good corrosion resistance; the second step is to impart amine functionality to the surface by treating the modified Mg with 3-amino-propyltrimethoxysilane. We characterized the two-layer anticorrosive coating of Mg alloy AZ31 by Fourier transform infrared spectroscopy, static contact angle measurement and optical profilometry, potentiodynamic polarization and AC impedance measurements. Furthermore, heparin was covalently conjugated onto the silane-treated AZ31 to render the coating haemocompatible, as demonstrated by reduced platelet adhesion on the heparinized surface. The method reported here is also applicable to the preparation of other types of biofunctional, anti-corrosive coatings and thus of significant interest in biodegradable implant applications. PMID:23313945

Liu, Xiao; Yue, Zhilian; Romeo, Tony; Weber, Jan; Scheuermann, Torsten; Moulton, Simon; Wallace, Gordon

2013-11-01

107

Finite element analyses for optimization design of biodegradable magnesium alloy stent.  

PubMed

Stents made of biodegradable magnesium alloys are expected to provide a temporary opening into a narrowed arterial vessel until it remodels and will progressively disappear thereafter. Inferior mechanical properties and fast corrosion of the magnesium alloys are the two crucial factors that impede the clinical application of the magnesium alloy stents (MAS). In the present study, gradual strut width, addition of the peak-to-valley unit and introduction of the annealing technology were designed and investigated by finite element analysis in order to improve the performance of the MAS. Two experiments were carried out for a preliminary validation of the simulation. PMID:25063172

Li, Junlei; Zheng, Feng; Qiu, Xun; Wan, Peng; Tan, Lili; Yang, Ke

2014-09-01

108

Finite Element Simulation Of Magnesium AZ31 Alloy Sheet In Warm Hydroforming  

Microsoft Academic Search

Hydroforming of magnesium (Mg) alloy sheet metal offers the possibility to form geometrically complex sheet metal parts that are applicable within automotive and electronic industry etc. However, due to the limited formability of Mg alloy at ambient temperature hydroforming of Mg alloy sheet metal has to be conducted at elevated temperature. In the present study an experimental warm hydroforming process

Mikkel Steffensen; Joachim Danckert

2007-01-01

109

Quality issues in laser welding of automotive aluminum and magnesium alloys  

Microsoft Academic Search

Achievement of defect-free and structurally sound welds based on scientific principles has been an important goal of contemporary welding research. In the welding of aluminum and magnesium alloys, porosity formation and alloying element loss have been two major quality problems. The research to be presented focuses on the alleviation of these problems through quantitative understanding of alloying element loss and

Hailiang Zhao

2001-01-01

110

Thermodynamic criteria for the removal of impurities from end-of-life magnesium alloys by evaporation and flux treatment  

Microsoft Academic Search

In this paper, the possibility of removing impurities during magnesium recycling with pyrometallurgical techniques has been evaluated by using a thermodynamic analysis. For 25 different elements that are likely to be contained in industrial magnesium alloys, the equilibrium distribution ratios between the metal, slag and gas phases in the magnesium remelting process were calculated assuming binary systems of magnesium and

Takehito Hiraki; Osamu Takeda; Kenichi Nakajima; Kazuyo Matsubae; Shinichiro Nakamura; Tetsuya Nagasaka

2011-01-01

111

Deformation Processing of Anisotropic Metals.  

National Technical Information Service (NTIS)

CONTENTS: Superplasticity in the Al-Cu eutectic alloy, Superplasticity in some titanium and zirconium alloys, Superplasticity in electroplated composites of lead and tin, Superplasticity in pellet- and ingot-extrusions of the magnesium alloy ZK60.

W. A. Backofen, D. L. Holt, D. Lee, P. Martin, F. J. Azzarto

1966-01-01

112

Superplasticity in thin magnesium alloy sheets and deformation mechanism maps for magnesium alloys at elevated temperatures  

Microsoft Academic Search

Rolling processes for fabricating thin AZ61 and AZ31 alloy sheets adequate for superplastic forming have been developed. Superplastic behavior of the sheets was evaluated in the temperature range 573693 K and compared that of the initial materials having relatively coarse grains. Existing deformation mechanism maps for face-centered cubic and body-centered cubic metals were reviewed and found to be deficient in

W.-J Kim; S. W Chung; C. S Chung; D Kum

2001-01-01

113

Mean flank temperature measurement in high speed dry cutting of magnesium alloy  

Microsoft Academic Search

Magnesium in the molten state is flammable when exposed to oxygen. The risk of fire is the main concern during cutting operation. High speed dry cutting is preferable in cutting magnesium alloys due to there being no extra part cleaning work required, the environmental benefits and the ecological concerns. However, fire ignition could happen when the cutting temperature is close

F. Z. Fang; L. C. Lee; X. D. Liu

2005-01-01

114

Quasi-crystalline grain-boundary phase in the magnesium die-cast alloy ZA85  

Microsoft Academic Search

The microstructures of a fine and a coarse-grained magnesium alloy with 8 wt.% Zn and 5 wt.% Al were investigated. Both microstructures consist of dendritic magnesium grains with a coarse intermetallic phase at the grain boundaries. Our investigations showed that during solidification a quasi-crystalline grain-boundary phase forms which exhibits a pronounced thermal and mechanical stability.

M Vogel; O Kraft; G Dehm; E Arzt

2001-01-01

115

Effect of materials and temperature on the forward extrusion of magnesium alloys  

Microsoft Academic Search

Magnesium alloys are being extensively used in weight-saving applications and as a potential replacement for plastics in electronic and computer applications. However, processing of magnesium has always been a challenge for manufacturing industries owing to their high brittleness despite their good EMI shielding property and high specific strength. Despite these advantages, they are limited by their processability. The present work

Margam Chandrasekaran; Yong Ming Shyan John

2004-01-01

116

In vitro studies of biomedical magnesium alloys in a simulated physiological environment: a review.  

PubMed

In spite of the immense potential of biodegradable magnesium alloys, the fast degradation rates of Mg-based biomedical implants in the physiological environment impose severe limitations in many clinical applications. Consequently, extensive in vitro studies have been carried out to investigate the materials' performance and fathom the associated mechanisms. Here, an up-to-date review of the in vitro studies on biomedical magnesium alloys in a simulated physiological environment is provided. This review focuses on four topics: (1) materials selection and in vitro biocompatibility of biomedical magnesium alloys; (2) in vitro degradation of biomedical magnesium alloys in simulated physiological environments, specifically discussing corrosion types, degradation rates, corrosion products and impact of the constituents in body fluids on materials degradation; (3) selection of suitable test media for in vitro assessment; and (4) future research trends. PMID:21145436

Xin, Y; Hu, T; Chu, P K

2011-04-01

117

Nondestructive evaluation of an environmentally friendly conversion coating for magnesium alloys using optical measurement techniques  

E-print Network

these harmful chromates out of the coating system and continue to use magnesium alloys, an environmentally friendly conversion coating has been developed. This paper explores the best types of methods used to evaluate the thickness and coating coverage...

Zuniga, David

2006-10-30

118

Magnesium  

MedlinePLUS

... diagnostic procedures. It is also used as an antacid for acid indigestion. Some people use magnesium for ... follows:Dyspepsia (heartburn or sour stomach) as an antacid. Various magnesium compounds are used. Magnesium hydroxide seems ...

119

Effect of magnesium on strength and microstructure of Aluminium Copper Magnesium Alloy  

E-print Network

Abstract: Cast Al Cu- Mg alloys have w idely used in aircraft, aerospace, ships and boat making, industrial and architectural applications for their good mechanical properties, high strength-to-weight ratio. An intensive study of these cast aluminium family has been found in the literature in terms of enhancing the mechanical properties. The objective of this paper was to investigate the influence of magnesium on microstrructural changes and mechanical properties such as tensile strength and hardness of the Al4Cu alloys. The modifications of Al4Cu by adding Mg of 0.5 to 2 % in the interval of 0.5 % mixing w ith stirrer and casted by gravity die casting, subsequently the specimens w ere subjected T6 type heat treatment for 5 hr at 175?C. The effect of Mg and ageing on microstructure was studied by using optical microscope w ith image analysis software for measuring grain size and dendrite arm spacing. The mechanical properties such as tensile strength and hardness were studied using universal testing machine and Brinell hardness tester respectively. The micro-structural analysis result shows the 2 % addition of Mg reduces the 20 % grain size and 21.52 % dendrite structure. The tensile strength and hardness increasing with % of Mg. The addition of 2 % Mg increases tensile strength 57.9 % and hardness of 25%. Aging specimens showed that 1 % of Mg influence more on grain refinement and mechanical properties due to smaller the grain size.

unknown authors

120

Microstructure of a pressure die cast magnesium4wt.% aluminium alloy modified with rare earth additions  

Microsoft Academic Search

Addition of cerium-rich mixtures of rare earth (RE) elements to aluminium-containing magnesium pressure die cast alloys is known to improve the creep properties at elevated temperatures. In the present investigation, a detailed description of the microstructure of a magnesium-4 wt.% aluminium alloy containing 1.4 wt.% of a cerium-rich mixture of RE elements is presented. Particle types occurring and their distribution

G. Pettersen; H. Westengen; R. Hier; O. Lohne

1996-01-01

121

Fatigue behaviour of friction stir processed AZ91 magnesium alloy produced by high pressure die casting  

Microsoft Academic Search

The room temperature fatigue properties of AZ91 magnesium alloy produced by high pressure die casting (HPDC) as cast, heat treated, friction stir processed (FSP) and FSP and heat treated were studied. The fatigue properties of the material were evaluated for the HPDC magnesium alloy in the as-received state and after a solution treatment at 415C for 2h and an ageing

P.. Cavaliere; P. P. De Marco

2007-01-01

122

Effect of temperature on the dynamic compressive properties of magnesium alloy and its nanocomposite  

NASA Astrophysics Data System (ADS)

Magnesium alloys are very attractive in applications such as automotive, railway and aerospace industries due to their low density in comparison with aluminum and steel alloys. Magnesium-based composites exhibit high specific properties compared to unreinforced magnesium alloys and they are found to be promising for mechanical applications under impact and high temperature conditions beyond those possible with magnesium alloys. In the present study, the effect of temperature variation has been investigated for both magnesium alloy AZ31B and the same alloy reinforced with silicon carbide nano-particles at high strain rates. The temperature is varied in the range from -30C to 200C at a high strain rate of 3300 s-1. Lower stresses and larger strains to peak compressive stresses are observed with increasing temperature. An analytic comparison between AZ31B alloy and AZ31B nanocomposite was also examined and results reveal that AZ31B nanocomposite displays superior strength properties with slightly weaker ductility than AZ31B alloy at all three temperature variations. The result of this is an improved energy absorption capability possessed by AZ31B nanocomposite.

Xiao, Jing; Shu, D. W.; Goh, Kok Swee

2014-06-01

123

Sliding friction and wear of magnesium alloy AZ91D produced by two different methods  

Microsoft Academic Search

Alloy AZ91D is a leading magnesium alloy used for structural applications. It contains aluminum and zinc as principal alloying elements. This alloy is normally die-cast, but recent developments in semi-solid injection molding (Thixomolding), which offers certain processing advantages, produces a slightly different microstructure than die-casting, and it was of interest to determine whether the two processing routes would measurably affect

Peter J Blau; Matthew Walukas

2000-01-01

124

Research of {0001} crystal orientation for magnesium alloys solidified in a fashion of cellular crystals  

NASA Astrophysics Data System (ADS)

The magnesium alloy grew in a fashion of cellular crystals during the process of unidirectional solidification, and the {0001} crystal face orientation in the cast ingot of the magnesium alloy was studied. The theoretical model and methodology were set up, and a corresponding experiment was carried out to verify the theoretical analysis results. The experimental results indicate that the {0001} crystal face of magnesium crystals parallels to the width direction for the thin-plate cast ingot when the magnesium grows in a manner of cellular crystals. The separation angle between the {0001} crystal face of magnesium crystals and the vertical axis line of the cast ingot is about 62 for the circular column cast ingot, which distributes in cone-type. The theoretical analysis results are basically in agreement with the experimental ones of previous literatures and this paper.

Chang, Guo-Wei; Chen, Shu-Ying; Li, Qing-Chun; Yue, Xu-Dong; Qi, Yi-Hui

2012-02-01

125

In Vitro Biocompatibility and Endothelialization of Novel Magnesium-Rare Earth Alloys for Improved Stent Applications  

PubMed Central

Magnesium (Mg) based alloys are the most advanced cardiovascular stent materials. This new generation of stent scaffold is currently under clinical evaluation with encouraging outcomes. All these Mg alloys contain a certain amount of rare earth (RE) elements though the exact composition is not yet disclosed. RE alloying can usually enhance the mechanical strength of different metal alloys but their toxicity might be an issue for medical applications. It is still unclear how RE elements will affect the magnesium (Mg) alloys intended for stent materials as a whole. In this study, we evaluated MgZnCaY-1RE, MgZnCaY-2RE, MgYZr-1RE, and MgZnYZr-1RE alloys for cardiovascular stents applications regarding their mechanical strength, corrosion resistance, hemolysis, platelet adhesion/activation, and endothelial biocompatibility. The mechanical properties of all alloys were significantly improved. Potentiodynamic polarization showed that the corrosion resistance of four alloys was at least 310 times higher than that of pure Mg control. Hemolysis test revealed that all the materials were non-hemolytic while little to moderate platelet adhesion was found on all materials surface. No significant cytotoxicity was observed in human aorta endothelial cells cultured with magnesium alloy extract solution for up to seven days. Direct endothelialization test showed that all the alloys possess significantly better capability to sustain endothelial cell attachment and growth. The results demonstrated the promising potential of these alloys for stent material applications in the future. PMID:24921251

Zhao, Nan; Watson, Nevija; Xu, Zhigang; Chen, Yongjun; Waterman, Jenora; Sankar, Jagannathan; Zhu, Donghui

2014-01-01

126

In vitro biocompatibility and endothelialization of novel magnesium-rare Earth alloys for improved stent applications.  

PubMed

Magnesium (Mg) based alloys are the most advanced cardiovascular stent materials. This new generation of stent scaffold is currently under clinical evaluation with encouraging outcomes. All these Mg alloys contain a certain amount of rare earth (RE) elements though the exact composition is not yet disclosed. RE alloying can usually enhance the mechanical strength of different metal alloys but their toxicity might be an issue for medical applications. It is still unclear how RE elements will affect the magnesium (Mg) alloys intended for stent materials as a whole. In this study, we evaluated MgZnCaY-1RE, MgZnCaY-2RE, MgYZr-1RE, and MgZnYZr-1RE alloys for cardiovascular stents applications regarding their mechanical strength, corrosion resistance, hemolysis, platelet adhesion/activation, and endothelial biocompatibility. The mechanical properties of all alloys were significantly improved. Potentiodynamic polarization showed that the corrosion resistance of four alloys was at least 3-10 times higher than that of pure Mg control. Hemolysis test revealed that all the materials were non-hemolytic while little to moderate platelet adhesion was found on all materials surface. No significant cytotoxicity was observed in human aorta endothelial cells cultured with magnesium alloy extract solution for up to seven days. Direct endothelialization test showed that all the alloys possess significantly better capability to sustain endothelial cell attachment and growth. The results demonstrated the promising potential of these alloys for stent material applications in the future. PMID:24921251

Zhao, Nan; Watson, Nevija; Xu, Zhigang; Chen, Yongjun; Waterman, Jenora; Sankar, Jagannathan; Zhu, Donghui

2014-01-01

127

Corrosion resistance of aged die cast magnesium alloy AZ91D  

Microsoft Academic Search

The corrosion behaviour of die cast magnesium alloy AZ91D aged at 160C was investigated. The corrosion rate of the alloy decreases with ageing time in the initial stages and then increases again at ageing times greater than 45h. The dependence of the corrosion rate on ageing time can be related to the changes in microstructure and local composition during ageing.

Guangling Song; Amanda L Bowles; David H StJohn

2004-01-01

128

Vertical vibration-assisted magnetic abrasive finishing and deburring for magnesium alloy  

Microsoft Academic Search

The ultimate goal of this project is to develop an efficient finishing process enabling unskilled operators to finish automatically the complicated micro-curved surface and edge surface of the magnesium alloy. The results achieved in the first phase as described in this paper focus on the basic characteristics of the plane and edge surface finishing and deburring of this alloy by

Shaohui Yin; Takeo Shinmura

2004-01-01

129

The influence of surface microchemistry in protective film formation on multi-phase magnesium alloys  

NASA Astrophysics Data System (ADS)

The high strength:weight ratio of magnesium alloys makes them an ideal metal for automotive and aerospace applications where weight reduction is of significant concern. Unfortunately, magnesium alloys are highly susceptible to corrosion particularly in salt-spray conditions. This has limited their use in the automotive and aerospace industries, where exposure to harsh service conditions is unavoidable. The simplest way to avoid corrosion is to coat the magnesium-based substrate by a process such as electroless plating, which is a low-cost, non line of sight process. Magnesium is classified as a difficult to plate metal due to its high reactivity. This means that in the presence of air magnesium very quickly forms a passive oxide layer that must be removed prior to plating. Furthermore, high aluminium content alloys are especially difficult to plate due to the formation of intermetallic species at the grain boundaries, resulting in a non-uniform surface potential across the substrate and thereby further complicating the plating process. The objective of this study is to understand how the magnesium alloy microstructure influences the surface chemistry of the alloy during both pretreatment and immersion copper coating of the substrate. A combination of scanning electron microscopy, energy dispersive spectroscopy and scanning Auger microscopy has been used to study the surface chemistry at the various stages of the coating process. Our results indicate that the surface chemistry of the alloy is different on the aluminum rich ? phase of the material compared to the magnesium matrix which leads to preferential deposition of the metal on the aluminum rich phase of the alloy.

Gray-Munro, J. E.; Luan, B.; Huntington, L.

2008-02-01

130

In vitro degradation behaviour of a friction stir processed magnesium alloy.  

PubMed

In this study, the in vitro degradation behaviour of a friction stir processed AZ31 magnesium alloy was investigated. Electrochemical experiments in simulated body fluid suggest that friction stir processing marginally enhances the degradation resistance of the alloy, which could be attributed to the dissolution of secondary phase particles. Homogenisation of the microstructure reduces galvanic corrosion. It is envisaged that the beneficial effect would be more pronounced for magnesium alloys which contain high volume fraction of galvanic corrosion inducing secondary phase particles. PMID:21894540

Bobby Kannan, M; Dietzel, W; Zettler, R

2011-11-01

131

FORGED PIECES FROM MAGNESIUM ALLOYS AND THEIR UTILIZATION IN AUTOMOTIVE INDUSTRY  

E-print Network

The paper presents an investigation on the effect of process variables and material condition on forgeability of magnesium wrought alloys of Mg-Al-Zn group, AZ31, AZ61 and AZ91. The experimental work includes studies of forging capabilities of the alloys in closed-die forging at hot and warm-working temperatures. Forging tests are performed for material both in as-cast and asworked condition, for two variants of workpiece geometry. The different variants of the workpiece indicated fracture-related problems in forging magnesium alloys in the warm-working temperature regime, which involved interaction between material condition and process variables, and state of stress. By means of numerical calculations it was concluded, that in addition to material condition, a favourable stale of stress, provided by a closed-die, can greatly improving the forgeability of magnesium alloys in the warm-working range.

Miroslav Greger; Radim Kocich; Vlastimil Karas

132

Warm Deep Drawing Of Rectangular Cups With Magnesium Alloy AZ31 Sheets  

SciTech Connect

Recently, magnesium alloys have been widely applied in automotive and electronic industries as the lightest weight structural and functional materials. Warm forming of magnesium alloys has attracted much attention due to the very poor formability of Mg alloys at room temperature. The formability of magnesium alloy sheet at elevated temperature is significantly affected by the processing parameters. Among them the forming temperature, the punch speed, the geometrical shape of the blank, the blank holder force and the lubrication are probably the most relevant. In this research, the deep drawing of rectangular cups with AZ31 sheets was conducted at elevated temperatures with different process parameters. The finite element analyses were performed to investigate the effects of the process parameters on the formability of rectangular cup drawing and to predict the process defects during the process. The material yield condition was modeled using the isotropic Von Mises criterion. The flow stress data were obtained from tensile tests.

Ren, L. M. [Department of Mechanical and Management Engineering (DIMeG), Polytechnic of Bari, 70126 Bari (Italy); Institute of Metal Research, Chinese Academy of Sciences, 110016 Shenyang (China); Palumbo, G.; Tricarico, L. [Department of Mechanical and Management Engineering (DIMeG), Polytechnic of Bari, 70126 Bari (Italy); Zhang, S. H. [Institute of Metal Research, Chinese Academy of Sciences, 110016 Shenyang (China)

2007-05-17

133

Low-temperature superplasticity and internal friction in microcrystalline Mg alloys processed by ECAP  

Microsoft Academic Search

Excellent low-temperature superplasticity (<300 C) was observed in the ECAP-processed materials: elongations to failure are 810% and 570% at a strain rate of 310?3 s?1 for ZK60 and AZ91 alloys, respectively. Internal friction can be practically used to determine the optimum temperature for superplasticity.

V. N. Chuvildeev; T. G. Nieh; M. Yu. Gryaznov; A. N. Sysoev; V. I. Kopylov

2004-01-01

134

Magnesium  

MedlinePLUS

... supplement, and present in some medicines (such as antacids and laxatives). Magnesium is a cofactor in more ... Very large doses of magnesium-containing laxatives and antacids (typically providing more than 5,000 mg/day ...

135

Effect of Ca addition on the oxidation resistance of AZ91 magnesium alloys at elevated temperatures  

Microsoft Academic Search

AZ91 magnesium alloys containing 0.275.22 wt.% Ca, were melted and cast to study the effects of Ca addition on oxidation\\u000a resistance at elevated temperatures. An ignition temperature test showed that the ignition of AZ91 alloy occurred at about\\u000a 350450 C below the melting point, whereas that of the Ca-containing AZ91 alloys did so at above 650 C. Weight gain measurements

Byung-Ho Choi; Bong-Sun You; Won-Wook Park; Yan-Bin Huang; Ik-Min Park

2003-01-01

136

FUNDAMENTAL STUDIES OF THE FRICTION-STIR WELDING OF MAGNESIUM ALLOYS TO 6061-T6 ALUMINUM  

Microsoft Academic Search

Wrought magnesium (Mg) alloy AZ31B-H24 and semi- solid-cast Mg alloy AZ91D (~3% primary solid fraction) were friction-stir welded (FSW) to 6061-T6 aluminum (Al). Numerous welds were made with the Mg alloys and 6061-T6 Al in alternating advancing and retreating sides. Optical metallography was used to observe and confirm the weld zone characteristics unique to dissimilar welds. Dynamic recrystallization (DRX) was

Anand C. Somasekharan; Lawrence E. Murr

137

A thousandfold creep strengthening by Ca addition in die-cast AM50 magnesium alloy  

Microsoft Academic Search

The effect of calcium addition on the microstructure and creep strength of the die-cast AM50 magnesium alloy was investigated.\\u000a The ?-Mg grains with the diameter of 4.9 m are surrounded by the eutectic phases for the AM50-1.72 mass pct Ca alloy, while the ?(Mg17Al12) particles are located mainly on the grain boundaries of the ? grains for the AM50 alloy.

Yoshihiro Terada; Rie Sota; Naoya Ishimatsu; Tatsuo Sato; Koichi Ohori

2004-01-01

138

Forming Analysis of AZ31 Magnesium Alloy Sheets by Means of a Multistep Inverse Approach  

SciTech Connect

This paper applies a multi-step inverse approach to predict the forming of AZ31 magnesium alloy sheets. An in-house finite element code named INAPH, which implements the inverse approach formulation by Guo et al. (Int. J. Numer. Methods Eng., 30, 1385-1401), has been used for the forming analysis. This inverse approach uses the deformation theory of plasticity and assumes that the deformation is independent of the loading history. Failure during forming is predicted by a stress-based criterion or a forming limit diagram-based criterion. The INAPH predictions have been compared with experimental results of Takuda et al (Journal of Materials Processing Technology, 89-90:135-140) and incremental analysis using ABAQUS. The multi-step inverse analysis has been shown to very quickly and fairly accurately predict stress, plastic strain, thickness distributions and failure locations on deeply drawn parts made of AZ31 magnesium alloy. The capability of INAPH to predict the formability of magnesium alloys has also been demonstrated at various temperatures. As magnesium alloys possess very limited formability at room temperature, and their formability becomes better at higher temperatures (> 100oC), the inverse analysis constitutes an efficient and valuable tool to predict forming of magnesium alloy parts as a function of temperature. In addition, other processing and design parameters such as the initial dimensions, final desired shape, blank holder forces, and friction can be quickly adjusted to assess the forming feasibility.

Nguyen, Ba Nghiep; Bapanapalli, Satish K.

2009-04-01

139

An EBSP investigation of alternate microstructures for superplasticity in aluminum-magnesium alloys  

SciTech Connect

This study proposes to provide insight into alternative grain boundary structures in two aluminum-magnesium alloys processed to achieve superplastic behavior. A commercially processes superplastic 5083 aluminum alloy, SKY5083, and a laboratory processed, non-commercial superplastic Al-10Mg-0.1Zr alloy have been selected for examination. Although alloy content, processing routes, and deformation conditions vary for each material, a comparison of results may provide evidence that alternate grain structures and boundary misorientation distributions may support superplasticity in the GBS regime, depending on the TMP processing and alloy system chosen.

McNelley, T.R.; McMahon, M.E. [Naval Postgraduate School, Monterey, CA (United States)] [Naval Postgraduate School, Monterey, CA (United States); Hales, S.J. [A.S. and M., Inc., Hampton, VA (United States)] [A.S. and M., Inc., Hampton, VA (United States)

1997-02-15

140

Studies on the inuence of chloride ion and pH on the corrosion and electrochemical behaviour of AZ91D magnesium alloy  

E-print Network

91D magnesium alloy R. AMBAT, N.N. AUNG and W. ZHOU School of Mechanical and Production Engineering in revised form 20 January 2000 Key words: AZ91D alloy, chloride ion, corrosion, die-cast, ingot, magnesium of morphology. The corrosion product consisted of magnesium hydroxide, fallen b particles and magnesium

Zhou, Wei

141

Novel process for recycling magnesium alloy employing refining and solid oxide membrane electrolysis  

NASA Astrophysics Data System (ADS)

Magnesium is the least dense engineering metal, with an excellent stiffness-to-weight ratio. Magnesium recycling is important for both economic and environmental reasons. This project demonstrates feasibility of a new environmentally friendly process for recycling partially oxidized magnesium scrap to produce very pure magnesium at low cost. It combines refining and solid oxide membrane (SOM) based oxide electrolysis in the same reactor. Magnesium and its oxide are dissolved in a molten flux. This is followed by argon-assisted evaporation of dissolved magnesium, which is subsequently condensed in a separate condenser. The molten flux acts as a selective medium for magnesium dissolution, but not aluminum or iron, and therefore the magnesium collected has high purity. Potentiodynamic scans are performed to monitor the magnesium content change in the scrap as well as in solution in the flux. The SOM electrolysis is employed in the refining system to enable electrolysis of the magnesium oxide dissolved in the flux from the partially oxidized scrap. During the SOM electrolysis, oxygen anions are transported out of the flux through a yttria stabilized zirconia membrane to a liquid silver anode where they are oxidized. Simultaneously, magnesium cations are transported through the flux to a steel cathode where they are reduced. The combination of refining and SOM electrolysis yields close to 100% removal of magnesium metal from partially oxidized magnesium scrap. The magnesium recovered has a purity of 99.6w%. To produce pure oxygen it is critical to develop an inert anode current collector for use with the non-consumable liquid silver anode. In this work, an innovative inert anode current collector is successfully developed and used in SOM electrolysis experiments. The current collector employs a sintered strontium-doped lanthanum manganite (La0.8Sr0.2MnO 3-delta or LSM) bar, an Inconel alloy 601 rod, and a liquid silver contact in between. SOM electrolysis experiments with the new LSM-Inconel current collector are carried out and performance comparable to the state-of-the-art SOM electrolysis for Mg production employing the non-inert anode has been demonstrated. In both refining and SOM electrolysis, magnesium solubility in the flux plays an important role. High magnesium solubility in the flux facilitates refining. On the other hand, lower magnesium solubility benefits the SOM electrolysis. The dissolution of magnesium imparts electronic conductivity to the flux. The effects of the electronic conductivity of the flux on the SOM electrolysis performance are examined in detail through experiments and modeling. Methods for mitigating the negative attributes of the electronic conductivity during SOM electrolysis are presented.

Guan, Xiaofei

142

Solubility of zirconium in liquid magnesium and the ML5 alloy  

Microsoft Academic Search

1.It was found that zinc, copper, misch metal, and calcium do not affect the solubility of zirconium in magnesium but promote refining of the structure of the Mg-Zr alloy, while nickel, manganese, silicon, tin, aluminum, beryllium, and iron lower the solubility of zirconium and promote coarsening of the structure.A lower solubility of zirconium in magnesium is promoted by elements which

V. M. Babkin

1968-01-01

143

Corrosion protection of AZ91 magnesium alloy by anodizing in niobium and zirconium-containing electrolytes  

Microsoft Academic Search

A new Nb+Zr-based anodized coating was designed for the corrosion protection of AZ91 magnesium alloy. Polarization curves and electrochemical impedance diagrams plotted in Na2SO4 electrolyte showed its high protective effect. Analysis of the chemical composition by X-ray photoelectron spectroscopy indicated that the coating mainly consisted of (i) magnesium metaborate and metaphosphate, (ii) MgF2 and ZrF4, and (iii) Nb2O5, ZrO2 and

H. Ardelean; I. Frateur; S. Zanna; A. Atrens; P. Marcus

2009-01-01

144

Relationship between internal porosity and fracture strength of die-cast magnesium AM60B alloy  

Microsoft Academic Search

A die-cast magnesium alloy was examined with the use of X-ray tomography. Five tensile samples cut from different locations of a thin-walled, high-pressure magnesium die-casting were analyzed. The size and locations of pores in each sample were obtained from the X-ray tomography data. A critical local strain model was used to predict the fracture properties of the tensile samples. The

J. P. Weiler; J. T. Wood; R. J. Klassen; E. Maire; R. Berkmortel; G. Wang

2005-01-01

145

Texture evolution of five wrought magnesium alloys during route A equal channel angular extrusion: Experiments and simulations  

Microsoft Academic Search

Equal channel angular extrusion (ECAE) has been demonstrated to induce unusual deformation textures and resulting properties in magnesium alloys, such as the remarkably enhanced room temperature ductility first reported by Mukai et al. [Mukai T, Yamanoi M, Watanabe H, Higashi K. Scr Mater 2001;45:89]. This paper documents a wide range of textures which evolve during ECAE of magnesium alloys. The

S. R. Agnew; P. Mehrotra; T. M. Lillo; G. M. Stoica; P. K. Liaw

2005-01-01

146

Coupled thermo-mechanical FE simulation of the hot splitting spinning process of magnesium alloy AZ31  

Microsoft Academic Search

Magnesium alloy AZ31 shows excellent ductility and formability at elevated temperatures, and using hot splitting spinning it can be formed into a structural component subjected to impact loadings, such as, a wheel hub of aero undercarriage or kinds of light whole wheels. In this paper, based on the analysis of microstructures and deformation characteristics of magnesium alloy AZ31, a reasonable

He Yang; Liang Huang; Mei Zhan

2010-01-01

147

Computational Materials Science and Surface Engineering Effect of cooling rate on the solidification behavior of magnesium alloys  

Microsoft Academic Search

Purpose: The goal of this paper is to present the thermal characteristics of magnesium alloy using the novel Universal Metallurgical Simulator and Analyzer Platform. Design\\/methodology\\/approach: The objective of this work is determine the liquidus, solidus temperature and beginning nucleation temperature to understanding crystallization of magnesium alloys. Findings: The research show that the thermal analysis carried out on UMSA Technology Platform

L. A. Dobrza?ski; M. Krl; T. Ta?ski; R. Maniara

148

Effects of Electrode Force on the Characteristic of Magnesium Alloy Joint Welded by Resistance Spot Welding with Cover Plates  

Microsoft Academic Search

Magnesium alloy AZ31B sheets were welded using the technique of resistance spot welding with cover plates. The effects of electrode force on the joining performance and pore formation during welding were investigated. The results reveal that the enhanced electrode force is an effective way to inhibit pore formation and improve magnesium alloy resistance spot welding performance.

Ranfeng Qiu; Hongxin Shi; Hua Yu; Keke Zhang; Yimin Tu; S. Satonaka

2010-01-01

149

One-step electrochemical fabrication of bilayered MgO/polymer coating on magnesium alloy  

NASA Astrophysics Data System (ADS)

This research demonstrates a novel one-step electrochemical method to fabricate thick bilayer coatings on magnesium alloy in acid phosphate electrolyte containing aniline monomer and styrene-acrylic emulsion (SAE) with pulsed DC voltage. The morphologies, XRD and FTIR results show that the bilayer coating consists of an inner oxide layer and an outer polyaniline (PANI)/SAE composite layer. It is believed that the bilayered structure achieved results from a hybrid process combining electropolymerization (EPM) of aniline, electrophoretic deposition (EPD) of SAE and plasma electrolyte oxidation (PEO) of magnesium alloy substrate. Electrochemical corrosion tests indicate that the bilayer coating can provide superior corrosion protection to the magnesium alloy substrate in 3.5 wt.% NaCl solution.

Liang, Jun; Zhang, Ren-Hui; Peng, Zhen-Jun; Liu, Bai-Xing

2014-09-01

150

Thermodynamic criteria for the removal of impurities from end-of-life magnesium alloys by evaporation and flux treatment  

NASA Astrophysics Data System (ADS)

In this paper, the possibility of removing impurities during magnesium recycling with pyrometallurgical techniques has been evaluated by using a thermodynamic analysis. For 25 different elements that are likely to be contained in industrial magnesium alloys, the equilibrium distribution ratios between the metal, slag and gas phases in the magnesium remelting process were calculated assuming binary systems of magnesium and an impurity element. It was found that calcium, gadolinium, lithium, ytterbium and yttrium can be removed from the remelted end-of-life (EoL) magnesium products by oxidization. Calcium, cerium, gadolinium, lanthanum, lithium, plutonium, sodium, strontium and yttrium can be removed by chlorination with a salt flux. However, the other elements contained in magnesium alloy scrap are scarcely removed and this may contribute toward future contamination problems. The third technological option for the recycling of EoL magnesium products is magnesium recovery by a distillation process. Based on thermodynamic considerations, it is predicted that high-purity magnesium can be recovered through distillation because of its high vapor pressure, yet there is a limit on recoverability that depends on the equilibrium vapor pressure of the alloying elements and the large energy consumption. Therefore, the sustainable recycling of EoL magnesium products should be an important consideration in the design of advanced magnesium alloys or the development of new refining processes.

Hiraki, Takehito; Takeda, Osamu; Nakajima, Kenichi; Matsubae, Kazuyo; Nakamura, Shinichiro; Nagasaka, Tetsuya

2011-06-01

151

Galvanic corrosion of magnesium alloy AZ91D in contact with an aluminium alloy, steel and zinc  

Microsoft Academic Search

An investigation was carried out into the galvanic corrosion of magnesium alloy AZ91D in contact with zinc, aluminium alloy A380 and 4150 steel. Specially designed test panels were used to measure galvanic currents under salt spray conditions. It was found that the distributions of the galvanic current densities on AZ91D and on the cathodes were different. An insulating spacer between

Guangling Song; Birgir Johannesson; Sarath Hapugoda; David StJohn

2004-01-01

152

Discharge and Corrosion Performance of AP65 Magnesium Alloy in Simulated Seawater: Effect of Temperature  

NASA Astrophysics Data System (ADS)

The discharge and corrosion performance of AP65 magnesium alloy in simulated seawater with different temperatures is investigated by electrochemical techniques and corrosion morphology observation. The results indicate that AP65 alloy can hardly be activated at a large current density in the 0 C simulated seawater, whereas the activation time is shortened, and the potential exhibits a significantly negative shift in the 35 C simulated seawater. However, the increase in temperature promotes the localized corrosion and thus is detrimental to the anode efficiency of AP65 alloy. Moreover, the effect of seawater temperature and current density on the surface morphology of AP65 alloy during the discharge process is also analyzed.

Wang, Naiguang; Wang, Richu; Peng, Chaoqun; Peng, Bing; Feng, Yan; Hu, Chengwang

2014-09-01

153

Influence of Cobalt on the Properties of Load-Sensitive Magnesium Alloys  

PubMed Central

In this study, magnesium is alloyed with varying amounts of the ferromagnetic alloying element cobalt in order to obtain lightweight load-sensitive materials with sensory properties which allow an online-monitoring of mechanical forces applied to components made from Mg-Co alloys. An optimized casting process with the use of extruded Mg-Co powder rods is utilized which enables the production of magnetic magnesium alloys with a reproducible Co concentration. The efficiency of the casting process is confirmed by SEM analyses. Microstructures and Co-rich precipitations of various Mg-Co alloys are investigated by means of EDS and XRD analyses. The Mg-Co alloys' mechanical strengths are determined by tensile tests. Magnetic properties of the Mg-Co sensor alloys depending on the cobalt content and the acting mechanical load are measured utilizing the harmonic analysis of eddy-current signals. Within the scope of this work, the influence of the element cobalt on magnesium is investigated in detail and an optimal cobalt concentration is defined based on the performed examinations. PMID:23344376

Klose, Christian; Demminger, Christian; Mroz, Gregor; Reimche, Wilfried; Bach, Friedrich-Wilhelm; Maier, Hans Jurgen; Kerber, Kai

2013-01-01

154

Preparation of aluminium-magnesium alloys and some valuable salts from used beverage cans.  

PubMed

The purpose of this work is to recover standard aluminium-magnesium alloy(s) and some valuable salts from used beverage cans (UBCs). The suggested method updated the current recycling technology by augmenting removal of the coating paint, decreasing magnesium loss during melting process and improving hydrochloric acid leaching of the formed slag. Iron impurity present in the leaching solution, was removed by oxidation using oxygen gas or hydrogen peroxide and filtered as goethite. Results obtained revealed that a mixture of methyl ethyl ketone/dimethyl formamide entirely removes the paint coating at room temperature. The process compares favorably to the current methods involving firing or swell peeling. The coating decomposes to titanium dioxide by heating at 750 degrees C for 30 min. Standard compositions of Al-Mg alloys are formulated using secondary magnesium. The extent of recovery (R) of these alloy(s) is a function of the melting time and temperature and type of the flux. The maximum (R) value amounts to 94.4%. Sodium borate/chloride mix decreases magnesium loss to a minimum. The extent of leaching valuable salts from the slag increases with increasing the molarity, stoichiometric ratio and leaching temperature of the acid used. Removal of iron is a function of the potential of the oxidation process. Stannous chloride has been recovered from the recovered and dried salts by distillation at 700-750 degrees C. PMID:12623092

Rabah, Mahmoud A

2003-01-01

155

An Investigation to Double Hit Deformation Behavior of AZ31 Magnesium Alloy  

SciTech Connect

In recent years magnesium alloys have been used in different industries due to their outstanding properties. The hot deformation processes are recognized to be the most applicable forming routes for these alloys. These are usually performed through multi-stage straining. Accordingly the static restoration processes may play important roles on their final microstructure and mechanical properties. In the present work double hit compression tests were applied on AZ31 magnesium alloy. The results were analyzed relying on the fractional softening relationship. The effects of strain rate and inter-pass time were discussed. Microstructural observations were addressed to describe the effects of static recrystallization on the double hit deformation behavior of AZ31 alloy.

Shamsi, M.; Hanzaki, A. Zarei; Naei, H. [School of Metallurgy and Material, university of Tehran, Tehran (Iran, Islamic Republic of)

2007-04-07

156

Effects of antimony addition on the microstructures of ZA84 magnesium alloy  

Microsoft Academic Search

The effects of antimony (Sb) on the microstructures of as-cast Mg8Zn4Al (ZA84) magnesium alloy were investigated by using optical microscopy, SEM, EDX, and XRD, etc. The results indicated that the microstructures of as-cast alloys containing Sb consisted of solid solution ?(Mg), ternary phases ? [Mg32(Al, Zn)49] and ? (Al2Mg5Zn2), eutectic mixture phase [?(Mg)+?], a newly formed dual phase MgZn2, and

Jianqiang Wang; Zhanlai Ding; Fangjuan Qi; Hao Zhu; Yunchang Fan

2010-01-01

157

Effect of high-temperature plastic deformation on the properties of precipitation-hardening magnesium alloys  

Microsoft Academic Search

1.Heating the Mg-3% Nd alloy to a temperature guaranteeing a solid solution of alloying elements in magnesium and high-temperature plastic deformation (80% strain) produce higher strength characteristics at a testing temperature of 250C than those resulting from treatment T6 (quenching+aging) but lower than those resulting from treatment T8 (quenching +10% cold plastic deformation + aging).2.At room temperature the strength characteristics

M. E. Drits; Z. A. Sviderskaya; L. L. Rokhlin; A. A. Oreshkina

1968-01-01

158

Microstructure evolution and low temperature superplasticity of ZK40 magnesium alloy subjected to ECAP  

Microsoft Academic Search

Microstructure evolution and superplastic behaviors of ZK40 magnesium alloy were investigated in the temperature range of\\u000a 473623 K. Transmission electron microscopy (TEM) was used to study the microstructure changes. After the alloy had been processed\\u000a by equal channel angular pressing (ECAP) for one pass through the die, significant twinning was found to have occurred, and\\u000a the mean grain size was

Li Lin; Zheng Liu; Lijia Chen; Teng Liu; Shiding Wu

2004-01-01

159

Electrochemical corrosion behavior of composite coatings of sealed MAO film on magnesium alloy AZ91D  

Microsoft Academic Search

Protective composite coatings were prepared on magnesium alloy AZ91D by micro-arc oxidation (MAO) treatment plus a top coating with sealing agent using multi-immersion technique under low-pressure conditions. The corrosion resistance of AZ91D alloy with composite coatings was superior evidently to that with merely MAO film. SEM observations revealed that the sealing agent was integrated with MAO film by physically interlocking;

Hongping Duan; Keqin Du; Chuanwei Yan; Fuhui Wang

2006-01-01

160

Dynamic recrystallization and texture development during hot deformation of magnesium alloy AZ31  

Microsoft Academic Search

The dynamic recrystallization(DRX) and texture development, taking place during hot deformation of magnesium alloy AZ31 with a strong wire texture, were studied in compression at 673 K (0.73 Tm). Two kinds of samples were machined parallelly to the extruded and transverse directions of Mg alloy rods. New fine grains are evolved at original grain boundaries corrugated at low strains and

Xu-yue YANG; Ze-sheng JI; H. MIURA; T. SAKAI

2009-01-01

161

Formability of AZ31 magnesium alloy sheets at warm working conditions  

Microsoft Academic Search

Fine-grained AZ31 magnesium alloy sheets were prepared through hot-rolling process. To investigate the mechanical properties of the sheets, uniaxial tensile tests were conducted at various temperatures and strain rates. The formability of AZ31 alloy sheets at warm working conditions was evaluated by limit drawing ratio (LDR) tests and limit dome height (LDH) tests at temperatures from 50 to 240C. It

K. F. Zhang; D. L. Yin; D. Z. Wu

2006-01-01

162

Forgeability of MgAlZn magnesium alloys in hot and warm closed die forging  

Microsoft Academic Search

The paper presents an investigation on the effect of process variables and material condition on forgeability of magnesium wrought alloys of MgAlZn group, AZ31 and AZ61. The experimental work includes studies of forging capabilities of the alloys in closed-die forging at hot and warm-working temperatures. Forging tests were performed for material both in as-cast and as-worked condition, for two variants

P. Skubisz; J. Si?czak; S. Bednarek

2006-01-01

163

Low temperature superplasticity of AZ91 magnesium alloy with non-equilibrium grain boundaries  

Microsoft Academic Search

The superplastic behavior of a fine-grained AZ91 alloy, processed by equal channel angular extrusion, has been investigated in a low temperature range of 423523K. The experimental results showed a stress exponent of 2 and the activation energy for superplastic flow was in agreement with that for grain boundary diffusion of magnesium. The alloy with non-equilibrium grain boundary structures exhibited lower

M. Mabuchi; K. Ameyama; H. Iwasaki; K. Higashi

1999-01-01

164

An investigation on the microstructure of an AM50 magnesium alloy  

Microsoft Academic Search

The microstructure and the dislocation arrangement in the die cast AM50 magnesium alloy as well as in the stressed states have been investigated using conventional transmission electron microscopy (TEM), high-resolution TEM and energy dispersive X-ray analysis. The microstructure of the die cast AM50 alloy is found to mainly consist of ?-Mg, ?-Mg17Al12 and Al8Mn5 phases. Two kinds of ?-Mg17Al12 particles

R. M. Wang; A. Eliezer; E. M. Gutman

2003-01-01

165

Influence of Al addition on microstructure of die casting magnesium alloys  

Microsoft Academic Search

Purpose: In the following paper there have been the structure and properties of the MCMgAl9Zn1 magnesium cast alloy as-cast state and after a heat treatment presented. Design\\/methodology\\/approach: A casting cycle of alloys has been carried out in an induction crucible furnace using a protective salt bath Flux 12 equipped with two ceramic filters at the melting temperature of 75010C, suitable

L. A. Dobrza?ski a; T. Ta?ski; L. ?ek

2006-01-01

166

THE REACTIONS OF MAGNESIUM AND MAGNESIUM ALLOYS WITH GASES AT HIGH TEMPERATURES  

Microsoft Academic Search

The ignition temperature of Mg is influenced by numerous variables of ; which the most important appear to be alloying (or dissimilar metal contact) and ; the concentration of the Mg vapor over the heated metal. Most alloying elements ; lower the ignition temperature; however, Re additions inhibit the pyrophoricity ; of alloys up to temperatures in excess of their

1958-01-01

167

Formation of Ha-Containing Coating on AZ31 Magnesium Alloy by Micro-Arc Oxidation  

NASA Astrophysics Data System (ADS)

Magnesium and its alloys are potential biodegradable implant materials due to their attractive biological properties. But the use of magnesium is still hampered by its poor corrosion resistance in physiological fluids. In this study, a HA-containing coating was fabricated by micro-arc oxidation (MAO). The active plasma species of micro-discharge was studied by optical emission spectroscopy (OES). The microstructure and composition were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion behavior and apatite-forming ability were studied by electrochemical tests and immersed samples in simulated body fluids (SBF). The results show that the microdischarge channel model is gas discharges and oxide layer discharges. The elements from the substrate and electrolyte take part in the formation of the coating. The MAO coating significantly improves the corrosion resistance of AZ31 magnesium alloy and enhances the apatite formation ability.

Tang, Hui; Li, Deyu; Chen, Xiuping; Wu, Chao; Wang, Fuping

2013-08-01

168

The twin-roll casting of magnesium alloys  

NASA Astrophysics Data System (ADS)

Recently, technologies for twin-roll casting have been widely developed to efficiently fabricate the lightweight Mg alloy sheets that are quite attractive for numerous weight-sensitive applications. This paper reviews the recent progress in the twin-roll casting of Mg alloys, focusing on the processing aspects that have close relations to the solidification behavior of Mg alloy strips. In addition, recent attempts to develop new Mg alloys utilizing the metallurgical advantages attainable by this novel casting process are also presented.

Park, S. S.; Park, W.-J.; Kim, C. H.; You, B. S.; Kim, Nack J.

2009-08-01

169

Stamping of Thin-Walled Structural Components with Magnesium Alloy AZ31 Sheets  

Microsoft Academic Search

In the present study, the stamping process for manufacturing cell phone cases with magnesium alloy AZ31 sheets was studied using both the experimental approach and the finite element analysis. In order to determine the proper forming temperature and set up a fracture criterion, tensile tests and forming limit tests were first conducted to obtain the mechanical behaviors of AZ31 sheets

Fuh-Kuo Chen; Chih-Kun Chang

2005-01-01

170

Applications of Computer Simulation Methods in Plastic Forming Technologies for Magnesium Alloys  

SciTech Connect

Applications of computer simulation methods in plastic forming of magnesium alloy parts are discussed. As magnesium alloys possess very poor plastic formability at room temperature, various methods have been tried to improve the formability, for example, suitable rolling process and annealing procedures should be found to produce qualified magnesium alloy sheets, which have the reduced anisotropy and improved formability. The blank can be heated to a warm temperature or a hot temperature; a suitable temperature field is designed, tools should be heated or the punch should be cooled; suitable deformation speed should be found to ensure suitable strain rate range. Damage theory considering non-isothermal forming is established. Various modeling methods have been tried to consider above situations. The following situations for modeling the forming process of magnesium alloy sheets and tubes are dealt with: (1) modeling for predicting wrinkling and anisotropy of sheet warm forming; (2) damage theory used for predicting ruptures in sheet warm forming; (3) modeling for optimizing of blank shape and dimensions for sheet warm forming; (4) modeling in non-steady-state creep in hot metal gas forming of AZ31 tubes.

Zhang, S. H.; Zheng, W. T.; Shang, Y. L. [Institute of Metal Research, Chinese Academy of Sciences, Wenhua Road 72, Shenyang, 110016 (China); Wu, X. [Wayne State University, Detroit, MI 48202 (United States); Palumbo, G.; Tricarico, L. [Polytechnic of Bari, Bari, 70126 (Italy)

2007-05-17

171

PITTING CORROSION ON MAGNESIUM ALLOYS : A COMPARATIVE STUDY OF FIELD DATA USING EXTREME VALUE  

E-print Network

corrosion properties is to a large extent still in its cradle. Galvanic corrosion is a major obstacle, in particular for galvanic corrosion, are influenced by surface factors which may be of the same orderPITTING CORROSION ON MAGNESIUM ALLOYS : A COMPARATIVE STUDY OF FIELD DATA USING EXTREME VALUE

Maume-Deschamps, Véronique

172

Plastic anisotropy and the role of non-basal slip in magnesium alloy AZ31B  

Microsoft Academic Search

Mechanistic explanations for the plastic behavior of a wrought magnesium alloy are developed using a combination of experimental and simulation techniques. Parameters affecting the practical sheet formability, such as strain hardening rate, strain rate sensitivity, the degree of anisotropy, and the stresses and strains at fracture, are examined systematically by conducting tensile tests of variously oriented samples at a range

Sean R. Agnew; zgr Duygulu

2005-01-01

173

Tangential bending and stretching of thin magnesium alloy sheets in warm conditions  

Microsoft Academic Search

The present work aims at studying the tangential bending process (wiping) and the combined effect of a bending and stretching stress on thin (0.7mm) magnesium alloy (AZ31) sheets when working in warm conditions. The test equipment was designed in order to heat the sheet only in the bending region and to stretch the sheet after the wiping process; it was

G. Palumbo; D. Sorgente; L. Tricarico

2009-01-01

174

Failure prediction of magnesium alloy sheets deforming at warm temperatures using the Zener-Holloman parameter  

Microsoft Academic Search

In the present study, a new method of predicting fracture in magnesium alloy sheet deforming under warm-working conditions has been developed. The effects of temperature and strain rate have been incorporated into the ductile fracture criteria by formulating the damage growth resistance as a function of strain rate and temperature based on the finding of correlation between the fracture strain

Heung-Kyu Kim; Woo-Jin Kim

2010-01-01

175

Study on High Strain Rate Compression Superplasticity of As-Extruded AZ31 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The grain size of as-extruded AZ31 magnesium alloy was refined by isothermal annealing pretreatment through orthogonal experiment. By using the Gleeble-3800 thermal simulator, the compression superplasticity of as-extruded AZ31 magnesium alloy was studied. The high strain rate superplastic compression was realized. The process parameters of the superplastic compression were established and the mechanism of the superplastic deformation was analyzed. The effects of deformation temperature and strain rate on the superplastic flow were investigated. The results indicated that at 250C-300C and strain rate at 110-2s-1, the true strain values were all more than 2.03. As the temperature was 300C and the strain rate was 110-2s-1-110 s-1, the true strain values were all more than 2.18. The results showed that the as-extruded AZ31 magnesium alloy being refined presented good compression superplasticity. The main mechanism for the superplastic compressive deformation of the as-extruded AZ31 magnesium alloy was grain-boundary sliding, meanwhile, dynamic recrystallization also played a harmonious role during the superplastic deformation.

Lin, Fei; Li, Jie; Zhao, Hongwei; Sun, Lulu; Chen, Zhitong; Meng, Qingsen

2013-07-01

176

Effect of deep cryogenic treatment on microstructure, creep and wear behaviors of AZ91 magnesium alloy  

Microsoft Academic Search

This paper focuses on the effect of deep cryogenic treatment (?196C) on microstructure and mechanical properties of AZ91 magnesium alloy. The execution of deep cryogenic treatment on samples changed the distribution of ? precipitates. The tiny laminar ? particles almost dissolved in the microstructure and the coarse divorced eutectic ? phase penetrated into the matrix. This microstructural modification resulted in

Kaveh Meshinchi Asl; Alireza Tari; Farzad Khomamizadeh

2009-01-01

177

Anisotropy and Asymmetry of Yield in Magnesium Alloys at Room Temperature  

NASA Astrophysics Data System (ADS)

Mechanical anisotropy and asymmetry are often pronounced in wrought magnesium alloys and are detrimental to formability and service performance. Single crystals of magnesium are highly anisotropic due to the large difference in critical resolved shear stress between the softest and hardest deformation modes. Polycrystalline magnesium alloys exhibit lower anisotropy, influenced by texture, solute level, and precipitates. In this work, a fundamental study of the effects of alloying, precipitate formation, and texture on the change in anisotropy and asymmetry from the pure magnesium single crystal case to polycrystalline alloys has been performed. It is demonstrated that much of the reduction in anisotropy and asymmetry arises from overall strengthening as solute, precipitates, and grain boundary effects are accounted for. Precipitates are predicted to be more effective than solute in reducing anisotropy and asymmetry, but shape and habit are critical since precipitates produce highly anisotropic strengthening. A small deviation from an ideal basal texture (15 deg spread) has a very strong effect in reducing anisotropy and asymmetry, similar in magnitude to the maximum effect produced by precipitation. Elasto-plastic modeling suggests that this is due to a contribution from basal slip to initial plastic deformation, even when global yield is not controlled by this mode.

Robson, Joseph

2014-10-01

178

Modeling of microstructure evolution of magnesium alloy during the high pressure die casting process  

NASA Astrophysics Data System (ADS)

Two important microstructure characteristics of high pressure die cast magnesium alloy are the externally solidified crystals (ESCs) and the fully divorced eutectic which form at the filling stage of the shot sleeve and at the last stage of solidification in the die cavity, respectively. Both of them have a significant influence on the mechanical properties and performance of magnesium alloy die castings. In the present paper, a numerical model based on the cellular automaton (CA) method was developed to simulate the microstructure evolution of magnesium alloy during cold-chamber high pressure die casting (HPDC) process. Modeling of dendritic growth of magnesium alloy with six-fold symmetry was achieved by defining a special neighbourhood configuration and calculating of the growth kinetics from complete solution of the transport equations. Special attention was paid to establish a nucleation model considering both of the nucleation of externally solidified crystals in the shot sleeve and the massive nucleation in the die cavity. Meanwhile, simulation of the formation of fully divorced eutectic was also taken into account in the present CA model. Validation was performed and the capability of the present model was addressed by comparing the simulated results with those obtained by experiments.

Wu, Mengwu; Xiong, Shoumei

2012-07-01

179

Hot cracking in tungsten inert gas welding of magnesium alloy AZ91D  

E-print Network

strength. Considerable researches have been carried out to study optimisation of die casting parameters,391D.13­16 Previous researches have identified porosity as a major problem in welding of AZ91D die castings.10,11 Hot cracking is also known as one of the problems in joining magnesium alloys,12

Zhou, Wei

180

Superplastic behaviour of friction stir processed AZ91 magnesium alloy produced by high pressure die cast  

Microsoft Academic Search

The room temperature and hot tensile properties of AZ91 magnesium alloy produced by high pressure die cast after friction stir processing (FSP) were studied in the present paper. Such process is a modification of classical friction stir welding one in which the sheets are not joined but the stirring action of the tool, on the bulk material, is used to

P. Cavaliere; P. P. De Marco

2007-01-01

181

Use of Taguchi method to develop a robust design for the magnesium alloy die casting process  

Microsoft Academic Search

This study applies the Taguchi method to optimize the process parameters for the die casting of thin-walled magnesium alloy parts in computer, communications, and consumer electronics (3C) industries. The objectives of the Taguchi method for robust parameter design are to establish the optimal combination of design parameters and to reduce the variation in quality from a minimum number of experiments.

Der Ho Wu; Mao Sheng Chang

2004-01-01

182

Microstructures and mechanical properties of resistance spot welded magnesium alloy joints  

Microsoft Academic Search

The resistance spot welded magnesium alloy joints consist mainly of weld nugget and heat-affected zone (HAZ). The nugget contains two different structures, the cellular-dendritic structure at the edge of the nugget and the equiaxed dendritic structure in the center of the nugget. The structure transition is attributed to the changes of solidification conditions. In HAZ, the grain boundary melting occurred

D. Q. Sun; B. Lang; D. X. Sun; J. B. Li

2007-01-01

183

Study of the decomposition of the magnesium-based solid solutions in Mg-Sm-Tb alloys  

NASA Astrophysics Data System (ADS)

Kinetics and structural transformations upon the decomposition of a magnesium-based supersaturated solid solution in Mg-Sm-Tb alloys have been studied at various relations between the concentrations of terbium and samarium. It has been established that with increasing terbium content in the alloys the strengthening upon the decomposition of the supersaturated magnesium-based solid solution increases. The decomposition of the supersaturated magnesium-based solid solution in the Mg-Sm-Tb alloys with a percentage ratio (wt %) Tb: Sm of about 2.5 exhibits signs characteristic of the decomposition of the supersaturated solid solution in binary Mg-Tb alloys. With allowance for the equilibrium Mg-Sm-Tb phase diagram, this gives grounds to suppose that samarium is mainly dissolved in the products of the decomposition of the magnesium solid solution that are characteristic of Mg-Tb alloys.

Luk'yanova, E. A.; Rokhlin, L. L.; Dobatkina, T. V.; Tabachkova, N. Yu.

2013-07-01

184

Beating the Miscibility Barrier between Iron Group Elements and Magnesium by High-Pressure Alloying  

SciTech Connect

Iron and magnesium are almost immiscible at ambient pressure. The low solubility of Mg in Fe is due to a very large size mismatch between the alloy components. However, the compressibility of Mg is much higher than that of Fe, and therefore the difference in atomic sizes between elements decreases dramatically with pressure. Based on the predictions of ab initio calculations, we demonstrate in a series of experiments in a multianvil apparatus and in electrically and laser-heated diamond anvil cells that high pressure promotes solubility of magnesium in iron. At the megabar pressure range, more than 10 at. % of Mg can dissolve in Fe and then the alloy can be quenched to ambient conditions. A generality of the concept of high-pressure alloying between immiscible elements is demonstrated by its application to two other Fe group elements, Co and Ni.

Dubrovinskaia, N. [Bayerisches Geoinstitut, Universitaet Bayreuth, D-95440 Bayreuth (Germany); Lehrstuhl fuer Kristallographie, Physikalisches Institut, Universitaet Bayreuth, 95440 Bayreuth (Germany); Dubrovinsky, L.; Kantor, I. [Bayerisches Geoinstitut, Universitaet Bayreuth, D-95440 Bayreuth (Germany); Crichton, W. A. [European Synchrotron Radiation Facility, Grenoble 38043 (France); Dmitriev, V. [Swiss-Norwegian Beam Lines at ESRF, F-38043 Grenoble (France); Prakapenka, V.; Shen, G. [Consortium for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637 (United States); Vitos, L.; Johansson, B. [Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Brinellvaegen 23, SE-100 44 Stockholm (Sweden); Condensed Matter Theory Group, Department of Physics, Uppsala University, S-751 21 Uppsala (Sweden); Ahuja, R. [Condensed Matter Theory Group, Department of Physics, Uppsala University, S-751 21 Uppsala (Sweden); Abrikosov, I. A. [Department of Physics and Measurement Technology, Linkoepings University (Sweden)

2005-12-09

185

Magnesium and its alloys as orthopedic biomaterials: A review  

Microsoft Academic Search

As a lightweight metal with mechanical properties similar to natural bone, a natural ionic presence with significant functional roles in biological systems, and in vivo degradation via corrosion in the electrolytic environment of the body, magnesium-based implants have the potential to serve as biocompatible, osteoconductive, degradable implants for load-bearing applications. This review explores the properties, biological performance, challenges and future

Mark P. Staiger; Alexis M. Pietak; Jerawala Huadmai; George Dias

2006-01-01

186

In vivo testing of a bioabsorbable magnesium alloy serving as total ossicular replacement prostheses.  

PubMed

Magnesium alloys have been investigated in different fields of medicine and represent a promising biomaterial for implants due to characteristics like bioabsorbability and osteoinduction. The objective of this study was to evaluate the usability of magnesium as implant material in middle ear surgery. Magnesium implants were placed into the right middle ear of eighteen New Zealand White rabbits. Nine animals were euthanized after four weeks and nine animals after three month. The petrous bones were removed and embedded in epoxy resin. The specimens were then polished, stained and evaluated with the aid of a light microscope. The histological examination revealed a good biocompatibility. After four weeks, a beginning corrosion of the implant's surface and low amount of trabecular bone formation in the area of the stapes base plate was observed. A considerable degradation of implants and obvious bone formation was found three month after implantation. The magnesium alloy used in the present study partly corroded too fast, so that a complete bone reconstruction could not be established in time. The increased osteoinduction on the stapes base plate resulted in a tight bone-implant bonding. Thus, a promising application of magnesium could be a coating of biomaterials in order to improve the bony integration of implants. PMID:23292719

Lensing, Rebecca; Behrens, Peter; Mller, Peter Paul; Lenarz, Thomas; Stieve, Martin

2014-01-01

187

New insights into the fundamental chemical nature of ionic liquid film formation on magnesium alloy surfaces.  

PubMed

Ionic liquids (ILs) based on trihexyltetradecylphosphonium coupled with either diphenylphosphate or bis(trifluoromethanesulfonyl)amide have been shown to react with magnesium alloy surfaces, leading to the formation a surface film that can improve the corrosion resistance of the alloy. The morphology and microstructure of the magnesium surface seems critical in determining the nature of the interphase, with grain boundary phases and intermetallics within the grain, rich in zirconium and zinc, showing almost no interaction with the IL and thereby resulting in a heterogeneous surface film. This has been explained, on the basis of solid-state NMR evidence, as being due to the extremely low reactivity of the native oxide films on the intermetallics (ZrO2 and ZnO) with the IL as compared with the magnesium-rich matrix where a magnesium hydroxide and/or carbonate inorganic surface is likely. Solid-state NMR characterization of the ZE41 alloy surface treated with the IL based on (Tf)2N(-) indicates that this anion reacts to form a metal fluoride rich surface in addition to an organic component. The diphenylphosphate anion also seems to undergo an additional chemical process on the metal surface, indicating that film formation on the metal is not a simple chemical interaction between the components of the IL and the substrate but may involve electrochemical processes. PMID:20355890

Forsyth, Maria; Neil, Wayne C; Howlett, Patrick C; Macfarlane, Douglas R; Hinton, Bruce R W; Rocher, Nathalie; Kemp, Thomas F; Smith, Mark E

2009-05-01

188

Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature  

NASA Astrophysics Data System (ADS)

Using lightweight materials is the emerging need in order to reduce the vehicle's energy consumption and pollutant emissions. Being a lightweight material, magnesium alloys are increasingly employed in the fabrication of automotive and electronic parts. Presently, magnesium alloys used in automotive and electronic parts are mainly processed by die casting. The die casting technology allows the manufacturing of parts with complex geometry. However, the mechanical properties of these parts often do not meet the requirements concerning the mechanical properties (e.g. endurance strength and ductility). A promising alternative can be forming process. The parts manufactured by forming could have fine-grained structure without porosity and improved mechanical properties such as endurance strength and ductility. Because magnesium alloy has low formability resulted form its small slip system at room temperature it is usually formed at elevated temperature. Due to a rapid increase of usage of magnesium sheets in automotive and electronic industry it is necessary to assure database for sheet metal formability and plastic yielding properties in order to optimize its usage. Especially, plastic yielding criterion is a critical property to predict plastic deformation of sheet metal parts in optimizing process using CAE simulation. Von-Mises yield criterion generally well predicts plastic deformation of steel sheets and Hill'1979 yield criterion predicts plastic deformation of aluminum sheets. In this study, using biaxial tensile test machine yield loci of AZ31 magnesium alloy sheet were obtained at elevated temperature. The yield loci ensured experimentally were compared with the theoretical predictions based on the Von-Mises, Hill, Logan-Hosford, and Barlat model.

Park, Jingee; Lee, Jongshin; You, Bongsun; Choi, Seogou; Kim, Youngsuk

2007-05-01

189

Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature  

SciTech Connect

Using lightweight materials is the emerging need in order to reduce the vehicle's energy consumption and pollutant emissions. Being a lightweight material, magnesium alloys are increasingly employed in the fabrication of automotive and electronic parts. Presently, magnesium alloys used in automotive and electronic parts are mainly processed by die casting. The die casting technology allows the manufacturing of parts with complex geometry. However, the mechanical properties of these parts often do not meet the requirements concerning the mechanical properties (e.g. endurance strength and ductility). A promising alternative can be forming process. The parts manufactured by forming could have fine-grained structure without porosity and improved mechanical properties such as endurance strength and ductility. Because magnesium alloy has low formability resulted form its small slip system at room temperature it is usually formed at elevated temperature. Due to a rapid increase of usage of magnesium sheets in automotive and electronic industry it is necessary to assure database for sheet metal formability and plastic yielding properties in order to optimize its usage. Especially, plastic yielding criterion is a critical property to predict plastic deformation of sheet metal parts in optimizing process using CAE simulation. Von-Mises yield criterion generally well predicts plastic deformation of steel sheets and Hill'1979 yield criterion predicts plastic deformation of aluminum sheets. In this study, using biaxial tensile test machine yield loci of AZ31 magnesium alloy sheet were obtained at elevated temperature. The yield loci ensured experimentally were compared with the theoretical predictions based on the Von-Mises, Hill, Logan-Hosford, and Barlat model.

Park, Jingee; Lee, Jongshin [Graduate School, Kyungpook National University, Deagu 702-701 (Korea, Republic of); You, Bongsun [Department of Materials Technology, Korea Institute of Machinery and Materials, Changwon 641-831 (Korea, Republic of); Choi, Seogou [Digital Production Processing and Forming Team, Korea Institute of Industrial Technology, Incheon 406-800 (Korea, Republic of); Kim, Youngsuk [Department of Mechanical Engineering, Kyoungpook National University, Deagu 702-701 (Korea, Republic of)

2007-05-17

190

Corrosion Behavior of Magnesium Alloy AP65 in 3.5% Sodium Chloride Solution  

NASA Astrophysics Data System (ADS)

Magnesium alloy AP65 was prepared by melting and casting. The corrosion behavior of the as-cast and solid solution (T4)-treated AP65 alloys in 3.5% sodium chloride solution was investigated by corrosion morphology observation, immersion test, and electrochemical measurements. The results show that the second phase Mg17Al12 surrounded by a lead-enriched area distributes discontinuously along the grain boundaries in the as-cast AP65 alloy. The lead-enriched areas with high activity are susceptible to be attacked during immersion test and can act as places for preferential anodic dissolution. The corrosion resistance of the as-cast AP65 alloy can be improved after T4 treatment and the T4-treated alloy suffers general corrosion.

Wang, Nai-guang; Wang, Ri-chu; Peng, Chao-qun; Feng, Yan

2012-07-01

191

Finite Element Simulation Of Magnesium AZ31 Alloy Sheet In Warm Hydroforming  

SciTech Connect

Hydroforming of magnesium (Mg) alloy sheet metal offers the possibility to form geometrically complex sheet metal parts that are applicable within automotive and electronic industry etc. However, due to the limited formability of Mg alloy at ambient temperature hydroforming of Mg alloy sheet metal has to be conducted at elevated temperature. In the present study an experimental warm hydroforming process using a low melting point alloy as forming medium is presented and on the basis of this a 2D thermo-mechanical finite element model is setup in order to analyze the temperature distribution in the Mg alloy workpiece during forming. The results show that the temperature in the workpiece is nearly uniform and nearly identical to the temperature of the forming medium.

Steffensen, Mikkel; Danckert, Joachim [Department of Production, Aalborg University, Fibigerstraede 16, 9220 Aalborg (Denmark)

2007-05-17

192

An investigation of the effect of a magnetic field on the phosphate conversion coating formed on magnesium alloy  

NASA Astrophysics Data System (ADS)

In this paper, the influence of the magnetic field on the phosphate conversion coating formed on magnesium alloy has been studied by scanning ion selective electrode technique (SIET), X-rays phase-contrast radiography, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show that the superposition of a magnetic field during the phosphate conversion coating process can promote the generation of small hydrogen gas bubbles and accelerate their desorption. In addition, irrespective of the microstructure of the AZ91D magnesium alloy, it was found that the Mg2+ cations were distributed comparatively uniformly. A uniform smooth phosphate conversion coating could be obtained by immersion in the treatment solution when a magnetic field was applied perpendicular to the magnesium alloy. It may be expected to use magnetic field to control the formation of phosphate conversion coating on magnesium alloy.

Zhao, Ming; Li, Jianguo; He, Guangping; Xie, Honglan; Fu, Yanan

2013-10-01

193

A Feasiblity Study on Spot Friction Welding of Magnesium Alloy AZ31  

SciTech Connect

Spot friction welding (SFW) is a novel variant of the linear friction stir welding process with the potential to create strong joints between similar, as well as dissimilar sheet metals. It is particularly suitable for soft, low melting point metals such as aluminum, magnesium, and their alloys where resistance spot welding can cause defects such as voids, trapped gas and micro-cracks due to the intense heat requirement for joint formation. Up to now, spot friction welding has focused primarily on aluminum alloys. This paper presents a feasibility study on spot friction welding of AZ31, a wrought magnesium alloy available in sheet form. Lap joints of 1.58-mm-thick magnesium alloy AZ31B-O sheet were produced by spot friction welding. The spot welds were made in 2 sec with 15-mm-diameter pin tool rotating at 500-2,000 rpm. The tool was inserted into 2-sheet stack-ups to depths of either 2.4 or 2.8 mm relative to the top sheet surface. Tensile-shear testing showed that joint strengths up to 4.75 kN were obtained. The removal of surface oxides from the sheets prior to welding increased lap shear strengths about 50% at the 2.4-mm insertion depth and it promoted failure by nugget pull-out rather than by interface separation.

Santella, Michael L [ORNL; Pan, Dr. Tsung-Yu [Ford Motor Company; Frederick, David Alan [ORNL; Schwartz, William [ORNL

2007-01-01

194

Microstructure Refinement After the Addition of Titanium Particles in AZ31 Magnesium Alloy Resistance Spot Welds  

NASA Astrophysics Data System (ADS)

Microstructural evolution of AZ31 magnesium alloy welds without and with the addition of titanium powders during resistance spot welding was studied using optical microscopy, scanning electron microscopy, and transmission electron microscopy (TEM). The fusion zone of AZ31 magnesium alloy welds could be divided into columnar dendritic zone (CDZ) and equiaxed dendritic zone (EDZ). The well-developed CDZ in the vicinity of the fusion boundary was clearly restricted and the coarse EDZ in the central region was efficiently refined by adding titanium powders into the molten pool, compared with the as-received alloy welds. A microstructural analysis showed that these titanium particles of approximately 8 m diameter acted as inoculants and promoted the nucleation of ?-Mg grains and the formation of equiaxed dendritic grains during resistance spot welding. Tensile-shear testing was applied to evaluate the effect of titanium addition on the mechanical properties of welds. It was found that both strength and ductility of magnesium alloy welds were increased after the titanium addition. A TEM examination showed the existence of an orientation matching relationship between the added Ti particles and Mg matrix, i.e., [ {0 1bar{1}0} ]_{{Mg}} // [ { 1bar{2} 1bar{3}} ]_{{Ti}} {{and}} ( {000 2} )_{{Mg}} // ( 10bar{1}0)_{{Ti}} in some grains of Ti polycrystal particles. This local crystallographic matching could promote heterogeneous nucleation of the Mg matrix during welding. The diameter of the added Ti inoculant should be larger than 1.8 m to make it a potent inoculant.

Xiao, L.; Liu, L.; Esmaeili, S.; Zhou, Y.

2012-02-01

195

Application of an integrated RE\\/RP\\/CAD\\/CAE\\/CAM system for magnesium alloy shell of mobile phone  

Microsoft Academic Search

Magnesium alloys are becoming more and more popular because of their high specific strength, light specific weight, recyclability, and ability to shield electromagnetic shocks. This paper introduces an integrated RE\\/RP\\/CAD\\/CAE\\/CAM system for constructing a magnesium-alloy AZ31 shell for the mobile phone and developing related progressive dies using concurrent engineering (CE). This integrated system uses an optical scanning system (ATOS), a

Bor-Tsuen Lin; Chun-Chih Kuo

2009-01-01

196

Hot deformation behavior of ZE41A magnesium alloy  

Microsoft Academic Search

The deformation and failure behavior of ZE41A alloy in cast and heat treated conditions were investigated using tensile test at various temperatures, from 25 to 200C and at a strain rate range of 0.0050.05S?1. The stress and strain corresponding to the fracture were estimated. An analytical flow stress model is proposed in this study for the deformation behavior of alloy

M. Sivapragash; P. R. Lakshminarayanan; R. Karthikeyan; M. Hanumantha; R. R. Bhatt

2008-01-01

197

About some corrosion mechanisms of AZ91D magnesium alloy  

Microsoft Academic Search

The present work is dedicated to a study of the corrosion resistance of AZ91D (91% Mg) alloy in wet environments. Three industrial alloys obtained by die-casting or sand casting were subjected to salt spray corrosion tests (ASTM-B117 standard) and immersion tests. Weight loss kinetic curves were measured. Surface analysis was performed by X-ray photoelectron diffraction (XPS). After corrosion the sand

Gaia Ballerini; Ugo Bardi; Roberto Bignucolo; Giuseppe Ceraolo

2005-01-01

198

Effect of galvanic corrosion between precipitate and matrix on corrosion behavior of Ascast magnesium-aluminum alloys  

Microsoft Academic Search

In the present study, the corrosion behavior of an as-cast magnesium alloy was studies focusing on the galvanic corrosion\\u000a between a precipitate and Mg-rich matrix. Through immersion and electrochemical tests, the variation of the corrosion behavior\\u000a with the alloy composition and alloy system was discussed in detail. The corrosion rate of an as-cast alloy increased abruptly\\u000a to 9 wt.% Al

Choong Do Lee; Choon Sik Kang; Kwang Seon Shin

2000-01-01

199

Plastic deformation and surface damage mechanisms during hot-forming of aluminum and magnesium alloy sheets  

NASA Astrophysics Data System (ADS)

Material transfer and adhesion to die surface are major tribological issues encountered during hot-forming of aluminum and magnesium alloys, reducing process efficiency. This study aimed at understanding the tribological contact interface generated between material and die surface under dynamic conditions created by simultaneous effect of temperature and strain rate. Micromechanisms of plastic deformation occurring under simulated hot-forming conditions were identified and related to the coefficient of friction (COF). Sliding contact experiments were done using specially designed tribometer (operating temperature: 25 to 545C, strain rate: 10-3 to 10-1s-1). COF of AA5083(Al-4.5%Mg-0.7%Mn) and AZ31(Mg-3%Al-0.7%Zn) alloys were measured during their plastic deformation by the simultaneous effect of temperature and strain rate. The as received and plastically deformed surfaces were characterized using optical interferometry, SEM, FIB and TEM. Additionally, the force required to break the asperity junction formed at the first contact, or junction strength, was measured for both materials at different temperatures. Deformation mechanisms identified for AA5083 in the temperature range of 420 to 545C and strain rate range of 5x10-3 to 4x10-2 s-1 included diffusional flow, grain boundary sliding (GBS) and solute drag (SD) creep. Friction maps outlining general relationships between tribological behaviour and micromechanisms controlling deformation under a set of temperature, strain and strain rate were developed. GBS induced high surface roughness, resulting in high COF. Low average roughness and retention of strength reduced COF in SD region. Dynamic recrystallization was an additional factor controlling material transfer in magnesium AZ31 alloy. Changes in oxide layer morphology were established based on the microstructural characterization of sample's surface and subsurface. In AA5083 alloy, crack formation at temperatures <450C or oxide ligament formation at temperature >500C were found in the magnesium rich surface oxide. Magnesium rich surface oxide reduced COF, and low COF was found in the material having high magnesium. AZ31 alloy always showed lower COF compared to AA5083. This was confirmed by junction strength experiment where adhesion strength was found to be low in high magnesium content material. Therefore, this investigation on the plastic deformation and surface damage mechanism, and their relation with the tribological behaviour provided better understanding of the hot-forming process.

Das, Sarmistha

200

Cold Spray Al-5% Mg Coatings for the Corrosion Protection of Magnesium Alloys  

NASA Astrophysics Data System (ADS)

Poor corrosion resistance is a significant limitation of magnesium alloys as structural materials. To address this problem, the objective of this study was to apply to a magnesium alloy a corrosion-resistant barrier coating that has galvanic compatibility with magnesium and a hardness value no less than that of magnesium. Aluminum coatings were applied to ZE41A-T5 Mg by the cold spray process. A custom-made high-purity Al-5 wt.% Mg powder was produced by spray metal forming for the coating evaluation. In addition, coatings of commercially pure Al (99.5 wt.%), high-purity Al (99.95 wt.%), AA5356, and AA4047 were used for comparison. Coating evaluation included mechanical testing (hardness and adhesion strength) and corrosion testing (salt spray, galvanic coupling, and crevice corrosion). The Al-5% Mg powder resulted in the best overall performance, including a high hardness, 125 Hv100, and an adhesion strength, over 60 MPa, when treated for over 1000 h in a salt spray chamber and with a low galvanic current.

Deforce, Brian S.; Eden, Timothy J.; Potter, John K.

2011-12-01

201

Research on super-hydrophobic surface of biodegradable magnesium alloys used for vascular stents.  

PubMed

Micro-nanometer scale structure of nubby clusters overlay was constructed on the surface of an AZ31 magnesium alloy by a wet chemical method. The super-hydrophobicity was achieved with a water contact angle of 142 and a sliding angle of about 5. The microstructure and composition of the super-hydrophobic surface were characterized by SEM and FTIR. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion behavior, and the hemocompatibility of the super-hydrophobic surface was investigated by means of hemolytic and platelet adhesion tests. Results showed that the super-hydrophobic treatment could improve the corrosion resistance of magnesium alloys in PBS and inhibit blood platelet adhesion on the surface, which implied excellent hemocompatibility with controlled degradation. PMID:23623110

Wan, Peng; Wu, Jingyao; Tan, LiLi; Zhang, Bingchun; Yang, Ke

2013-07-01

202

Fatigue behaviour of friction stir processed AZ91 magnesium alloy produced by high pressure die casting  

SciTech Connect

The room temperature fatigue properties of AZ91 magnesium alloy produced by high pressure die casting (HPDC) as cast, heat treated, friction stir processed (FSP) and FSP and heat treated were studied. The fatigue properties of the material were evaluated for the HPDC magnesium alloy in the as-received state and after a solution treatment at 415 deg. C for 2 h and an ageing treatment at 220 deg. C for 4 h. The heat treatment resulted in a significant increase in the fatigue properties of the HPDC material, while no significance influence of heat treatment was recorded in the FSP condition. The morphology of fracture surfaces was examined by employing a field emission gun scanning electron microscope (FEGSEM)

Cavaliere, P. [INFM-Dept. of 'Ingegneria dell'Innovazione', Engineering Faculty, University of Lecce, Via per Arnesano, 73100, Lecce (Italy)]. E-mail: pasquale.cavaliere@unile.it; De Marco, P.P. [INFM-Dept. of 'Ingegneria dell'Innovazione', Engineering Faculty, University of Lecce, Via per Arnesano, 73100, Lecce (Italy)

2007-03-15

203

Investigation of interfacial interaction between uncoated and coated carbon fibres and the magnesium alloy AZ91.  

PubMed

Unidirectionally reinforced metal-matrix composites with a fibre volume content between 63 and 68% were processed by squeeze casting using T800 H carbon fibres and the magnesium alloy AZ91. The surface of the fibres was prepared by thermal desizing of the fibres or by deposition of a pyrolytic carbon (pyC) coating. Different interfacial conditions could be identified by transmission electron microscopy (TEM) and the single-fibre push-in test. TEM confirmed the formation of needle-like phases at the fibre surface or, for coated fibres, within the pyrolytic carbon coating. During loading by the Vickers type indenter an intense response was observed for composites of coated fibres and the magnesium alloy. This could by caused by stick-slip effects within the pyrolytic carbon coating. PMID:12397483

Dorner-Reisel, A; Nishida, Y; Klemm, V; Nestler, K; Marx, G; Mller, E

2002-10-01

204

Characterization of damage evolution in an AM60 magnesium alloy by computed tomography  

NASA Astrophysics Data System (ADS)

Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratories, California (SNL) are collaborating on the development of new techniques to study damage evolution and growth in material specimens subjected to mechanical loading. These techniques include metallography, radiography, computed tomography (CT) and modeling. The material specimens being studied include cast magnesium and aluminum alloys, and forged stainless steel. We will concentrate on characterizing monotonically loaded magnesium alloy specimens using computed tomography. Several notched tensile specimens were uniaxially loaded to different percentages of the failure load. Specimens were initially characterized by radiography and computed tomography to determine the preloaded state. Subsequent CT scans were performed after the samples were loaded to different percentages of the load failure. The CT volumetric data are being used to measure void size, distribution and orientation in all three dimensions nondestructively to determine the effect of void growth on the mechanical behavior of the materials.

Waters, Amy; Martz, Harry; Dolan, Ken; Horstemeyer, Mark; Rikard, Derrill; Green, Robert

1999-12-01

205

In vitro degradation and cytocompatibility of magnesium-zinc-strontium alloys with human embryonic stem cells.  

PubMed

Magnesium-based alloys have attracted great interest for medical applications due to their unique biodegradable capability and desirable mechanical properties. When considered for medical applications, the degradation rate of these alloys must be tailored so that: (i) it does not exceed the rate at which the degradation products can be excreted from the body, and (ii) it is slow enough so that the load bearing properties of the implant are not jeopardized and do not conflict prior to and during synthesis of new tissue. Implant integration with surrounding cells and tissues and mechanical stability are critical aspects for clinical success. This study investigated Magnesium-Zinc-Strontium (ZSr41) alloy degradation rates and the interaction of the degradation products with human embryonic stem cells (hESC) over a 72 hour period. An in vitro hESC model was chosen due to the higher sensitivity of ESCs to known toxicants which allows to potentially detect toxicological effects of new biomaterials at an early stage. Four distinct ZSr41 compositions (0.15 wt.%, 0.5 wt.%, 1 wt.%, and 1.5 wt.% Sr) were designed and produced through metallurgical processing. ZSr41 alloy mechanical properties, degradation, and cytocompatibility were investigated and compared to pure polished Magnesium (Mg). Mechanical properties evaluated included hardness, ultimate tensile strength, and elongation to failure. Degradation was characterized by measuring total weight loss of samples and pH change in the cell culture media. Cytocompatibility was studied by comparing fluorescence and phase contrast images of hESCs after co-culture with Mg alloys. Results indicated that the Mg-Zn-Sr alloy with 0.15 wt.% Sr improved cytocompatibility and provided slower degradation as compared with pure Mg. PMID:23366416

Cipriano, Aaron F; Guan, Ren-Guo; Cui, Tong; Zhao, Zhan-Yong; Garcia, Salvador; Johnson, Ian; Liu, Huinan

2012-01-01

206

Thermal analytical investigations of the magnesium alloys AM 60 and AZ 91 including the melting range  

Microsoft Academic Search

The following thermophysical properties were determined for the magnesium alloys AZ 91 and AM 60: The density in the temperature range 30500C, the specific heat capacity including the melting range, the melting point temperature, and the melting enthalpy. The following devices were used: NETZSCH DSC 404C Pegasus, NETZSCH DIL 402C as well as SETARAM TGDTA92 for thermogravimetric investigations within the

A. Lindemann; J. Schmidt; M. Todte; T. Zeuner

2002-01-01

207

Anomalous Strain Rate Sensitivity of Twinning in a Magnesium Alloy at High Temperature  

NASA Astrophysics Data System (ADS)

Anomalous strain rate sensitivity of twinning was observed in a Mg-Al-Mn magnesium alloy during extrusion around 723 K (450 C). The density of twins decreases as the ram speed increases. At 10 mm min-1, relatively high density twins are activated, but much fewer twins were observed at 30 mm min-1; at 50 mm min-1, twins were hardly seen. The negative strain rate sensitivity was ascribed to the interaction of twinning with defects.

Ma, Quancang; Li, Bin; Mcclelland, Zackery; Horstemeyer, Stephen J.

2013-10-01

208

A constitutive law for the thermo-mechanical modelling of magnesium alloy extrusion  

Microsoft Academic Search

Metal extrusion as one of the production processes for semi-finished products plays an important role for the optimisation\\u000a of wrought magnesium alloys. A mechanistic approach for the modelling of the coupled deformation and temperature fields is\\u000a presented here. It accounts for the strain rate and temperature dependence of the mechanical properties as well as for the\\u000a evolution of anisotropy and

Serkan Ertrk; Wolfgang Brocks; Jan Bohlen; Dietmar Letzig; Dirk Steglich

209

Laser Beam Welding of AZ31 Magnesium Alloy with Filler Strip  

Microsoft Academic Search

The 2-mm AZ31 magnesium alloy sheets were laser beam welded using filler metal in the shape of strip. Two kinds of the filler strips, i.e., AZ31 and AZ31 +1.5wt% Mn were adopted. The effects of the filler strip on the microstructures and tensile properties of the welded joints were investigated. As compared with the autogenous welding process, the welding process

Qiong Chen; Hongge Yan; Jihua Chen; Peilan Zeng; Zhaohui Yu; Bin Su

2010-01-01

210

Low-temperature plastic deformation of AZ31 magnesium alloy with different microstructures  

Microsoft Academic Search

The plastic deformation of AZ31 magnesium alloy under tension at temperatures of 4.2-295 K is studied as a function of its microstructure following squeeze casting (SC) and after severe plastic deformation (SPD) by hot rolling and equal-channel angular pressing. SPD reduces the average grain size and creates a texture that favors basal-plane dislocation glide. It is found that plastic deformation

Yu. Z. Estrin; P. A. Zabrodin; I. S. Braude; T. V. Grigorova; N. V. Isaev; V. V. Pustovalov; V. S. Fomenko; S. E. Shumilin

2010-01-01

211

Testing of general and localized corrosion of magnesium alloys: A critical review  

Microsoft Academic Search

The degradation of materials generally occurs via corrosion, fatigue, and wear. Once a magnesium (Mg) alloy is chosen for\\u000a a certain application, corrosion testing is generally required as a function of the expected service environment, the type\\u000a of corrosion expected in service, and the type of surface protection, depending on the material and its use in the intended\\u000a surface. In

Edward Ghali; Wolfgang Dietzel; Karl-Ulrich Kainer

2004-01-01

212

Effects of precipitation processes on damping and elastic modulus of WE 43 magnesium alloy  

Microsoft Academic Search

Mechanical spectroscopy, electrical resistivity and X-ray diffraction measurements were performed on commercial WE 43 magnesium alloy with different thermal histories in order to determine the precipitation processes which appears within the temperature range between room temperature and 823K.It has been found out that the precipitation process at temperatures of about 650K promotes two stages of precipitations. The first occurring at

O. A. Lambri; W. Riehemann; L. M. Salvatierra; J. A. Garc??a

2004-01-01

213

Galvanic corrosion properties of differently PVD-treated magnesium die cast alloy AZ91  

Microsoft Academic Search

Different types of PVD coatings and plasma treatments were applied for the surface treatment of magnesium die cast alloy AZ91 specimens. The different types of surface treatment were all developed by the authors and the fundamental properties are described elsewhere. The coating systems were:9 ?m CrN hard coating3 ?m TiN coating0.5 ?m plasma anodisation layer and 3 ?m Al2O3 coatingThe

H. Hoche; C. Blawert; E. Broszeit; C. Berger

2005-01-01

214

Cyclic deformation and fatigue behaviour of the magnesium alloy AZ91  

Microsoft Academic Search

In this report, the cyclic deformation behaviour of the die-casting magnesium alloy AZ91 was investigated at constant total strain amplitudes between 1.410?3 and 210?2 at room temperature and at 130C. The fatigue life data at both temperatures can be described well by the laws of Manson-Coffin and Basquin. The microstructural investigations performed show the strong influence of several microstructural features

G Eisenmeier; B Holzwarth; H. W Hppel; H Mughrabi

2001-01-01

215

Preparation and Characterization of 8YSZ Thermal Barrier Coatings on Rare Earth-Magnesium Alloy  

Microsoft Academic Search

Thermal barrier coatings (TBCs) of zirconia stabilized by 8wt.% yttria (8YSZ) on top of rare earth-magnesium alloy were fabricated\\u000a by atmospheric plasma spraying. Three coatings were prepared by controlling the substrate temperature with different cooling\\u000a media including cold water, compressed air, and natural cooling during deposition. The phase compositions, mechanical properties,\\u000a and thermal shock resistance of these coatings were investigated.

Xizhi Fan; Yangjia Liu; Zhenhua Xu; Ying Wang; Binglin Zou; Lijian Gu; Chunjie Wang; Xiaolong Chen; Zuhair S. Khan; Daowu Yang; Xueqiang Cao

2011-01-01

216

Characterisation of AZ31B magnesium alloy formability in warm forming conditions  

Microsoft Academic Search

Nowadays, magnesium alloys materials are more and more utilised in transportation industry in order to reduce the vehicles\\u000a mass, and thus to minimize air pollution and fuel consumption. Since they present a quite low formability at room temperature,\\u000a promising applications are developing in the area of sheet metal working in warm temperature conditions. The paper presents\\u000a a complete characterisation of

G. Ambrogio; C. Bruni; S. Bruschi; L. Filice; A. Ghiotti; M. Simoncini

2008-01-01

217

Air bending of AZ31 magnesium alloy in warm and hot forming conditions  

Microsoft Academic Search

The effect of the process parameters on springback of AZ31 magnesium alloy was investigated by performing air bending tests under warm and hot forming conditions. To this purpose, air bending experiments were carried out in the temperature range varying from 100 to 400C, with different values of the punch speed (0.45 and 4.5mm\\/s). Also the influence of the punch radius

C. Bruni; A. Forcellese; F. Gabrielli; M. Simoncini

2006-01-01

218

Warm negative incremental forming of magnesium alloy AZ31 Sheet: New lubricating method  

Microsoft Academic Search

The present study has been undertaken in order to investigate the suitable lubricants and lubricating methods, which can be employed to form a magnesium alloy AZ31 sheet by warm negative incremental forming (NIF). For the intended purpose, Nano-K2Ti4O9 whisker and organic binder were employed to improve the bonding strength at lubrication coating\\/sheet interface and lubricating properties at elevated temperatures. The

Qinglai Zhang; Fugui Xiao; Hailing Guo; Changsheng Li; Lin Gao; Xingwu Guo; Weidong Han; A. B. Bondarev

2010-01-01

219

Influence of anisotropy of the magnesium alloy AZ31 sheets on warm negative incremental forming  

Microsoft Academic Search

Single point incremental forming of the magnesium alloy AZ31 sheets, which were fabricated by hot extrusion, slab+hot\\/cold rolling, strip-casting rolling and cross-rolling, respectively, was investigated at elevated temperatures. The results show that the anisotropy of the sheets fabricated by casting slab+hot\\/cold rolling and cross-rolling is not remarkable, and the formability is improved significantly. The circular, square and rotary cone parts

Qinglai Zhang; Hailing Guo; Fugui Xiao; Lin Gao; A. B. Bondarev; Weidong Han

2009-01-01

220

Hot deformation and processing maps of extruded ZE41A magnesium alloy  

Microsoft Academic Search

The hot deformation behavior and microstructure evolution of extruded ZE41A magnesium alloy has been studied using the processing map. The compression tests were conducted in the temperature range of 250450C and the strain rate range of 0.0011.0s?1 to establish the processing map. The dynamic recrystallization (DRX) and instability zones were identified and validated through micrographs. The observations were performed in

S. Anbuselvan; S. Ramanathan

2010-01-01

221

A Microstructure Study on an AZ31 Magnesium Alloy Tube after Hot Metal Gas Forming Process  

Microsoft Academic Search

An AZ31 magnesium alloy tube has been deformed by the hot metal gas forming (HMGF) technique. Microstructures before and after\\u000a deformation have been investigated by using Electron Backscattered Diffraction (EBSD) and Electron Microscopy. Due to the\\u000a inhomogeneous distribution by induction heating, there is a temperature gradient distribution along the tube axis. Accordingly,\\u000a the deformation mechanism is also different. In the

Yi Liu; Xin Wu

2007-01-01

222

Fatigue crack growth behaviour of a die-cast magnesium alloy AZ91D  

Microsoft Academic Search

This paper deals with the room temperature fatigue crack growth behaviour of a die-cast magnesium alloy AZ91D. Short and long fatigue crack growth studies were done using single edge V-notched plate specimens under pulsating tension with a stress ratio of 0.1 and a frequency of 20 Hz at different maximum applied stress levels. Retardationacceleration in growth of short cracks was

P Venkateswaran; S Ganesh Sundara Raman; S. D Pathak; Y Miyashita; Y Mutoh

2004-01-01

223

Microstructure and creep behavior in AE42 magnesium die-casting alloy  

Microsoft Academic Search

The micro structural analysis of die-cast AE42 reveals a correlation between micro structure and creep strength. A lamellar-phase\\u000a Al11RE3, which dominates the interdendritic microstructure of the alloy, partly decomposes above 150C into Al2RE and Al (forming Mg17Al12). The increased solubility of aluminum in magnesium at higher temperatures may also promote the decomposition of Al11RE3. The creep strength decreases sharply with

Bob R. Powell; Vadim Rezhets; Michael P. Balogh; Richard A. Waldo

2002-01-01

224

Effects of magnetic fields on the phosphate conversion coating of AZ91D magnesium alloy  

NASA Astrophysics Data System (ADS)

An external high parallel magnetic fields (MF) was imposed on the barium phosphate process of AZ91D magnesium alloy. The influences of the permanent MF on the morphology, the phase composition and the corrosion resistance of the barium phosphate coatings were studied using scanning electron microscope, X-ray diffraction, salt spay test. The results show that the coatings with MF are more compact, uniform, and smooth, and have better the corrosion resistance than without MF.

Jin, HuaLan; Yang, XiangJie; Peng, WenYi; Guo, HongMin

2010-01-01

225

Improvement in tribological performances of magnesium alloy using amide compounds as lubricating additives during sliding  

Microsoft Academic Search

The tribological characteristics of a magnesium alloy, AZ91D (die-casting), are investigated in a sliding lubricating system using various amide compounds as lubricating additives on a Timken type tester against a bearing steel (AISI52100) ring. Results indicate that a significant improvement in the tribological performance exists using the amide compounds as additives. The number of amido group (CONH2) in additive molecules

W. Huang; B. Hou; M. Liu; Z. Li

2005-01-01

226

Fatigue and Fracture Characterization of HPDC AM6OB Magnesium Alloy at Cold Temperature  

NASA Astrophysics Data System (ADS)

An investigation of the fatigue and fracture characterization of the high pressure die cast (HPDC) AM60B magnesium alloy at -40 C temperature was conducted by means of the constant load amplitude fatigue test. The results demonstrated that low temperature had a significant influence on alloy's fatigue life; the life increased at -40 C temperature as compared to that at room temperature. The fracture surfaces of the tested specimens were observed under a scanning electron microscope (SEM) to further understand the fracture phenomenon at low temperature.

Nur Hossain, Md.; Taheri, Farid

2011-12-01

227

Effect of Al and Gd Solutes on the Strain Rate Sensitivity of Magnesium Alloys  

NASA Astrophysics Data System (ADS)

Pure magnesium and two binary alloys, Mg-1 wt pct Al and Mg-1.4 wt pct Gd, have been prepared with comparable grain sizes and textures. The alloys have been tensile tested at various strain rates and temperatures to examine the strain rate sensitivity (SRS). It has been found that Mg and Mg-Al show increasing SRS with increasing deformation temperatures. The Mg-Gd alloy showed decreasing SRS with increasing deformation temperatures and exhibited a negative SRS at 200 C and 250 C. Above these temperatures, the SRS returned to a positive value. The elongation to fracture was not effected by the SRS, and it has been concluded that for the alloys and conditions examined, the influences of mechanical twinning and dynamic recrystallization dominate the elongation behavior, rather than the SRS.

Stanford, N.; Sabirov, I.; Sha, G.; La Fontaine, A.; Ringer, S. P.; Barnett, M. R.

2010-03-01

228

Yield Asymmetry Design of Magnesium Alloys by Integrated Computational Materials Engineering  

SciTech Connect

Deformation asymmetry of magnesium alloys is an important factor on machine design in automobile industry. Represented by the ratio of compressive yield stress (CYS) against tensile yield stress (TYS), deformation asymmetry is strongly related to microstructure, characterized by texture and grain size. Modified intermediate phi-model, a polycrystalline viscoplasticity model, is used to predict the deformation behavior of magnesium alloys with different grain sizes. Validated with experimental results, integrated computational materials engineering is applied to find out the route in achieving desired asymmetry by thermomechanical processing. In some texture, for example, rolled texture, CYS/TYS is smaller than 1 under different loading directions. In some texture, for example, extruded texture, asymmetry is large along normal direction. Starting from rolled texture, the asymmetry will increased to close to 1 along rolling direction after compressed to a strain of 0.2. Our model shows that grain refinement increases CYS/TYS. Besides texture control, grain refinement can also optimize the yield asymmetry. After the grain size decreased to a critical value, CYS/TYS reaches to 1 since CYS increases much faster than TYS. By tailoring the microstructure using texture control and grain refinement, it is achievable to optimize yield asymmetry in wrought magnesium alloys.

Li, Dongsheng; Joshi, Vineet V.; Lavender, Curt A.; Khaleel, Mohammad A.; Ahzi, Said

2013-11-01

229

Development of a Binary Zn-Based Solder Alloy for Joining Wrought Magnesium Alloy AZ31B  

NASA Astrophysics Data System (ADS)

In the present article, the wrought magnesium alloy AZ31B sheets were soldered by means of high-frequency induction heating device using a novel binary Zn-based solder alloy in argon gas shield condition. The interfacial microstructure, phase constitution, and fracture morphology of the soldered joint were studied. The microhardness and shear strength of the soldered joint were tested. The experimental results exhibit that ?-Mg solid solution and ?-MgZn phase were formed in soldering region. Moreover, the ?-Mg7Zn3 phase in the original Zn-based solder alloy disappeared completely after the soldering process due to the fierce alloying between the molten binary Zn-based solder alloy and the base metal AZ31B during soldering. Test results show that the shear strength of the soldered joint is 28 MPa. The fracture morphology of the soldered joint displays an intergranular fracture mode, and the crack originates from ?-Mg + ?-MgZn eutectoid structure. The interaction between the molten Zn-based solder alloy and the base metal AZ31B leads the Zn-based solder alloy to be transformed into Mg-based soldering metal during soldering.

Ma, Li; Long, Weimin; Qiao, Peixin; He, Dingyong; Li, Xiaoyan

2013-01-01

230

Biocompatibility of fluoride-coated magnesium-calcium alloys with optimized degradation kinetics in a subcutaneous mouse model.  

PubMed

The principle of biodegradation has been considered for many years in the development of cardiovascular stents, especially for patients with congenital heart defects. A variety of materials have been examined with regard to their suitability for cardiovascular devices. Iron- and magnesium-based stents were investigated intensively during the last years. It has been shown, that iron, or iron based alloys have slow degradation kinetics whereas magnesium-based systems exhibit rapid degradation rates. Recently we have developed fluoride coated binary magnesium-calcium alloys with reduced degradation kinetics. These alloys exhibit good biocompatibility and no major adverse effects toward smooth muscle and endothelial cells in in vitro experiments. In this study, these alloys were investigated in a subcutaneous mouse model. Fluoride coated (fc) magnesium, as well as MgCa0.4%, MgCa0.6%, MgCa0.8%, MgCa1.0%, and a commercially available WE43 alloy were implanted in form of (fc) cylindrical plates into the subcutaneous tissue of NMRI mice. After a 3 and 6 months follow-up, the (fc) alloy plates were examined by histomorphometric techniques to assess their degradation rate in vivo. Our data indicate that all (fc) alloys showed a significant corrosion. For both time points the (fc) MgCa alloys showed a higher corrosion rate in comparison to the (fc) WE43 reference alloy. Significant adverse effects were not observed. Fluoride coating of magnesium-based alloys can be a suitable way to reduce degradation rates. However, the (fc) MgCa alloys did not exhibit decreased degradation kinetics in comparison to the (fc) WE43 alloy in a subcutaneous mouse model. PMID:22767427

Drynda, Andreas; Seibt, Juliane; Hassel, Thomas; Bach, Friedrich Wilhelm; Peuster, Matthias

2013-01-01

231

Electron beam-assisted healing of nanopores in magnesium alloys  

PubMed Central

Nanopore-based sensing has emerged as a promising candidate for affordable and powerful DNA sequencing technologies. Herein, we demonstrate that nanopores can be successfully fabricated in Mg alloys via focused electron beam (e-beam) technology. Employing in situ high-resolution transmission electron microscopy techniques, we obtained unambiguous evidence that layer-by-layer growth of atomic planes at the nanopore periphery occurs when the e-beam is spread out, leading to the shrinkage and eventual disappearance of nanopores. The proposed healing process was attributed to the e-beam-induced anisotropic diffusion of Mg atoms in the vicinity of nanopore edges. A plausible diffusion mechanism that describes the observed phenomena is discussed. Our results constitute the first experimental investigation of nanopores in Mg alloys. Direct evidence of the healing process has advanced our fundamental understanding of surface science, which is of great practical importance for many technological applications, including thin film deposition and surface nanopatterning. PMID:23719630

Zheng, He; Liu, Yu; Cao, Fan; Wu, Shujing; Jia, Shuangfeng; Cao, Ajing; Zhao, Dongshan; Wang, Jianbo

2013-01-01

232

Influence of deformation on precipitation in AZ80 magnesium alloy  

NASA Astrophysics Data System (ADS)

Precipitates in the conventionally processed (solution treatment followed by aging) AZ80 alloy are coarse, cellular, and incoherent. They nucleate and grow on the basal planes of the matrix or distribute discontinuously in the alloy. Their unique morphology and undesired distribution make them ineffective for precipitation strengthening. This condition, however, can be modified by applying selected deformation and heat treatment conditions. The effect of deformation and heat treatment on the morphology and distribution of precipitates has been studied. Deformation was introduced by hot extrusion, cold rolling, or equal channel angular pressing (ECAP). The microstructures were characterized using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results showed that cold deformation improved precipitation more significantly than hot deformation, and twinning promoted precipitation more effectively than slip. When ECAP was applied, the Bc-route induced more precipitates than the A-route.

Yang, Ping; Wang, Li-Na; Xie, Qing-Ge; Li, Ji-Zhong; Ding, Hua; Lu, Lin-Lin

2011-06-01

233

Electron beam-assisted healing of nanopores in magnesium alloys  

NASA Astrophysics Data System (ADS)

Nanopore-based sensing has emerged as a promising candidate for affordable and powerful DNA sequencing technologies. Herein, we demonstrate that nanopores can be successfully fabricated in Mg alloys via focused electron beam (e-beam) technology. Employing in situ high-resolution transmission electron microscopy techniques, we obtained unambiguous evidence that layer-by-layer growth of atomic planes at the nanopore periphery occurs when the e-beam is spread out, leading to the shrinkage and eventual disappearance of nanopores. The proposed healing process was attributed to the e-beam-induced anisotropic diffusion of Mg atoms in the vicinity of nanopore edges. A plausible diffusion mechanism that describes the observed phenomena is discussed. Our results constitute the first experimental investigation of nanopores in Mg alloys. Direct evidence of the healing process has advanced our fundamental understanding of surface science, which is of great practical importance for many technological applications, including thin film deposition and surface nanopatterning.

Zheng, He; Liu, Yu; Cao, Fan; Wu, Shujing; Jia, Shuangfeng; Cao, Ajing; Zhao, Dongshan; Wang, Jianbo

2013-05-01

234

Friction Stir Lap Welding of Magnesium Alloy to Steel: A Preliminary Investigation  

NASA Astrophysics Data System (ADS)

An initial study was made to evaluate the feasibility of joining magnesium alloy AZ31 sheet to galvanized steel sheet in a lap configuration using friction stir welding (FSW). Two different automotive sheet steels were used for comparative evaluation of the dissimilar joining potential: a 0.8 mm thick, electrogalvanized (EG) mild steel, and a 1.5 mm thick hot-dipped galvanized (HDG) high-strength, low-alloy (HSLA) steel. These steels were joined to 2.33 mm thick AZ31B magnesium sheet. A single FSW tool design was used for both dissimilar welds, and the process parameters were kept the same. The average peak load for the AZ31-1.5 mm steel weld joint in lap shear mode was found to be 6.3 1.0 kN. For the AZ31-0.8 mm steel weld, joint strength was 5.1 1.5 kN. Microstructural investigation indicates melting of the Zn coating present on the steel sheets, and subsequent alloying with the Mg sheet resulted in the formation of a solidified Zn-Mg alloy layer.

Jana, S.; Hovanski, Y.; Grant, G. J.

2010-12-01

235

Friction Stir Lap Welding of Magnesium Alloy to Steel: A Preliminary Investigation  

SciTech Connect

An initial study was made to evaluate the feasibility of joining Magnesium alloy AZ31 sheet to galvanized steel sheet in lap configuration using friction stir welding (FSW). Two different automotive sheet steels were used for comparative evaluation of the dissimilar joining potential; a 0.8mm thick, electro galvanized (EG) mild steel, and a 1.5mm thick hot dipped galvanized (HDG) high-strength, low-alloy steel (HSLA). These steels were joined to 2.33mm thick AZ31B magnesium sheet. A single FSW tool design was used for both dissimilar welds, and process parameters were kept the same. Average peak load for the AZ31-1.5 mm steel weld joint in lap shear mode was found to be 6.3 1.0 kN. For the AZ31-0.8 mm steel weld, joint strength was 5.1 1.5 kN. Microstructural investigation indicates melting of the Zn coating at the interface and subsequent alloying with the Mg sheet resulting in formation of solidified Zn-Mg alloy layer at AZ31/steel interface.

Jana, Saumyadeep; Hovanski, Yuri; Grant, Glenn J.

2010-12-01

236

Thermodynamic and kinetic destabilization of magnesium hydride using Mg-In solid solution alloys.  

PubMed

Efforts to thermodynamically destabilize magnesium hydride (MgH2), so that it can be used for practical hydrogen storage applications, have been a difficult challenge that has eluded scientists for decades. This letter reports that MgH2 can indeed be destabilized by forming solid solution alloys of magnesium with group III and IVB elements, such as indium. Results of this research showed that the equilibrium hydrogen pressure of a Mg-0.1In alloy is 70% higher than that of pure MgH2. The temperature at 1 bar hydrogen pressure (T1bar) of Mg-0.1In alloy was reduced to 262.9 C from 278.9 C, which is the T1bar of pure MgH2. Furthermore, the kinetic rates of dehydrogenation of Mg-0.1In alloy hydride doped with a titanium intermetallic (TiMn2) catalyst were also significantly improved compared with those of MgH2. PMID:23855837

Zhou, Chengshang; Fang, Zhigang Zak; Lu, Jun; Zhang, Xiaoyi

2013-07-31

237

Electrophoretic deposition of nanostructured hydroxyapatite coating on AZ91 magnesium alloy implants with different surface treatments  

NASA Astrophysics Data System (ADS)

Bio-absorbable magnesium (Mg) based alloys have been introduced as innovative orthopedic implants during recent years. It has been specified that rapid degradation of Mg based alloys in physiological environment should be restrained in order to be utilized in orthopedic trauma fixation and vascular intervention. In this developing field of healthcare materials, micro-arc oxidation (MAO), and MgF2 conversion coating were exploited as surface pre-treatment of AZ91 magnesium alloy to generate a nanostructured hydroxyapatite (n-HAp) coating via electrophoretic deposition (EPD) method. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM) techniques were used to characterize the obtained powder and coatings. The potentiodynamic polarization tests were carried out to evaluate the corrosion behavior of the coated and uncoated specimens, and in vitro bioactivity evaluation were performed in simulated body fluid. Results revealed that the MAO/n-HAp coated AZ91 Mg alloy samples with a rough topography and lower corrosion current density leads to a lower Mg degradation rate accompanied by high bioactivity.

Rojaee, Ramin; Fathi, Mohammadhossein; Raeissi, Keyvan

2013-11-01

238

Modelling of laser cladding of magnesium alloys with pre-placed powders  

NASA Astrophysics Data System (ADS)

As a surface engineering technique, high-power laser cladding, has shown great potential for improving the corrosion resistance of magnesium alloys. Its main advantage over other processes, is its ability to form relatively thick protective coatings on selected areas where improved properties are desired. It is also a 'clean' process. However, previous research studies have found that in laser cladding of magnesium alloys, the problem of a high degree of dilution cannot be easily overcome. Moreover, in-depth studies using analytical or numerical modelling can rarely be found in the literature for addressing laser cladding with pre-placed powders with the aim of predicting the level of dilution. In the first phase of this study, a simplified thermal model based on the finite element method (FEM) was developed to study the phenomenon of dilution in laser cladding of a magnesium alloy. In the model, the powder bed was treated as a continuum, and a high power continuous wave (CW) laser was employed. The results of the simulations of the FEM model together with those of the statistical analyses showed that although, under normal cladding conditions, a process window can be established for achieving good interfacial bonding between the substrate and the clad coating, a low dilution level was extremely difficult to achieve. This was primarily attributed to the low melting point and the high thermal diffusivity of magnesium as well as the relatively long laser-material interaction time. To overcome the dilution problem, the double-layer cladding technique was explored, and was found to be able to produce low dilution clads with improved corrosion resistance. In considering the improvement of corrosion resistance that can be caused by laser surface modification to magnesium alloys, a comparison was made between the techniques of laser surface melting and laser cladding. The results of the potentiodynamic polarisation tests showed that the improvement obtained from laser surface melting was far less than that could be provided by laser cladding. Although, laser surface melting could effect a rapid solidification, and as a consequence, a homogenised microstructure was obtained, this has not changed the extreme position of magnesium in the electrochemical series nor has it changed the fact that magnesium cannot form self-healing passivating surface films in corrosive environments. On the contrary, the application of laser cladding could completely change the surface chemistry of magnesium alloys and create a more noble surface coating. However, it must be recognised that to benefit most from laser cladding, a low level of dilution is desirable. Accordingly, a careful selection of the laser processing parameters is needed. To achieve this, the 3-D numerical FEM model presented in the present research has shown to be of great value. (Abstract shortened by UMI.)

Guo, Li-Feng

239

Development of Very High Strength and Ductile Dilute Magnesium Alloys by Dispersion of Quasicrystal Phase  

NASA Astrophysics Data System (ADS)

Very high strengths, with tensile yield strength from 377 to 405 MPa, combined with elongation to failure of over 12 pct, have been achieved in Mg-Zn-Y dilute alloys by direct extrusion. Alloys Mg-6 xZn- xY, where x = 0.2, 0.35, and 0.5 (at. pct) were chill cast in a steel mold and direct extruded at a temperature in the range 508 K to 528 K (235 C to 255 C), which produced an average grain size of about 1 ?m. Quasicrystalline i-phase particles were dispersed in the matrix with size ranging from 50 nm to 1 ?m. In addition, high density of nano-precipitates of average size 15 nm was dispersed in matrix. Thus we have developed magnesium alloys of very high strength combined with ductility by a simple process using extrusion with very little addition of yttrium.

Singh, Alok; Osawa, Yoshiaki; Somekawa, Hidetoshi; Mukai, Toshiji; Parrish, Catherine J.; Shih, Donald S.

2014-07-01

240

Microstructural stability and creep properties of die casting Mg-4Al-4RE magnesium alloy  

SciTech Connect

The AE44 (Mg-4Al-4RE) alloy was prepared by a hot-chamber die casting method. The microstructure, microstructural stability and creep properties at 175 deg. C were investigated. The microstructure was analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and the Rietveld method. The results show that die cast AE44 magnesium alloy consists of {alpha}-Mg, Al{sub 11}RE{sub 3}, Al{sub 2}RE and Al{sub 2.12}RE{sub 0.88} phases. The Al{sub 11}RE{sub 3} phase is thermally stable at 175 deg. C whereas the metastable Al{sub 2.12}RE{sub 0.88} phase undergoes a transition into the equilibrium Al{sub 2}RE phase. The alloy investigated is characterized by good creep properties at temperatures of 175 deg. C and 200 {sup o}C.

Rzychon, Tomasz, E-mail: tomasz.rzychon@polsl.pl [Silesian University of Technology, Faculty of Materials Science and Metallurgy, Krasinskiego 8, 40-019 Katowice (Poland); Kielbus, Andrzej; Cwajna, Jan [Silesian University of Technology, Faculty of Materials Science and Metallurgy, Krasinskiego 8, 40-019 Katowice (Poland); Mizera, Jaroslaw [Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland)

2009-10-15

241

Anticorrosion and cytocompatibility behavior of MAO/PLLA modified magnesium alloy WE42.  

PubMed

Recently, biodegradable magnesium alloys have been introduced in the field of cardiovascular stents to avoid the specific drawbacks of permanent metallic implants. However, the major obstacle of the clinical use of magnesium-based materials is their rapid corrosion rate. In this paper, a composite micro-arc oxidation/poly-L: -lactic acid (MAO/PLLA) coating was fabricated on the surface of the magnesium alloy WE42 to improve its corrosion resistance and the cytocompatibility of the modified materials was also investigated for safety aim. In our study, the morphology of materials was analyzed by Scanning electron microscopy. Potentiodynamic polarization was used to evaluate the corrosion behavior of the samples and corrosion weight loss was used to demonstrate their degradation rate. Furthermore, we applied cytotoxicity test in testing the cytocompatibility of the modified samples. The results showed that the PLLA coating effectively sealed the microcracks and micropores on the surface of the MAO coating by physical interlocking to interfere the corrosion ions. The corrosion rate was decreased and the cyototoxicity test showed that the MAO/PLLA composite coating WE42 had good cytocompatibility. PMID:21630093

Guo, Meiqing; Cao, Lu; Lu, Ping; Liu, Yin; Xu, Xinhua

2011-07-01

242

An Environmentally Friendly Process Involving Refining and Membrane-Based Electrolysis for Magnesium Recovery from Partially Oxidized Scrap Alloy  

NASA Astrophysics Data System (ADS)

Magnesium is recovered from partially oxidized scrap alloy by combining refining and solid oxide membrane (SOM) electrolysis. In this combined process, a molten salt eutectic flux (45 wt.% MgF2-55 wt.% CaF2) containing 10 wt.% MgO and 2 wt.% YF3 was used as the medium for magnesium recovery. During refining, magnesium and its oxide are dissolved from the scrap into the molten flux. Forming gas is bubbled through the flux and the dissolved magnesium is removed via the gas phase and condensed in a separate condenser at a lower temperature. The molten flux has a finite solubility for magnesium and acts as a selective medium for magnesium dissolution, but not aluminum or iron, and therefore the magnesium recovered has high purity. After refining, SOM electrolysis is performed in the same reactor to enable electrolysis of the dissolved magnesium oxide in the molten flux producing magnesium at the cathode and oxygen at the SOM anode. During SOM electrolysis, it is necessary to decrease the concentration of the dissolved magnesium in the flux to improve the faradaic current efficiency and prevent degradation of the SOM. Thus, for both refining and SOM electrolysis, it is very important to measure and control the magnesium solubility in the molten flux. High magnesium solubility facilitates refining whereas lower solubility benefits the SOM electrolysis process. Computational fluid dynamics modeling was employed to simulate the flow behavior of the flux stirred by the forming gas. Based on the modeling results, an optimized design of the stirring tubes and its placement in the flux are determined for efficiently removing the dissolved magnesium and also increasing the efficiency of the SOM electrolysis process.

Guan, Xiaofei; Pal, Uday B.; Powell, Adam C.

2013-10-01

243

Coating of biodegradable magnesium alloy bone implants using nanostructured diopside (CaMgSi2O6)  

NASA Astrophysics Data System (ADS)

Magnesium alloys with their biodegradable characteristic can be a very good candidate to be used in orthopedic implants. However, magnesium alloys may corrode and degrade too fast for applications in the bone healing procedure. In order to enhance the corrosion resistance and the in vitro bioactivity of a magnesium alloy, a nanostructured diopside (CaMgSi2O6) film was coated on AZ91 magnesium alloy through combined micro-arc oxidation (MAO) and electrophoretic deposition (EPD) methods. The crystalline structures, morphologies and compositions of the coated and uncoated substrates were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy. Polarization, electrochemical impedance spectroscopy, and immersion test in simulated body fluid (SBF) were employed to evaluate the corrosion resistance and the in vitro bioactivity of the samples. The results of our investigation showed that the nanostructured diopside coating deposited on the MAO layer increases the corrosion resistance and improves the in vitro bioactivity of the biodegradable magnesium alloy.

Razavi, Mehdi; Fathi, Mohammadhossein; Savabi, Omid; Beni, Batoul Hashemi; Razavi, Seyed Mohammad; Vashaee, Daryoosh; Tayebi, Lobat

2014-01-01

244

Research on Water Based Coating Containing Nano-Silica for Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Due to magnesium's active chemical property, a novel environmental protective water based metallic coating was developed, which mainly contains metal flake, nano-silica, silicate and silane. The coating's properties were investigated by neutral salt spray test, micro-hardness testing, adhesion test and electrochemical technique etc. Meanwhile the coating surface and microstructure was observed by scanning electron microscopy (SEM). Furthermore, the effect of nano silica on the coating was also explored. Results showed that an excellent adhesive, heat-resisting, protective coating for AZ91D magnesium alloy could be achieved by this technique. It also indicated that nano silica could greatly improve the properties of coating. In the paper, mechanism of nano silica coating was also discussed.

Huang, Wei; Zheng, Tianliang; Li, Di

245

Novel magnesium alloy Mg-2La caused no cytotoxic effects on cells in physiological conditions.  

PubMed

Using several different in vitro assays, a new biodegradable magnesium alloy Mg-2La, composed of 98% magnesium and 2% lanthanum, was investigated as a possible implant material for biomedical applications. An in vitro cytotoxicity test, according to EN ISO 10993-5/12, with L929 and human osteoblastic cells identified no toxic effects on cell viability at physiological concentrations (at 50% dilutions and higher). The metabolic activity of human osteoblasts in the 100% extract was decreased to <70% and was therefore rated as cytotoxic. The degradation rates of Mg-2La were evaluated in phosphate buffered saline and four different cell culture media. The degradation rates were shown to be influenced by the composition of the solution, and the addition of fetal bovine serum slightly accelerated the corrosive process. The results of these in vitro experiments suggest that Mg-2La is a promising candidate for use as an orthopedic implant material. PMID:24907760

Weizbauer, Andreas; Seitz, Jan-Marten; Werle, Peter; Hegermann, Jan; Willbold, Elmar; Eifler, Rainer; Windhagen, Henning; Reifenrath, Janin; Waizy, Hazibullah

2014-08-01

246

Study of second phase in bioabsorbable magnesium alloys: Phase stability evaluation via Dmol{sup 3} calculation  

SciTech Connect

Thermodynamical stabilities of four conventional second phases as well as magnesium matrix in bioabsorbable magnesium alloys were investigated theoretically via computer calculation method. Model of individual phase and systems including phase and four water molecular (phase-4H{sub 2}O) were established to simulate the in vitro and in vivo environment. Local orbital density functional theory approach was applied to calculate the total energy for the individual phase and phase-4H{sub 2}O system. The results demonstrated that all the second phases possessed higher phase stability compared with magnesium matrix, but the phase stability was quite different for different types of second phases or second phase-4H{sub 2}O systems. Furthermore, a schematic process of inflammation reaction caused by magnesium alloy implants was proposed for the further evaluation on biocompatibility of different second phases.

Yang, Huazhe [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Department of Biophysics, China Medical University, Shenyang 110001 (China); Liu, Chen [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Wan, Peng; Tan, Lili; Yang, Ke, E-mail: kyang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

2013-11-01

247

Spectroscopic study of plasma during electrolytic oxidation of magnesium- and aluminium-alloy  

NASA Astrophysics Data System (ADS)

We present the results of an optical emission spectroscopy study of Plasma during Electrolytic Oxidation (PEO) of magnesium- and aluminum-alloy. Plasma electron number density Ne diagnostics is performed either from the H? line shape or from the width or shift of non-hydrogenic ion lines of aluminum and magnesium. The line profile analysis of the H? suggests presence of two PEO processes characterized by relatively low electron number densities Ne?1.21015 cm-3 and Ne?2.31016 cm-3. Apart from these two low Ne processes, there is the third one related to the ejection of evaporated anode material through micro-discharge channels. This process is characterized by larger electron density Ne=(1.2-1.6)1017 cm-3, which is detected from the shape and shift of aluminum and magnesium singly charged ion lines. Two low Ne values detected from the H? and large Ne measured from the widths and shift of ion lines suggest presence of three types of discharges during PEO with aluminum- and magnesium-alloy anode. On the basis of present and earlier results one can conclude that low Ne processes do not depend upon anode material or electrolyte composition.The electron temperature of 4000 K and 33,000 K are determined from relative intensities of Mg I and O II lines, respectively. The attention is drawn to the possibility of Ne application for Te evaluation using Saha equation what is of importance for PEO metal plasma characterization. During the course of this study, difficulties in the analysis of spectral line shapes are encountered and the ways to overcome some of the obstacles are demonstrated.

Jovovi?, J.; Stojadinovi?, S.; iovi?, N. M.; Konjevi?, N.

2012-10-01

248

Bioresorbable Drug-Eluting Magnesium-Alloy Scaffold for Treatment of Coronary Artery Disease  

PubMed Central

The introduction of metallic drug-eluting stents has reduced the risk of restenosis and widened the indications of percutaneous coronary intervention in treatment of coronary artery disease. However, this medical device can induce hypersensitive reaction that interferes with the endothelialization and healing process resulting in late persistent or acquired malapposition of the permanent metallic implant. Delayed endotheliaization and malapposition may lead to late and very late stent thrombosis. Bioresorbable scaffolds (BRS) have been introduced to potentially overcome these limitations, as they provide temporary scaffolding and then disappear, liberating the treated vessel from its cage. Magnesium is an essential mineral needed for a variety of physiological functions in the human body and its bioresorbable alloy has the strength-to-weight ratio comparable with that of strong aluminum alloys and alloy steels. The aim of this review is to present the new developments in Magnesium BRS technology, to describe its clinical application and to discuss the future prospects of this innovative therapy. PMID:24351829

Campos, Carlos M.; Muramatsu, Takashi; Iqbal, Javaid; Zhang, Ya-Jun; Onuma, Yoshinobu; Garcia-Garcia, Hector M.; Haude, Michael; Lemos, Pedro A.; Warnack, Boris; Serruys, Patrick W.

2013-01-01

249

Material Behavior Based Hybrid Process for Sheet Draw-Forging Thin Walled Magnesium Alloys  

SciTech Connect

Magnesium alloys are conventionally formed at the elevated temperatures. The thermally improved formability is sensitive to the temperature and strain rate. Due to limitations in forming speeds, tooling strength and narrow processing windows, complex thin walled parts cannot be made by traditional warm drawing or hot forging processes. A hybrid process, which is based on the deformation mechanism of magnesium alloys at the elevated temperature, is proposed that combines warm drawing and hot forging modes to produce an aggressive geometry at acceptable forming speed. The process parameters, such as temperatures, forming speeds etc. are determined by the FEM modeling and simulation. Sensitivity analysis under the constraint of forming limits of Mg alloy sheet material and strength of tooling material is carried out. The proposed approach is demonstrated on a conical geometry with thin walls and with bottom features. Results show that designed geometry can be formed in about 8 seconds, this cannot be formed by conventional forging while around 1000s is required for warm drawing. This process is being further investigated through controlled experiments.

Sheng, Z.Q.; Shivpuri, R. [Industrial, Welding and System Engineering at the Ohio State University, Columbus, Oh, 43210 (United States)

2005-08-05

250

Structure and formation mechanism of phosphate conversion coating on die-cast AZ91D magnesium alloy  

Microsoft Academic Search

Phosphate conversion coating, which is considered as an alternative to chromium conversion coating for improving the corrosion resistance of die-cast AZ91D magnesium alloy is studied. The structure and formation mechanism of the coating was investigated in details using ESEM\\/EDX, XRD, EPMA, ICP and electrochemical method. It was found that the conversion coating was composed of complex phosphate containing magnesium and

Wanqiu Zhou; Dayong Shan; En-Hou Han; Wei Ke

2008-01-01

251

Influence of texture and grain size on work hardening and ductility in magnesium-based alloys processed by ECAP and rolling  

Microsoft Academic Search

Equal channel angular pressing (ECAP) and large-strain hot rolling (LSHR) are widely used methods for refining the grain size in magnesium alloys. The hardening capability of the processed materials confers the resistance to develop tensile mechanical instabilities, therefore controlling ductility. In this work various magnesium alloys were processed using ECAP, LSHR and annealing treatments in order to control the texture

J. A. del Valle; F. Carreo; O. A. Ruano

2006-01-01

252

Analysis of Nugget Formation During Resistance Spot Welding on Dissimilar Metal Sheets of Aluminum and Magnesium Alloys  

NASA Astrophysics Data System (ADS)

The nugget formation of resistance spot welding (RSW) on dissimilar material sheets of aluminum and magnesium alloys was studied, and the element distribution, microstructure, and microhardness distribution near the joint interface were analyzed. It was found that the staggered high regions at the contact interface of aluminum and magnesium alloy sheets, where the dissimilar metal melted together, tended to be the preferred nucleation regions of nugget. The main technical problem of RSW on dissimilar metal sheets of aluminum and magnesium alloys was the brittle-hard Al12Mg17 intermetallic compounds distributed in the nugget, with hardness much higher than either side of the base materials. Microcracks tended to generate at the interface of the nugget and base materials, which affected weld quality and strength.

Luo, Yi; Li, Jinglong

2014-10-01

253

Diffusion Bonding Behavior and Characterization of Joints Made Between 316L Stainless Steel Alloy and AZ31 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The 316L austenitic stainless steel and AZ31 magnesium alloy have physical and mechanical properties which makes these alloys suitable in a number of high technology based industries such as the aerospace and automotive sectors. However, for these alloys to be used in engineering applications, components must be fabricated and joined successfully. The differences in the physical and metallurgical properties between these two alloys prevents the use of conventional fusion welding processes commonly employed in aerospace and transport industry. Therefore, alternative techniques need to be developed and diffusion bonding technology is a process that has considerable potential to join these two dissimilar alloys. In this research work both solid-state and transient liquid phase (TLP) bonding processes were applied. The solid-state bonding of 316L steel to AZ31 magnesium alloy was possible at a bonding temperature of 550C for 120 minutes using a pressure of 1.3 MPa. The interface characterization of the joint showed a thin intermetallic zone rich in Fe-Al was responsible for providing a metallurgical bond. However, low joint shear strengths were recorded and this was attributed to the poor surface to surface contact. The macro-deformation of the AZ31 alloy prevented the use of higher bonding pressures and longer bonding times. In order to overcome these problems, the TLP bonding process was implemented using pure Cu and Ni foils as interlayers which produced a eutectic phase at the bonding temperature. This research identified the bonding mechanism through microstructural and differential scanning calorimetry investigations. The microstructural characterization of the TLP joints identified intermetallics which became concentrated along the 316L steel/AZ31 bond interface due to the "pushing effect" of the solid/liquid interface during isothermal solidification stage of bonding. The size and concentration of the intermetallics had a noticeable effect on the final joint strength properties. TLP bonding using electrodeposited coatings of Cu and Ni were used as a way of controlling the volume of eutectic liquid formed at the joint. Theoretical and experimental work showed that the use of thin coatings was successful in reducing the size and amount of intermetallics formed at the joint and this had the effect on increasing joint shear strength values.

Elthalabawy, Waled Mohamed

254

Synthesis of hybrid sol-gel coatings for corrosion protection of we54-ae magnesium alloy  

NASA Astrophysics Data System (ADS)

The present work shows some preliminary results related to the synthesis, characterization and corrosion evaluation of different hybrid sol-gel coatings applied on the WE54-AE magnesium alloy attending to the two experimental variables, i.e. the precursors ratio and the aging time, which may affect the quality and the electrochemical properties of the coatings resultant. The experimental results confirmed that, under some specific experimental conditions, it was possible to obtain homogeneous and uniform, porous coatings with good corrosion resistance that also permit to accommodate corrosion inhibitors.

Hernndez-Barrios, C. A.; Duarte, N. Z.; Hernndez, L. M.; Pea, D. Y.; Coy, A. E.; Viejo, F.

2013-11-01

255

Microstructure and tensile properties of squeeze cast magnesium alloy AM50  

NASA Astrophysics Data System (ADS)

High-pressure die cast magnesium alloy AM50 is currently used extensively in large and complex shaped thin-wall automotive components. For further expansion of the alloy usage in automobiles, novelmanufacturing processes need to be developed. In this study, squeeze casting of AM50 alloy with a relatively thick cross section was carried out using a hydraulic press with an applied pressure of 70 MPa. Microstructure and mechanical properties of the squeeze cast AM50 with a cross-section thickness of 10 mm were characterized in comparison with the die cast counterpart. The squeeze cast AM50 alloy exhibits virtually no porosity in the microstructure as evaluated by both optical microscopy and the density measurement technique. The results of tensile testing indicate the improved tensile properties, specifically ultimate tensile strength and elongation, for the squeeze cast samples over the conventional high-pressure die cast parts. The analysis of tensile behavior show that the strain-hardening rate during the plastic deformation of the squeeze cast specimens is constantly higher than that of the die cast specimens. The scanning electron microscopy fractography evidently reveals the ductile fracture features of the squeeze cast alloy AM50.

Zhou, Ming; Hu, Henry; Li, Naiyi; Lo, Jason

2005-08-01

256

Tribological properties of the AZ91D magnesium alloy hardened with silicon carbide and by severe plastic deformation  

Microsoft Academic Search

Results of investigation of the tribological contact characteristics of R18 tool steel in interface with AZ91D magnesium alloy\\u000a hardened with SiC disperse powder filler and by severe plastic deformation (SPD)specifically, equal-channel angular pressing\\u000a (ECAP)are presented. It is established that introduction of the SiC powder filler into the magnesium alloy increases the\\u000a friction coefficient and reduces the wear rate. The size

V. I. Semenov; Y.-R. Jeng; S.-J. Huang; Y.-Zh. Dao; S.-J. Hwang; L. Sh. Shuster; S. V. Chertovskikh; P.-Ch. Lin

2009-01-01

257

Effect of explosive bonds on acoustic loss of aluminium-magnesium alloys  

NASA Astrophysics Data System (ADS)

The amplitude-independent mechanical quality factors of the commercial aluminium-magnesium alloys 5056 and 5456 were measured from 50 mK to 300 K in torsional mechanical resonators in which the rotation axis coincides with an essentially flat explosive-bond plane. The 1 kHz resonators were configured to minimize extraneous internal friction effects. The results are compared with those obtained in similar experiments on a 5056 resonator in which there were no explosive bonds. Numerical estimates of the quality factor of the bond material are obtained. From high-resolution resonant frequency measurements, the superconducting transition temperatures were determined and the effect of superconductivity on the torsion modulus was observed. The work was motivated by recent proposals to fabricate massive spherical resonant gravitational wave detectors from explosively bonded stacks of aluminium alloy plates.

Duffy, W.; Dalal, S.

258

Endothelialization of novel magnesium-rare earth alloys with fluoride and collagen coating.  

PubMed

Magnesium (Mg) alloys are promising scaffolds for the next generation of cardiovascular stents because of their better biocompatibility and biodegradation compared to traditional metals. However, insufficient mechanical strength and high degradation rate are still the two main limitations for Mg materials. Hydrofluoric acid (HF) treatment and collagen coating were used in this research to improve the endothelialization of two rare earth-based Mg alloys. Results demonstrated that a nanoporous film structure of fluoride with thickness of ~20 m was formed on the Mg material surface, which improved the corrosion resistance. Primary human coronary artery endothelial cells (HCAECs) had much better attachment, spreading, growth and proliferation (the process of endothelialization) on HF-treated Mg materials compared to bare- or collagen-coated ones. PMID:24670478

Zhao, Nan; Workman, Benjamin; Zhu, Donghui

2014-01-01

259

Influence of selected alloying elements on the stability of magnesium dihydride for hydrogen storage applications: A first-principles investigation  

NASA Astrophysics Data System (ADS)

MgH2 is a promising compound for hydrogen storage. Its relatively high stability has been the main obstacle for practical applications. Here, first-principles calculations of MgH2 and MgH2-X (X=Al, Ti, Fe, Ni, Cu, or Nb) were carried out to investigate the influences of selected alloying elements on the stability of the magnesium hydride. The full-potential linearized augmented plane-wave method within the generalized gradient approximation was used in the present study. The influence of alloying elements on the stability of magnesium dihydride was investigated through calculations of the total energy of the considered systems. It was shown that the alloying elements considered here decrease the heat of formation of (Mg,X)H2i.e., destabilizing the hydridewith decreasing order of effect from Cu, Ni, Al, Nb, and Fe to Ti. The destabilization of the magnesium hydride by the alloying elements was due to a weakened bonding between magnesium and hydrogen atoms. Hence, the dehydrogenation properties of MgH2 are expected to be improved to a different extent by the addition of alloying elements.

Song, Y.; Guo, Z. X.; Yang, R.

2004-03-01

260

Design and development of self-passivating biodegradable magnesium alloys using selective element oxidation  

NASA Astrophysics Data System (ADS)

Metallic biomaterials such as stainless steels, titanium alloys, and cobalt-chromium alloys have been used as structural implant materials for many years. However, due to their limitations in temporary implant applications, there has been increased interest in the development of a biodegradable structural implant device. Magnesium (Mg) alloys have shown great potential as a material for biodegradable structural implant applications. However, low strength and high degradation rate of Mg under physiological conditions are major limitations, causing the implant to lose its structural integrity before the healing process is complete. The main aim of this work was to investigate the possibility of designing Mg-based alloys with ability to form selective protective oxides, thereby aiding in the reduction of the initial degradation rate. A thermodynamics-driven design was utilized to select three elements, namely Gadolinium (Gd), Scandium (Sc) and Yttrium (Y), due to the low enthalpy of formation associated with their oxide species. First, binary alloys were cast under inert atmosphere, solution treated and investigated for degradation rate in Hanks' solution. The Mg-Gd binary alloy showed the fastest degradation rate whereas the Mg-Sc binary alloy showed the slowest degradation rate. The degradation of Mg-Gd and Mg-Y was 18 and 5 times faster than Mg-Sc alloy, respectively. The microstructural analysis of the alloys was performed using X-ray Diffraction (XRD), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). It was observed that the grain size of Mg-Sc alloys is significantly smaller than Mg-Gd and Mg-Y alloys and can be a contributing factor to the reduction in degradation rate. The hardness behavior of the alloys was also investigated using Vickers microhardness Testing. To understand the oxidation behavior and kinetics, samples were oxidized in pure oxygen environment and investigated using microstructural and thermogravimetric analysis (TGA). Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were also used to characterize the chemistry of the surface oxides. Selective oxidation of the alloying species was observed on the surface of all the alloys, indicating a strong driving force for their formation out of solid solution Mg. The degradation rate of the oxidized samples was also investigated in Hanks' solution and compared with the rate of freshly polished samples. The oxide formation on Mg-Y alloys was found to be most protective as it reduced the degradation rate by more than 50%. On the other hand, oxidized Mg-Sc samples did not show any appreciable decline in degradation rate as compared to polished samples. Based on the information gathered from the binary alloys, ternary alloy system was selected. The thermodynamic and empirical models were applied to predict the properties of the alloy. The models were validated using the techniques mentioned above. It was observed that the predictions matched with the experimental results.

Brar, Harpreet Singh

261

Multipass cold drawing of magnesium alloy minitubes for biodegradable vascular stents.  

PubMed

Magnesium alloys possess highly limited room-temperature formabilities. This presents a technological barrier to the fabrication of minitubes for biodegradable vascular stents. The research was aimed at developing precision forming technology to fabricate ZM21 magnesium alloy minitubes with a refined microstructure. A multipass cold drawing process with a moving mandrel was successfully developed to convert seamless hollow billets through five passes of cold drawing and an interpass annealing treatment into minitubes with an outside diameter of 2.9 mm and a wall thickness of 0.217 mm, ready for laser cutting into vascular stents. It was found that a cumulative reduction in cross-section area as much as 32% could be applied to the material without causing fracture. However, a further reduction in cross-section area required annealing at 300C for 1h to change a twinned microstructure into a recrystallized grain structure and to regain formability. The interpass annealing treatment after the fourth pass led to a reduction in drawing force by 22%, in comparison with the drawing force at the fourth pass of drawing. The variations in the outside diameter and wall thickness of the minitubes could be kept within 5 and 12 ?m, respectively. Further research is directed toward improvements in dimensional precisions. PMID:23706237

Fang, Gang; Ai, Wei-jiang; Leeflang, Sander; Duszczyk, Jurek; Zhou, Jie

2013-08-01

262

Manufacture of gradient micro-structures of magnesium alloys using two stage extrusion dies  

NASA Astrophysics Data System (ADS)

This paper aims to manufacture magnesium alloy metals with gradient micro-structures using hot extrusion process. The extrusion die was designed to have a straight channel part combined with a conical part. Materials pushed through this specially-designed die generate a non-uniform velocity distribution at cross sections inside the die and result in different strain and strain rate distributions. Accordingly, a gradient microstructure product can be obtained. Using the finite element analysis, the forming temperature, effective strain, and effective strain rate distributions at the die exit were firstly discussed for various inclination angles in the conical die. Then, hot extrusion experiments with a two stage die were conducted to obtain magnesium alloy products with gradient micro-structures. The effects of the inclination angle on the grain size distribution at cross sections of the products were also discussed. Using a die of an inclination angle of 15, gradient micro-structures of the grain size decreasing gradually from 17 ?m at the center to 4 ?m at the edge of product were achieved.

Hwang, Yeong-Maw; Huang, Tze-Hui; Alexandrov, Sergei; Naimark, Oleg Borisovich; Jeng, Yeau-Ren

2013-12-01

263

Flow behaviour of magnesium alloy AZ31B processed by equal-channel angular pressing  

NASA Astrophysics Data System (ADS)

Magnesium alloys are characterised by their low density, high specific strength and stiffness. But, the potential application of Mg is limited by its low room-temperature ductility & formability. Formability can be improved by developing an ultrafine grained (UFG) structure. Equal channel angular pressing (ECAP) is a well known process that can be used to develop an ultrafine grained microstructure. The aim of this study was to investigate the flow behaviour of AZ31B magnesium alloy after ECAP. The specimen was subjected to three passes of ECAP with a die angle of 120 using processing route Bc. The processing temperature was 523 K for the first pass and 423 K for the subsequent two passes. The microstructure characterisation was done. Compression tests of ECAPed and annealed specimens were carried out at strain rates of 0.01 - 1s-1 and deformation temperatures of 200 - 300C using computer servo-controlled Gleeble-3800 system. The value of activation energy Q and the empirical materials constants of A and n were determined. The equations relating flow stress and Zener-Hollomon parameter were proposed. In the case annealed AZ31, the activation energy was determined to be 154 kJ/mol, which was slightly higher than the activation energy of 144 kJ/mol for ECAPed AZ31.

Arun, M. S.; Chakkingal, U.

2014-08-01

264

Mechanical Properties and Microstructure of AZ31B Magnesium Alloy Processed by I-ECAP  

NASA Astrophysics Data System (ADS)

Incremental equal channel angular pressing (I-ECAP) is a severe plastic deformation process used to refine grain size of metals, which allows processing very long billets. As described in the current article, an AZ31B magnesium alloy was processed for the first time by three different routes of I-ECAP, namely, A, BC, and C, at 523 K (250 C). The structure of the material was homogenized and refined to ~5 microns of the average grain size, irrespective of the route used. Mechanical properties of the I-ECAPed samples in tension and compression were investigated. Strong influence of the processing route on yield and fracture behavior of the material was established. It was found that texture controls the mechanical properties of AZ31B magnesium alloy subjected to I-ECAP. SEM and OM techniques were used to obtain microstructural images of the I-ECAPed samples subjected to tension and compression. Increased ductility after I-ECAP was attributed to twinning suppression and facilitation of slip on basal plane. Shear bands were revealed in the samples processed by I-ECAP and subjected to tension. Tension-compression yield stress asymmetry in the samples tested along extrusion direction was suppressed in the material processed by routes BC and C. This effect was attributed to textural development and microstructural homogenization. Twinning activities in fine- and coarse-grained samples have also been studied.

Gzyl, Michal; Rosochowski, Andrzej; Pesci, Raphael; Olejnik, Lech; Yakushina, Evgenia; Wood, Paul

2013-11-01

265

Stamping of Thin-Walled Structural Components with Magnesium Alloy AZ31 Sheets  

SciTech Connect

In the present study, the stamping process for manufacturing cell phone cases with magnesium alloy AZ31 sheets was studied using both the experimental approach and the finite element analysis. In order to determine the proper forming temperature and set up a fracture criterion, tensile tests and forming limit tests were first conducted to obtain the mechanical behaviors of AZ31 sheets at various elevated temperatures. The mechanical properties of Z31 sheets obtained from the experiments were then adopted in the finite element analysis to investigate the effects of the process parameters on the formability of the stamping process of cell phone cases. The finite element simulation results revealed that both the fracture and wrinkle defects could not be eliminated at the same time by adjusting blank-holder force or blank size. A drawbead design was then performed using the finite element simulations to determine the size and the location of drawbead required to suppress the wrinkle defect. An optimum stamping process, including die geometry, forming temperature, and blank dimension, was then determined for manufacturing the cell phone cases. The finite element analysis was validated by the good agreement between the simulation results and the experimental data. It confirms that the cell phone cases can be produced with magnesium alloy AZ31 sheet by the stamping process at elevated temperatures.

Chen, F.-K.; Chang, C.-K. [Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan (China)

2005-08-05

266

Experimental investigation of anisotropy evolution of AZ31 magnesium alloy sheets under tensile loading  

SciTech Connect

Increasing demand for lighter final products has created new opportunities for the application of new light weight materials. Due to high strength to density ratio and good magnetic resistance properties, magnesium alloys are good candidates to replace steel and aluminum for same application. However, limited numbers of active slip deformation mechanisms, result in a decreased formability at room temperature. Furthermore, wrought magnesium alloys have an initial crystallographic texture, remained from the prior rolling operations, which makes them highly anisotropic. In this paper, tensile tests are performed at room temperature and 200 deg. C at different strain rates and orientations relative to the rolling direction, including rolling, 30 deg., 45 deg., 60 deg. and transverse orientation. The strain rates adopted for these experiments varied from 0.001 to 1.0. The testing results show the effect of temperature on the strain rate sensitivity of AZ31 sheets. The extent of deformation is continuously recorded using two separate high temperature extensometers. The results of testing show an increase in the r-values with the plastic deformation. The strain rate sensitivity of AZ31 increased as the temperature was elevated. At higher strain rates the measured r-values are larger and the slope of its evolution with the plastic strain is steeper.

Tari, D. Ghaffari; Worswick, M. J. [University of Waterloo, 200 University Ave West, Waterloo, Ontario (Canada)

2011-05-04

267

Experimental investigation of anisotropy evolution of AZ31 magnesium alloy sheets under tensile loading  

NASA Astrophysics Data System (ADS)

Increasing demand for lighter final products has created new opportunities for the application of new light weight materials. Due to high strength to density ratio and good magnetic resistance properties, magnesium alloys are good candidates to replace steel and aluminum for same application. However, limited numbers of active slip deformation mechanisms, result in a decreased formability at room temperature. Furthermore, wrought magnesium alloys have an initial crystallographic texture, remained from the prior rolling operations, which makes them highly anisotropic. In this paper, tensile tests are performed at room temperature and 200 C at different strain rates and orientations relative to the rolling direction, including rolling, 30, 45, 60 and transverse orientation. The strain rates adopted for these experiments varied from 0.001 to 1.0. The testing results show the effect of temperature on the strain rate sensitivity of AZ31 sheets. The extent of deformation is continuously recorded using two separate high temperature extensometers. The results of testing show an increase in the r-values with the plastic deformation. The strain rate sensitivity of AZ31 increased as the temperature was elevated. At higher strain rates the measured r-values are larger and the slope of its evolution with the plastic strain is steeper.

Tari, D. Ghaffari; Worswick, M. J.

2011-05-01

268

Manufacture of gradient micro-structures of magnesium alloys using two stage extrusion dies  

SciTech Connect

This paper aims to manufacture magnesium alloy metals with gradient micro-structures using hot extrusion process. The extrusion die was designed to have a straight channel part combined with a conical part. Materials pushed through this specially-designed die generate a non-uniform velocity distribution at cross sections inside the die and result in different strain and strain rate distributions. Accordingly, a gradient microstructure product can be obtained. Using the finite element analysis, the forming temperature, effective strain, and effective strain rate distributions at the die exit were firstly discussed for various inclination angles in the conical die. Then, hot extrusion experiments with a two stage die were conducted to obtain magnesium alloy products with gradient micro-structures. The effects of the inclination angle on the grain size distribution at cross sections of the products were also discussed. Using a die of an inclination angle of 15, gradient micro-structures of the grain size decreasing gradually from 17 ?m at the center to 4 ?m at the edge of product were achieved.

Hwang, Yeong-Maw; Huang, Tze-Hui [Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, No. 70, Lien-Hai Rd., Kaohsiung, 804, Taiwan (China); Alexandrov, Sergei [Institute for Problems in Mechanics, Russian Academy of Sciences, Moscow (Russian Federation); Naimark, Oleg Borisovich [Institute of Continuous Media Mechanics, Russian Academy of Sciences, Perm (Russian Federation); Jeng, Yeau-Ren [Department of Mechanical Engineering and Advanced Institute of Manufacturing with High-tech Innovations, National Chung Cheng University, Ming-Hsiung, Chia-Yi 621, Taiwan (China)

2013-12-16

269

Effect of ECAP processing on corrosion resistance of AE21 and AE42 magnesium alloys  

NASA Astrophysics Data System (ADS)

Corrosion properties of AE21 and AE42 magnesium alloys were investigated in the extruded state and after subsequent 8 passes of Equal Channel Angular Pressing (ECAP) via route Bc, by Electrochemical Impedance Spectroscopy (EIS) in 0.1 M NaCl solution. The resulting microstructure was observed by the Transmission Electron Microscope (TEM) and the Scanning Electron Microscope (SEM). Corrosion layer created after 7 days of immersion was observed by (SEM) in order to explain different evolution of the corrosion resistance after ECAP processing in both alloys. It was found that Al-rich Al11RE3 dispersed particles (present in both alloys) strongly influence the corrosion process and enhance the corrosion resistance. Ultra-fine grained structure was found to reduce the corrosion resistance in AE21. On the other hand, the microstructure of AE42 after ECAP and particularly the better distribution of the alloying elements in the matrix enhance the corrosion resistance when compared to the extruded material.

Minrik, P.; Krl, R.; Jane?ek, M.

2013-09-01

270

Abrasion resistance of magnesium alloys with surface films generated from phosphonate imidazolium ionic liquids  

NASA Astrophysics Data System (ADS)

Surface films formed by treatment with the ionic liquids (ILs) 1,3-dimethylimidazolium methylphosphonate (LMP101), 1-ethyl-3-methylimidazolium methylphosphonate (LMP102) and 1-ethyl-3-methylimidazolium ethylphosphonate (LEP102) on magnesium alloys have been studied. The abrasion resistance of the coated alloys was studied by microscratching under progressively increasing load, and compared with that of the uncoated materials. Abrasion-protective phosphorus-containing films are generated on AZ31B, with an order of abrasion resistance as a function of the IL of LEP102 > LMP101 > LMP102, with a reduction in penetration depth of a 67% for the sample treated with LEP102 with respect to the uncovered alloy. This is attributed to the formation of a continuous adhered phosphorus-containing film. In contrast, the abrasion resistance of EZ33A alloy is not improved due to the presence of the less reactive Zn-rich phase at the grain boundaries, which prevents the formation of a continuous protective layer. The results are discussed from contact angles, SEM-EDX and XPS analysis.

Espinosa, T.; Jimnez, A. E.; Martnez-Nicols, G.; Sanes, J.; Bermdez, M. D.

2014-11-01

271

Transient Liquid Phase Diffusion Bonding of Magnesium Alloy (Mg-AZ31) to Titanium Alloy (Ti-6Al-4V)  

NASA Astrophysics Data System (ADS)

The magnesium alloy Mg-AZ31 and titanium alloy Ti-6Al-4V have physical characteristics and mechanical properties that makes it attractive for a wide range of engineering applications in the aerospace and automotive industries. However, the differences in melting temperature and coefficient of thermal expansion hinder the use of traditional fusion welding techniques. Transient liquid phase (TLP) bonding of magnesium alloy Mg-AZ31 and titanium alloy Ti-6Al- 4V was performed and different interlayer types and configurations were used to facilitate joint formation. The joining of these alloys using Ni foils was successful at a bonding temperature of 515C, bonding pressure 0.2 MPa, for bonding time of 5 minutes. At the Ni/Mg-AZ31 bond interface, the formation of a eutectic liquid between Mg and Ni was observed. The formation of Mg2Ni and Mg3AlNi2 were identified along the bond interface resulting in an isothermally solidified joint. At the Ni/Ti-6Al-4V interface, the solid-state diffusion process results in joint formation. The use of double Ni-Cu sandwich joint resulted in further enhancement in joint formation and this produced joints with greater shear strength values. The configuration of Mg-AZ31/Cu- Ni/Ti-6Al-4V or Mg-AZ31/Ni-Cu/Ti-6Al-4V influence the mechanism of bonding and the type of intermetallics formed within the joint. The application of thin Ni electrodeposited coatings resulted in further enhancements of joint quality due to better surface-to-surface contact and a reduction in the formation of intermetallics at the joint. The effect of Cu nano-particles in the coatings was found to decrease the eutectic zone width and this resulted in an increase the shear strength of the joints. The highest shear strength of 69 MPa was possible with bonds made using coatings containing Cu nano-particle dispersion.

Atieh, Anas Mahmoud

272

High-strain-rate superplasticity at low temperature in a ZK61 magnesium alloy produced by powder metallurgy  

Microsoft Academic Search

In the present study, superplastic behavior of a pseudo single phase magnesium alloy, ZK61, was investigated at about half the absolute melting point. The material was produced by the P\\/M route, and had a fine grain size of [approximately]500 nm. It is demonstrated that the P\\/M ZK61 alloy can behave in a superplastic manner at a high strain rate of

Hiroyuki Watanabe; Toshiji Mukai; Mamoru Mabuchi; Kenji Higashi

1999-01-01

273

Thermodynamic investigation of the effect of alkali metal impuries on the processing of aluminum and magnesium alloys  

Microsoft Academic Search

Aluminum and magnesium alloys are widely used in the automobile and aerospace industries as structural materials due to their light weight, high specific strength and good formability. However, they suffer from the poor hot rolling characteristics due to undesired impurities like calcium, potassium, lithium and sodium. They increase the hydrogen solubility in the melt and promote the formation of porosity

Shengjun Zhang

2006-01-01

274

Warm Deep Drawing of Rectangular Parts of AZ31 Magnesium Alloy Sheet Adopting Variable Blank Holder Force  

SciTech Connect

AZ31 magnesium alloy sheet with good shape and formability is fabricated by warm cross rolling. Uniaxial tensile tests are conducted using a Gleeble 3500 thermal - mechanical simulator, and the mechanical properties of AZ31 magnesium alloy sheet are analyzed. A warm deep drawing process of square part is also simulated by the finite element method. The influences of blank holder force on the formability are numerically investigated. A double-action hydraulic press that can realize adjustable blank holder forces is developed and its working principle and control system are introduced. Some warm deep drawing experiments of square parts of AZ31 magnesium alloy sheet are also performed. Different variation schemes of the blank holder force with the stroke of the punch are tested, and the experiment results are compared. Results show that the suitable blank holder force variation scheme is a ladder curve with the punch stroke. Adopting the variable blank holder force technique can improve 13.2% of the drawing depth of square parts of AZ31 magnesium alloy sheet.

Peng Yinghong; Chang Qunfeng; Li Dayong [School of Mechanical Engineering, Shanghai Jiaotong University, 200240 (China); Zeng Xiaoqin [School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200240 (China)

2007-05-17

275

Selection of FSW tool pin profile, shoulder diameter and material for joining AZ31B magnesium alloy An experimental approach  

Microsoft Academic Search

In this investigation, an attempt was made to select proper tool pin profile, tool shoulder diameter and tool material to friction stir weld AZ31B magnesium alloy. Five tool pin profiles, five tool materials and three tool shoulder diameters were used to fabricate the joints. Tensile properties of the joints were evaluated and correlated with the weld zone microstructure and hardness.

G. Padmanaban; V. Balasubramanian

2009-01-01

276

Influence of texture on dynamic recrystallization and deformation mechanisms in rolled or ECAPed AZ31 magnesium alloy  

Microsoft Academic Search

Equal channel angular pressing (ECAP) and hot rolling are widely used processing routes in magnesium alloys. These routes induce different textures that affect their mechanical properties. In the present work, the influence of the texture on dynamic recrystallization (DRX) and deformation mechanisms was investigated. During tensile deformation at moderate temperatures, a stronger enhancement of DRX in rolled samples than in

J. A. del Valle; O. A. Ruano

2008-01-01

277

Microstructure and mechanical properties of GTA surface modified composite layer on magnesium alloy AZ31 with SiC P  

Microsoft Academic Search

A novel fabrication process of surface modified composite layer by gas tungsten arc (GTA) surface modification process was used to deposit SiC particles on the surface of magnesium alloy AZ31. This method is an effective technique in producing a high performance surface modified composite layer. The microstructure and mechanical properties of the GTA surface modified composite layer were evaluated. The

Ding Wenbin; Jiang Haiyan; Zeng Xiaoqin; Li Dehui; Yao Shoushan

2007-01-01

278

Phosphate coatings on magnesium alloy AM60 part 1: study of the formation and the growth of zinc phosphate films  

Microsoft Academic Search

The corrosion protection by zinc phosphate conversion coating on magnesium alloy AM60 is studied. Three phosphatation solutions containing phosphoric acid, phosphate ions, nitrates and nitrites added with zinc and fluorides were used. Therefore, the present investigation aims to study the role of the phosphating bath components on the phosphating process and to enhance the possibility of obtaining phosphate layers on

L. Kouisni; M. Azzi; M. Zertoubi; F. Dalard; S. Maximovitch

2004-01-01

279

An investigation on microstructural and mechanical properties of solid mould investment casting of AZ91D magnesium alloy  

Microsoft Academic Search

In this work, AZ91D magnesium alloy was cast in solid plaster mould using vacuum assistance. The influence of process parameters and wall thickness on the microstructure and tensile properties of cast specimens was studied. Within the range of experimental parameters, it was found that casting and mould preheating temperatures have minor influence on mechanical properties. However, gating design proved to

S. Lun Sin; D. Dub; R. Tremblay

2008-01-01

280

Development and evaluation of a magnesium-zinc-strontium alloy for biomedical applications--alloy processing, microstructure, mechanical properties, and biodegradation.  

PubMed

A new biodegradable magnesium-zinc-strontium (Mg-Zn-Sr) alloy was developed and studied for medical implant applications. This first study investigated the alloy processing (casting, rolling, and heat treatment), microstructures, mechanical properties, and degradation properties in simulated body fluid (SBF). Aging treatment of the ZSr41 alloy at 175 C for 8h improved the mechanical properties when compared to those of the as-cast alloy. Specifically, the aged ZSr41 alloy had an ultimate tensile strength of 270 MPa, Vickers hardness of 71.5 HV, and elongation at failure of 12.8%. The mechanical properties of the ZSr41 alloy were superior as compared with those of pure magnesium and met the requirements for load-bearing medical implants. Furthermore, the immersion of the ZSr41 alloy in SBF showed a degradation mode that progressed cyclically, alternating between pitting and localized corrosion. The steady-state average degradation rate of the aged ZSr41 alloy in SBF was 0.96 g/(m(2)hr), while the pH of SBF immersion solution increased. The corrosion current density of the ZSr41 alloy in SBF solution was 0.41 mA/mm(2), which was much lower than 1.67 mA/mm(2) for pure Mg under the same conditions. In summary, compared to pure Mg, the mechanical properties of the new ZSr41 alloy improved while the degradation rate decreased due to the addition of Zn and Sr alloying elements and specific processing conditions. The superior mechanical properties and corrosion resistance of the new ZSr41 alloy make it a promising alloy for next-generation implant applications. PMID:23910262

Guan, Ren-guo; Cipriano, Aaron F; Zhao, Zhan-yong; Lock, Jaclyn; Tie, Di; Zhao, Tong; Cui, Tong; Liu, Huinan

2013-10-01

281

Solidification, growth mechanisms, and associated properties of aluminum-silicon and magnesium lightweight casting alloys  

NASA Astrophysics Data System (ADS)

Continually rising energy prices have inspired increased interest in weight reduction in the automotive and aerospace industries, opening the door for the widespread use and development of lightweight structural materials. Chief among these materials are cast Al-Si and magnesium-based alloys. Utilization of Al-Si alloys depends on obtaining a modified fibrous microstructure in lieu of the intrinsic flake structure, a process which is incompletely understood. The local solidification conditions, mechanisms, and tensile properties associated with the flake to fiber growth mode transition in Al-Si eutectic alloys are investigated here using bridgman type gradient-zone directional solidification. Resulting microstructures are examined through quantitative image analysis of two-dimensional sections and observation of deep-etched sections showing three-dimensional microstructural features. The transition was found to occur in two stages: an initial stage dominated by in-plane plate breakup and rod formation within the plane of the plate, and a second stage where the onset of out-of-plane silicon rod growth leads to the formation of an irregular fibrous structure. Several microstructural parameters were investigated in an attempt to quantify this transition, and it was found that the particle aspect ratio is effective in objectively identifying the onset and completion velocity of the flake to fiber transition. The appearance of intricate out-of-plane silicon instability formations was investigated by adapting a perturbed-interface stability analysis to the Al-Si system. Measurements of silicon equilibrium shape particles provided an estimate of the anisotropy of the solid Si/liquid Al-Si system and incorporation of this silicon anisotropy into the model was found to improve prediction of the instability length scale. Magnesium alloys share many of the benefits of Al-Si alloys, with the added benefit of a 1/3 lower density and increased machinability. Magnesium castings often contain additions of heavier elements, such as zinc, zirconium, and rare earth elements, which significantly improve high temperature performance. However, additions of these elements can lead to macrosegregational effects in castings, which are detectable by radiographic scans. The effect of these flow-line indications on alloy mechanical properties is not well quantified. An examination of these flow-line indications and their effects on mechanical properties in three magnesiumbased casting alloys was performed here in order to determine the best practice for dealing with affected castings. Preliminary results suggest the flow-lines do not measurably impact bulk material properties. Three additional methods of characterizing three-dimensional material structures are also presented: a minimum spanning tree analysis is utilized to quantify local structure in Cu-Zr liquid phase simulations obtained from molecular dynamics; the radial distribution function is applied to directionally solidified Al-Si structures in an attempt to extract local spacing data; and the critical diameter measurement is also defined and applied to irregular eutectic Al-Si structures.

Hosch, Timothy Al

282

Rate sensitivity and tension-compression asymmetry in AZ31B magnesium alloy sheet.  

PubMed

The constitutive response of a commercial magnesium alloy rolled sheet (AZ31B-O) is studied based on room temperature tensile and compressive tests at strain rates ranging from 10(-3) to 10(3)?s(-1). Because of its strong basal texture, this alloy exhibits a significant tension-compression asymmetry (strength differential) that is manifest further in terms of rather different strain rate sensitivity under tensile versus compressive loading. Under tensile loading, this alloy exhibits conventional positive strain rate sensitivity. Under compressive loading, the flow stress is initially rate insensitive until twinning is exhausted after which slip processes are activated, and conventional rate sensitivity is recovered. The material exhibits rather mild in-plane anisotropy in terms of strength, but strong transverse anisotropy (r-value), and a high degree of variation in the measured r-values along the different sheet orientations which is indicative of a higher degree of anisotropy than that observed based solely upon the variation in stresses. This rather complex behaviour is attributed to the strong basal texture, and the different deformation mechanisms being activated as the orientation and sign of applied loading are varied. A new constitutive equation is proposed to model the measured compressive behaviour that captures the rate sensitivity of the sigmoidal stress-strain response. The measured tensile stress-strain response is fit to the Zerilli-Armstrong hcp material model. PMID:24711496

Kurukuri, Srihari; Worswick, Michael J; Ghaffari Tari, Dariush; Mishra, Raja K; Carter, Jon T

2014-05-13

283

Failure Analysis of Warm Stamping of Magnesium Alloy Sheet Based on an Anisotropic Damage Model  

NASA Astrophysics Data System (ADS)

Based on the frame work of continuum damage mechanics, a research work of anisotropic damage evolution in warm stamping process of magnesium alloy sheets has been carried out by means of a combined experimental-numerical method. The aim was to predict formability of warm stamping of AZ31 Mg alloy sheets by taking the thermal and damage effects into account. In the presented work, a temperature-dependent anisotropic yield function suitable for cold rolling sheet metals together with an anisotropic damage model was implemented into the a VUMAT subroutine for ABAQUS/EXPLICIT. The evolution of internal damage in the form of void growth and coalescence in AZ31 Mg alloy sheet was observed by means of scanning electron microscopy (SEM). Moreover, a coupled thermo-mechanical simulation of the stamping process was performed using the implemented code at different temperatures. The parameters employed in the simulation were determined by the standard tensile tests and algebraic manipulation. The overall anisotropic damage process from crack initiation to final propagation in local area of blank was simulated. Numerical results show that the prediction of the site of crack initiation and the orientation of crack propagation are consistent with the data observed in warm stamping experiments.

Zhao, P. J.; Chen, Z. H.; Dong, C. F.

2014-11-01

284

Failure Analysis of Warm Stamping of Magnesium Alloy Sheet Based on an Anisotropic Damage Model  

NASA Astrophysics Data System (ADS)

Based on the frame work of continuum damage mechanics, a research work of anisotropic damage evolution in warm stamping process of magnesium alloy sheets has been carried out by means of a combined experimental-numerical method. The aim was to predict formability of warm stamping of AZ31 Mg alloy sheets by taking the thermal and damage effects into account. In the presented work, a temperature-dependent anisotropic yield function suitable for cold rolling sheet metals together with an anisotropic damage model was implemented into the a VUMAT subroutine for ABAQUS/EXPLICIT. The evolution of internal damage in the form of void growth and coalescence in AZ31 Mg alloy sheet was observed by means of scanning electron microscopy (SEM). Moreover, a coupled thermo-mechanical simulation of the stamping process was performed using the implemented code at different temperatures. The parameters employed in the simulation were determined by the standard tensile tests and algebraic manipulation. The overall anisotropic damage process from crack initiation to final propagation in local area of blank was simulated. Numerical results show that the prediction of the site of crack initiation and the orientation of crack propagation are consistent with the data observed in warm stamping experiments.

Zhao, P. J.; Chen, Z. H.; Dong, C. F.

2014-08-01

285

Design factors influencing weldability of the Mg-4Y-3RE cast magnesium alloy  

NASA Astrophysics Data System (ADS)

Due to low density and good strength properties, magnesium alloys are increasingly used as a structural material They are used, amongst others, for large-size castings in sand moulds, pressure and precision castings. Welding and pad welding is used to repair casting defects, such as misruns, micro-shrinkage, cracks, etc. The most frequent reason for disqualifying of welded joints made to repair the castings is hot cracking which occurs as a result of tensile stresses formed in the material during welding. The Mg-4Y-3RE (WE43) alloy with addition of yttrium and rare earth and zirconium elements used for testing is creep resistant to 300C. The alloy is used in the automotive industry, for example for engine blocks and in aerospace industry for gearbox housings. This paper describes the welding and remelting tests of the Mg-4Y-3RE (WE43) castings in conditions of constant and variable stiffness. It has been concluded that hot cracks are formed as a result of eutectic melting in the areas of contact of ? - Mg solid solution crystals.

Kierzek, A.; Adamiec, J.

2011-05-01

286

Biocorrosion resistance of coated magnesium alloy by microarc oxidation in electrolyte containing zirconium and calcium salts  

NASA Astrophysics Data System (ADS)

The key to use magnesium alloys as suitable biodegradable implants is how to adjust their degradation rates. We report a strategy to prepare biocompatible ceramic coating with improved biocorrosion resistance property on AZ91D alloy by microarc oxidation (MAO) in a silicate-K2ZrF6 solution with and without Ca(H2PO4)2 additives. The microstructure and biocorrosion of coatings were characterized by XRD and SEM, as well as electrochemical and immersion tests in simulated body fluid (SBF). The results show that the coatings are mainly composed of MgO, Mg2SiO4, m-ZrO2 phases, further Ca containing compounds involve the coating by Ca(H2PO4)2 addition in the silicate-K2ZrF6 solution. The corrosion resistance of coated AZ91D alloy is significantly improved compared with the bare one. After immersing in SBF for 28 d, the Si-Zr5-Ca0 coating indicates a best corrosion resistance performance.

Wang, Ya-Ming; Guo, Jun-Wei; Wu, Yun-Feng; Liu, Yan; Cao, Jian-Yun; Zhou, Yu; Jia, De-Chang

2014-09-01

287

Tribology and Tool Wear of Hot Dip Galvanized Zinc Magnesium Alloys on Cold Rolled Steel Sheets  

NASA Astrophysics Data System (ADS)

Recently zinc based coatings on cold rolled steel with improved functionality in terms of forming and/or corrosion behaviour have been intensively investigated in the steel industry1,2,3. One of the most promising products are zinc magnesium alloys produced in hot dip galvanizing process. These coatings were already introduced in construction industry a few years ago1. With some modifications the improved properties of the coating are also interesting for automotive industry. In the present work the tribological potential of hot dip galvanized zinc magnesium coatings (HDG/ZM) produced at an industrial line under regular production, was studied in terms of sliding properties, adhesive and abrasive tool wear. First a short introduction into surface morphology of HDG/ZM will be given. For the tribological characterization of the material, which is the main topic of the contribution, different tests were performed on hot dip galvanised zinc magnesium material and results were compared with classic hot dip galvanized zinc coating (HDG/Z). The investigations are mainly based on the strip draw test which allows the determination of the friction coefficient directly by using a constant contact pressure. Deep drawing property was tested by forming model cups. The abrasive tool wear was tested using a standard test for material used in automotive industry. The adhesive tool wear was investigated by characterizing the coating material transferred to the tool in the strip draw test. All performed tests show an improved drawability of HDG/ZM compared to classical HDG/Z reference material. However the most promising difference between HDG/ZM and HDG/Z is that galling was found to be less for HDG/ZM than for HDG/Z. Therefore HDG/ZM is an interesting system not only with respect to corrosion protection but also in terms of tribology and provides clear advantages in formability.

Raab, A. E.; Berger, E.; Freudenthaler, J.; Leomann, F.; Walch, C.

2011-05-01

288

Tribology and Tool Wear of Hot Dip Galvanized Zinc Magnesium Alloys on Cold Rolled Steel Sheets  

SciTech Connect

Recently zinc based coatings on cold rolled steel with improved functionality in terms of forming and/or corrosion behaviour have been intensively investigated in the steel industry. One of the most promising products are zinc magnesium alloys produced in hot dip galvanizing process. These coatings were already introduced in construction industry a few years ago. With some modifications the improved properties of the coating are also interesting for automotive industry. In the present work the tribological potential of hot dip galvanized zinc magnesium coatings (HDG/ZM) produced at an industrial line under regular production, was studied in terms of sliding properties, adhesive and abrasive tool wear.First a short introduction into surface morphology of HDG/ZM will be given. For the tribological characterization of the material, which is the main topic of the contribution, different tests were performed on hot dip galvanised zinc magnesium material and results were compared with classic hot dip galvanized zinc coating (HDG/Z). The investigations are mainly based on the strip draw test which allows the determination of the friction coefficient directly by using a constant contact pressure. Deep drawing property was tested by forming model cups. The abrasive tool wear was tested using a standard test for material used in automotive industry. The adhesive tool wear was investigated by characterizing the coating material transferred to the tool in the strip draw test.All performed tests show an improved drawability of HDG/ZM compared to classical HDG/Z reference material. However the most promising difference between HDG/ZM and HDG/Z is that galling was found to be less for HDG/ZM than for HDG/Z. Therefore HDG/ZM is an interesting system not only with respect to corrosion protection but also in terms of tribology and provides clear advantages in formability.

Raab, A. E.; Berger, E.; Freudenthaler, J.; Leomann, F.; Walch, C. [Research and Development, Forming Technology voestalpine Stahl GmbH, Voest-Alpine Strasse 3, 4031 Linz (Austria)

2011-05-04

289

Constitutive acoustic-emission elastic-stress behavior of magnesium alloy  

NASA Technical Reports Server (NTRS)

Repeated laoding and unloading of a magnesium alloy below the macroscopic yield stress result in continuous acoustic emissions which are generally repeatable for a given specimen and which are reproducible between different specimens having the same load history. An acoustic emission Bauschinger strain model is proposed to describe the unloading emission behavior. For the limited range of stress examined, loading and unloading stress delays of the order of 50 MN/sq m are observed, and they appear to be dependent upon the direction of loading, the stress rate, and the stress history. The stress delay is hypothesized to be the manifestation of an effective friction stress. The existence of acoustic emission elastic stress constitutive relations is concluded, which provides support for a previously proposed concept for the monitoring of elastic stresses by acoustic emission.

Williams, J. H., Jr.; Emerson, G. P.

1977-01-01

290

Monitoring evolution of stress in individual grains and twins in a magnesium alloy aggregate  

SciTech Connect

Crystallographic twinning is a strain accommodation mechanism extensively observed in low-symmetry crystals. In hexagonal metals (HCP), twinning transformation results in abrupt crystallographic reorientation of grain domains, and strongly affects the mechanical response, texture evolution, plastic formability and internal stress evolution. Recent fundamental advances in constitutive descriptions ofHCP's indicate the need for a basic characterization oftwinning mechanisms. Here we use the emerging technique of 3DXRD [9-12], for the first time, to in-situ monitor the twin nucleation and growth in individual grains inside the bulk of a magnesium alloy aggregate. At the same time, we accomplish the first direct measurement of the evolving triaxial stress states in both the parent grain and its twin. We show that the stress state of the twin is radically different from that of the parent and interpret the three-dimensional response in the light of the constraints placed on the parent and the twin by the surrounding polycrystalline medium.

Clausen, Bjorn [Los Alamos National Laboratory; Aydiner, Cahit C [Los Alamos National Laboratory; Tome, Carlos N [Los Alamos National Laboratory; Brown, Donald W [Los Alamos National Laboratory; Bernier, Joel V [LLNL; Lienert, Ulrich [ANL

2008-01-01

291

Influence of edge effects on local corrosion rate of magnesium alloy/mild steel galvanic couple.  

PubMed

The effect of the insulator-mixed-material edge on the galvanic corrosion rate of magnesium alloy (AE44)-mild steel (MS) couple is experimentally studied using scanning vibrating electrode technique (SVET), profilometry, and classical electrochemistry. The local and average corrosion rates estimated from the experimental depth of anodic attack profile of AE44-MS couple are validated by 2D and 3D corrosion numerical models. Our study demonstrates experimentally and theoretically that the presence of the insulator edge increases the local current density, which enhances the corrosion rate. The extent of the local corrosion rate enhancement and its effect on the overall corrosion rate of the mixed material is discussed and depends on the mixed material's geometry and the edge type. PMID:23046096

Trinh, Dao; Dauphin Ducharme, Philippe; Mengesha Tefashe, Ushula; Kish, Joseph R; Mauzeroll, Janine

2012-11-20

292

Grain Refinement of AZ31 Magnesium Alloy Weldments by AC Pulsing Technique  

NASA Astrophysics Data System (ADS)

The current study has investigated the influence of alternating current pulsing on the structure and mechanical properties of AZ31 magnesium alloy gas tungsten arc (GTA) weldments. Autogenous full penetration bead-on-plate GTA welds were made under a variety of conditions including variable polarity (VP), variable polarity mixed (VPM), alternating current (AC), and alternating current pulsing (ACPC). AC pulsing resulted in significant refinement of weld metal when compared with the unpulsed conditions. AC pulsing leads to relatively finer and more equiaxed grain structure in GTA welds. In contrast, VP, VPM, and AC welding resulted in predominantly columnar grain structures. The reason for this grain refinement may be attributed to the periodic variations in temperature gradient and solidification rate associated with pulsing as well as weld pool oscillation observed in the ACPC welds. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, tensile strength, and ductility.

Kishore Babu, N.; Cross, C. E.

2012-11-01

293

Metallurgical Evaluation of AZ31B-H24 Magnesium Alloy Friction Stir Welds  

NASA Astrophysics Data System (ADS)

Friction Stir welding of 3.175 mm (0.125 in.) thick plates of AZ31-H24 magnesium alloy was performed using several travel velocities and tool-rotation speeds. After production the welds were cross-sectioned and a metallurgical characterization was performed using optical microscopy, and scanning electron microscopy. Assessment of the weld nugget or stirred zone shows evidence of dynamic recrystallization and the start of grain growth in some spots of this region compared to the parent metal. Recrystallization was identified in the thermomechanically affected zone (TAZ) as well. The mechanical properties of the weld are correlated with the corresponding microstructures present in the weld nugget and TMAZ. Corrosion resistance of the weld was assessed using Electrochemical Impedance Spectroscopy (EIS) techniques and immersion tests in a corrosive environment; it showed better corrosion resistance than the base metal.

Pareek, M.; Polar, A.; Rumiche, F.; Indacochea, J. E.

2007-10-01

294

Multi-Objective Optimization of a Wrought Magnesium Alloy for High Strength and Ductility  

SciTech Connect

An optimization technique is coupled with crystal plasticity based finite element (CPFE) computations to aid the microstructural design of a wrought magnesium alloy for improved strength and ductility. The initial microstructure consists of a collection of sub-micron sized grains containing deformation twins. The variables used in the simulations are crystallographic texture, and twin spacing within the grains. It is assumed that plastic deformation occurs mainly by dislocation slip on two sets of slip systems classified as hard and soft modes. The hard modes are those slip systems that are inclined to the twin planes and the soft mode consists of dislocation glide along the twin plane. The CPFE code calculates the stress-strain response of the microstructure as a function of the microstructural parameters and the length-scale of the features. A failure criterion based on a critical shear strain and a critical hydrostatic stress is used to define ductility. The optimization is based on the sequential generation of an initial population defined by the texture and twin spacing variables. The CPFE code and the optimizer are coupled in parallel so that new generations are created and analyzed dynamically. In each successive generation, microstructures that satisfy at least 90% of the mean strength and mean ductility in the current generation are retained. Multiple generation runs based on the above procedure are carried out in order to obtain maximum strength-ductility combinations. The implications of the computations for the design of a wrought magnesium alloy are discussed. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.

Radhakrishnan, Balasubramaniam [ORNL; Gorti, Sarma B [ORNL; Patton, Robert M [ORNL; Simunovic, Srdjan [ORNL

2013-01-01

295

Potentiostatic control of ionic liquid surface film formation on ZE41 magnesium alloy.  

PubMed

The generation of potentially corrosion-resistant films on light metal alloys of magnesium have been investigated. Magnesium alloy, ZE41 [Mg-Zn-Rare Earth (RE)-Zr, nominal composition approximately 4 wt % Zn, approximately 1.7 wt % RE (Ce), approximately 0.6 wt % Zr, remaining balance, Mg], was exposed under potentiostatic control to the ionic liquid trihexyl(tetradecyl)phosphonium diphenylphosphate, denoted [P(6,6,6,14)][DPP]. During exposure to this IL, a bias potential, shifted from open circuit, was applied to the ZE41 surface. Electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) were used to monitor the evolution of film formation on the metal surface during exposure. The EIS data indicate that, of the four bias potentials examined, applying a potential of -200 mV versus OCP during the exposure period resulted in surface films of greatest resistance. Both EIS measurements and scanning electron microscopy (SEM) imaging indicate that these surfaces are substantially different to those formed without potential bias. Time of flight-secondary ion mass spectrometry (ToF-SIMS) elemental mapping of the films was utilized to ascertain the distribution of the ionic liquid cationic and anionic species relative to the microstructural surface features of ZE41 and indicated a more uniform distribution compared with the surface following exposure in the absence of a bias potential. Immersion of the treated ZE41 specimens in a chloride contaminated salt solution clearly indicated that the ionic liquid generated surface films offered significant protection against pitting corrosion, although the intermetallics were still insufficiently protected by the IL and hence favored intergranular corrosion processes. PMID:20433137

Efthimiadis, Jim; Neil, Wayne C; Bunter, Andrew; Howlett, Patrick C; Hinton, Bruce R W; MacFarlane, Douglas R; Forsyth, Maria

2010-05-01

296

Modeling and experimental study on heat transfer in squeeze casting of magnesium alloy AM60 and aluminum alloy A443  

NASA Astrophysics Data System (ADS)

This study developed a solution algorithm based on the function specification method to solve the inverse heat conduction equations. By this solution, the casting-die interfacial heat transfer coefficients (IHTC) in light metal squeeze castings were determined accurately and the pressurized solidification was simulated precisely. This goal was accomplished in the four stages. First, a model was developed to simulate fluid flow in forced convection and heat transfer in pressurized solidification of a cylindrical simple shape squeeze casting. Pressure-dependent heat transfer coefficients (HTC) and non-equilibrium solidification temperatures were determined by experimental measurements. With the measured HTC and temperatures under the different pressures, the temperature distributions and the cooling behaviours of squeeze cast were simulated. In the second stage, a different wall-thickness 5-step casting mould was designed, and squeeze casting of magnesium alloy AM60 was performed under an applied pressure 30, 60 and 90 MPa in a hydraulic press. With measured temperatures, heat fluxes and IHTCs were evaluated using the polynomial curve fitting method and numerical inverse method. The accuracy of these curves was analyzed by the direct modeling calculation. The results indicated that heat flux and IHTCs determined by the inverse method were more accurately than those from the extrapolated fitting method. In the third stage, the inverse method was applied to an aluminum alloy A443 and magnesium alloy AM60. As the applied hydraulic pressure increased, the IHTC peak value of each step was increased accordingly. Compared to the thin steps at the upper cavity, the relatively thick steps attained higher peak IHTCs and heat fluxes values due to high local pressures and high melt temperature. The empirical equations relating IHTC to the local pressures and solidification temperature at the casting surface were derived and summarized. Finally, the IHTC values calculated by inverse method were applied to simulate the solidification process of the 5-step casting model. The results showed that the numerical calculated temperatures were in well agreement with experimental ones. It is adequately demonstrated that the inverse method is a feasible and effective tool for determination of the IHTC.

Sun, Zhizhong

297

The study of microstructure and mechanical properties of twin-roll cast AZ31 magnesium alloy after constrained groove pressing  

NASA Astrophysics Data System (ADS)

Microstructure investigation and microhardness mapping were done on the material with ultra-fine grained structure prepared by constrained groove pressing of twin-roll cast AZ31 magnesium strips. The microstructure observations showed significant drop of the grain size from 200 gm to 20 gm after constrained groove pressing. Moreover, the heterogeneities in the microhardness along the cross-section observed in the as-cast strip were replaced by the bands of different microhardness in the constrained groove pressed material. It is shown that the constrained groove pressing technique is a good tool for the grain refinement of magnesium alloys.

Zimina, M.; Bohlen, J.; Letzig, D.; Kurz, G.; Cieslar, M.; Znk, J.

2014-08-01

298

The processing of difficult-to-work alloys by ECAP with an emphasis on magnesium alloys  

Microsoft Academic Search

The equal-channel angular pressing of pure metals is conducted most expeditiously by pressing at room temperature using a die with a channel angle of 90. However, these conditions may lead to cracking of the billets or massive segmentation when applied to hard and difficult-to-work alloys. This paper uses finite element modeling to explore the procedures for successfully pressing these more

Roberto B. Figueiredo; Paulo R. Cetlin; Terence G. Langdon

2007-01-01

299

Influence of coating bath chemistry on the deposition of 3-mercaptopropyl trimethoxysilane films deposited on magnesium alloy.  

PubMed

Magnesium alloys have a low specific density and a high strength to weight ratio. This makes them sought after light weight construction materials for automotive and aerospace applications. These materials have also recently become of interest for biomedical applications. Unfortunately, the use of magnesium alloys in many applications has been limited due to its high susceptibility to corrosion. One way to improve the corrosion resistance of magnesium alloys is through the deposition of protective coatings. Many of the current pretreatments/coatings available use toxic chemicals such as chromates and hydrofluoric acid. One possible environmentally friendly alternative is organosilane coatings which have been shown to offer significant corrosion protection to both aluminum alloys and steels. Organosilanes are ambifunctional molecules that are capable of covalent bonding to metal hydroxide surfaces. In order for covalent bonding to occur, the organosilane must undergo hydrolysis in the coating bath followed by a condensation reaction with the surface. There are a number of factors that influence the rates of these reactions such as pH and concentration of reactants. These factors can also influence competing reactions in solution such as oligomerization. The rates of hydrolysis and condensation of 3-mercaptopropyltrimethoxy silane in methanol have been analyzed with (1)H NMR and ATR-FTIR. The results indicate that organosilane oligomers begin to form in solution before the molecules are fully hydrolyzed. The organosilane films deposited on magnesium alloy AZ91 at a variety of concentrations and pre-hydrolysis times were characterized with a combination of ATR-FTIR, ellipsometry and SEM/EDS. The results show that both organosilane film thickness and uniformity are affected by the chemistry occurring in the coating bath prior to deposition. PMID:20064643

Scott, A F; Gray-Munro, J E; Shepherd, J L

2010-03-15

300

Development of Magnesium Flat Cell Battery.  

National Technical Information Service (NTIS)

A second series of five cell stacks was assembled using AZ21X1 magnesium alloy anode plates. The six lots included increased quantities of magnesium bromide and magnesium perchlorate electrolytes, two concentrations of magnesium perchlorate electrolyte an...

P. F. Albert

1967-01-01

301

Characterization of AZ31B wrought magnesium alloy joints welded by high power fiber laser  

SciTech Connect

A 6 kW fiber laser is used to weld AZ31B wrought magnesium alloy and the characterization of welded joints are studied by the observations of bead size, microstructure and mechanical properties. The accepted joints without macro-defects can be obtained when the laser power is in the range of 2.5 to 4.0 kW. Typical hexagonal dendrites are observed in the fusion zone, whose average semi-axis length increases with increasing heat input or decreasing welding speed. The minimum ultimate tensile strength of welded joints reaches 227 MPa, 94.6% of the base metal. And when the heat input reduces to 48 J/mm or lower, the joints are fractured in the base metal, showing stronger failure strength compared to the base metal. For the joints ruptured in the weld metal, the fracture surface is characterized by a ductile-brittle mixed pattern consisting of both dimples and cleavages. Finally, the formation mechanism of pore in the welds is discussed and summarized by the pore morphologies on the fracture surface. - Highlights: {yields} Accepted joints of AZ31B Mg alloy are produced by high power fiber laser. {yields} Optimal welding parameters are summarized by experimental observations. {yields} Obvious hexagonal dendrites are observed in the fusion zone. {yields} The joints are stronger than base metal as the heat input is lower than 48 J/mm. {yields} Pore formation mechanism of welded joints is discussed and summarized.

Wang Zemin; Gao Ming, E-mail: mgao@mail.hust.edu.cn; Tang Haiguo; Zeng Xiaoyan

2011-10-15

302

Improving the packing density of calcium phosphate coating on a magnesium alloy for enhanced degradation resistance.  

PubMed

In this study, an attempt was made to improve the packing density of calcium phosphate (CaP) coating on a magnesium alloy by tailoring the coating solution for enhanced degradation resistance of the alloy for implant applications. An organic solvent, ethanol, was added to the coating solution to decrease the conductivity of the coating solution so that hydrogen bubble formation/bursting reduces during the CaP coating process. Experimental results confirmed that ethanol addition to the coating solution reduces the conductivity of the solution and also decreases the hydrogen evolution/bubble bursting. In vitro electrochemical experiments, that is, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization showed that CaP coating produced in 30% (v/v) ethanol containing coating solution (3E) exhibits significantly higher degradation resistance (i.e., ~50% higher polarization resistance and ~60% lower corrosion current) than the aqueous solution coating. Scanning electron microscope (SEM) analysis of the coatings revealed that the packing of 3E coating was denser than that of aqueous coating, which can be attributed to the lower hydrogen evolution in the former than in the latter. Further increase in the ethanol content in the coating solution was not beneficial; in fact, the coating produced in 70% (v/v) ethanol containing solution (7E) showed degradation resistance much inferior to that of the aqueous coating, which is due to low thickness of 7E coating. PMID:23008190

Kannan, M Bobby

2013-05-01

303

ZM-21 magnesium alloy corrosion properties and cryogenic to elevated temperature mechanical properties  

NASA Technical Reports Server (NTRS)

The mechanical properties of bare ZM-21 magnesium alloy flat tensile specimens were determined for test temperatures of +400 F, +300 F, +200 F, +80 F, 0 F, -100 F, -200 F, and -320 F. The ultimate tensile and yield strengths of the material increased with decreasing temperature with a corresponding reduction in elongation values. Stress corrosion tests performed under: (1) MSFC atmospheric conditions; (2) 95% relative humidity; and (3) submerged in 100 ppm chloride solution for 8 weeks indicated that the alloy is not susceptible to stress corrosion. The corrosion tests indicated that the material is susceptible to attack by crevice corrosion in high humidity and chemical type attack by chloride solution. Atmospheric conditions at MSFC did not produce any adverse effects on the material, probably due to the rapid formation of a protective oxide coating. In both the mechanical properties and the stress corrosion evaluations the test specimens which were cut transverse to the rolling direction had superior properties when compared to the longitudinal properties.

Montana, J. W.; Nelson, E. E.

1972-01-01

304

Microstructure and Fatigue Properties of a Friction Stir Lap Welded Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Friction stir welding (FSW), being an enabling solid-state joining technology, can be suitably applied for the assembly of lightweight magnesium (Mg) alloys. In this investigation, friction stir lap welded (FSLWed) joints of AZ31B-H24 Mg alloy were characterized in terms of the welding defects, microstructure, hardness, and fatigue properties at various combinations of tool rotational rates and welding speeds. It was observed that the hardness decreased from the base metal (BM) to the stir zone (SZ) across the heat-affected zone (HAZ) and thermomechanically affected zone (TMAZ). The lowest value of hardness appeared in the SZ. With increasing tool rotational rate or decreasing welding speed, the average hardness in the SZ decreased owing to increasing grain size, and a Hall-Petch-type relationship was established. Fatigue fracture of the lap welds always occurred at the interface between the SZ and TMAZ on the advancing side where a larger hooking defect was present (in comparison with the retreating side). The welding parameters had a significant influence on the hook height and the subsequent fatigue life. A relatively "cold" weld, conducted at a rotational rate of 1000 rpm and welding speed of 20 mm/s, gave rise to almost complete elimination of the hooking defect, thus considerably (over two orders of magnitude) improving the fatigue life. Fatigue crack propagation was basically characterized by the formation of fatigue striations concomitantly with secondary cracks.

Naik, B. S.; Chen, D. L.; Cao, X.; Wanjara, P.

2013-08-01

305

Microstructure Evolution in As-Cast and SIMA-Processed AE42 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

In the present study, microstructural evolutions of AE42 magnesium alloy via strain-induced melt activation process and the effect of different process parameters are studied. Scanning electron microscope, metallographic observations, and quantitative metallographic method were used for microstructural characterization. The results show that the consumption of supersaturated aluminum during partial remelting led to a decrease in Al/RE ratio and consequently blocky shape Al2RE starts to appear in the microstructure. Furthermore, it was seen that lanthanum and praseodymium did not contribute in precipitate formation and only improved the hardness of the matrix. The effect of compression ratio on the microstructure of treated alloys was confirmed through the increase of both liquid fraction and entrapped pool as well as the kinetic of microstructural changes. Moreover, the effect of compression ratio and holding time on shape factor, liquid fraction, and particle size of the globular structure were measured. It was found that the best result could be achieved at 35% deformation and 40 min holding of the samples at 610 C.

Nayyeri, Mohammad Javad; Dehghani, Kamran

2014-09-01

306

Shock response of boron carbide based composites infiltrated with magnesium alloys  

NASA Astrophysics Data System (ADS)

The fully dense composites were obtained by vacuum infiltrating the boron carbide compacts (80% green density) with liquid AZ91 magnesium alloy (850 ^oC) and with the melt of 50/50 AZ91-silicon mixture (1050 ^oC). The densities, the elastic moduli and the Vickers hardness values of the obtained composites were, respectively, 2.44 g/cm^3 and 2.54 g/cm^3, 300 and 350 GPa, and 1200 and 1800 HV. The impact response of the composites was studied in a series of VISAR -instrumented planar impact experiments with velocities of W and Cu impactors ranged from 100 to 1000 m/s. It was found that velocity histories recorded for the composites produced by infiltration with Mg-Si alloy contain a distinct elastic precursor front followed by a plastic ramp. On the contrary, the velocity histories of the composites infiltrated with AZ91 do not display any step-like front; the amplitude of the elastic wave grows gradually from zero level and transforms smoothly into the plastic front. The influence of the composites microstructure on the compressive elastic-plastic behavior and on the dynamic tensile (spall) strength is discussed.

Kafri, Mathan; Dariel, Moshe; Frage, Nahum; Zaretsky, Eugene

2011-06-01

307

Transient Heat and Material Flow Modeling of Friction Stir Processing of Magnesium Alloy using Threaded Tool  

SciTech Connect

A three-dimensional transient computational fluid dynamics (CFD) model was developed to investigate the material flow and heat transfer during friction stir processing (FSP) in an AZ31B magnesium alloy. The material was assumed to be a non-Newtonian viscoplastic fluid, and the Zener-Hollomon parameter was used to describe the dependence of material viscosity on temperature and strain rate. The material constants used in the constitutive equation were determined experimentally from compression tests of the AZ31B Mg alloy under a wide range of strain rates and temperatures. A dynamic mesh method, combining both Lagrangian and Eulerian formulations, was used to capture the material flow induced by the movement of the threaded tool pin. Massless inert particles were embedded in the simulation domain to track the detailed history of material flow. The actual FSP was also carried out on a wrought Mg plate where temperature profiles were recorded by embedding thermocouples. The predicted transient temperature history was found to be consistent with that measured during FSP. Finally, the influence of the thread on the simulated results of thermal history and material flow was studied by comparing two models: one with threaded pin and the other with smooth pin surface.

Yu, Zhenzhen [ORNL; Zhang, Wei [ORNL; Choo, Hahn [ORNL; Feng, Zhili [ORNL

2012-01-01

308

Effect of magnesium on the lead induced corrosion and SCC of alloy 800 in neutral crevice solution at high temperature  

NASA Astrophysics Data System (ADS)

Dissolved magnesium species in the feed water reduce the incidence of lead-induced stress corrosion cracking (PbSCC) of Alloy 800. The passivity of material was improved by replacing a part of chlorides in the lead-contaminated chemistry with magnesium chloride, as indicated by: (1) a higher pitting potential; (2) lower passive current densities; (3) a film structure with less defects and more spinel oxides. According to the constant extension rate tensile (CERT) tests conducted in the neutral crevice solutions at 300 C, lead contamination would reduce the ultimate tensile strength (UTS) and elongation of material. The CERT test results were in agreement with the fracture morphology observations. Magnesium addition significantly reduced the detrimental effect of lead contamination.

Palani, A.; Lu, B. T.; Tian, L. P.; Luo, J. L.; Lu, Y. C.

2010-01-01

309

An A Priori Hot-Tearing Indicator Applied to Die-Cast Magnesium-Rare Earth Alloys  

NASA Astrophysics Data System (ADS)

Hot-tearing susceptibility is an important consideration for alloy design. Based on a review of previous research, an a priori indicator for the prediction of an alloy's hot-tearing susceptibility is proposed in this article and is applied to a range of magnesium-rare earth (RE)-based alloys. The indicator involves taking the integral over the solid fraction/temperature curve between the temperature when feeding becomes restricted (coherency) and that when a three-dimension network of solid is formed (coalescence). The hot-tearing propensity of Mg-RE alloys is found to vary greatly depending on which RE is primarily used, due to the difference in the solidification range. Mg-Nd alloys are the most susceptible to hot tearing, followed by Mg-Ce-based alloys, while Mg-La alloys show almost no hot tearing. The proposed indicator can be well applied to hot-tearing propensity of the Mg-RE alloys. It is expected that the indicator could be used as an estimation of the relative hot-tearing propensity in other alloy systems as well.

Easton, Mark A.; Gibson, Mark A.; Zhu, Suming; Abbott, Trevor B.

2014-07-01

310

Abnormal macropore formation during double-sided gas tungsten arc welding of magnesium AZ91D alloy  

SciTech Connect

One of the major concerns during gas tungsten arc (GTA) welding of cast magnesium alloys is the presence of large macroporosity in weldments, normally thought to occur from the presence of gas in the castings. In this study, a double-sided GTA welding process was adopted to join wrought magnesium AZ91D alloy plates. Micropores were formed in the weld zone of the first side that was welded, due to precipitation of H{sub 2} as the mushy zone freezes. When the reverse side was welded, the heat generated caused the mushy zone in the initial weld to reform. The micropores in the initial weld then coalesced and expanded to form macropores by means of gas expansion through small holes that are present at the grain boundaries in the partially melted zone. Macropores in the partially melted zone increase with increased heat input, so that when a filler metal is used the macropores are smaller in number and in size.

Shen Jun [College of Mechanical Engineering, Chongqing University, Chongqing 400044 (China)], E-mail: shenjun2626@163.com; You Guoqiang; Long Siyuan [College of Mechanical Engineering, Chongqing University, Chongqing 400044 (China); Pan Fusheng [College of Material Science and Engineering, Chongqing University, Chongqing 400044 (China)

2008-08-15

311

Magnesium surface segregation and oxidation in AlMg alloys studied with local probe scanning Auger-scanning electron microscopy  

Microsoft Academic Search

Magnesium surface segregation and oxidation were investigated in AlMg alloys with a surface texture characterized by branched and dendritic disordered features of low Mg concentration having a lateral 2-D fractal dimension DB?1.77. Phase separation of areas with high (?38% at.) and low (?14% at.) Mg content allows direct observation of distinct differences in Mg surface segregation and oxidation across disordered

D. T. L. van Agterveld; G. Palasantzas; J. Th. M. De Hosson

1999-01-01

312

Mechanisms of plastic deformation in AZ31 magnesium alloy investigated by acoustic emission and transmission electron microscopy  

Microsoft Academic Search

The effect of deformation conditions on plastic deformation and acoustic emission (AE) in hot-rolled magnesium alloy AZ31 has been investigated in the temperature range of 20200C by constant strain rate tensile tests. Two sets of samples differing in the preheating temperature before individual passes of hot rolling have been studied. Both the yield stress and the tensile strength decrease with

Milo Jane?ek; Robert Krl; Patrik Dobro?; Frantiek Chmelk; Vladimr upk; Frank Hollnder

2007-01-01

313

Tribological properties of duplex MAO\\/DLC coatings on magnesium alloy using combined microarc oxidation and filtered cathodic arc deposition  

Microsoft Academic Search

The combined microarc oxidation (MAO) and filtered cathode arc deposition process was used to deposit duplex MAO\\/DLC coating on AM60B magnesium alloy. The microstructure and composition of the resulting duplex coating were analyzed by Raman spectroscopy, X-ray photoelectron spectroscope (XPS) and scanning electron microscope (SEM). The tribological behaviors of the duplex coating were studied by ball-on-disk friction testing. It is

Jun Liang; Peng Wang; Litian Hu; Jingcheng Hao

2007-01-01

314

Mechanical and fracture properties of an AZ91 Magnesium alloy reinforced by Si and SiC particles  

Microsoft Academic Search

A commercial AZ91 magnesium alloy (nominal composition Mg9%Al; 1%Zn; 0.3%Mn, balance Mg in weight percent) reinforced with SiC particles and modified by the addition of Si has been used in this study. Formation of an in situ composite (MgMg2Si) results in strong bonding between Mg2Si and the matrix interface. Samples were deformed in compression in the temperature interval from room

Z. Trojanov; V. Grtnerov; A. Jger; A. Nmen; M. Chalupov; P. Pal?ek; P. Luk?

2009-01-01

315

Corrosion resistance of AZ91D magnesium alloy with electroless plating pretreatment and NiTiO 2 composite coating  

Microsoft Academic Search

In this paper, a protective multilayer coating, with electroless Ni coating as bottom layer and electrodeposited NiTiO2 composite coating as top layer, was successfully prepared on AZ91D magnesium alloy by a combination of electroless and electrodeposition techniques. Scanning electron microscopy and X-ray diffraction were employed to investigate the surface, cross-section morphologies and phase structure of coatings, respectively. The electrochemical corrosion

Shiyan Zhang; Qing Li; Xiaokui Yang; Xiankang Zhong; Yan Dai; Fei Luo

2010-01-01

316

Ductility of an aluminum4.4 wt. pct. magnesium alloy at warm- and hot-working temperatures  

Microsoft Academic Search

An AA5182 aluminum alloy sheet, containing 4.4wt. pct. magnesium, was subjected to tensile testing at temperatures from 100 to 400 C under strain rates from 10?3 up to 310?2s?1. Flow stress, tensile elongation and reduction-in-area were measured and are correlated with deformation and fracture mechanisms. At slow strain rates and elevated temperatures, solute-drag creep produces large tensile elongations, up to

Jung-Kuei Chang; Ken Takata; Koji Ichitani; Eric M. Taleff

2010-01-01

317

On the influence of process variables on the thermal conditions and properties of high pressure die-cast magnesium alloys  

Microsoft Academic Search

The influence of pressure and velocity in high-pressure magnesium die casting on the thermal conditions and on the casting properties is studied. Specimens with the shape of a tensile test plate with a thickness of 12 mm and a length of 295 mm were cast using the alloys AM20HP, AM50HP, AS41, AE42, AZ91HP. Two gate velocities of the liquid metal

Nahed A. El-Mahallawy; Mohamed A Taha; Engenius Pokora; Friedrich Klein

1998-01-01

318

Microstructure and mechanical properties of ZA104 (0.30.6Ca) die-casting magnesium alloys  

Microsoft Academic Search

In this paper, the microstructure of die-cast and slowly cooled specimens of two new experimental magnesium alloys (ZA104 + 0.3Ca and ZA104 + 0.6Ca) is examined. Microanalysis of specimens has revealed the presence of ?-Mg phase (matrix) and two intermetallic compounds containing calcium with different Zn\\/Al ratios. These compounds, which have a crystal structure close to that of ? phase

Z. Zhang; R. Tremblay; D. Dub

2004-01-01

319

Knitting of dislocation networks by means of stress-induced climb in an aluminium-magnesium alloy  

Microsoft Academic Search

An aluminium-2% magnesium alloy solidified to a pronounced sub-structure shows, when tested in tension, at approximately 300C an abrupt change in the mode of plastic deformation. Above this transition temperature, where the flow stress maintains a steady value up to high strains, restoration is suggested to occur by means of a stress-induced knitting process combined with dislocation annihilation, when vacancies

V. K. Lindroos; H. M. Miekk-oja

1968-01-01

320

The effect of zirconium grain refinement on the corrosion behaviour of magnesium-rare earth alloy MEZ  

Microsoft Academic Search

Corrosion performance of sand cast magnesium alloy MEZ was investigated for unrefined (MEZU) and Zr-grain-refined (MEZR) microstructures in 5% NaCl solution using salt spray, immersion, in situ examination of the corrosion morphology, ESEM, electron probe microanalysis, hydrogen evolution and polarisation curves. MEZU demonstrated higher rates of anodic dissolution and cathodic hydrogen evolution than MEZR. The central zirconium-rich areas within the

Guangling Song; David StJohn

2002-01-01

321

Surface composition, microstructure and corrosion resistance of AZ31 magnesium alloy irradiated by high-intensity pulsed ion beam  

SciTech Connect

High-intensity pulsed ion beam (HIPIB) irradiation of AZ31 magnesium alloy is performed and electrochemical corrosion experiment of irradiated samples is carried out by using potentiodynamic polarization technology in order to explore the effect of HIPIB irradiation on corrosion resistance of magnesium alloy. The surface composition, cross-sectional morphology and microstructure are characterized by using electron probe microanalyzer, optical microscope and transmission electron microscope, respectively. The results indicated that HIPIB irradiation leads to a significant improvement in corrosion resistance of magnesium alloy, in terms of the considerable increase in both corrosion potential and pitting breakdown potential. The microstructural refinement and surface purification induced by HIPIB irradiation are responsible for the improved corrosion resistance. - Research Highlights: {yields} A modified layer about 30 {mu}m thick is obtained by HIPIB irradiation. {yields} Selective ablation of element/impurity phase having lower melting point is observed. {yields} More importantly, microstructural refinement occurred on the irradiated surface. {yields} The modified layer exhibited a significantly improved corrosion resistance. {yields} Improved corrosion resistance is ascribed to the combined effect induced by HIPIB.

Li, P., E-mail: pli@sqnc.edu.cn [Department of Physics and Information Engineering, Shangqiu Normal University, Shangqiu 476000 (China); Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Lei, M.K., E-mail: surfeng@dlut.edu.cn [Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Zhu, X.P. [Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China)

2011-06-15

322

Electrochemical characteristics of calcium-phosphatized AZ31 magnesium alloy in 0.9 % NaCl solution.  

PubMed

Magnesium alloys suffer from their high reactivity in common environments. Protective layers are widely created on the surface of magnesium alloys to improve their corrosion resistance. This article evaluates the influence of a calcium-phosphate layer on the electrochemical characteristics of AZ31 magnesium alloy in 0.9 % NaCl solution. The calcium phosphate (CaP) layer was electrochemically deposited in a solution containing 0.1 M Ca(NO3)2, 0.06 M NH4H2PO4 and 10 ml l(-1) of H2O2. The formed surface layer was composed mainly of brushite [(dicalcium phosphate dihidrate (DCPD)] as proved by energy-dispersive X-ray analysis. The surface morphology was observed by scanning electron microscopy. Immersion test was performed in order to observe degradation of the calcium phosphatized surfaces. The influence of the phosphate layer on the electrochemical characteristics of AZ31, in 0.9 % NaCl solution, was evaluated by potentiodynamic measurements and electrochemical impedance spectroscopy. The obtained results were analysed by the Tafel-extrapolation method and equivalent circuits method. The results showed that the polarization resistance of the DCPD-coated surface is about 25 times higher than that of non-coated surface. The CaP electro-deposition process increased the activation energy of corrosion process. PMID:24477876

Hadzima, Branislav; Mhaede, Mansour; Pastorek, Filip

2014-05-01

323

Dual-beam laser welding of AZ31B magnesium alloy in zero-gap lap joint configuration  

NASA Astrophysics Data System (ADS)

Porosity within laser welds of magnesium alloys is one of the main roadblocks to achieving high quality joints. One of the causes of pore formation is the presence of pre-existing coatings on the surface of magnesium alloy such as oxide or chromate layers. In this study, single-beam and dual-beam laser heat sources are investigated in relation to mitigation of pores resulting from the presence of the as-received oxide layer on the surface of AZ31B-H24 magnesium alloy during the laser welding process. A fiber laser with a power of up to 4 kW is used to weld samples in a zero-gap lap joint configuration. The effect of dual-beam laser welding with different beam energy ratios is studied on the quality of the weld bead. The purpose of this paper is to identify the beam ratio that best mitigates pore formation in the weld bead. The laser molten pool and the keyhole condition, as well as laser-induced plasma plume are monitored in real-time by use of a high speed charge-coupled device (CCD) camera assisted with a green laser as an illumination source. Tensile and microhardness tests were used to measure the mechanical properties of the laser welded samples. Results showed that a dual-beam laser configuration can effectively mitigate pore formation in the weld bead by a preheating-welding mechanism.

Harooni, Masoud; Carlson, Blair; Kovacevic, Radovan

2014-03-01

324

XII. Soft x-ray spectra of magnesium-aluminium, magnesium-silicon and aluminium-silicon alloys  

Microsoft Academic Search

The soft x-ray L spectra of the elements Mg, Al and Si have been determined in all three of the sets of binary alloys, and have been compared with the spectra of the pure elements. Several differences appear : (a) a widening of the emission edges with alloying, (b) in one case a probable diminution of band width and (c)

K. Das Gupta; E. Wood

1955-01-01

325

Fabrication of nanocrystalline aluminum-magnesium alloy powders by electrodeposition and their characterization  

NASA Astrophysics Data System (ADS)

Aluminum-magnesium alloy powders can potentially be used as hydrogen storage materials. In order to enhance the kinetics of hydrogenation it is desirable to have agglomerates of fine powders with very small grain size. In this study, nanocrystalline Al-Mg alloys in the form of powders were successfully fabricated by the electrodeposition technique using an organometallic based electrolyte. Mg was introduced into the electrolyte by a process called "pre-electrodeposition". The mechanism for Mg accumulation can be explained considering the electrode reactions as well as the chemical changes in the electrolyte. Using a copper cathode, the effects of the electrolyte composition and current density on composition of the deposit, its constituent phases and morphology were investigated. The magnesium content of the deposits improved with increasing Mg concentration in the electrolyte, temperature and current density. Depending on the composition, the deposits consisted of FCC-Al(Mg) and HCP-Mg(Al) phases and no intermetallic phase was found except for long deposition times. Generally, the deposits formed initially on the copper substrate with three dendritic morphologies namely, rod-like, feather-like and small globular, which eventually evolved into the large globular morphology. This observation is attributed to the establishment of spherical diffusion conditions at the sharp dendrite tips. Potentiostatic studies suggested that the appearance of different morphologies is associated with differing rates of deposition. While the initial dendrites consisted of the FCC Al-rich phase, the large globular morphology manifested as both FCC Al-rich and HCP Mg-rich phases, with the latter always forming over the former. The observation of formation of only the FCC phase implies that the nucleation barrier for the HCP phase on the copper substrate is quite high. The investigation of the effect of substrate, namely, Cu, graphite and Mg, revealed that the HCP phase can directly nucleate on an oxide-free Mg surface. This finding can be explained in terms of surface/interfacial energies. Detailed TEM analysis revealed that the observed morphologies consist of randomly distributed nanocrystalline grains except for the feather-like dendrites, which exhibited a strong crystallographic texture.

Tatiparti, Sankara Sarma V.

326

Microstructure and corrosion behavior of die-cast AM60B magnesium alloys in a complex salt solution: A slow positron beam study  

SciTech Connect

The microstructure and corrosion behavior of high pressure die-cast (HPDC) and super vacuum die-cast (SVDC) AM60B magnesium alloys were investigated in a complex salt solution using slow positron beam technique and potentiodynamic polarization tests. The experiments revealed that a CaCO3 film was formed on the surface of the alloys and that the rate of CaCO3 formation for the SVDC alloy with immersion time was slower than that of the HPDC alloy. The larger volume fraction of b-phase in the skin layer of the SVDC alloy than that of the HPDC alloy was responsible for the better corrosion resistance.

Liu, Y.F. [Wuhan University] [Wuhan University; Qin, Q.L. [Wuhan University] [Wuhan University; Yang, W. [Wuhan University] [Wuhan University; Wen, W. [University of Kentucky] [University of Kentucky; Zhai, T. [University of Kentucky] [University of Kentucky; Yu, B. [University of Alberta] [University of Alberta; Liu, D.Y. [University of Alberta] [University of Alberta; Luo, A. [GM Research and Development Center] [GM Research and Development Center; Song, GuangLing [ORNL] [ORNL

2014-01-01

327

The galvanic corrosion behavior of depleted uranium in synthetic seawater coupled to aluminum, magnesium, and mild steel  

SciTech Connect

The galvanic corrosion behavior of a depleted uranium-titanium alloy (Du-.75Ti) coupled to MgZk60A-T5, AA-7075-T6, bare steel-4340, and coated steel-4340 exposed to ASTM seawater was investigated by monitoring the galvanic current with time. Gravimetric measurements, polarization resistance measurements, and concepts of ''mixed-potential'' theory were used to calculate corrosion rates. It was demonstrated that galvanic currents must be monitored over extended periods of time to detect changes in the galvanic corrosion behavior. Good agreement was obtained for corrosion rates calculated using the concepts of ''mixed-potential'' theory and those obtained from gravimetric measurements.

McIntyre, J.F.; LeFeave, E.P.; Musselman, K.A.

1987-01-01

328

In vitro degradation of four magnesium-zinc-strontium alloys and their cytocompatibility with human embryonic stem cells.  

PubMed

Magnesium alloys have attracted great interest for medical applications due to their unique biodegradable capability and desirable mechanical properties. When designed for medical applications, these alloys must have suitable degradation properties, i.e., their degradation rate should not exceed the rate at which the degradation products can be excreted from the body. Cellular responses and tissue integration around the Mg-based implants are critical for clinical success. Four magnesium-zinc-strontium (ZSr41) alloys were developed in this study. The degradation properties of the ZSr41 alloys and their cytocompatibility were studied using an in vitro human embryonic stem cell (hESC) model due to the greater sensitivity of hESCs to known toxicants which allows to potentially detect toxicological effects of new biomaterials at an early stage. Four distinct ZSr41 alloys with 4 wt% zinc and a series of strontium compositions (0.15, 0.5, 1, and 1.5 wt% Sr) were produced through metallurgical processing. Their degradation was characterized by measuring total mass loss of samples and pH change in the cell culture media. The concentration of Mg ions released from ZSr41 alloy into the cell culture media was analyzed using inductively coupled plasma atomic emission spectroscopy. Surface microstructure and composition before and after culturing with hESCs were characterized using field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. Pure Mg was used as a control during cell culture studies. Results indicated that the Mg-Zn-Sr alloy with 0.15 wt% Sr provided slower degradation and improved cytocompatibility as compared with pure Mg control. PMID:23361966

Cipriano, Aaron F; Zhao, Tong; Johnson, Ian; Guan, Ren-Guo; Garcia, Salvador; Liu, Huinan

2013-04-01

329

Accurate parameter identification for crystal plasticity finite-element analysis in a magnesium alloy sheet  

NASA Astrophysics Data System (ADS)

A new procedure of parameter identification for crystal plasticity finite-element analysis in a rolled Magnesium alloy sheet was proposed. The procedure consisted of the following four steps; (1) the parameters for basal slip are estimated to achieve a fit with the initial yield stress under uniaxial tension, (2) a ratio between the parameters for the prismatic slip and the pyramidal-2 slip is estimated to achieve a fit with the evolution of Lankford value, (3) with keeping the ratio, the parameters for the prismatic slip and the pyramidal-2 slip as well as those of basal slip are adjusted to achieve a fit with the stress-strain curve under uniaxial tension, and (4) the parameters for the twinning are estimated to achieve a fit with the stress-strain curve under uniaxial compression. Using the conventional parameters, the evolution of Lankford value was surprisingly larger than that of the experiment although the stress-strain curve was in good agreement with the experimental result. On the other hand, when the newly-identified parameters were used, both the stress-strain curve and the evolution of Lankford value were in good agreement with the experimental results, showing that the proposed procedure gave more accurate parameters.

Hama, Takayuki; Hosokawa, Naohiro; Takuda, Hirohiko

2013-12-01

330

Degradation behaviors of surface modified magnesium alloy wires in different simulated physiological environments  

NASA Astrophysics Data System (ADS)

The degradation behaviors of the novel high-strength AZ31B magnesium alloy wires after surface modification using micro-arc-oxidization (MAO) and subsequently sealing with poly-L-lactic acid (PLLA) in different simulated physiological environments were investigated. The results show the surface MAO micropores could be physically sealed by PLLA, thus forming an effective protection to corrosion resistance for the wires. In simulated gastric fluid (SGF) at a low pH value (1.5 or 2.5), the treated wires have a high degradation rate with a rapid decrease of mass, diameter, mechanical properties and a significant increase of pH value of the immersion fluid. However, surface modification could effectively reduce the degradation rate of the treated wires in SGF with a pH value above 4.0. For the treated wires in simulated intestinal fluid at pH = 8.5, their strength retention ability is higher than that in strong acidic SGF. And the loss rate of mass is faster than that of diameter, while the pH value of the immersion fluid decreases. It should be noted that the modified wires in simulated body environment have the best strength retention ability. The wires show the different degradation behaviors indicating their different degradation mechanisms, which are also proposed in this work.

Li, Xuan; Shi, Chao; Bai, Jing; Guo, Chao; Xue, Feng; Lin, Ping-Hua; Chu, Cheng-Lin

2014-09-01

331

CHARACTERIZATION AND FORMABILITY OF CONTINUOUS-CAST AZ31B MAGNESIUM ALLOY SHEETS  

SciTech Connect

The goal of this work is to understand the inter-relationship between the initial properties of continuous-cast magnesium alloy (AZ31B) sheets and their subsequent formability and post-formed mechanical performance for use in cost-effective, lightweight, automotive body panels. As-received sheets, provided by the Automotive Metals Division (AMD-602) team, were characterized by surface roughness measurements using mechanical profilometry. The arithmetic mean deviation of profile (Ra) and the maximum two-point height of profile (Ry) of the as-received sheets ranged from ~0.2-2 ?m and ~2-15 ?m, respectively. Several commercial lubricants were evaluated by thermal analysis and the liquid phase of the lubricants was found to evaporate/decompose upon heating leaving behind a solid residue upon heating to temperatures exceeding ~125-150C. Elevated temperature bending-under-tension (BUT) friction tests were conducted at 350C and the coefficient-of-friction values ranged from a minimum of ~0.1 (for tungsten disulfide lubricant) to ~0.7 when no lubricant was used. These results, in conjunction with those from the forming trials conducted by the AMD-602 team, will be eventually used to determine the role of sheet-die friction in determining the formability of AZ31B sheets.

Rohatgi, Aashish; Herling, Darrell R.; Nyberg, Eric A.

2009-09-24

332

Experimental data confirm numerical modeling of the degradation process of magnesium alloys stents.  

PubMed

Biodegradable magnesium alloy stents (MAS) could present improved long-term clinical performances over commercial bare metal or drug-eluting stents. However, MAS were found to show limited mechanical support for diseased vessels due to fast degradation. Optimizing stent design through finite element analysis (FEA) is an efficient way to improve such properties. Following previous FEA works on design optimization and degradation modeling of MAS, this work carried out an experimental validation for the developed FEA model, thus proving its practical applicability of simulating MAS degradation. Twelve stent samples of AZ31B were manufactured according to two MAS designs (an optimized one and a conventional one), with six samples of each design. All the samples were balloon expanded and subsequently immersed in D-Hanks' solution for a degradation test lasting 14 days. The experimental results showed that the samples of the optimized design had better corrosion resistance than those of the conventional design. Furthermore, the degradation process of the samples was dominated by uniform and stress corrosion. With the good match between the simulation and the experimental results, the work shows that the FEA numerical modeling constitutes an effective tool for design and thus the improvement of novel biodegradable MAS. PMID:23128160

Wu, Wei; Chen, Shanshan; Gastaldi, Dario; Petrini, Lorenza; Mantovani, Diego; Yang, Ke; Tan, Lili; Migliavacca, Francesco

2013-11-01

333

Microstructure and mechanical properties of AZ91 magnesium alloy subject to deep cryogenic treatments  

NASA Astrophysics Data System (ADS)

AZ91 magnesium alloy was subjected to a deep cryogenic treatment. X-ray diffraction (XRD), scanning electronic microscopy (SEM), and transmission electronic microscopy (TEM) methods were utilized to characterize the composition and microstructure of the treated samples. The results show that after two cryogenic treatments, the quantity of the precipitate hardening ? phase increases, and the sizes of the precipitates are refined from 8-10 ?m to 2-4 ?m. This is expected to be due to the decreased solubility of aluminum in the matrix at low temperature and the significant plastic deformation owing to internal differences in thermal contraction between phases and grains. The polycrystalline matrix is also noticeably refined, with the sizes of the subsequent nanocrystalline grains in the range of 50-100 nm. High density dislocations are observed to pile up at the grain boundaries, inducing the dynamic recrystallization of the microstructure, leading to the generation of a nanocrystalline grain structure. After two deep cryogenic treatments, the tensile strength and elongation are found to be substantially increased, rising from 243 MPa and 4.4% of as-cast state to 299 MPa and 5.1%.

Li, Gui-rong; Wang, Hong-ming; Cai, Yun; Zhao, Yu-tao; Wang, Jun-jie; Gill, Simon P. A.

2013-09-01

334

A Microstructure Study on an AZ31 Magnesium Alloy Tube after Hot Metal Gas Forming Process  

NASA Astrophysics Data System (ADS)

An AZ31 magnesium alloy tube has been deformed by the hot metal gas forming (HMGF) technique. Microstructures before and after deformation have been investigated by using Electron Backscattered Diffraction (EBSD) and Electron Microscopy. Due to the inhomogeneous distribution by induction heating, there is a temperature gradient distribution along the tube axis. Accordingly, the deformation mechanism is also different. In the middle area of deformation zone where the temperature is 410 C, almost no twinning has been found, whereas at the edge areas of deformation zone where the temperature is 200 C, a high density of twins has been found. EBSD experiments show a weak (0001) fiber texture along the radial direction of the tube before and after deformation in the high-temperature zone. EBSD experiments on the low temperature deformation region were not successful due to the high stored energy. Schmid factor analysis on the EBSD data shows that, despite the (0001) fiber texture, there are still many grains favoring basal slip along both the axis direction and hoop direction.

Liu, Yi; Wu, Xin

2007-06-01

335

Degradation behaviors of surface modified magnesium alloy wires in different simulated physiological environments  

NASA Astrophysics Data System (ADS)

The degradation behaviors of the novel high-strength AZ31B magnesium alloy wires after surface modification using micro-arc-oxidization (MAO) and subsequently sealing with poly-L-lactic acid (PLLA) in different simulated physiological environments were investigated. The results show the surface MAO micropores could be physically sealed by PLLA, thus forming an effective protection to corrosion resistance for the wires. In simulated gastric fluid (SGF) at a low pH value (1.5 or 2.5), the treated wires have a high degradation rate with a rapid decrease of mass, diameter, mechanical properties and a significant increase of pH value of the immersion fluid. However, surface modification could effectively reduce the degradation rate of the treated wires in SGF with a pH value above 4.0. For the treated wires in simulated intestinal fluid at pH = 8.5, their strength retention ability is higher than that in strong acidic SGF. And the loss rate of mass is faster than that of diameter, while the pH value of the immersion fluid decreases. It should be noted that the modified wires in simulated body environment have the best strength retention ability. The wires show the different degradation behaviors indicating their different degradation mechanisms, which are also proposed in this work.

Li, Xuan; Shi, Chao; Bai, Jing; Guo, Chao; Xue, Feng; Lin, Ping-Hua; Chu, Cheng-Lin

2014-08-01

336

Determination of boron in aluminum and aluminum-magnesium alloy by charged particle activation analysis  

SciTech Connect

Charge particle activation analysis is applied to the determination of boron in aluminum and aluminum-magnesium alloy. The /sup 10/B(p,..cap alpha..)/sup 7/Be, the /sup 10/B(d,..cap alpha..n)/sup 7/Be, and the /sup 10/B(d,n)/sup 11/C reactions are used. Proton activation allows an instrumental determination. When the /sup 10/B(d,..cap alpha..n)/sup 7/Be reaction is used, beryllium-7 is separated from the matrix by liquid-liquid extraction; beryllium acetylacetonate is extracted with carbon tetrachloride after complexation of other metal ions with ethylenediaminetetraacetic acid. After back extraction beryllium is precipitated as beryllium hydroxide and heated to beryllium oxide. When the /sup 10/B(d,n)/sup 11/C reaction is used, carbon-11 is separated as carbon dioxide by dissolution of the sample in a mixture of sulfuric acid, phosphoric acid, water, and potassium dichromate. The chemical yield of both separation methods was determined. The results obtained have a relative standard deviation of 5-9% at the 1-33 ..mu..g/g concentration. The different nuclear reactions yield results that are in good mutual agreement and also agree satisfactorily with those of nonnuclear analytical methods.

Mortier, R.; Vandecasteele, C.; Strijckmans, K.; Hoste, J.

1984-10-01

337

Effect of microstructure on the zinc phosphate conversion coatings on magnesium alloy AZ91  

NASA Astrophysics Data System (ADS)

The effect of the microstructure, particularly of ?-Mg17Al12 phase, on the formation and growth of zinc phosphate conversion coatings on magnesium alloy AZ91 (AZ91) was studied. The zinc phosphate coatings were formed on AZ91 with different microstructures produced by heat treatment. The effect of the microstructure on the zinc phosphate coatings were examined using optical microscope (OM), X-ray diffraction (XRD), coatings weight and etching weight balances, scanning electron microscopy (SEM) and salt immersion test. Results showed that as-cast AZ91 contained a high volume fraction of the ?-Mg17Al12 phase and it was dissolved into ?-Mg phase during heat treatment at 400 C. The ?-phase became center for hydrogen evolution during phosphating reaction (cathodic sites). The decreased volume fraction of the ?-phase caused decreasing both coatings weight and etching weight of the phosphating process. However, it increased the crystal size of the coatings and improved corrosion resistance of AZ91 by immersing in 0.5 M NaCl solution. Results also showed that the structure of the zinc phosphate conversion on AZ91 consisted of two layers: an outer crystal Zn3(PO4)24H2O (hopeite) and an inner which was mainly composed of MgZn2(PO4)2 and Mg3(PO4)2. A mechanism for the formation of two layers of the coatings was also proposed in this study.

Van Phuong, Nguyen; Moon, Sungmo; Chang, Doyon; Lee, Kyu Hwan

2013-01-01

338

Formation and stability of organic acid monolayers on magnesium alloy AZ31: The role of alkyl chain length and head group chemistry  

NASA Astrophysics Data System (ADS)

Magnesium wrought alloy AZ31 has a 30% lower density than aluminum alloys and provides the opportunity to reduce vehicle weight and hence to reduce fuel consumption. Today, the use in industrial applications is limited due to low corrosion resistance. Carboxylic and phosphonic acids were investigated as promising alternatives for corrosion protection on AZ31 magnesium wrought alloy. Adsorption and orientation of organic monolayers were studied as a function of aliphatic chain lengths and head groups. As final result, the octadecylphosphonic acid led to a measureable lowering of the corrosion current density and inhibited the growth of the oxide film under humid conditions.

Szillies, S.; Thissen, P.; Tabatabai, D.; Feil, F.; Frbeth, W.; Fink, N.; Grundmeier, G.

2013-10-01

339

Resistance-Spot-Welded AZ31 Magnesium Alloys: Part I. Dependence of Fusion Zone Microstructures on Second-Phase Particles  

NASA Astrophysics Data System (ADS)

A comparison of microstructural features in resistance spot welds of two AZ31 magnesium (Mg) alloys, AZ31-SA (from supplier A) and AZ31-SB (from supplier B), with the same sheet thickness and welding conditions, was performed via optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). These alloys have similar chemical composition but different sizes of second-phase particles due to manufacturing process differences. Both columnar and equiaxed dendritic structures were observed in the weld fusion zones of these AZ31 SA and SB alloys. However, columnar dendritic grains were well developed and the width of the columnar dendritic zone (CDZ) was much larger in the SB alloy. In contrast, columnar grains were restricted within narrow strip regions, and equiaxed grains were promoted in the SA alloy. Microstructural examination showed that the as-received Mg alloys contained two sizes of Al8Mn5 second-phase particles. Submicron Al8Mn5 particles of 0.09 to 0.4 ?m in length occured in both SA and SB alloys; however, larger Al8Mn5 particles of 4 to 10 ?m in length were observed only in the SA alloy. The welding process did not have a great effect on the populations of Al8Mn5 particles in these AZ31 welds. The earlier columnar-equiaxed transition (CET) is believed to be related to the pre-existence of the coarse Al8Mn5 intermetallic phases in the SA alloy as an inoculant of ?-Mg heterogeneous nucleation. This was revealed by the presence of Al8Mn5 particles at the origin of some equiaxed dendrites. Finally, the columnar grains of the SB alloy, which did not contain coarse second-phase particles, were efficiently restrained and equiaxed grains were found to be promoted by adding 10 ?m-long Mn particles into the fusion zone during resistance spot welding (RSW).

Xiao, L.; Liu, L.; Zhou, Y.; Esmaeili, S.

2010-03-01

340

In-vitro characterization of stress corrosion cracking of aluminium-free magnesium alloys for temporary bio-implant applications.  

PubMed

The complex interaction between physiological stresses and corrosive human body fluid may cause premature failure of metallic biomaterials due to the phenomenon of stress corrosion cracking. In this study, the susceptibility to stress corrosion cracking of biodegradable and aluminium-free magnesium alloys ZX50, WZ21 and WE43 was investigated by slow strain rate tensile testing in a simulated human body fluid. Slow strain rate tensile testing results indicated that each alloy was susceptible to stress corrosion cracking, and this was confirmed by fractographic features of transgranular and/or intergranular cracking. However, the variation in alloy susceptibility to stress corrosion cracking is explained on the basis of their electrochemical and microstructural characteristics. PMID:25063163

Choudhary, Lokesh; Singh Raman, R K; Hofstetter, Joelle; Uggowitzer, Peter J

2014-09-01

341

Mechanical Properties of AZ31 Magnesium Alloy Under Severe Plastic Deformation Through Rolling and Heat Treatment Affects  

NASA Astrophysics Data System (ADS)

AZ31 Magnesium alloy is a light alloy consisting of 96 wt% magnesium, 3 wt% aluminum, and 1 wt% zinc that is 34% lighter than aluminum with fairly good strength and other properties. However, the ductility is poor due to its HCP structure that does not satisfy the Taylor Criterion for independent slip planes. Research into how to improve the strength and ductility through plastic deformation was conducted at University of Nevada in Reno. Different sizes of AZ31B were received from a Chinese magnesium company. Each size went through severe plastic deformation by rolling at different temperatures. Most of the sample went through annealing at different temperatures for different times. The mechanical properties and microstructure of each sample were collected. These samples were compared to one another with the control samples to determine any effects from the severe plastic deformation and/or heat treatment affects. From the analysis of the data collected, there was a correlation between the mechanical properties, annealing temperature, and annealing time. The mechanical properties were higher at lower annealing temperatures than at the higher annealing temperatures. In addition, there was a drastic increase in all mechanical properties between 3 and 5 hours of annealing for an unknown reason. Precipitates are seen within the microstructure of some of the samples. Most of the microstructures showed equiaxed grains throughout the majority of the samples. The grains that were not equiaxed showed elongation due to the extrusion process and possibly from the rolling process.

Busch, Eric Michael

342

Micro-extrusion of ECAP processed magnesium alloy for production of high strength magnesium micro-gears  

Microsoft Academic Search

Micro-gear extrusion of the fine-grained equal channel angular pressed (ECAPed) AZ31 alloy was successfully performed. High strength gears (yield stress >350MPa) could be produced by effective grain-refinement through ECAP and texture restoration to the original state before ECAP by subsequent extrusion.

W. J. Kim; Y. K. Sa

2006-01-01

343

Evaluating the improvement of corrosion residual strength by adding 1.0 wt.% yttrium into an AZ91D magnesium alloy  

SciTech Connect

The influence of yttrium on the corrosion residual strength of an AZ91D magnesium alloy was investigated detailedly. Scanning electron microscope was employed to analyze the microstructure and the fractography of the studied alloys. The microstructure of AZ91D magnesium alloy is remarkably refined due to the addition of yttrium. The electrochemical potentiodynamic polarization curve of the studied alloy was performed with a CHI 660b electrochemical station in the three-electrode system. The result reveals that yttrium significantly promotes the overall corrosion resistance of AZ91D magnesium alloy by suppressing the cathodic reaction in corrosion process. However, the nucleation and propagation of corrosion pits on the surface of the 1.0 wt.% Y modified AZ91D magnesium alloy indicate that pitting corrosion still emerges after the addition of yttrium. Furthermore, stress concentration caused by corrosion pits should be responsible for the drop of corrosion residual strength although the addition of yttrium remarkably weakens the effect of stress concentration at the tip of corrosion pits in loading process.

Wang Qiang [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun, 130025 (China); Liu Yaohui, E-mail: liuyaohui2005@yahoo.com [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun, 130025 (China); Fang Shijie [Department of Mechanical and Electrical Engineering, Luoyang Institute of Science and Technology, Luoyang 471023 (China); Song Yulai; Zhang Dawei; Zhang Lina; Li Chunfang [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun, 130025 (China)

2010-06-15

344

Interfacial reaction in squeeze cast SICW\\/AZ91 magnesium alloy composite  

Microsoft Academic Search

It is well known that the interface between the matrix and the reinforcement plays an important role in the properties of metal matrix composites (MMCs). Interfacial structure and its effect on the properties of aluminum matrix composites have been extensively studied. The interface of Mg-MMCs is very different from that of Al-MMCs, due to high reactivity of magnesium. As magnesium

Jihong Li; M. Zheng; M. Zhao; C. Yao; J. Li

1996-01-01

345

Effect of reverse bending on texture, structure, and mechanical properties of sheets of magnesium alloys with zinc and zirconium  

NASA Astrophysics Data System (ADS)

Effect of low-cycle room-temperature reverse bending on the crystallographic texture, metallo-graphic structure, and mechanical properties of sheets of ZE10 magnesium alloy after hot rolling and annealing has been studied. The initial texture is characterized by a wide scatter of basal poles in the transverse direction. In the process of reverse bending, the changes in the initial texture and structure (which is represented by equiaxed grains containing twins) lead to regular changes in the anisotropy of mechanical properties.

Shkatulyak, N. M.; Usov, V. V.; Volchok, N. A.; Bryukhanov, A. A.; San'kova, S. V.; Rodman, M.; Shaper, M.; Klose, C.

2014-06-01

346

Microstructure and second-phase particles in low- and high-pressure die-cast magnesium alloy AM50  

Microsoft Academic Search

The microstructure and phase composition of low-pressure die-cast (LPDC) and high-pressure diecast (HPDC) magnesium alloy\\u000a AM50 were examined by transmission electron microscopy (TEM) techniques in combination with optical microscopy, scanning electron\\u000a microscopy (SEM), and electron-probe microanalysis (EPMA). It has been established that the dimensions and morphology of the\\u000a constituent phases (?-Mg solid solution, Mg17Al12, and Al8Mn5) depend on the processing

Val Y. Gertsman; Jian Li; Su Xu; James P. Thomson; Mahi Sahoo

2005-01-01

347

Characterization of High-Frequency Induction Brazed Magnesium Alloy Joint with an Al-Mg-Zn Filler Metal  

NASA Astrophysics Data System (ADS)

In this paper, a novel Al-Mg-Zn filler metal was designed to join magnesium alloy AZ31B plates by means of high-frequency induction brazing in argon gas shield condition. The microstructure and the mechanical properties of the brazed joint were investigated. The experimental results showed that the brazed joint contained large amount of ?-Mg and ?-Mg17(Al, Zn)12 phases. The homogeneous Mg32(Al, Zn)49 phase in the original filler metal was consumed due to the intensive alloying during the brazing process. The results indicate that the shear strength of the brazed joint is 35 MPa. The fracture morphology of the brazed joint exhibits intergranular fracture mode, and the fracture originates from the hard ?-Mg17(Al, Zn)12 phase.

Ma, Li; He, Dingyong; Li, Xiaoyan; Jiang, Jianmin

2011-03-01

348

Surface morphology, microstructure and properties of as-cast AZ31 magnesium alloy irradiated by high intensity pulsed ion beams  

NASA Astrophysics Data System (ADS)

High intensity pulsed ion beam (HIPIB) irradiation was performed as surface modification to improve the properties of as-cast AZ31 magnesium (Mg) alloys. The surface morphology and microstructure of the irradiated Mg alloys were characterized and their microhardness, wear resistance and corrosion resistance before and after HIPIB irradiation were measured. The results show that the formation of crater on the surface was attributed to the particles impacted from the irradiated cathode material. HIPIB irradiation resulted in more vacancy defects on the surface of the material. Moreover, new dislocations were generated by the reaction between vacancies, and the dislocation configuration was also changed. These variations caused by the HIPIB are beneficial for improving the material properties. After 10 shots of irradiation, the average microhardness increased by 27.1% but the wear rate decreased by 38.5%. The corrosion rate was reduced by 24.8% according to the salt spray corrosion experiment.

Ma, Xuesong; Zhang, Gang; Wang, Guotian; Zhu, Guoliang; Zhou, Wei; Wang, Jun; Sun, Baode

2014-08-01

349

Mechanical Properties, Microstructure and Crystallographic Texture of Magnesium AZ91-D Alloy Welded by Friction Stir Welding (FSW)  

NASA Astrophysics Data System (ADS)

The objective of the study was to characterize the properties of a magnesium alloy welded by friction stir welding. The results led to a better understanding of the relationship between this process and the microstructure and anisotropic properties of alloy materials. Welding principally leads to a large reduction in grain size in welded zones due to the phenomenon of dynamic recrystallization. The most remarkable observation was that crystallographic textures appeared from a base metal without texture in two zones: the thermo-mechanically affected and stir-welded zones. The latter zone has the peculiarity of possessing a marked texture with two components on the basal plane and the pyramidal plane. These characteristics disappeared in the thermo-mechanically affected zone (TMAZ), which had only one component following the basal plane. These modifications have been explained by the nature of the plastic deformation in these zones, which occurs at a moderate temperature in the TMAZ and high temperature in the SWZ.

Kouadri-Henni, A.; Barrallier, L.

2014-10-01

350

Role of biomineralization on the degradation of fine grained AZ31 magnesium alloy processed by groove pressing.  

PubMed

Groove pressing (GP) has been successfully adopted to achieve fine grain size up to 7 ?m in AZ31 magnesium alloy with an initial grain size of 55 ?m. The effect of microstructural evolution and surface features on wettability, corrosion resistance, bioactivity and cell adhesion were investigated with an emphasis to study the influence of deposited phases when the samples were immersed in simulated body fluid (SBF 5). The role of microstructure was also evaluated without any surface treatments or coatings on the material. GPed samples exhibit improved hydrophilicity compared to the annealed sample. After immersion in SBF, specimens were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) analysis and X-ray diffraction (XRD) methods. More amount of white precipitates composed of hydroxyapatite and magnesium phosphate along with magnesium hydroxide was observed on the surfaces of groove pressed specimens as compared to the annealed specimens with an increase in immersion time in SBF. Corrosion behavior of the samples estimated using potentiodynamic polarization curves indicate good corrosion resistance for GPed samples before and after immersion in SBF. The MTT assay using rat skeletal muscle (L6) cells revealed that both the processed and unprocessed samples are nontoxic and cell adhesion was promising for GPed sample. PMID:23827614

Sunil, B Ratna; Kumar, Arun Anil; Sampath Kumar, T S; Chakkingal, Uday

2013-04-01

351

Dynamic behavior and constitutive modeling of magnesium alloys AZ91D and AZ31B under high strain rate compressive loading  

NASA Astrophysics Data System (ADS)

The dynamic stress-strain characteristics of magnesium alloys have not been sufficiently studied experimentally. Thus, the present work investigated compressive dynamic stress-strain characteristics of two representative magnesium alloys: AZ91D and AZ31B at high strain rates and elevated temperatures. In order to use the stress-strain characteristics in numerical simulations to predict the impact response of components, the stress-strain characteristics must be modeled. The most common approach is to use accepted constitutive laws. The results from the experimental study of the response of magnesium alloys AZ91D and AZ31B under dynamic compressive loading, at different strain rates and elevated temperatures are presented here. Johnson-Cook model was used to best fit the experimental data. The material parameters required by the model were obtained and the resultant stress-strain curves of the two alloys for each testing condition were plotted. It is found that the dynamic stress-strain relationship of both magnesium alloys are strain rate and temperature dependent and can be described reasonably well at high strain rates and room temperature by Johnson-Cook model except at very low strains. This might be due to the fact that the strain rate is not strictly constant in the early stage of deformation.

Xiao, Jing; Ahmad, Iram Raza; Shu, D. W.

2014-03-01

352

The effect of high-intensity pulsed ion beam on surface structures of MAO film on magnesium alloy AZ31  

NASA Astrophysics Data System (ADS)

Micro-arc oxidation (MAO) films on AZ31 magnesium alloy were modified by high-intensity pulsed ion beam (HIPIB) irradiation with ion energy of 300 keV at 200 A/cm2 with up to 10 shots. Scanning electron microscopy, X-ray diffractometry and micro-hardness testers were used to characterize the surface properties of the irradiated MAO films. The thickness of remelted layer increased and then decreased, and the maximal value of 10 ?m was obtained at 200 A/cm2 with 5 shots. The phase structure of the ablated surface still consisted of Mg2SiO4 and MgO, which are the same as that of the original ones. Surface roughness of the ablated surface increased and then decreased with the increase of shot number. The surface roughness for the original MAO film is about 2.10 ?m, it decreased to 1.18 ?m with 1 shot irradiation and then increased to 4.13 ?m with irradiation shots up to 10. Correspondingly, the surface energy of the ablated surface augmented, resulting in the tedious decrease of static contact angle from 145.9 for original film to 49.7 for the film with 10 shots. The ablation modification enhanced the continuity and compaction of the MAO films on AZ31 magnesium alloy.

Han, X. G.; Zhu, F.; Zhu, X. P.; Lei, M. K.; Xu, J. J.

2013-07-01

353

Mesoscale Modeling and Validation of Texture Evolution during Asymmetric Rooling and Static Recrystallization of Magnesium Alloy AZ31B  

SciTech Connect

The focus of the present research is to develop an integrated deformation and recrystallization model for magnesium alloys at the microstructural length scale. It is known that in magnesium alloys nucleation of recrystallized grains occurs at various microstructural inhomogeneities such as twins and localized deformation bands. However, there is a need to develop models that can predict the evolution of the grain structure and texture developed during recrystallization and grain growth, especially when the deformation process follows a complicated deformation path such as in asymmetric rolling. The deformation model is based on a crystal plasticity approach implemented at the length scale of the microstructure that includes deformation mechanisms based on dislocation slip and twinning. The recrystallization simulation is based on a Monte Carlo technique that operates on the output of the deformation simulations. The nucleation criterion during recrystallization is based on the local stored energy and the Monte Carlo technique is used to simulate the growth of the nuclei due to local stored energy differences and curvature. The model predictions are compared with experimental data obtained through electron backscatter analysis and neutron diffraction.

Radhakrishnan, Balasubramaniam [ORNL; Gorti, Sarma B [ORNL; Stoica, Grigoreta M [ORNL; Muralidharan, Govindarajan [ORNL; Stoica, Alexandru Dan [ORNL; Wang, Xun-Li [ORNL; Specht, Eliot D [ORNL; Kenik, Edward A [ORNL; Muth, Thomas R [ORNL

2012-01-01

354

Optimizing Diffusion Bonding Parameters in AA6061-T6 Aluminum and AZ80 Magnesium Alloy Dissimilar Joints  

NASA Astrophysics Data System (ADS)

The main difficulty when joining magnesium (Mg) and aluminum (Al) alloys by fusion welding lies in the formation of oxide films and brittle intermetallic in the bond region which affects the integrity of the joints. However, diffusion bonding is a suitable process to join these two materials as no such characteristic defects are produced at the joints. The diffusion bonding process parameters such as bonding temperature, bonding pressure, holding time, and surface roughness of the specimen play a major role in determining the joint strength. In this investigation, an attempt was made to develop empirical relationships to predict the strengths of diffusion bonded AZ80 magnesium and AA6061 aluminum alloys dissimilar joints from the process parameters based on central composite factorial design. Response surface methodology was applied to optimize the process parameters to attain the maximum shear strength and bonding strength of the joint. From this investigation, it was found that the bonds produced with the temperature of 405.87 C, pressure of 7.87 MPa, holding time of 29.02 min and surface roughness of 0.10 ?m exhibited maximum shear strength and bonding strength of 57.70 and 76.90 MPa, respectively. The intermetallic formation at the interface was identified.

Joseph Fernandus, M.; Senthilkumar, T.; Balasubramanian, V.; Rajakumar, S.

2012-11-01

355

Utility of micro-indentation technique for characterization of the constitutive behavior of skin and interior microstructures of die-cast magnesium alloys  

Microsoft Academic Search

There has been increasing thrust lately on the development of lightweight cast magnesium alloy components for structural automotive and other applications. The microstructure of the high-pressure die-cast Mg alloys usually contains a fine-grained skin having a microstructure significantly different from that of the bulk material. Characterization of the local constitutive behavior of the skin microstructure is of interest as it

Zhaohui Shan; Arun M Gokhale

2003-01-01

356

Influence of heat treatment on degradation behavior of bio-degradable die-cast AZ63 magnesium alloy in simulated body fluid  

Microsoft Academic Search

The effects of hybrid aging and solution treatments on the degradation of bio-degradable die-cast AZ63 magnesium alloy in 371C Tyrode's simulated body fluid have been investigated. The heat treatment is observed to alter the microstructure of the alloy. The amount of ?-Mg17Al2 precipitates is larger and their distribution is more homogeneous. The homogeneous microstructure enhances the corrosion resistance of the

Chenglong Liu; Yunchang Xin; Guoyi Tang; Paul K. Chu

2007-01-01

357

Effect of high-temperature annealing on the structure of cast magnesium alloy AM60 + 0.3% TiC  

Microsoft Academic Search

The composition and structure of magnesium alloy AM60 with additional 0.3 wt.% TiC are considered after casting into a steel\\u000a mold. Changes in the composition and in structure in the process of high-temperature annealing (at 420 C) are determined.

N. M. Rusin

2006-01-01

358

In vivo assessment of the host reactions to the biodegradation of the two novel magnesium alloys ZEK100 and AX30 in an animal model  

PubMed Central

Background Most studies on biodegradable magnesium implants published recently use magnesium-calcium-alloys or magnesium-aluminum-rare earth-alloys. However, since rare earths are a mixture of elements and their toxicity is unclear, a reduced content of rare earths is favorable. The present study assesses the in vivo biocompatibility of two new magnesium alloys which have a reduced content (ZEK100) or contain no rare earths at all (AX30). Methods 24 rabbits were randomized into 4 groups (AX30 or ZEK100, 3 or 6 months, respectively) and cylindrical pins were inserted in their tibiae. To assess the biodegradation ?CT scans and histological examinations were performed. Results The ?CT scans showed that until month three ZEK100 degrades faster than AX30, but this difference is leveled out after 6 months. Histology revealed that both materials induce adverse host reactions and high numbers of osteoclasts in the recipient bone. The mineral apposition rates of both materials groups were high. Conclusions Both alloys display favorable degradation characteristics, but they induce adverse host reactions, namely an osteoclast-driven resorption of bone and a subsequent periosteal formation of new bone. Therefore, the biocompatibility of ZEK100 and AX30 is questionable and further studies, which should focus on the interactions on cellular level, are needed. PMID:22429539

2012-01-01

359

Evaluating the Superplastic Flow of a Magnesium AZ31 Alloy Processed by Equal-Channel Angular Pressing  

NASA Astrophysics Data System (ADS)

Experiments show that the magnesium AZ31 (Mg-3 pct Al-1 pct Zn) alloy exhibits excellent superplastic properties at 623 K (350 C) after processing by equal-channel angular pressing using a die with a channel angle of 135 deg and a range of decreasing processing temperatures from 473 K to 413 K (200 C to 140 C). A maximum elongation to failure of ~1200 pct was achieved in this alloy at a tensile strain rate of 1.0 10-4 s-1. Microstructural inspection showed evidence for cavity formation and grain growth during tensile testing with the grain growth leading to significant strain hardening. An examination of the experimental data shows that grain boundary sliding is dominant during superplastic flow. Furthermore, a comprehensive review of the present results and extensive published data for the AZ31 alloy shows the exponent of the inverse grain size is given by p ? 2 which is consistent with grain boundary sliding as the rate-controlling flow mechanism.

Figueiredo, Roberto B.; Langdon, Terence G.

2014-07-01

360

Fluoride ions as modifiers of the oxide layer produced by plasma electrolytic oxidation on AZ91D magnesium alloy  

NASA Astrophysics Data System (ADS)

Plasma electrolytic oxidation (PEO) is a powerful technique allowing hardening and corrosion protection of valve metals due to formation of an oxide layer on the metal surface. PEO produces much thicker oxide layers as compared to anodizing, which is of critical importance for many technological applications. The present research investigated the influence of the fluoride ion concentration on the composition, structure and morphology of PEO layers on the magnesium alloy AZ91D. The obtained oxide layers were characterized with XRD, SEM, EDS and tested for corrosion resistance by linear sweep voltammetry in 3.5% NaCl medium. During this investigation it was found that KF addition produces significant changes in the structure and properties of the oxide layers. Fluorine was detected as an amorphous phase in the vicinity of the base metal for both alloys and plausible mechanism was suggested to explain these phenomena. Fluoride ions have pronounced catalytic activity and their presence considerably increases the thickness of the oxide layer. Depending on the process parameters, significant improvement of the corrosion stability of AZ91D alloy is achieved by the use of PEO.

Kazanski, Barbara; Kossenko, Alexey; Zinigrad, Michael; Lugovskoy, Alex

2013-12-01

361

Effect of Minor Alloying Elements on Localized Corrosion Behavior of Aluminum-Copper-Magnesium based Solid Solution Alloys  

NASA Astrophysics Data System (ADS)

The effects and mechanistic roles of a minor alloying element, Ni, on the localized corrosion behavior were explored by studying (Al75Cu 17Mg8)97Ni3 and Al70Cu 18Mg12 amorphous alloys. To explore the minor alloying element limited to the outer surface layers, the corrosion behavior of Al70Cu 18Mg12 amorphous alloy in solutions with and without Ni 2+ was also studied. Both Ni alloying and Ni2+ in solution improved the localized corrosion resistance of the alloys by ennobling the pitting and repassivation potentials. Pit growth by the selective dissolution of Al and Mg was also suppressed by Ni alloying. Remaining Cu and Ni reorganized into a Cu-rich polycrystalline nanoporous structure with continuous ligaments in pits. The minor Ni alloying and Ni2+ in solution suppressed the coarsening of the ligaments in the dealloyed nanoporous structure. The presence of relatively immobile Ni atoms at the surface suppressed the surface diffusion of Cu, which reduced the coarsening of the nanoporous structure, resulting in the formation of 10 to 30 nm wide Cu ligaments. Two mechanistic roles of minor alloying elements in the improvement of the pitting corrosion resistance of the solid solution alloys are elucidated. The first role is the suppression of active dissolution by altering the atomic structure. Ni in solid solution formed stronger bonds with Al, and reduces the probability of weaker Al-Al bonds. The second role is to hinder dissolution by producing a greater negative shift of the true interfacial potential at the dissolution front under the dealloyed layer due to the greater Ohmic resistance through the finer porous structure. These effects contributed to the elevation of pitting potentials by ennobling the applied potential required to produce enough dissolution for the stabilization of pits. Scientifically, this thesis advances the state of understanding of alloy dissolution, particularly the role of minor alloying elements on preferential oxidation at the atomic, nanometer, and micrometer scales. Technological implementations of the findings of the research are also discussed, including a new route to synthesize nanoporous materials with tunable porosity and new corrosion mitigation strategies for commercial Al-based alloys containing the detrimental Al2CuMg phase.

Aburada, Tomohiro

362

Research on Water Based Coating Containing Nano-Silica for Magnesium Alloy  

Microsoft Academic Search

Due to magnesium's active chemical property, a novel environmental protective water based metallic coating was developed, which mainly contains metal flake, nano-silica, silicate and silane. The coating's properties were investigated by neutral salt spray test, micro-hardness testing, adhesion test and electrochemical technique etc. Meanwhile the coating surface and microstructure was observed by scanning electron microscopy (SEM). Furthermore, the effect of

Wei Huang; Tianliang Zheng; Di Li

2006-01-01

363

Low temperature superplasticity in an AZ91 magnesium alloy processed by ECAE  

Microsoft Academic Search

An AZ91 alloy with a very small grain size of about 1 ?m was processed by ECAE. The alloy showed a large elongation of 661% at a low temperature of 473 K, which is 0.5Tm. The strain rate sensitivity was about 0.3, suggesting that the low temperature superplasticity for the AZ91 alloy is related to viscous-glide of dislocations. However, the

M. Mabuchi; H. Iwasaki; K. Yanase; K. Higashi

1997-01-01

364

Effect of Rare-Earth Additions on the Texture of Wrought Magnesium Alloys: The Role of Grain Boundary Segregation  

NASA Astrophysics Data System (ADS)

Magnesium alloys that contain certain rare-earth (RE) additions are known to have improved formability and this can be partly attributed to the different texture they display after recrystallization. Previous experimental work has identified segregation of RE to grain boundaries and dislocations as being potentially important in producing this change in behavior. In the present paper, two classical models (Langmuir-McClean and Cahn-Lcke-Stwe) are used to explore the likely effect of RE additions on grain boundary solute concentration and drag. It is demonstrated that a wide range of RE elements are predicted to segregate strongly to grain boundaries due to the large atomic size misfit with magnesium. The maximum level of segregation is produced for elements such as Y or Gd that combine a high misfit and high bulk solubility. Segregated Y is predicted to produce a solute drag pressure on migrating boundaries several orders of magnitude greater than that obtained by Al or Zn additions. It is demonstrated that while this drag is predicted to be insufficient to strongly retard static recrystallization under typical annealing conditions, it is expected to suppress dynamic recrystallization by any mechanism requiring boundary migration.

Robson, Joseph D.

2014-07-01

365

Study on the corrosion residual strength of the 1.0 wt.% Ce modified AZ91 magnesium alloy  

SciTech Connect

The effect of corrosion on the tensile behaviour of the 1.0 wt.% Ce modified AZ91 magnesium alloy was investigated by the immersion of the test bar in 3.5 wt.% NaCl aqueous solution for 0, 12, 40, 108, 204, 372 and 468 h with the subsequent tensile tests in this paper. The fractography was analyzed by scanning electron microscopy. The results show that pitting corrosion should be responsible for the drop of the corrosion residual strength within the testing time. The depth of the corrosion pits was statistically and quantitatively obtained by an optical microscopy and the maximal value was recorded as the extreme depth of the corrosion pit. Furthermore, the corrosion residual strength is linearly dependent on the extreme depth of the corrosion pit, which can be attributed to the loss of cross-sectional area and the emergence of stress concentration caused by the initiation and development of corrosion pits.

Li Chunfang [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun 130025 (China); Liu Yaohui, E-mail: liuyaohui2005@yahoo.com [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun 130025 (China); Wang Qiang; Zhang Lina; Zhang Dawei [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun 130025 (China)

2010-01-15

366

Polishing-assisted galvanic corrosion in the dissimilar friction stir welded joint of AZ31 magnesium alloy to 2024 aluminum alloy  

SciTech Connect

Galvanic corrosion of a dissimilar friction stir welded 2024-T3 Al/AZ31B-H24 Mg joint prepared using a water-based and a non-water-based polishing solution was characterized. Microstructure and the distribution of chemical elements were analyzed using optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The stir zone polished using water-based solution was observed to be much more susceptible to galvanic corrosion attack than that obtained using non-water-based polishing solution. The location of corrosion attack was observed in the narrow regions of AZ31 Mg alloy adjacent to Al2024 regions in the stir zone. The occurrence of galvanic corrosion was due to the formation of Mg/Al galvanic couples with a small ratio of anode-to-cathode surface area. The corrosion product was primarily the porous magnesium hydroxide with characteristic microcracks and exhibited a low microhardness value.

Liu, C. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada); Chen, D.L. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada)], E-mail: dchen@ryerson.ca; Bhole, S. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada); Cao, X.; Jahazi, M. [Aerospace Manufacturing Technology Centre, Institute For Aerospace Research, National Research Council Canada, 5145 Decelles Avenue, Montreal, Quebec H3T 2B2 (Canada)

2009-05-15

367

Section thickness, macrohardness and yield strength in high-pressure diecast magnesium alloy AZ91  

Microsoft Academic Search

The yield strength of high-pressure diecast (hpdc) test bars of alloy AZ91 increases with decreasing section thickness while its hardness remains approximately constant. This behaviour is in contrast with that of the gravity cast alloy, whose hardness scales with the yield strength. Vickers hardness measured on the surface of hpdc test bars using increasing loads shows that the subsurface porosity

C. H. Cceres; W. J. Poole; A. L. Bowles; C. J. Davidson

2005-01-01

368

Processing maps for hot deformation of rolled AZ31 magnesium alloy plate: Anisotropy of hot workability  

Microsoft Academic Search

Processing maps on rolled AZ31 magnesium plate have been developed in the range 300550C and 0.000310s?1 by hot compression of specimens parallel to the rolling direction (RD), the transverse direction (TD), or the normal direction (ND) with a view to examine whether the hot workability is anisotropic. The processing map for RD specimens exhibited a single wide domain of workability

Y. V. R. K. Prasad; K. P. Rao

2008-01-01

369

Physical metallurgy of metastable Bcc lanthanide-magnesium alloys for R = La, Gd, and Dy  

SciTech Connect

Bcc La-Mg, Gd-Mg, and Dy-Mg alloys have been prepared by an ice water/acetone quench from liquid melts. Single-phase alloys could be retained in a window around the eutectoid composition: 13 to 22 at. pct Mg, 23.6 to 29 at. pct Mg, and 27 to 29 at. pct Mg for La, Gd, and Dy alloys, respectively. At the center of the windows, x-ray diffraction peaks are extremely sharp as in equilibrium bcc structures; however, as alloy composition is moved away from the eutectoid, line broadening is observed. Reversion of the bcc phase to the equilibrium microstructure for R-Mg alloys (R = La, Gd, or Dy) has been characterized by differential thermal analysis (DTA) or differential scanning calorimetry (DSC) and isothermal annealing. La-Mg alloys revert directly to {alpha}La (dhcp) + LaMg at about 350{degrees}C when heated at 10{degrees}C/min. In contrast, the Gd and Dy alloys revert by a two-step process: first, a transition to an intermediate distorted hcp phase between 300{degrees}C and 400{degrees}C, and, second, the relaxation of this phase to {alpha}R (hcp) + RMg at about 490{degrees}C when heated at 10{degrees}C/min. Isothermal annealing and high temperature x-ray diffraction confirm the nature of these reactions.

Herchenroeder, J.W. (Delco Remy, Div. of General Motors Corp., IN (US)); Manfrinetti, P. (via acquistapace 4/5, 15067 Novi Ligure, AL (IT)); Gschneidner, K.A. Jr. (Ames Lab. and Dept. of Materials Science and Engineering, Iowa State Univ., Ames, IA (US))

1989-09-01

370

Microstructure and mechanical properties of ZA62 based magnesium alloys with calcium addition  

Microsoft Academic Search

As-cast microstructure and mechanical properties of Mg-6Zn-2Al-0.3Mn (ZA62) alloys with calcium addition were investigated. The as-cast microstructure of the base alloy ZA62 consists of the a-Mg matrix and eutectic phase Mg51Zn20. The Mg51Zn20 eutectic was gradually replaced by MgZn phase and Mg32(Al,Zn)49 phase when calcium is added into the base alloy. Further addition of calcium leads to the increase of

Xiao-feng WAN; Yang-shan SUN; Feng XUE; Jing BAI; Wei-jian TAO

2010-01-01

371

Effect of magnesium content on the semi solid cast microstructure of hypereutectic aluminum-silicon alloys  

NASA Astrophysics Data System (ADS)

A comprehensive study of microstructural evolution of A390 hypereutectic aluminum-silicon alloy (Al-17%Si-4.5%Cu-0.5%Mg) with addition of Mg contents up to 10% was carried out during semi solid metal processing as well as conventional casting. As a first step, the FACTSAGE thermodynamic databank and software was applied in order to investigate the phase diagram, the solidification behavior as well as the identification of the components that are formed during the solidification of A390 alloy with different Mg contents for equilibrium and non-equilibrium (Schiel) conditions. With higher Mg content between 4.2 - 7.2 %, the Mg2Si intermetallic phase is solidified in the eutectic network according to the ternary reaction together the primary silicon due to the binary reaction of Liq ? Si + Mg2Si. However the primary silicon is still the first solidified phase in this critical Mg zone. For Mg contents greater than 7.2%, the Mg2Si solidifies first as a primary phase. In fact, the Mg2Si is solidified during the primary, the binary and the ternary reactions and can be observed in the microstructure as a eutectic phase and a pro-eutectic phase with different morphology. In the next stage, the experimental tests were carried out in order to verify the accuracy of the results obtained by the FACTSAGE software. The microstructures of the A390 and the 6 and 10 wt% Mg alloys were investigated using conventional casting and rheocasting (stir casting) processes with continuous cooling solidification. The results showed that, for both processes, the microstructure of the eutectic network for high Mg alloys, specifically the eutectic Si phase is modified compared to the eutectic Si in the microstructure of A390 alloy. However the alloys with 6% and 10% Mg have a similar eutectic morphology. The eutectic formation temperature was measured by placing the thermocouple into the melt for determination of the cooling curves. DSC (Differential Scanning Calorimeter) test were also carried out. The results are in good agreement with the FACTSAGE results confirming the reduction of eutectic formation temperature with addition of Mg up to 4.2% and nearly the same temperature for 6 and 10% Mg alloys. Finally, the hardness of the A390 and the 6 and 10% Mg alloys was evaluated for conventionally cast samples and after T6 heat treatment. As expected, the high Mg content alloys showed higher hardness values compared to the A390 alloy. This is a significant finding because A390 is used in high wear resistance applications at medium or elevated temperature. Therefore, the A390 alloy with higher Mg addition can improve the wear resistance of this alloy. The reason for the increased in hardness of Mg can be attributed to the modification of eutectic silicon in the matrix, the presence of eutectic Mg2 Si in the matrix as well as the increase of solid fraction of primary phases from 6.1% for A390 to 12.2% for the 10% Mg alloy. The T6 heat treatment increased the value of hardness for all samples. However, contrary to the as-cast samples, the hardness of A390 alloy in T6 condition shows higher increase than the high Mg alloys. This phenomenon can be attributed to the precipitation hardening of alpha-Al phase during the heat treatment. Since the matrix of A390 consists of more alpha-Al phase when compared to the high Mg content alloys, the increases in hardness of A390 alloy is more significant.

Hekmat-Ardakan, Alireza

372

Comparative study of CW, nanosecond- and femtosecond-pulsed laser microcutting of AZ31 magnesium alloy stents.  

PubMed

Magnesium alloys constitute an interesting solution for cardiovascular stents due to their biocompatibility and biodegradability in human body. Laser microcutting is the industrially accepted method for stent manufacturing. However, the laser-material interaction should be well investigated to control the quality characteristics of the microcutting process that concern the surface roughness, chemical composition, and microstructure of the final device. Despite the recent developments in industrial laser systems, a universal laser source that can be manipulated flexibly in terms of process parameters is far from reality. Therefore, comparative studies are required to demonstrate processing capabilities. In particular, the laser pulse duration is a key factor determining the processing regime. This work approaches the laser microcutting of AZ31 Mg alloy from the perspective of a comparative study to evaluate the machining capabilities in continuous wave (CW), ns- and fs-pulsed regimes. Three industrial grade machining systems were compared to reach a benchmark in machining quality, productivity, and ease of postprocessing. The results confirmed that moving toward the ultrashort pulse domain the machining quality increases, but the need for postprocessing remains. The real advantage of ultrashort pulsed machining was the ease in postprocessing and maintaining geometrical integrity of the stent mesh after chemical etching. Resultantly, the overall production cycle time was shortest for fs-pulsed laser system, despite the fact that CW laser system provided highest cutting speed. PMID:24985208

Gkhan Demir, Ali; Previtali, Barbara

2014-06-01

373

Novel method for controllable fabrication of a superhydrophobic CuO surface on AZ91D magnesium alloy.  

PubMed

A novel method for controllable fabrication of a superhydrophobic CuO surface on AZ91D magnesium alloy is reported in this paper. Hierarchical structure composed of micro/nano-featherlike CuO was obtained by electrodeposition of Cu-Zn alloy coating and subsequently an electrochemical anodic treatment in alkaline solution. After modification with lauric acid, the surface became hydrophobicity/superhydrophobicity. The formation of featherlike CuO structures was controllable by varying the coating composition. By applying SEM, ICP-AES, and water contact angle analysis, the effects of coating composition on the surface morphology and hydrophobicity of the as-prepared surfaces were detailedly studied. The results indicated that at the optimal condition, the surface showed a good superhydrophobicity with a water contact angle as high as 155.5 1.3 and a sliding angle as low as about 3. Possible growth mechanism of featherlike CuO hierarchical structure was discussed. Additionally, the anticorrosion effect of the superhydrophobic surface was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. The interface model for anticorrosion mechanism of superhydrophobic surface in corrosive medium was proposed. Besides, the mechanical stability test indicated that the resulting superhydrophobic surfaces have good mechanical stability. PMID:22845176

She, Zuxin; Li, Qing; Wang, Zhongwei; Li, Longqin; Chen, Funan; Zhou, Juncen

2012-08-01

374

Preliminary research on a novel bioactive silicon doped calcium phosphate coating on AZ31 magnesium alloy via electrodeposition.  

PubMed

A silicon doped calcium phosphate coating was obtained successfully on AZ31 alloy substrate via pulse electrodeposition. A novel dual-layer structure was observed with a porous lamellar-like and outer block-like apatite layer. In vitro immersion tests were adopted in simulated body fluid within 28 days of immersion. Slow degradation rate obtained from weight loss was observed for the Si-doped Ca-P coating, which was also consistent with the results of electrochemical experiments showing an enhanced corrosion resistance for the coating. Further formation of an apatite-like layer on the surface after immersion proved better integrity and biomineralization performance of the coating. Biological characterization was carried out for viability, proliferation and differentiation of MG63 osteoblast-like cells. The coating showed a good cell growth and an enhanced cell proliferation. Moreover, an increased activity of osteogenic marker ALP was found. All the results demonstrated that the Si-doped calcium phosphate was perspective to be used as a coating for magnesium alloy implants to control the degradation rate and enhance the bioactivity, which would facilitate the rapidity of bone tissue repair. PMID:24433888

Qiu, Xun; Wan, Peng; Tan, Lili; Fan, Xinmin; Yang, Ke

2014-03-01

375

Phase Stability of Low-Density, Multiprincipal Component Alloys Containing Aluminum, Magnesium, and Lithium  

NASA Astrophysics Data System (ADS)

A series of low-density, multiprincipal component alloys containing high concentrations of Al, Mg, Li, Zn, Cu and/or Sn was designed using a strategy based on high-entropy alloys (HEAs). The alloys were prepared by induction melting under high-purity argon atmosphere, and the resulting microstructures were characterized in the as-cast condition. The resulting microstructures are multiphase and complex and contain significant volume fractions of disordered solutions and intermetallic compounds. By analyzing the atomic size difference, enthalpy of mixing, entropy of mixing, electronegativity difference, and valence electron concentration among the constituent elements, modified phase formation rules are developed for low-density multiprincipal component alloys that are more restrictive than previously established limits based on more frequently studied HEAs comprising mostly transition metals. It is concluded that disordered solid solution phases are generally less stable than competing ordered compounds when formulated from low-density elements including Al, Mg, and Li.

Yang, X.; Chen, S. Y.; Cotton, J. D.; Zhang, Y.

2014-10-01

376

Dry Sliding Wear Characteristics of Gravity Die-Cast Magnesium Alloys  

NASA Astrophysics Data System (ADS)

The paper deals with the wear behavior of conventional cast Mg-Sn-based alloys. The alloys were studied through pin- on- disk wear test under four different loading conditions; namely, 9.8, 19.6, 29.4, and 39.2 N. The study highlights the cumulative wear loss, volumetric wear loss, dry sliding wear rate, and coefficient of friction of the alloys. The volumetric wear increased with increasing applied load. The wear mechanism was studied with scanning electron microscope. The wear occurs mainly by plowing mechanism and also by delamination. During wear, extensive plastic deformation and work hardening occurred. Microstructural analysis has been carried out for all the alloys at different loading conditions.

Poddar, Palash; Das, Arpan; Sahoo, K. L.

2014-04-01

377

Phase Stability of Low-Density, Multiprincipal Component Alloys Containing Aluminum, Magnesium, and Lithium  

NASA Astrophysics Data System (ADS)

A series of low-density, multiprincipal component alloys containing high concentrations of Al, Mg, Li, Zn, Cu and/or Sn was designed using a strategy based on high-entropy alloys (HEAs). The alloys were prepared by induction melting under high-purity argon atmosphere, and the resulting microstructures were characterized in the as-cast condition. The resulting microstructures are multiphase and complex and contain significant volume fractions of disordered solutions and intermetallic compounds. By analyzing the atomic size difference, enthalpy of mixing, entropy of mixing, electronegativity difference, and valence electron concentration among the constituent elements, modified phase formation rules are developed for low-density multiprincipal component alloys that are more restrictive than previously established limits based on more frequently studied HEAs comprising mostly transition metals. It is concluded that disordered solid solution phases are generally less stable than competing ordered compounds when formulated from low-density elements including Al, Mg, and Li.

Yang, X.; Chen, S. Y.; Cotton, J. D.; Zhang, Y.

2014-07-01

378

Titanium and Magnesium Co-Alloyed Hematite Thin Films for Photoelectrochemical Water Splitting  

SciTech Connect

Using a combination of density functional theory calculation and materials synthesis and characterization we examine the properties of charge-compensated Ti and Mg co-alloyed hematite thin films for the application of photoelectrochemical (PEC) water splitting. We find that the charge-compensated co-alloying results in the following effects: (1) It enhances the solubility of Mg and Ti, which leads to reduced electron effective mass and therefore increased electron mobility; (2) It tunes the carrier density and therefore allows the optimization of electrical conductivity; and (3) It reduces the density of charged defects and therefore reduces carrier recombination. As a result, the Ti and Mg co-alloyed hematite thin films exhibit improved water oxidation photocurrent magnitudes as compared to pure hematite thin films. Our results suggest that charge-compensated co-alloying is a plausible approach for engineering hematite for the application of PEC water splitting.

Tang, H.; Yin, W. J.; Matin, M. A.; Wang, H.; Deutsch, T.; Al-Jassim, M. M.; Turner, J. A.; Yan, Y.

2012-04-01

379

Mechanical Flow Response and Anisotropy of Ultra-Fine Grained Magnesium and Zinc Alloys  

E-print Network

mechanical and tribological properties. Both alloys have been successfully processed using equal channel angular extrusion (ECAE) following different processing routes in order to produce samples with a wide variety of microstructures and crystallographic...

Al Maharbi, Majid H.

2011-02-22

380

Effect of Texture on Formability and Mechanical Anisotropy of a Severe Plastically Deformed Magnesium Alloy  

E-print Network

in better low temperature formability and better control of mechanical flow anisotropy. AZ31B Mg alloy has been successfully processed using equal channel angular extrusion (ECAE) following different processing routes, multiple passes, and different...

Modarres Razavi, Sonia

2012-02-14

381

Developing superplasticity in a magnesium alloy through a combination of extrusion and ECAP  

Microsoft Academic Search

A new processing procedure was applied to a cast Mg-9% Al alloy. This procedure involves the sequential application of extrusion and equal-channel angular pressing and is designated EX-ECAP. Experiments show that the Mg-9% Al alloy has an initial grain size of ~50 ?m after casting but this is reduced to ~12 ?m after extrusion and it is further reduced to

K. Matsubara; Y. Miyahara; Z. Horita; T. G. Langdon

2003-01-01

382

Serrated flow and enhanced ductility in coarse-grained aluminum-magnesium alloys  

NASA Astrophysics Data System (ADS)

Aluminum 5XXX alloys are of industrial importance and interest as they combine a wide range of desirable strength, forming and welding characteristics with a high resistance to corrosion. The presence of Mg in these alloys ensures favorable mechanical properties. However, the room temperature stretching performance of these alloys is limited. Moreover, Al-Mg alloys are known for being susceptible to the Portevin-LeChatelier effect when deformed at room temperature. Nevertheless, improvements in ductility can be achieved through warm forming, especially when the ductility approaches superplastic levels. The aim of this study was to test for enhanced ductility in three coarse-grained Al-Mg alloys namely, super-pure Al-3%Mg and Al-5%Mg, and commercial AA 5056 alloy. The temperature-dependent flow stress and rate sensitivity behavior of these alloys was investigated by means of tensile testing using ASTM E8M-04 standard samples. Samples were deformed to 10% strain to allow enough deformation to occur such that serrations in the dynamic strain aging (DSA) temperature/strain rate range would be rendered visible on a stress-strain curve. Using this information, the regions of negative and higher-than-normal strain rate sensitivity ('m') were plotted and tensile tests to failure were performed in the vicinity of maximum 'm'. ASTM E2448-06 standard samples for superplasticity tensile testing were used in this case. A maximum ductility of 170% was recorded with these samples and this was found to increase to nearly 300% when the gage length was shortened. It was observed that the DSA serrations were more prominent at lower strain rates, higher temperatures and higher Mg contents. The results of this study show clearly that if the rate sensitivity is high enough, then enhanced ductility in coarse-grained materials is possible at temperatures well below the maximum test temperature.

Samuel, Ehab

383

Effect of Microstructure on Cavitation during Hot Deformation of a Fine-Grained Aluminum-Magnesium Alloy as Revealed through Three-Dimensional Characterization  

NASA Astrophysics Data System (ADS)

The effect of microstructure on cavitation developed during hot deformation of a fine-grained AA5083 aluminum-magnesium alloy is investigated. Two-point correlation functions and three-dimensional (3-D) microstructure characterization reveal that cavitation depends strongly on the mechanism that controls plastic deformation. Grain-boundary-sliding (GBS) creep produces large, interconnected cavities rapidly during plastic straining. Solute-drag (SD) creep produces isolated cavities with less total volume fraction at a given strain. The 3-D microstructure data reveal adjacency between various microstructural features. Cavities are observed to be preferentially adjacent to large Al6(Mn,Fe) particles and to Mg-Si particles of all observed sizes. These data suggest that cavities preferentially nucleate at Mg-Si particles and at large Al6(Mn,Fe) particles. This result may be applied to reduce cavitation in commercial hot-forming operations utilizing aluminum-magnesium alloys.

Chang, Jung-Kuei Brian; Taleff, Eric M.; Krajewski, Paul E.

2009-12-01

384

Effect of Na2SiO3 concentration on the properties of AZ31 magnesium alloy prepared by electrolytic plasma processing  

NASA Astrophysics Data System (ADS)

The effect of Na2SiO3 concentration on the dense ceramic oxide coatings prepared on a AZ31 magnesium alloy through electrolytic plasma processing in a NaOH-Na2SiF6 electrolytic solution, have been investigated. The x-ray diffraction (XRD) results showed that the coating formed in silicate electrolyte was mainly composed of MgO, Mg2SiO4. Scanning electron microscopy (SEM) micrographs reveals that the number of pores on coatings decreases by increasing concentration of Na2SiO3 and coatings prepared in 12-20 g/L of Na2SiO3 show similar surface morphologies. The observed micro-hardness of coating layers is over 1000 Hv, which is much larger than that of the original AZ31 magnesium alloy without electrolytic plasma processing.

Ahn, Byung-Hyun; Lee, Dong-Gun; Cho, Ho-Je; Lee, Seung-Rok; Ahmed, Faheem; Anwar, M. S.; Koo, Bon-Heun

2013-11-01

385

Synthesis, Characterization and Cold Workability of Cast Copper-Magnesium-Tin Alloys  

NASA Astrophysics Data System (ADS)

The use of Mg as an alloying element in copper alloys has largely been overlooked in scientific literature and technological applications. Its supposed tribological compatibility with iron makes it an interesting option to replace Pb in tribological alloys. This work describes the casting process of high-quality thin slabs of Cu-Mg-Sn alloys with different compositions by means of conventional methods. The resulting phases were analyzed using X-ray diffraction, scanning electron microscopy, optical microscopy, and energy dispersive X-ray spectroscopy techniques. Typical dendritic ?-Cu, eutectic Cu2Mg(Sn) and eutectoid non-equilibrium microstructures were found. Tensile tests and Vickers microhardness show the excellent hardening capability of Mg as compared to other copper alloys in the as-cast condition. For some of the slabs and compositions, cold rolling reductions of over 95 pct have been easily achieved. Other compositions and slabs have failed during the deformation process. Failure analysis after cold rolling reveals that one cause for brittleness is the presence of casting defects such as microshrinkage and inclusions, which can be eliminated. However, for high Mg contents, a high volume fraction of the intermetallic phase provides a contiguous path for crack propagation through the connected interdendritic regions.

Bravo Bnard, Agustn Eduardo; Martnez Hernndez, David; Gonzlez Reyes, Jos Gonzalo; Ortiz Prado, Armando; Schouwenaars Franssens, Rafael

2014-02-01

386

Improvement of corrosion properties in an aluminum-sprayed AZ31 magnesium alloy by a post-hot pressing and anodizing treatment  

Microsoft Academic Search

The corrosion protection afforded by an aluminum arc-spray coating and a post-treatment consisted of hot pressing and anodizing on an AZ31 magnesium alloy has been studied by using polarization and electrochemical impedance techniques. The corrosion current densities of the Al arc-sprayed AZ31 specimens in their spray-coated condition, and after hot pressed under 500 and 1600 MPa conditions, were found to

Liu-Ho Chiu; Chun-Chin Chen; Chih-Fu Yang

2005-01-01

387

Constitutive prediction and dependence of tensile properties of high-pressure die-cast AM60B and AZ91D magnesium alloy on microporosity  

Microsoft Academic Search

The effect of micro-voids on the tensile property of high-pressure die-cast AM60B and AZ91D magnesium alloy was investigated\\u000a through systematic experimental approaches, with a constitutive prediction on the load carrying capacity and strain-related\\u000a factors. The strain rate sensitivity was measured through the incremental strain rate change test, and the microporosity was\\u000a measured from a comparison between the area of the

Choong Do Lee

2006-01-01

388

Development and compatibility of magnesium matrix fuel plates clad with 6061 aluminum alloy.  

SciTech Connect

Aluminum (Al) is a commonly used matrix for research reactor fuel plates. It has been found that a reaction between the fuel and the aluminum matrix may reduce or increase the irradiation stability of the fuel. To further understand the contribution of the reaction to the irradiation stability, experiments to develop a non-reacting matrix were performed. The work focused on magnesium (Mg), which is an excellent non-reacting matrix candidate and has a neutron absorption coefficient similar to Al. To avoid the formation of a liquid Al/Mg phase, improvements were made to the roll bonding process to achieve acceptable bonding at 415 C. After these methods were developed, fuel plates were produced with two fuels, uranium (U)-2 w/o molybdenum (Mo) and U-10-w/o Mo with two matrices, Al and Mg. A reaction between the magnesium and the 6061 Al cladding was discovered to take place during the processing at 415 C. To minimize the amount of reaction, methods were successfully developed to roll bond the fuel plates at 275 C. No reaction zone was observed in fuel plates processed at 275 C. Using this method, fuel plates with a Mg matrix are planned to be fabricated and included in the next irradiation matrix for the RERTR high density fuel development program.

Wiencek, T. C.

1998-10-22

389

Grain Refinement of Magnesium Alloys: A Review of Recent Research, Theoretical Developments, and Their Application  

NASA Astrophysics Data System (ADS)

This paper builds on the "Grain Refinement of Mg Alloys" published in 2005 and reviews the grain refinement research on Mg alloys that has been undertaken since then with an emphasis on the theoretical and analytical methods that have been developed. Consideration of recent research results and current theoretical knowledge has highlighted two important factors that affect an alloy's as-cast grain size. The first factor applies to commercial Mg-Al alloys where it is concluded that impurity and minor elements such as Fe and Mn have a substantially negative impact on grain size because, in combination with Al, intermetallic phases can be formed that tend to poison the more potent native or deliberately added nucleant particles present in the melt. This factor appears to explain the contradictory experimental outcomes reported in the literature and suggests that the search for a more potent and reliable grain refining technology may need to take a different approach. The second factor applies to all alloys and is related to the role of constitutional supercooling which, on the one hand, promotes grain nucleation and, on the other hand, forms a nucleation-free zone preventing further nucleation within this zone, consequently limiting the grain refinement achievable, particularly in low solute-containing alloys. Strategies to reduce the negative impact of these two factors are discussed. Further, the Interdependence model has been shown to apply to a broad range of casting methods from slow cooling gravity die casting to fast cooling high pressure die casting and dynamic methods such as ultrasonic treatment.

StJohn, D. H.; Easton, M. A.; Qian, M.; Taylor, J. A.

2013-07-01

390

Corrosion resistance of AZ91D magnesium alloy with electroless plating pretreatment and Ni-TiO{sub 2} composite coating  

SciTech Connect

In this paper, a protective multilayer coating, with electroless Ni coating as bottom layer and electrodeposited Ni-TiO{sub 2} composite coating as top layer, was successfully prepared on AZ91D magnesium alloy by a combination of electroless and electrodeposition techniques. Scanning electron microscopy and X-ray diffraction were employed to investigate the surface, cross-section morphologies and phase structure of coatings, respectively. The electrochemical corrosion behaviors of coatings in 3.5 wt.% NaCl solutions were evaluated by electrochemical impedance spectroscopy, open circuit potential and potentiodynamic polarization techniques. The results showed that the corrosion process of Ni-TiO{sub 2} composite coating was mainly composed of three stages in the long-term immersion test in the aggressive media, and could afford better corrosion and mechanical protection for the AZ91D magnesium alloy compared with single electroless Ni coating. The micro-hardness of the Ni-TiO{sub 2} composite coating improved more than 5 times than that of the AZ91D magnesium alloy.

Zhang Shiyan [School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Li Qing, E-mail: liqingswu@yeah.net [School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Yang Xiaokui [School of Materials Science and Engineering, Southwest University, Chongqing, 400715 (China); Zhong Xiankang; Dai Yan; Luo Fei [School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

2010-03-15

391

Localized Corrosion Behavior of Aluminum-Magnesium-Silicon Alloy in Ground Water  

Microsoft Academic Search

The localized corrosion behavior of Al-Mg-Si alloy (Al 6063, UNS A96063) in five types of ground waters found in Japan was studied in terms of the relationship between chemical composition of the ground water and the electrochemical characteristics. Localized corrosion (nodular pitting corrosion surrounded with white corrosion products) occurred in all aerated, original ground water after immersion for 480 h,

F. Sato; Y. Asakawa

1999-01-01

392

Assessment of Biodegradable Magnesium Alloys for Enhanced Mechanical and Biocompatible Properties  

Microsoft Academic Search

Biomaterials have been used for more than a century in the human body to improve body functions and replace damaged tissues. Currently approved and commonly used metallic biomaterials such as, stainless steel, titanium, cobalt chromium and other alloys have been found to have adverse effects leading in some cases, to mechanical failure and rejection of the implant. The physical or

Puneet Kamal S Gill

2012-01-01

393

Influence of preliminary extrusion conditions on the superplastic properties of a magnesium alloy processed by ECAP  

Microsoft Academic Search

The microstructures and properties of a two-phase Mg8% Li alloy were evaluated in three different conditions: after casting; after casting followed by extrusion at different temperatures and speeds; and after casting, extrusion and processing by ECAP for four passes at room temperature using a die with a channel angle of 135. The results show extrusion introduces significant grain refinement and

Mitsuaki Furui; Hiroki Kitamura; Hiroshi Anada; Terence G. Langdon

2007-01-01

394

Failure analysis of AZ31 magnesium alloy sheets based on the extended GTN damage model  

NASA Astrophysics Data System (ADS)

Based on the Gurson-Tvergaard-Needleman (GTN) model and Hill's quadratic anisotropic yield criterion, a combined experimental-numerical study on fracture initiation in the process of thermal stamping of Mg alloy AZ31 sheets was carried out. The aim is to predict the formability of thermal stamping of the Mg alloy sheets at different temperatures. The presented theoretical framework was implemented into a VUMAT subroutine for ABAQUS/EXPLICIT. Internal damage evolution due to void growth and coalescence developed at different temperatures in the Mg alloy sheets was observed by scanning electron microscopy (SEM). Moreover, the thermal effects on the void growth, coalescence, and fracture behavior of the Mg alloy sheets were analyzed by the extended GTN model and forming limit diagrams (FLD). Parameters employed in the GTN model were determined from tensile tests and numerical iterative computation. The distribution of major and minor principal strains in the specimens was determined from the numerical results. Therefore, the corresponding forming limit diagrams at different stress levels and temperatures were drawn. The comparison between the predicted forming limits and the experimental data shows a good agreement.

Wang, Rui-ze; Chen, Zhang-hua; Li, Yu-jie; Dong, Chao-fang

2013-12-01

395

Microstructural characterization of a die-cast magnesium-rare earth alloy  

Microsoft Academic Search

Microstructural characterization of high-pressure die-cast alloy MEZ (Mg2.5RE0.35Zn0.3Mn) reveals equiaxed dendrites of ?-Mg with a partially divorced interdendritic eutectic. Detailed diffraction studies coupled with WDS analysis reveal the presence of a continuous Mg12RE intermetallic phase in the eutectic aggregate along with fine Mg particles.

I. P Moreno; T. K Nandy; J. W Jones; J. E Allison; T. M Pollock

2001-01-01

396

The influence of biodegradable magnesium alloys on the osteogenic differentiation of human mesenchymal stem cells.  

PubMed

The postdegradation effect of pure Mg, Mg-1Y, Mg-5Al, and Mg-2Ca alloys on the differentiation, proliferation and gene expression of human mesenchymal stem cells (hMSCs) was investigated. It was revealed that that Mg(2+) ions result in an increase in cell proliferation. However, we observed a maximum concentration (approximately 8.0 10(-4) M) that was favourable to ATP production, above which ATP production began to decrease. In contrast to proliferation, no maximum concentration for osteogenic differentiation was observed, with increasing concentration of Mg(2+) ions resulting in an increase in osteogenic differentiation across the entire tested range. Interestingly, the Mg-2Ca alloy had minimal effect on osteogenic differentiation, with Mg-1Y and pure Mg having a superior effect on the proliferation and differentiation of hMSCs. This was also observed from gene expression data, where these alloys upregulated TGF?-1, SMAD4, FGF-2, FGF-10, and BMP-2, while SOX-2, SOX-9, and TNF-? were downregulated. Increased expression of TGF?-1, SMAD4, BMPs, and COLIA1 protein provided further evidence to support osteogenic differentiation and that the influence of the alloying extracts on differentiation may be via the SMAD signaling pathway. 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 4346-4357, 2014. PMID:24677428

Li, Rachel W; Kirkland, Nicholas T; Truong, John; Wang, Jian; Smith, Paul N; Birbilis, Nick; Nisbet, David R

2014-12-01

397

High strain rate superplasticity of TiC particulate reinforced magnesium alloy composite by vortex method  

SciTech Connect

The superplastic characteristics of a Mg-5%Zn/TiCp composite, fabricated by vortex method, extrusion, and hot-rolling, were investigated. The following results were obtained: (1) the strain rate sensitivity (m value) of the composite with Vf = 0.20 is about 0.33; (2) the hot-rolled composite exhibited a total elongation of 340% at strain rates 0.067 s{sup {minus}1} at 743 K; (3) the fracture surface of the composite showed fibrous features, indicating the presence of partial melting, since the composite was deformed apparently above the solidus temperature of the Mg-5%Zn matrix; (4) the presence of the liquid phase can enhance HSRS phenomenon in magnesium based composite.

Lim, S.W.; Imai, Tsunemichi; Nishida, Yoshinori [National Industrial Research Inst. of Nagoya (Japan)] [National Industrial Research Inst. of Nagoya (Japan); Choh, Takao [Nagoya Univ. (Japan)] [Nagoya Univ. (Japan)

1995-06-01

398

The Effect of Thermomechanical Processing on the Tensile, Fatigue, and Creep Behavior of Magnesium Alloy AM60  

SciTech Connect

Tensile, fatigue, fracture toughness, and creep experiments were performed on a commercially available magnesium-aluminum alloy (AM60) after three processing treatments: (1) as-THIXOMOLDED (as-molded), (2) THIXOMOLDED then thermomechanically processed (TTMP), and (3) THIXOMOLDED then TTMP then annealed (annealed). The TTMP procedure resulted in a significantly reduced grain size and a tensile yield strength greater than twice that of the as-molded material without a debit in elongation to failure ({epsilon}{sub f}). The as-molded material exhibited the lowest strength, while the annealed material exhibited an intermediate strength but the highest {epsilon}{sub f} (>1 pct). The TTMP and annealed materials exhibited fracture toughness values almost twice that of the as-molded material. The as-molded material exhibited the lowest fatigue threshold values and the lowest fatigue resistance. The annealed material exhibited the greatest fatigue resistance, and this was suggested to be related to its balance of tensile strength and ductility. The fatigue lives of each material were similar at both room temperature (RT) and 423 K (150 C). The tensile-creep behavior was evaluated for applied stresses ranging between 20 and 75 MPa and temperatures between 373 and 473 K (100 and 200 C). During both the fatigue and creep experiments, cracking preferentially occurred at grain boundaries. Overall, the results indicate that thermomechanical processing of AM60 dramatically improves the tensile, fracture toughness, and fatigue behavior, making this alloy attractive for structural applications. The reduced creep resistance after thermomechanical processing offers an opportunity for further research and development.

Chen, Zhe [Michigan State University, East Lansing; Huang, J [Thixomat, Incorporated; Decker, R [Thixomat, Incorporated; Lebeau, S [Thixomat, Incorporated; Walker, Larry R [ORNL; Cavin, Odis Burl [ORNL; Watkins, Thomas R [ORNL; Boehlert, C. J. [Michigan State University, East Lansing

2011-01-01

399

Exceptional superplasticity in an AZ61 magnesium alloy processed by extrusion and ECAP  

Microsoft Academic Search

Experiments were conducted on a commercial AZ61 alloy to evaluate the potential for achieving an ultrafine grain size and superplastic ductilities through the use of the EX-ECAP two-step processing procedure of extrusion plus equal-channel angular pressing. The results show that EX-ECAP gives excellent grain refinement with grain sizes of ?0.6 and ?1.3?m after pressing at 473 and 523K, respectively. The

Yuichi Miyahara; Zenji Horita; Terence G. Langdon

2006-01-01

400

Microstructure and aging behavior of conventional and nanocrystalline aluminum-copper-magnesium alloys with scandium additions  

NASA Astrophysics Data System (ADS)

The influence of small amounts of scandium (0.15 and 0.3 wt.%) on the microstructure, aging behavior and mechanical properties of 2618 (Al-Cu-Mg-Fe-Ni) and C416 (Al-Cu-Mg-Ag-Mn) alloys was studied. It was observed the overall precipitation sequence and the general morphology of the aging curve were not affected by the addition of small amounts of Sc. It was also observed that a separate population of small Al3Sc particles improved the aging response and mechanical properties of low-Cu, low-Sc Al-Cu-Mg alloys, while the formation of Al5-8Cu7-4Sc particles resulted in a decrease of the mechanical properties in high-Cu Sc-containing alloys. The Sc-modified with the best aging response (2618 + 0.15 % Sc) was cryomilled in order to produce Al-Cu-Mg-Fe-Ni-Sc nanocrystalline powders. Bulk nanocrystalline samples were consolidated from the cryomilled powder using three different techniques: hot isostatic pressing and extrusion, spark plasma sintering, cold spraying. The influence of consolidation technique on the microstructure, aging behavior and mechanical properties was analyzed. The extruded and spark plasma sintered Al-Cu-Mg-Fe-Ni-Sc nanocrystalline samples presented a bimodal grain structure consisting of coarse-grained regions located at the inter-particle region, and nanocrystalline regions at the particle interiors. The aging behavior of the nanocrystalline Al-Cu-Mg-Fe-Ni-Sc alloy was characterized by softening instead of hardening. This behavior was rationalized on the basis of changes in the precipitation processes that occur in the nanocrystalline state. On the other hand, the cold spray process promoted the formation of truly nanocrystalline coatings. The mechanisms influencing the coating formation of conventional and nanocrystalline Al-Cu-Mg-Fe-Ni-Sc samples were analyzed.

Zuniga, Alejandro

401

Realization of high strength and high ductility for AZ61 magnesium alloy by severe warm working  

Microsoft Academic Search

Extruded Mg6%Al1%Zn (AZ61) alloy bar was subjected to 4-pass Equal Channel Angular Extrusion (ECAE) processing at 448573K. At the processing temperature of 448K, extremely fine grains with the average grain size of 0.5?m are formed as a result of dynamic recrystallization originated by fine Mg17Al12 (?) phase particles having 50100nm diameter dynamically-precipitated during ECAE processing. The sizes of both ?

Yu Yoshida; Keita Arai; Shota Itoh; Shigeharu Kamado; Yo Kojima

2005-01-01

402

Evaluation of microstructural effects on corrosion behaviour of AZ91D magnesium alloy  

Microsoft Academic Search

The effect of microconstituents on the corrosion and electrochemical behaviour of AZ91D alloy prepared by die-casting and ingot casting route has been investigated in 3.5% NaCl solution at pH 7.25. The experimental techniques used include constant immersion technique, in-situ corrosion monitoring, and potentiodynamic polarisation experiments. Surface examination and analytical studies were carried out using optical and scanning electron microscopy, EDX

Rajan Ambat; Naing Naing Aung; W Zhou

2000-01-01

403

The use of mechanical alloying for the preparation of palladized magnesium bimetallic particles for the remediation of PCBs.  

PubMed

The kinetic rate of dechlorination of a polychlorinated biphenyl (PCB-151) by mechanically alloyed Mg/Pd was studied for optimization of the bimetallic system. Bimetal production was first carried out in a small-scale environment using a SPEX 8000M high-energy ball mill with 4-?m-magnesium and palladium impregnated on graphite, with optimized parameters including milling time and Pd-loading. A 5.57-g sample of bimetal containing 0.1257% Pd and ball milled for 3 min resulted in a degradation rate of 0.00176 min(-1)g(-1) catalyst as the most reactive bimetal. The process was then scaled-up, using a Red Devil 5400 Twin-Arm Paint Shaker, fitted with custom plates to hold milling canisters. Optimization parameters tested included milling time, number of ball bearings used, Pd-loading, and total bimetal mass milled. An 85-g sample of bimetal containing 0.1059% Pd and ball-milled for 23 min with 16 ball bearings yielded the most reactive bimetal with a degradation rate of 0.00122 min(-1)g(-1) catalyst. Further testing showed adsorption did not hinder extraction efficiency and that dechlorination products were only seen when using the bimetallic system, as opposed to any of its single components. The bimetallic system was also tested for its ability to degrade a second PCB congener, PCB-45, and a PCB mixture (Arochlor 1254); both contaminants were seen to degrade successfully. PMID:21807459

Coutts, Janelle L; Devor, Robert W; Aitken, Brian; Hampton, Michael D; Quinn, Jacqueline W; Clausen, Christian A; Geiger, Cherie L

2011-09-15

404

Numerical and experimental evaluation of Nd:YAG laser welding efficiency in AZ31 magnesium alloy butt joints  

NASA Astrophysics Data System (ADS)

In this paper, energy aspects related to the efficiency of laser welding process using a 2 kW Nd:YAG laser were investigated and reported. AZ31B magnesium alloy sheets 3.3 mm thick were butt-welded without filler using Helium and Argon as shielding gases. A three-dimensional and semi-stationary finite element model was developed to evaluate the effect of laser power and welding speed on the absorption coefficient, the melting and welding efficiencies. The modeled volumetric heat source took into account a scale factor, and the shape factors given by the attenuation of the beam within the workpiece and the beam intensity distribution. The numerical model was calibrated using experimental data on the basis of morphological parameters of the weld bead. Results revealed a good correspondence between experiment and simulation analysis of the energy aspects of welding. Considering results of mechanical characterization of butt joints previously obtained, the optimization of welding condition in terms of mechanical properties and energy parameters was performed. The best condition is represented by the lower laser power and higher welding speed that corresponds to the lower heat input given to the joint.

Scintilla, Leonardo Daniele; Tricarico, Luigi

2013-02-01

405

Characterization of High Strain Rate Mechanical behavior of AZ31 magnesium alloy using 3D Digital Image Correlation  

SciTech Connect

Characterization of the material mechanical behavior at sub-Hopkinson regime (0.1 to 1000 s{sup -1}) is very challenging due to instrumentation limitations and the complexity of data analysis involved in dynamic loading. In this study, AZ31 magnesium alloy sheet specimens are tested using a custom designed servo-hydraulic machine in tension at nominal strain rates up to 1000 s{sup -1}. In order to resolve strain measurement artifacts, the specimen displacement is measured using 3D Digital Image correlation instead from actuator motion. The total strain is measured up to {approx} 30%, which is far beyond the measurable range of electric resistance strain gages. Stresses are calculated based on the elastic strains in the tab of a standard dog-bone shaped specimen. Using this technique, the stresses measured for strain rates of 100 s{sup -1} and lower show little or no noise comparing to load cell signals. When the strain rates are higher than 250 s{sup -1}, the noises and oscillations in the stress measurements are significantly decreased from {approx} 250 to 50 MPa. Overall, it is found that there are no significant differences in the elongation, although the material exhibits slight work hardening when the strain rate is increased from 1 to 100 s{sup -1}.

Wang, Yanli [ORNL; Xu, Hanbing [ORNL; ERDMAN III, DONALD L [ORNL; Starbuck, J Michael [ORNL; Simunovic, Srdjan [ORNL

2011-01-01

406

Mechanical properties and microstructures of a magnesium alloy gas tungsten arc welded with a cadmium chloride flux  

SciTech Connect

Gas tungsten arc (GTA) welds were prepared on 5-mm thick plates of wrought magnesium AZ31B alloy, using an activated flux. The microstructural characteristics of the weld joint were investigated using optical and scanning microscopy, and the fusion zone microstructure was compared with that of the base metal. The elemental distribution was also investigated by electron probe microanalysis (EPMA). Mechanical properties were determined by standard tensile tests on small-scale specimens. The as-welded fusion zone prepared using a CdCl{sub 2} flux exhibited a larger grain size than that prepared without flux; the microstructure consisted of matrix {alpha}-Mg, eutectic {alpha}-Mg and {beta}-Al{sub 12}Mg{sub 17}. The HAZ was observed to be slightly wider for the weld prepared with a CdCl{sub 2} flux compared to that prepared without flux; thus the tensile strength was lower for the flux-prepared weld. The fact that neither Cd nor Cl was detected in the weld seam by EPMA indicates that the CdCl{sub 2} flux has a small effect on convection in the weld pool.

Zhang, Z.D. [State Key Laboratory of Material Surface Modification by Laser, Ion, and Beams, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Liu, L.M. [State Key Laboratory of Material Surface Modification by Laser, Ion, and Beams, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China)], E-mail: liulm@dlut.edu.cn; Shen, Y.; Wang, L. [State Key Laboratory of Material Surface Modification by Laser, Ion, and Beams, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China)

2008-01-15

407

Microstructural Evolution and Flow Behavior of Twin-Roll Cast AZ41 Magnesium Alloy during Hot Compression  

NASA Astrophysics Data System (ADS)

Microstructural evolution and flow behavior of twin-roll cast AZ41 magnesium alloy during hot compression were characterized by employing deformation temperature of 300C, 350C and 400C, and strain rate ranging from 10-3 to 10-2s-1. When compressed at different temperature (300C, 350C and 400C) and strain rate (10-3 and 10-2s-1) all stress strain curves showed a flow softening behavior before strained to 0.51 due to dynamic recrystallization, even though concurrent twinning was quite active. Twinning contributed to the flow hardening behavior appeared during the end of hot compression (? > 0.51) at a strain rate of 10-2s-1 and elevated temperature (300C, 350C and 400C) in spite of the softening effect of concurrently occurred dynamic recrystallization. TEM image showed that discontinuous recrystallization occurred when deformed at elevated temperature as high as 400C and the strain rate ranging from 10-2 to 10-3s-1. It is suggested that dislocation slip, twinning and recrystallization develop in a cyclic mode from initial stage to the end of hot compression.

Liu, Zhiyi; Chen, Xu; Hou, Yanhui; Kang, Sukbong

2012-12-01

408

Microstructure and Mechanical Properties of Fiber-Laser-Welded and Diode-Laser-Welded AZ31 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The microstructures, tensile properties, strain hardening, and fatigue strength of fiber-laser-welded (FLW) and diode-laser-welded (DLW) AZ31B-H24 magnesium alloys were studied. Columnar dendrites near the fusion zone (FZ) boundary and equiaxed dendrites at the center of FZ, with divorced eutectic ?-Mg17Al12 particles, were observed. The FLW joints had smaller dendrite cell sizes with a narrower FZ than the DLW joints. The heat-affected zone consisted of recrystallized grains. Although the DLW joints fractured at the center of FZ and exhibited lower yield strength (YS), ultimate tensile strength (UTS), and fatigue strength, the FLW joints failed at the fusion boundary and displayed only moderate reduction in the YS, UTS, and fatigue strength with a joint efficiency of ~91 pct. After welding, the strain rate sensitivity basically vanished, and the DLW joints exhibited higher strain-hardening capacity. Stage III hardening occurred after yielding in both base metal (BM) and welded samples. Dimple-like ductile fracture characteristics appeared in the BM, whereas some cleavage-like flat facets together with dimples and river marking were observed in the welded samples. Fatigue crack initiated from the specimen surface or near-surface defects, and crack propagation was characterized by the formation of fatigue striations along with secondary cracks.

Chowdhury, S. M.; Chen, D. L.; Bhole, S. D.; Powidajko, E.; Weckman, D. C.; Zhou, Y.

2011-07-01

409

Hydroxyapatite-Coated Magnesium-Based Biodegradable Alloy: Cold Spray Deposition and Simulated Body Fluid Studies  

NASA Astrophysics Data System (ADS)

A simple modified cold spray process in which the substrate of AZ51 alloys were preheated to 400 C and sprayed with hydroxyapatite (HAP) using high pressure cold air nozzle spray was designed to get biocompatible coatings of the order of 20-30 ?m thickness. The coatings had an average modulus of 9 GPa. The biodegradation behavior of HAP-coated samples was tested by studying with simulated body fluid (SBF). The coating was characterized by FESEM microanalysis. ICPOES analysis was carried out for the SBF solution to know the change in ion concentrations. Control samples showed no aluminum corrosion but heavy Mg corrosion. On the HAP-coated alloy samples, HAP coatings started dissolving after 1 day but showed signs of regeneration after 10 days of holding. All through the testing period while the HAP coating got eroded, the surface of the sample got deposited with different apatite-like compounds and the phase changed with course from DCPD to ?-TCP and ?-TCMP. The HAP-coated samples clearly improved the biodegradability of Mg alloy, attributed to the dissolution and re-precipitation of apatite showed by the coatings as compared to the control samples.

Noorakma, Abdullah C. W.; Zuhailawati, Hussain; Aishvarya, V.; Dhindaw, B. K.

2013-10-01

410

Quantitative characterization of processing-microstructure-properties relationships in pressure die-cast magnesium alloys  

NASA Astrophysics Data System (ADS)

The central goal of this research is to quantitatively characterize the relationships between processing, microstructure, and mechanical properties of important high-pressure die-cast (HPDC) Mg-alloys. For this purpose, a new digital image processing technique for automatic detection and segmentation of gas and shrinkage pores in the cast microstructure is developed and it is applied to quantitatively characterize the effects of HPDC process parameters on the size distribution and spatial arrangement of porosity. To get better insights into detailed geometry and distribution of porosity and other microstructural features, an efficient and unbiased montage based serial sectioning technique is applied for reconstruction of three-dimensional microstructures. The quantitative microstructural data have been correlated to the HPDC process parameters and the mechanical properties. The analysis has led to hypothesis of formation of new type of shrinkage porosity called, "gas induced shrinkage porosity" that has been substantiated via simple heat transfer simulations. The presence of inverse surface macrosegregation has been also shown for the first time in the HPDC Mg-alloys. An image analysis based technique has been proposed for simulations of realistic virtual microstructures that have realistic complex pore morphologies. These virtual microstructures can be implemented in the object oriented finite elements framework to model the variability in the fracture sensitive mechanical properties of the HPDC alloys.

Lee, Soon Gi

411

Effects of addition of magnesium on interface structure and high-strain-rate superplasticity in Si{sub 3}N{sub 4}-reinforced Al-alloy composites  

SciTech Connect

The mechanical properties and interface structure of fine-grained Al-Cu alloy and Al-Cu-Mg alloy composites, reinforced with Si{sub 3}N{sub 4} whiskers (Si{sub 3}N{sub 4}w) and particles (Si{sub 3}N{sub 4}p), are investigated to reveal the role of magnesium addition in high-strain-rate superplasticity. The Al-Cu alloy composites, which exhibit lower elongations (< 100%), have clear interfaces between the Al-matrix and Si{sub 3}N{sub 4} crystals without any interfacial reaction. On the other hand, the interfaces in the Al-Cu-Mg alloy composites, which exhibit high elongations (> 280%), show strong reaction between the Al-matrix and Si{sub 3}N{sub 4} crystals. The result suggests that the addition of magnesium causes the reaction between the Al-matrix and Si{sub 3}N{sub 4} crystals, and consequently that partially melting of the reaction phases at the tensile-testing temperature results in the relaxation of stress concentration and suppresses the development of microcracks and cavities at the interfaces during superplastic deformation.

Jeong, H.G.; Hiraga, K. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research] [Tohoku Univ., Sendai (Japan). Inst. for Materials Research; Mabuchi, M. [National Industrial Research Inst. of Nagoya (Japan)] [National Industrial Research Inst. of Nagoya (Japan); Higashi, K. [Osaka Prefecture Univ., Sakai, Osaka (Japan). Dept. of Metallurgy and Materials Science] [Osaka Prefecture Univ., Sakai, Osaka (Japan). Dept. of Metallurgy and Materials Science

1998-11-02

412

Resistance Spot Welded AZ31 Magnesium Alloys, Part II: Effects of Welding Current on Microstructure and Mechanical Properties  

NASA Astrophysics Data System (ADS)

Resistance spot welding of AZ31 magnesium alloys from different suppliers, AZ31-SA (from supplier A) and AZ31-SB (from supplier B), was studied and compared in this article. The mechanical properties and microstructures have been studied of welds made with a range of welding currents. For both groups of welds, the tension-shear fracture load ( F C) and fracture toughness ( K C) increased with the increase in welding current. The F C and K C of AZ31-SA welds were larger than those of AZ31-SB welds. The fracture surfaces of AZ31-SB welds were relatively flatter than those of AZ31-SA. Microstructural examination via optical microscope demonstrated that almost all weld nuggets comprised two different zones, the columnar dendritic zone (CDZ), which grew epitaxially from the fusion boundary, and the equiaxed dendritic zone (EDZ), which formed in the center of the nugget. The nature and extent of the CDZ seemed to be critical to the strength and toughness of spot welds because of its position adjacent to the inherent external circular crack-like notch of spot welds and the stress concentration in this region. The width and microstructure of the CDZ were different between AZ31-SA and AZ31-SB. The AZ31-SA alloy produced finer and shorter columnar dendrites, whereas the AZ31-SB alloy produced coarser and wider columnar dendrites. The width of the CDZ close to the notch decreased with the increase of current. The CDZ disappeared when the current was higher than a critical value, which was about 24 kA for AZ31-SA and 28 kA for AZ31-SB. The microhardness of the two base materials was the same, but within the CDZ and EDZ, the hardness was greater in AZ31-SA than AZ31-SB welds. It is believed that the different microstructures of spot welds between AZ31-SA and AZ31-SB resulted in different mechanical properties; in particular, K C increased with the welding current because of the improved columnar-to-equiaxed transition.

Liu, L.; Xiao, L.; Feng, J. C.; Tian, Y. H.; Zhou, S. Q.; Zhou, Y.

2010-10-01

413

Characterization of complex, solid-state flow and mixing in the friction-stir welding (FSW) of aluminum alloy 6061-T6 to magnesium alloy AZ91D using color metallography  

Microsoft Academic Search

Semi-solid-cast magnesium (Mg) alloy AZ91D (3% solid fraction) was friction-stir welded (FSW) to aluminum (Al) alloy 6061-T6\\u000a in continuous non-porous welds. The resulting welds were analyzed in order to understand the solid-state mixing mechanisms\\u000a that create the chaotic intercalated weld zone microstructure characterized by swirls and vortexes of dynamically recrystallized\\u000a material. Severe plastic deformation in the solid-state is accommodated by

A. C. Somasekharan; L. E. Murr

2006-01-01

414

Mechanical properties of several magnesium and aluminum composites. Final report  

Microsoft Academic Search

Several composites of magnesium and aluminum alloys were tested in order to assess and evaluate their mechanical properties. The magnesium alloys were AZ91 C, ZE41 A, and commercially pure magnesium, reinforced with 40% by volume continuous graphite fiber. The tensile properties of these composites were not superior to those of unreinforced magnesium and estimates of their fracture toughness were low.

N. Tsangarakis; B. Taleghani

1992-01-01

415

Mechanism of the formation of stannate and cerium conversion coatings on AZ91D magnesium alloys  

NASA Astrophysics Data System (ADS)

The characteristics of the formation of conversion coatings on an AZ91D Mg alloy were detailed. Because the galvanic effect prevailed around the eutectic ? + ?, alkaline stannate conversion coatings nucleated first near the ? phase where plenty Mg2+ were present. Conversely, the formation of cerium conversion coatings largely relied on an increase in the interfacial pH. Intense dissolution of the primary ? phase in acid cerium nitrate solution caused hydrogen bubble evolution, which, in turn, resulted in blisters. It is evident that the galvanic corrosion routes on the AZ91D depend on the pH of the conversion coating solution.

Lee, Y. L.; Chu, Y. R.; Chen, F. J.; Lin, C. S.

2013-07-01

416

Detection of defects in laser welding of AZ31B magnesium alloy in zero-gap lap joint configuration by a real-time spectroscopic analysis  

NASA Astrophysics Data System (ADS)

The effect of surface oxide layer existing at the lap-joint faying surface of magnesium sheets is investigated on the keyhole dynamics of the weld pool and weld bead qualities. It is observed that by removing the oxide layer from the faying surface of the lap joint, a high quality weld can be achieved in the laser welding process. However, the presence of an oxide layer deteriorates the quality of the weld by forming pores at the interface of the two overlapped sheets. The purpose of this paper is to identify the correlation between the integrity of the weld and the interaction between the laser and material. A spectroscopy sensor was applied to detect the spectra emitted from a plasma plume during the laser welding of AZ31B magnesium alloy in a zero-gap lap joint configuration. The electron temperature was calculated by applying a Boltzmann plot method based on the detected spectra, and the correlation between the pore formation and the spectral signals was studied. The laser molten pool and the keyhole condition were monitored in real-time by a high speed charge-coupled device (CCD) camera. A green laser was used as an illumination source in order to detect the influence of the oxide layer on the dynamic behavior of the molten pool. Results revealed that the detected spectrum and weld defects had a meaningful correlation for real-time monitoring of the weld quality during laser welding of magnesium alloys.

Harooni, Masoud; Carlson, Blair; Kovacevic, Radovan

2014-05-01

417

Magnesium Gluconate  

MedlinePLUS

Magnesium gluconate is used to treat low blood magnesium. Low blood magnesium is caused by gastrointestinal disorders, prolonged vomiting or ... disease, or certain other conditions. Certain drugs lower magnesium levels as well.This medication is sometimes prescribed ...

418

Microstructure and Creep Behavior of High-Pressure Die-Cast Magnesium Alloy AE44  

NASA Astrophysics Data System (ADS)

The microstructure and creep behavior of a high-pressure die-cast AE44 (Mg-4Al-4RE) alloy have been studied. The creep properties were evaluated at 423 K and 448 K (150 C and 175 C) under stresses in the range 90 to 110 MPa. The microstructures before and after creep were examined by transmission electron microscopy (TEM). After creep, AE44 exhibits anomalously high stress exponents ( n = 67 at 423 K [150 C] and n = 41 at 448 K [175 C]) and stress-dependant activation energies ranging from 221 to 286 kJ/mol. The dislocation substructure developed during creep is characterized by extensive nonbasal slip and isolated but well-defined subgrain boundaries. It is shown that the anomalously high stress exponents cannot be rationalized by the threshold stress approach that is commonly adopted in analyzing the creep behavior of dispersion-strengthened alloys or metal matrix composites. A comparison in creep resistance is also made between AE44 and AE42 (Mg-4Al-2RE).

Zhu, S. M.; Nie, J. F.; Gibson, M. A.; Easton, M. A.; Bakke, P.

2012-11-01

419

The corrosion performance of die-cast magnesium alloy MRI230D in 3.5% NaCl solution saturated with Mg(OH){sub 2}  

SciTech Connect

The environmental behavior of die-cast magnesium alloy MRI230D designated for high-temperature applications was evaluated in comparison with regular AZ91D alloy. The microstructure examination was carried out using SEM, TEM, and X-ray diffraction analysis; the corrosion performance in 3.5% NaCl solution was evaluated by immersion test, salt spray testing, potentiodynamic polarization analysis, and stress corrosion behavior by Slow Strain Rate Testing (SSRT). Although the general corrosion resistance of MRI230D was slightly improved compared to that of AZ91D alloy its stress corrosion resistance was relatively reduced. The variations in the environmental behavior of the two alloys were mainly due to the differences in their chemical composition and microstructure after die casting. In particular, the differences were related to the reduced Al content in MRI230D and the addition of Ca to this alloy, which consequently affected its relative microstructure and electrochemical characteristics. - Research Highlights: {yields}Corrosion and SCC resistance of a new Mg alloy MRI230D was evaluated vs. regular AZ91D. {yields}MRI230D has a minor advantage in corrosion performance compared with AZ91D. {yields}The SCC resistance of MRI230D by SSRT analysis was relatively reduced. {yields}The reduced SCC resistance of MRI230D was due to the detrimental effect of Ca on ductility.

Aghion, E., E-mail: egyon@bgu.ac.il; Lulu, N.

2010-11-15

420

Effects of temperature-dependent material properties and shielding gas on molten pool formation during continuous laser welding of AZ91 magnesium alloy  

NASA Astrophysics Data System (ADS)

Laser welding processes are widely used for fabrications in many engineering applications such as aerospace and automotives. In this paper, a moving distributed heat source model based on Goldak's method [1] has been implemented into finite volume thermal simulations in order to predict temperature distributions during the welding process of a magnesium alloy and to study the effects of variations in thermal properties, absorption coefficient and gas shielding on the computed temperature distributions and weld pool dimensions. The main conclusion is the significant effects of varying the thermal conductivity and absorption coefficient of magnesium. Also, it has been seen that the shielding gas, besides its main role of protection against oxidation, has a significant effect on the width of the weld pool. Finally, the obtained results have been compared to the experimental ones and a satisfactory correlation has been observed, indicating the reliability of the model developed in this study.

Bannour, Sana; Abderrazak, Kamel; Mhiri, Hatem; Le Palec, Georges

2012-11-01

421

Recrystallization and superplasticity at 300 C in an aluminum-magnesium alloy  

NASA Technical Reports Server (NTRS)

Variations in thermomechanical processing (TMP) which regulate the microstructural characteristics and superplastic response of an Al-10Mg-0.1Zr alloy at 300 C were evaluated. Mechanical property data revealed that the superplastic ductility can be enhanced by simultaneously increasing the total rolling strain, the reduction per pass, and the duration of reheating intervals between passes during isothermal rolling. Texture and microscopy data were consistent with the development of a refined microstructure by recovery-dominated processes, i.e., continuous recrystallization, during the processing. The mechanisms by which a refined substructure can be progressively converted into a fine-grained structure during repeated cycles of deformation and annealing are addressed. A qualitative description of the complex sequence of developments leading to a microstructure better suited to support superplastic response is presented.

Hales, S. J.; Mcnelley, T. R.; Mcqueen, H. J.

1991-01-01

422

The Small Fatigue Crack Growth Behavior of an AM60 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The effects of thermomechanical processing and subsequent heat treatment on the small fatigue crack growth (FCG) behavior of an AM60 (Mg-6.29Al-0.28Mn wt pct) alloy were evaluated. The effects of mechanical loading parameters, such as maximum stress and load-ratio, on the small FCG behavior were also determined. Maximum stress did not appear to affect the crack propagation rate of small cracks in the stress and crack size ranges considered. Materials with different microstructures and yield stresses, introduced by different processing conditions, showed similar crack growth rates at equivalent stress intensity factor ranges. The effect of load ratio on small crack growth rates was recorded. Fracture surface characterization suggested that the fatigue crack propagation mechanism was a mixture of transgranular and intergranular cracking. Porosity and other material defects played respective important roles in determining the fatigue crack initiation and propagation behavior.

Chen, Zhe; Shyam, Amit; Huang, Jack; Decker, Ray F.; LeBeau, Steve E.; Boehlert, Carl J.

2013-02-01

423

Magnesium Research and Technology Development  

SciTech Connect

The Magnesium Research and Technical Development (MR&TD) project supports efforts to increase using magnesium in automotive applications, including improving technology, lowering costs and increasing the knowledge needed to enable alloy and manufacturing process optimization. MR&TD supports the U.S. Department of Energy (DOE)/United States Automotive Materials Partnership (USAMP) Magnesium Front End Research and Development (MFERD) project in collaboration with China and Canada. The MR&TD projects also maintains the magnesium bibliographic database at magnesium.pnl.gov.

Nyberg, Eric A.; Joost, William; Smith, Mark T.

2009-12-30

424

Effects of rare-earth elements and Ca additions on the microstructure and mechanical properties of AZ31 magnesium alloy processed by ECAP  

Microsoft Academic Search

The effects of 0.6wt.%RE, 0.6wt.%Ca and 0.3wt.%RE+0.3wt.%Ca additions on the microstructure and mechanical properties of equal channel angularly pressed (ECAPed) AZ31 magnesium alloy were investigated. After extruding, the materials were ECAPed for 1, 2, and 4 passes using route BC. After 4 passes of ECAP, AZ31 showed lower yield stress and higher ductility respect to the as-extruded condition, indicating that

S. M. Masoudpanah; R. Mahmudi

2009-01-01

425

Tensile properties of HK31XA-H24 magnesium-alloy sheet under rapid-heating conditions and constant elevated temperatures  

NASA Technical Reports Server (NTRS)

Specimens of HK31XA-H24 magnesium-alloy sheet from an experimental batch were heated to failure at nominal temperature rates from 0.2 F to 100 F per second under constant-load conditions. Rapid-heating yield and rupture stresses are presented and compared with the yield and ultimate stresses from elevated-temperature tensile stress-strain tests for 1/2-hour exposure. Linear temperature-rate parameters were used to correlate rapid-heating results by constructing master curves which can be used for predicting yield stresses and temperatures and for estimating rupture stresses and temperatures.

Gibbs, Thomas W

1956-01-01

426

Effects of NaAlO 2 on structure and corrosion resistance of microarc oxidation coatings formed on AM60B magnesium alloy in phosphateKOH electrolyte  

Microsoft Academic Search

Microarc oxidation coatings on AM60B magnesium alloy were prepared in phosphateKOH electrolytes with and without NaAlO2 addition. The effect of NaAlO2 on the characteristic of breakdown voltage in different concentrations of NaAlO2 has been studied. The compositions, structure and morphologies of the oxide coatings formed in different concentrations of NaAlO2 were determined by energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray

Jun Liang; Baogang Guo; Jun Tian; Huiwen Liu; Jinfang Zhou; Weimin Liu; Tao Xu

2005-01-01

427

Resistivity and Magneto-Optical Evidence for Variable and Incomplete Connectivity in Dense, High Critical Current Density C-alloyed Magnesium Diboride  

Microsoft Academic Search

Carbon-doped magnesium diboride was fabricated from pre-reacted pure MgB2 by\\u000amechanical alloying. The sample set had excellent critical current densities\\u000aJc(8T,4.2K) ranging from 15-60 kA\\/cm2, depending on composition.\\u000aMagneto-optical imaging detected regions up to 0.5 mm in size which were nearly\\u000a100% dense with Jc 2-6 times that of the matrix. Evaluation of resistivity\\u000acurves using the Rowell method predicts

B. J. Senkowicz; A. A. Polyanskii; R. J. Mungall; E. E. Hellstrom; D. C. Larbalestier

2006-01-01

428

Texture Development in a Friction Stir Lap-Welded AZ31B Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The present study was aimed at characterizing the microstructure, texture, hardness, and tensile properties of an AZ31B-H24 Mg alloy that was friction stir lap welded (FSLWed) at varying tool rotational rates and welding speeds. Friction stir lap welding (FSLW) resulted in the presence of recrystallized grains and an associated hardness drop in the stir zone (SZ). Microstructural investigation showed that both the AZ31B-H24 Mg base metal (BM) and SZ contained ?-Mg17Al12 and Al8Mn5 second phase particles. The AZ31B-H24 BM contained a type of basal texture (0001)<110> with the (0001) plane nearly parallel to the rolled sheet surface and <110> directions aligned in the rolling direction. FSLW resulted in the formation of another type of basal texture (0001)<100> in the SZ, where the basal planes (0001) became slightly tilted toward the transverse direction, and the prismatic planes (100) and pyramidal planes (101) exhibited a 30 deg + ( n - 1) 60 deg rotation ( n = 1, 2, 3, ) with respect to the rolled sheet normal direction, due to the shear plastic flow near the pin surface that occurred from the intense local stirring. With increasing tool rotational rate and decreasing welding speed, the maximum intensity of the basal poles (0001) in the SZ decreased due to a higher degree of dynamic recrystallization that led to a weaker or more random texture. The tool rotational rate and welding speed had a strong effect on the failure load of FSLWed joints. A combination of relatively high welding speed (20 mm/s) and low tool rotational rate (1000 rpm) was observed to be capable of achieving a high failure load. This was attributed to the relatively small recrystallized grains and high intensity of the basal poles in the SZ arising from the low heat input as well as the presence of a small hooking defect.

Naik, B. S.; Chen, D. L.; Cao, X.; Wanjara, P.

2014-09-01

429

Liquid phase formation of alkyl- and perfluoro-phosphonic acid derived monolayers on magnesium alloy AZ31 and their chemical properties.  

PubMed

Alkyl- and perfluoro-phosphonic acid derived SAMs were successfully formed on Mg alloy by liquid phase method for the first time. The chemical and anticorrosive properties of the prepared SAMs on magnesium alloys were characterized using contact angle measurements, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and electrochemical measurements. Water contact angle measurements revealed that the maximum advancing/receding water contact angles of n-octyl (OP: CH(3)(CH(2))(7)PO(OH)(2)), n-dodecyl (DP: CH(3)(CH(2))(11)PO(OH)(2)), n-octadecyl (ODP: CH(3)(CH(2))(17)PO(OH)(2)) phosphonic acid, and 2-(perfluorohexyl)ethyl (PFEP: CF(3)(CF(2))(5)CH(2)CH(2)PO(OH)(2)) phosphonic acid were 105.1/64.7, 108.3/69.6, 111.9/75.2, and 115.2/67.4 respectively. In the case of alkylphosphonic acid SAMs (OP, DP, and ODP), the advancing and receding water contact angles increased with an increase in the preparation time. The angle-resolved XPS (AR-XPS) data revealed that the film thicknesses of the OP, DP, ODP, PFEP on Mg alloy were estimated to be 0.8, 1.2, 1.7, and 1.1 nm, respectively. The XPS O 1s data support that the phosphonic acid derived SAM is covalently bound to the oxide or hydroxide surface of the Mg alloy in a monodenate or bidenate manner. Chemical stability of the alkyl- and perfluoro-phosphonic acid modified Mg alloy surfaces was investigated using aqueous solutions at pH=4.0, 7.0, and 10.0. The contact angles of OP, DP, and PFEP modified Mg surface decreased rapidly within the first 5 min after immersion in all the aqueous solutions and were less than 20. On the other hand, the contact angles of the ODP modified Mg alloy after immersion in aqueous solutions at pH 4, 7 and 10 for 5 min were 45.1, 89.3, and 85.5, respectively. The ODP modified Mg alloy had highest chemical stability in four types of the phosphonic acid derived SAMs used in this study, indicating that the molecular density of ODP on Mg alloy would be higher than those of OP, DP, PFEP on Mg alloy. The corrosion resistance of ODP modified Mg alloy was investigated by potentiodynamic polarization curve measurements. The ODP modified Mg alloy exhibits protective properties in a solution containing Cl(-) ions compared to unmodified Mg alloy. PMID:21565354

Ishizaki, Takahiro; Teshima, Katsuya; Masuda, Yoshitake; Sakamoto, Michiru

2011-08-01

430

Chemistry and electrochemistry of environment-assisted cracking of an aluminum-zinc-magnesium-copper alloy  

NASA Astrophysics Data System (ADS)

The mechanism of environment-assisted cracking (EAC) of 7xxx-series alloys is unclear, involving uncertain contributions of hydrogen embrittlement (HE) and anodic dissolution (AD). Fundamental understanding of the EAC mechanism is lacking in part because the role of the crack environment is not well understood. The objective of this research was to characterize and understand the role of the crack chemistry and electrochemistry during aqueous EAC of AA 7050. The crack environment can differ significantly from bulk conditions. Cations, produced by AD, hydrolyze causing local acidification; anions from the bulk electrolyte concentrate within the crack to maintain charge neutrality; ohmic potential drop results from ion migration and diffusion. A positive correlation exists between da/dt and [Al3+]Tip in chromate-chloride electrolyte wherein tip dissolution dominates flank corrosion in establishing the crack chemistry. Tip pH was 2 to 4 and determined by the reaction Al3+ + H 2O = AlOH2+ + H+. The tip potential (ETip) was approximately -0.90 VSCE and independent of EApp . The low ETip and pH promote H+ reduction, generating atomic and molecular H. Hydrogen bubbles restrict ion movement, substantially increasing the effective crack resistance over bulk conditions. Absorbed atomic hydrogen facilitates HE. The spontaneous transition from slow, incubation to high-rate da/dt coincides with the establishment of a critical aggressive tip chemistry and tip depolarization. Development of the critical occluded chemistry necessary for accelerated da/dt is a competitive process between opposing forces: AD, hydrolysis and migration promote an aggressive environment whereas diffusion reduces concentration gradients, thereby retarding the formation of an aggressive chemistry. Quantitative assessment of the contribution of tip dissolution to crack advance is hindered by a lack of knowledge of two key parameters: the tip corrosion front height and the effective crack conductivity. Modeling of the ECrack distribution reveals that, for a reasonable range of values of these two unknowns, the crack tip dissolution kinetics are sufficient to account for substantial fraction of the observed da/dt of peak-aged AA 7050. However, modeling also indicates that AD cannot account for the strong E App-dependence of da/dt, suggesting that HE also plays a significant role in the crack tip damage mechanism.