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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

Influence of t5 Treatment on Microstructure and Properties of Extruded ZK60 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

As-cast ZK60 magnesium alloy that has been treated by homogenizing was forward extruded at 380°C and different extrusion ratios. Half of the extruded samples were treated by T5 treatment (10 hours at 170°C). The microstructure and mechanical properties of extruded samples that have been treated by T5 treatment and not been treated by T5 treatment have been measured. Experimental results show that the T5 treatment of extruded ZK60 magnesium alloy will cause the tensile strength and hardness to increase in some sort, the yield strength to increase obviously, but elongation to decrease slightly. When ZK60 magnesium alloy is extruded at 380°C, the second phase, MgZn and a small quantity of MnZn2, will precipitate, and the distribution of second phase is even and dispersed. After T5 treatment, the change of grain size is not obvious, but the quantity of precipitated phase obviously increases comparing with extruded samples, and some of the precipitated phase aggregate and grow.

Zhang, Zhimin; Zhang, Baohong

3

Superplasticity and internal friction in microcrystalline AZ91 and ZK60 magnesium alloys processed by equal-channel angular pressing  

Microsoft Academic Search

Low-temperature superplasticity (LTSP) and internal friction in microcrystalline ZK60 and AZ91 magnesium alloys processed by equal-channel angular pressing (ECAP) are reported. Excellent low-temperature superplasticity (<300°C) was observed in ECAP-processed materials: elongations to failure are 810 and 570% in ZK60 and AZ91 alloys, respectively, at a strain rate of 3×10?3s?1. Internal friction can be practically used to determine the optimum temperature

V. N. Chuvil’deev; T. G. Nieh; M. Yu. Gryaznov; V. I. Kopylov; A. N. Sysoev

2004-01-01

4

Microstructural evolution of an ECAE-formed ZK60RE magnesium alloy in the semi-solid state  

Microsoft Academic Search

AZ91D magnesium alloy semi-solid billets prepared by the strain-induced melt activation (SIMA) process have been proposed or reported in previous literature. However, no detailed investigation has been conducted regarding Mg–Zn–Zr series magnesium alloys. In this paper, the microstructural evolution of ZK60 magnesium alloy with a rare earth (RE) addition during partial remelting has been studied. Equal channel angular extrusion (ECAE)

Zude Zhao; Qiang Chen; Yanbin Wang; Dayu Shu

2009-01-01

5

The effect of grain refinement by warm equal channel angular extrusion on room temperature twinning in magnesium alloy ZK60  

Microsoft Academic Search

The effect of the grain structure produced by warm equal channel angular extrusion (ECAE) on twinning under subsequent room temperature deformation of magnesium alloy ZK60 was investigated. It was shown that a bi-modal grain structure, characteristics of which are determined by the ECAE temperature and the number of passes, has a strong effect on the tendency to room temperature twinning.

R. Lapovok; P. F. Thomson; R. Cottam; Y. Estrin

2005-01-01

6

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

7

Microstructure, texture evolution, mechanical properties and corrosion behavior of ECAP processed ZK60 magnesium alloy for biodegradable applications.  

PubMed

Ultra-fine grained ZK60 Mg alloy was obtained by multi-pass equal-channel angular pressing at different temperatures of 250°C, 200°C and 150°C. Microstructural observations showed a significant grain refinement after ECAP, leading to an equiaxed and ultrafine grain (UFG) structure with average size of 600nm. The original extrusion fiber texture with planes oriented parallel to extrusion direction was gradually undermined during ECAP process and eventually it was substituted by a newly stronger texture component with considerably higher intensity, coinciding with ECAP shear plane. A combination of texture modification and grain refinement in UFG samples led to a marked reduction in mechanical asymmetric behavior compared to the as-received alloy, as well as adequate mechanical properties with about 100% improvement in elongation to failure while keeping relatively high tensile strength. Open circuit potential, potentiodynamic and weight loss measurements in a phosphate buffer solution electrolyte revealed an improved corrosion resistance of UFG alloy compared to the extruded one, stemming from a shift of corrosion regime from localized pitting in the as-received sample to a more uniform corrosion mode with reduced localized attack in ECAP processed alloy. Compression tests on immersed samples showed that the rate of loss of mechanical integrity in the UFG sample was lower than that in the as-received sample. PMID:24971801

Mostaed, Ehsan; Hashempour, Mazdak; Fabrizi, Alberto; Dellasega, David; Bestetti, Massimiliano; Bonollo, Franco; Vedani, Maurizio

2014-09-01

8

Influence of ECAP process on mechanical and corrosion properties of pure Mg and ZK60 magnesium alloy for biodegradable stent applications.  

PubMed

Equal channel angular pressing (ECAP) was performed on ZK60 alloy and pure Mg in the temperature range 150-250 °C. A significant grain refinement was detected after ECAP, leading to an ultrafine grain size (UFG) and enhanced formability during extrusion process. Comparing to conventional coarse grained samples, fracture elongation of pure Mg and ZK60 alloy were significantly improved by 130% and 100%, respectively, while the tensile strength remained at high level. Extrusion was performed on ECAP processed billets to produce small tubes (with outer/inner diameter of 4/2.5 mm) as precursors for biodegradable stents. Studies on extruded tubes revealed that even after extrusion the microstructure and microhardness of the UFG ZK60 alloy were almost stable. Furthermore, pure Mg tubes showed an additional improvement in terms of grain refining and mechanical properties after extrusion. Electrochemical analyses and microstructural assessments after corrosion tests demonstrated two major influential factors in corrosion behavior of the investigated materials. The presence of Zn and Zr as alloying elements simultaneously increases the nobility by formation of a protective film and increase the local corrosion damage by amplifying the pitting development. ECAP treatment decreases the size of the second phase particles thus improving microstructure homogeneity, thereby decreasing the localized corrosion effects. PMID:25482411

Mostaed, Ehsan; Vedani, Maurizio; Hashempour, Mazdak; Bestetti, Massimiliano

2014-01-01

9

Laser cladding of stainless steel on magnesium ZK60\\/SiC composite  

Microsoft Academic Search

Laser cladding of stainless steel on ZK60\\/SiC composite was achieved by using a two-step method, i.e. thermal spray and laser re-melting. This was made possible by using interlayers of brass and copper, as a result, good metallurgical bond interfaces were obtained. However, the rapid solidification condition caused liquid phase separation. As a consequence, small spheroids of copper-rich phase were formed

T. M. Yue; Q. W. Hu; Z. Mei; H. C. Man

2001-01-01

10

Influences of current density on tribological characteristics of ceramic coatings on ZK60 Mg alloy by plasma electrolytic oxidation.  

PubMed

Current density is a key factor of plasma electrolytic oxidation process. Its influences on structure, mechanical, and tribological characteristics of ceramic coatings on ZK60 Mg alloy by pulsed bipolar microplasma oxidation in Na(3)PO(4) solution were studied in this paper. Thickness, structure, composition, mechanical property, and tribological characteristics of the coatings were studied by eddy current coating thickness gauge, scanning electron microscope (SEM), X-ray diffraction (XRD), nanoindentation measurements, and ball-on-disk friction testing. The results show that all the coatings prepared under different current densities are composed of MgO phase. The amount of MgO phase, thickness and friction coefficient of the coatings increased with the increasing current density. Among three ceramic coatings produced under three current densities, the coating produced under the current density of 7 A/dm(2) got the highest nanohardness and lowest wear rate with the value of 1.7 GPa and 1.27 x 10(-5) mm(3)/Nm. PMID:20356285

Wu, Xiaohong; Su, Peibo; Jiang, Zhaohua; Meng, Song

2010-03-01

11

Corrosion resistance enhancement of magnesium ZK60\\/SiC composite by Nd:YAG laser cladding  

Microsoft Academic Search

Magnesium-based metal matrix composites (MMCs) which possess high specific stiffness and strength are attractive in applications where it is advantageous to employ low density structural materials, such as in aerospace, automotive and sports industries. However, it is well known that magnesium is one of the most active structural metals, and is usually susceptible to galvanic corrosion when in contact with

T. M. Yue; A. H. Wang; H. C. Man

1999-01-01

12

Fracture and deformation potential of magnesium alloys at low temperatures  

NASA Astrophysics Data System (ADS)

Thermal dependency of uni-axial mechanical properties in ZK60 and fracture resistance of AZ31 magnesium alloys were determined at low temperatures regime. In ZK60, this mechanical behavior was characterized in terms of stress, strain, deformation and fracture modes, followed by Acoustic Emission (AE) tracking. In AZ31, fracture toughness was assessed in relation to crack orientations, accompanied by fracture modes classification and AE monitoring. As for the former alloy, a moderate decrease in ductility was found, followed by a considerable increase in stresses, while decreasing test temperature. In addition, regardless of low temperatures, slip is still a predominant deformation mode, which controls the early stages of plastic deformation. The transition to mechanical twinning propagation mode controls the linear strain hardening stage. This transition was found to be temperature-dependent, expressed by a moderate decrease in transition strain, whereas the transition stress remains almost constant. In AZ31 alloy, a significant decrease in fracture toughness was found in the L-T orientation at low temperatures. This transition was accompanied by a mixed fracture mode, a pop-in phenomenon in the load-cod curves and by changes in AE parameters. The unlike mechanical behavior at low temperature of ZK60 compared to AZ31 was attributed to the occurrence of additional slip deformation mechanisms, based on literature findings concerning the addition of elements to pure magnesium.

Bussiba, A.; Kupiec, M.; Ifergane, S.; Stechman, A.; Ben-Artzi, A.

2002-05-01

13

Magnesium and magnesium alloys  

Microsoft Academic Search

This new handbook is the most comprehensive publication of engineering information on commercial magnesium alloys under one cover in the last sixty years. Prepared with the cooperation of the International Magnesium Association, it presents the industrial practices currently used throughout the world, as well as the properties of the products critical to their proper application. Contents include: general characteristics; physical

M. Avedesian; H. Baker

1998-01-01

14

Surface characterization and cytotoxicity response of biodegradable magnesium alloys.  

PubMed

Magnesium alloys have raised an immense amount of interest to many researchers because of their evolution as a new kind of third generation materials. Due to their biocompatibility, density, and mechanical properties, magnesium alloys are frequently reported as prospective biodegradable implant materials. Moreover, magnesium alloys experience a natural phenomenon to biodegrade in aqueous solutions due to its corrosion activity, which is excellent for orthopedic and cardiovascular applications. However, a major concern with such alloys is fast and non-uniform corrosion degradation. Controlling the degradation rate in the physiological environment determines the success of biodegradable implants. In this investigation, three different grades of magnesium alloys: AZ31B, AZ91E and ZK60A were studied for their corrosion resistance and biocompatibility. Scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy and contact angle meter are used to study surface morphology, chemistry, roughness and wettability, respectively. Additionally, the cytotoxicity of the leached metal ions was evaluated by using a tetrazolium based bio-assay, MTS. PMID:25687006

Pompa, Luis; Rahman, Zia Ur; Munoz, Edgar; Haider, Waseem

2015-04-01

15

The Dynamic Flow and Failure Behavior of Magnesium and Magnesium Alloys  

NASA Astrophysics Data System (ADS)

We review the dynamic behavior of magnesium alloys through a survey of the literature and a comparison with our own high-strain-rate experiments. We describe high-strain-rate experiments (at typical strain rates of 103 s-1) on polycrystalline pure magnesium as well as two magnesium alloys, AZ31B and ZK60. Both deformation and failure are considered. The observed behaviors are discussed in terms of the fundamental deformation and failure mechanisms in magnesium, considering the effects of grain size, strain rate, and crystallographic texture. A comparison of current results with the literature studies on these and other Mg alloys reveals that the crystallographic texture, grain size, and alloying elements continue to have a profound influence on the high-strain-rate deformation behavior. The available data set suggests that those materials loaded so as to initiate extension twinning have relatively rate-insensitive strengths up to strain rates of several thousand per second. In contrast, some rate dependence of the flow stress is observed for loading orientations in which the plastic flow is dominated by dislocation mechanisms.

Eswar Prasad, K.; Li, B.; Dixit, N.; Shaffer, M.; Mathaudhu, S. N.; Ramesh, K. T.

2014-01-01

16

Experimental Studies on Dynamic Mechanical Behaviors and Anti-Projectile Capabilities of Extruded Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Dynamic mechanical behaviors of Mg-Gd-Y series extruded magnesium alloy and its ?-?curves are measured by using of Hopkinson pressure bar technique. According to the concept of efficiency of absorption energy, this thesis compares Mg-Gd-Y series extruded alloy with ZK60 extruded magnesium alloy. Being obtained similitude numbers by means of normalizing processing for governing equations of the continuum mechanics and according to the viewpoint of equal density of area, the comparative experiment of anti-projectile capabilities is elaborately designed between Mg-Gd-Y alloy and the 7A52 aluminum alloy. The result has validated that anti-projectile capability of Mg-Gd-Y alloy is better than those of 7A52 alloy under the condition of equal density of area. The relative technique approaches for improving anti-projectile capability of Mg-Gd-Y alloy are put forward making use of similitude numbers. Finally, the basic characters of effect of adiabatic shear are revealed by micro analysis.

Fan, Yafu; Zhao, Baorong

17

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

18

Electrodeposition on magnesium alloy diecasting.  

E-print Network

??Magnesium alloy diecasting AZ91CC, AZ61CC', AZ91HC and AZ71HC were electroplated using different pretreatment sequences which incorporated conventional zincate immersion processes. Satisfactory peel adhesion in excess… (more)

Wan, Katy Y.

1986-01-01

19

Innovations in cast magnesium alloys  

Microsoft Academic Search

This article examines questions related to aspects of the production of castings of magnesium alloys in molds made by volumetric\\u000a stamping without the use of the corresponding tooling. Information is presented on features of the gating-feeding systems\\u000a used to obtain magnesium-alloy castings in molds made by volumetric stamping. Also examined are features of the effect of\\u000a small additions of calcium

V. D. Belov; A. V. Koltygin; N. A. Belov; I. V. Plisetskaya

2010-01-01

20

CO2 laser welding of magnesium alloys  

Microsoft Academic Search

Metallic alloys with a low mass density can be considered to be basic materials in aeronautic and automotive industry. Magnesium alloys have better properties than aluminum alloys in respect of their low density and high resistance to traction. The main problems of magnesium alloy welding are the inflammability, the crack formation and the appearance of porosity during the solidification. The

Mohammed Dhahri; Jean Eric Masse; J. F. Mathieu; Gerard Barreau; Michel L. Autric

2000-01-01

21

Magnesium secondary alloys: Alloy design for magnesium alloys with improved tolerance limits against impurities  

Microsoft Academic Search

The development of secondary magnesium alloys requires a completely different concept compared with standard alloys which obtain their corrosion resistance by reducing the levels of impurities below certain alloy and process depending limits. The present approach suitable for Mg–Al based cast and wrought alloys uses a new concept replacing the ?-phase by ?-phase, which is able to incorporate more impurities

C. Blawert; D. Fechner; D. Höche; V. Heitmann; W. Dietzel; K. U. Kainer; P. Živanovi?; C. Scharf; A. Ditze; J. Gröbner; R. Schmid-Fetzer

2010-01-01

22

The corrosion performance of anodised magnesium alloys  

Microsoft Academic Search

The corrosion performance of anodised magnesium and its alloys, such as commercial purity magnesium (CP-Mg) and high-purity magnesium (HP-Mg) ingots, magnesium alloy ingots of MEZ, ZE41, AM60 and AZ91D and diecast AM60 (AM60-DC) and AZ91D (AZ91D-DC) plates, was evaluated by salt spray and salt immersion testing. The corrosion resistance was in the sequential order: AZ91D?AM60?MEZ?AZ91D-DC?AM60-DC>HP-Mg>ZE41>CP-Mg. It was concluded the corrosion

Zhiming Shi; Guangling Song; Andrej Atrens

2006-01-01

23

Microstructure of WE43 casting magnesium alloy  

Microsoft Academic Search

Purpose: WE43 is a high-strength magnesium alloy characterized by good mechanical properties both at an ambient and elevated temperature (up to 300°C). It contains mainly yttrium and neodymium. The aim of this paper is to present the results of research on the microstructure of the WE43 magnesium alloy in an as-cast condition. Design\\/methodology\\/approach: For the microstructure observation, a Reichert metallographic

T. Rzycho?; A. Kie?bus

24

Fracture of Magnesium Alloy in Cold Forging  

Microsoft Academic Search

In order to clarify the forming limit of magnesium alloy in cold forging, the workability of magnesium alloy AZ31B (Mg-3%Al-1%Zn) is examined by upsetting and backward extrusion. In the upsettability test, shear type fracture occurs at a small equivalent strain of about 0.15 at temperatures lower than 170°C. At a higher temperature, the flow stress curve has a peak at

R. Matsumoto; T. Kubo; K. Osakada

2007-01-01

25

A review on magnesium alloys as biodegradable materials  

Microsoft Academic Search

Magnesium alloys attracted great attention as a new kind of degradable biomaterials. One research direction of biomedical\\u000a magnesium alloys is based on the industrial magnesium alloys system, and another is the self-designed biomedical magnesium\\u000a alloys from the viewpoint of biomaterials. The mechanical, biocorrosion properties and biocompatibilities of currently reported\\u000a Mg alloys were summarized in the present paper, with the mechanical

Xue-Nan Gu; Yu-Feng Zheng

2010-01-01

26

Compressive deformation behaviour of magnesium alloys  

Microsoft Academic Search

The compressive deformation behaviour of magnesium alloys AZ91, AE42, AS21, QE22, ZE41, Mg4Li, and Mg8Li has been studied. The alloys were tested in the temperature range 23–300°C. The differences in the deformation behaviour of the alloys are discussed in terms of hardening and softening processes. Non-dislocation obstacles and forest dislocations are considered as the main obstacles for the moving dislocations,

Z. Trojanová; P. Luká?

2005-01-01

27

Newly developed magnesium alloys for powertrain applications  

Microsoft Academic Search

Several new magnesium alloys have been developed recently for high-temperature applications to obtain an optimal combination\\u000a of die cast-ability, creep resistance, mechanical properties, corrosion performance, and affordability. Unfortunately, it\\u000a is difficult to achieve an adequate combination of properties and, in fact, most of the new alloys can only partially meet\\u000a the required performance and cost. The ZE41 alloy, which is

E. Aghion; B. Bronfín; F. Von Buch; S. Schumann; H. Friedrich

2003-01-01

28

New magnesium alloys for transmission parts  

Microsoft Academic Search

Metallurgical aspects of the development of new magnesium alloys for the production of transmission parts and assemblies with\\u000a the use of sand mold casting, chill casting, and high-pressure die casting are considered. The approach suggested has been\\u000a used for creating new alloys with elevated creep resistance. The properties of the alloys are presented and compared with\\u000a the properties of known

B. Bronfin; N. Moscovitch

2006-01-01

29

Corrosion resistance of titanium ion implanted AZ91 magnesium alloy  

Microsoft Academic Search

Degradable metal alloys constitute a new class of materials for load-bearing biomedical implants. Owing to their good mechanical properties and biocompatibility, magnesium alloys are promising in degradable prosthetic implants. The objective of this study is to improve the corrosion behavior of surgical AZ91 magnesium alloy by titanium ion implantation. The surface characteristics of the ion implanted layer in the magnesium

Liu Chenglong; Xin Yunchang; Tian Xiubo; J. Zhao; Paul K. Chu

2007-01-01

30

Aluminium-magnesium alloys as corrosion resistant coatings for steel  

Microsoft Academic Search

The corrosion behaviour of binary aluminium-magnesium (Al?Mg) alloy coatings deposited on to steel panels using an unbalanced magnetron sputtering technique has been studied. Neutral salt fog tests have shown that the corrosion resistance of sputtered aluminium alloy coatings increases as the magnesium content is raised until an optimum is reached for alloys containing approximately 20 wt% Mg. Increasing the magnesium

K. R. Baldwin; R. I. Bates; R. D. Arnell; C. J. E. Smith

1996-01-01

31

Laser surface treatment of cast magnesium alloys  

Microsoft Academic Search

Purpose: The goal of this work was to investigate influence of laser treatment on structure and properties MCMgAl3Zn1, MCMgAl6Zn1, MCMgAl9Zn1 and MCMgAl12Zn1 cast magnesium alloys. Design\\/methodology\\/approach: Tests were made on the experimental MCMgAl3Zn1 MCMgAl6Zn1 MCMgAl9Zn1 and MCMgAl12Zn1 casting magnesium alloys. Laser treatment was made using the Rofin DL020 HPDL high power diode laser in the argon shield gas cover with

L. A. Dobrzañski; J. Domaga; T. Tañski; A. Klimpel; D. Janicki

32

Newly developed magnesium alloys for powertrain applications  

NASA Astrophysics Data System (ADS)

Several new magnesium alloys have been developed recently for high-temperature applications to obtain an optimal combination of die cast-ability, creep resistance, mechanical properties, corrosion performance, and affordability. Unfortunately, it is difficult to achieve an adequate combination of properties and, in fact, most of the new alloys can only partially meet the required performance and cost. The ZE41 alloy, which is used for most gravity-casting applications, has moderate strength and creep resistance combined with good cast-ability. Although this alloy exhibits poor corrosion resistance, it is still preferred for certain applications.

Aghion, E.; Bronfín, B.; von Buch, F.; Schumann, S.; Friedrich, H.

2003-11-01

33

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

34

A highly ductile magnesium alloy system  

NASA Astrophysics Data System (ADS)

Magnesium (Mg) alloys are finding increasing applications in industry mainly due to their high strength-to-weight ratio. However, they have intrinsically poor plastic deformation ability at room temperature. Therefore, the vast majority of Mg alloys are used only in cast state, severely limiting the development of their applications. We have recently discovered a new Mg alloy system that possesses exceptionally high ductility as well as good mechanical strength. The superior plasticity allows this alloy system to be mechanically deformed at room temperature, directly from an as-cast alloy plate, sheet or ingot into working parts. This type of cold mechanical forming properties has never been reported with any other Mg alloy systems.

Gao, W.; Liu, H.

2009-08-01

35

IRRADIATION EFFECTS IN SUPER PURITY ALUMINUM MAGNESIUM ALLOYS  

Microsoft Academic Search

The tensile properties of annealed samples of aluminum -magnesium alloys ; containing 0.001 to 2.8 wt. % magnesium have been determined in the irradiated ; and unirradiated condition. The increase in elastic limit caused by reactor ; irradiation is shown by two effects, an increase proportional to the integrated ; fast-neutron flux that is greater for alloys of lower magnesium

Piercy

1959-01-01

36

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

37

An electrolytic process for magnesium and its alloys production  

SciTech Connect

The largest amount of magnesium is used for aluminum-magnesium alloy production. The second largest use is in desulfurization of steel. A magnesium {minus}10 weight percent (w/o) aluminum alloy can also be used in both the above processes. Pure magnesium metal is not of much use for structural purposes. However, a magnesium {minus}10 w/o aluminum alloy melt which is also suitable for structural applications, can be produced as a bottom layer in an electrolytic magnesium production cell using a potassium chloride-magnesium chloride electrolyte at {approximately} 750 C. In this situation, the magnesium production process and the cell can be similar to the aluminum production process and its cell. The magnesium-aluminum alloys can be produced by electrolysis at far less cost than these alloys produced from the respective metals. The process can also be used to produce other magnesium alloys for use in the auto industry at comparatively far less cost. The largest increase in the magnesium usage in the future is going to be only in the magnesium alloys sector.

Sharma, R. [General Motors Research and Development Center, Warren, MI (United States). Physical Chemistry Dept.

1996-10-01

38

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

39

On the Modeling of Plastic Deformation of Magnesium Alloys  

Microsoft Academic Search

Magnesium alloys are promising materials due to their low density and therefore high specific strength. However, the industrial application is not well established so far, especially for wrought products such as sheets or profiles. Due to its hexagonal crystallographic structure, deformation mechanisms observed in magnesium alloys are rather different from those in face centered cubic metals such as aluminum alloys.

S. Ertuerk; D. Steglich; J. Bohlen; D. Letzig; W. Brocks

2007-01-01

40

Hardening and softening in selected magnesium alloys  

Microsoft Academic Search

The paper deals with the influence of temperature and solute atoms on the stress relaxation behaviour. Examples will be given on the deformation behaviour of selected magnesium alloys ZE41 and QE22. The testing temperature and strain rate strongly influence the behaviour. The temperature and strain rate dependences of the yield stress are in some cases non-monotonic. Post-relaxation effect—an increase of

P. Luká?; Z. Trojanová

2007-01-01

41

Twin-roll strip casting of magnesium alloys in China  

Microsoft Academic Search

The development status of twin-roll strip casting for magnesium alloys in China was summarized as well as the new progress when several kinds of twin-roll strip casting technologies were developed and used. Horizontal twin-roll casting (HTRC) of magnesium alloys has attracted much attention and has been industrialized in China. Vertical twin roll casting (VTRC) of the magnesium alloys can reach

Pei-dao DING; Fu-sheng PAN; Bin JIANG; Jian WANG; Hua-lun LI; Jiang-cai WU; Yue-wang XU; Yu WEN

2008-01-01

42

Feasibility study of twin roll casting process for magnesium alloys  

Microsoft Academic Search

This paper is concerned with the development of a strip casting technology for manufacturing magnesium alloy sheets. The aim of the work is to establish a manufacturing process and technology to facilitate the economical manufacture of high-quality magnesium alloy sheets. Magnesium alloy AZ31, AZ61, AM60 and AZ91 were used to investigate the appropriate manufacturing conditions for use in twin roll

H. Watari; T. Haga; N. Koga; K. Davey

2007-01-01

43

Effect of Al-Ti-B on Magnesium Alloy Micro-Alloyed with Ca  

Microsoft Academic Search

Effect of Al-Ti-B master alloy on the microstructure and mechanical properties was investigated in AZ31 magnesium alloys micro-alloyed with Ca. During the casting process, electromagnetic field was also introduced. The results suggest that the micro addition of Ca to magnesium alloy retards the oxidation rate during melting process, improves casting qualities of magnesium alloy ingots. The grain size of AZ31

Canfeng Fang; Guohong Qi; Xingguo Zhang; Hai Hao; Junze Jin

2009-01-01

44

On the precipitation of magnesium silicide in irradiated aluminium–magnesium alloys  

Microsoft Academic Search

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

M. Verwerft

2000-01-01

45

The role of magnesium in the electrochemical behaviour of 5XXX aluminium-magnesium alloys  

Microsoft Academic Search

An investigation concerning the effects of magnesium on the intergranular corrosion susceptibility of AA5XXX aluminium alloys was carried out. In the present work, magnesium is found to be highly mobile in the bulk metal as well as in the aluminium oxide. This mobility is also found to be dependent on the temperature and bulk magnesium concentration. Interestingly, the corrosion susceptibility

J. R. Flores Ramirez

2006-01-01

46

Electrodeposition of aluminium, aluminium\\/magnesium alloys, and magnesium from organometallic electrolytes  

Microsoft Academic Search

The electrodeposition of aluminum, magnesium, and the combination of these metals from nonaqueous media is discussed. Plating baths for depositing Al\\/Mg alloys or for plating essentially pure Mg were developed. These solutions contain alkali meal fluoride or quaternary ammonium halide\\/aluminium alkyl complexes and dialkyl magnesium dissolved in aromatic hydrocarbons. Alloy deposits over the whole composition range can be plated from

1988-01-01

47

PROTECTIVE ATMOSPHERES FOR THE HEAT TREATMENT OF MAGNESIUM ALLOYS  

Microsoft Academic Search

Most magnesium alloys are used for die castings whch, due to the presence of porous cores, cannot be heat treated at present without blistering. However, as technology improves, pore-free castings will become available whose properties can be optimised by heat treatment and environmentally hendly protective atmospheres mill be required for mass production processing. The remaining sand cast magnesium-zirconium alloys, malnly

PF Stratton

48

Laser surface treatment of magnesium alloys with silicon carbide powder  

Microsoft Academic Search

Purpose: . The aim of this work was to improve the surface layer cast magnesium cast alloys by laser surface treatment and determine the laser treatment parameters. Design\\/methodology\\/approach: The laser treatment of magnesium alloys with alloying SiC powder with the particle size below 75?m was carried out using a high power diode laser (HPDL). The resulting microstructure in the modified

L. A. Dobrzañski; S. Malara; T. Tañski; A. Klimpel; D. Janicki

49

Magnesium alloys laser (Nd:YAG) cladding and alloying with side injection of aluminium powder  

Microsoft Academic Search

The development of the high purity magnesium alloys (such as WE43) incites the designers to reconsider them, and the car industry appears, these days, the most interested to use this kind of alloy. However, due to their ignitability and tendency to oxidation, magnesium alloys require surface treatments. A series of experiments was carried out in order to improve the corrosion

Sorin Ignat; Pierre Sallamand; Dominique Grevey; Michel Lambertin

2004-01-01

50

CO2 laser welding of magnesium alloys  

NASA Astrophysics Data System (ADS)

Metallic alloys with a low mass density can be considered to be basic materials in aeronautic and automotive industry. Magnesium alloys have better properties than aluminum alloys in respect of their low density and high resistance to traction. The main problems of magnesium alloy welding are the inflammability, the crack formation and the appearance of porosity during the solidification. The laser tool is efficient to overcome the difficulties of manufacturing by conventional processing. Besides, the laser processing mainly using shielding gases allows an effective protection of the metal against the action of oxygen and a small heat affected zone. In this paper, we present experimental results about 5 kW CO2 laser welding of 4 mm-thick magnesium alloy plates provided by Eurocopter France. The focused laser beam has about 0.15 mm of diameter. We have investigated the following sample: WE43, alloy recommended in aeronautic and space applications, is constituted with Mg, Y, Zr, rare earth. More ductile, it can be used at high temperatures until 250 degrees Celsius for times longer than 5000 hours without effects on its mechanical properties. A sample of RZ5 (French Norm: GZ4TR, United States Norm ZE41) is composed of Mg, Zn, Zr, La, rare earth. This alloy has excellent properties of foundry and it allows to the realization of components with complex form. Also, it has a good resistance and important properties of tightness. The parameters of the process were optimized in the following fields: laser power: 2 to 5 kW, welding speed: 1 to 4.5 m/min, focal position: -3 mm to +3 mm below or on the top of the metal surface, shielding gas: helium with a flow of 10 to 60 l/min at 4 bars. Metallurgical analyses and mechanical control are made (macroscopic structure, microscopic structure, interpretations of the structures and localization of possible defects, analyse phases, chemical composition, hardness, tensile test etc.) to understand the parameters influence of welding on the obtained beads. For a given laser power, we considered that the welding speed as well as the focal position strongly influence the macroscopic and microscopic welding aspect, whereas the dependence with the flow of the protection gas is weak. For WE43, the bead appears correct in the macroscopic scale for a laser power of 2 kW, a speed of 2 m/min, a focal position on the metal surface or 1 mm under; and an output helium gas of 50 l/min. For RZ5, a correct weld is obtained with a 3 kW laser power, a welding speed of 2 m/min, a focal position of 1.5 mm under the surface and a 50 l/min output helium gas. The microscopic examination showed that the size of the grains has clearly reduced (reduction factor can be up to 35) without formation of porosities, neither cracks nor inclusions; indeed the measured Vickers microhardness of the weld bead is slightly higher than the basic metal. Experiments show that we obtained adequate parameters for high quality welding without using filler material. In future, we plan to weld at higher speed by optimizing the various parameters of the laser welding (power, focal position welding speed and gas flow, ...). Furthermore, we will try to weld samples with a thickness superior than 4 mm.

Dhahri, Mohammed; Masse, Jean Eric; Mathieu, J. F.; Barreau, Gerard; Autric, Michel L.

2000-02-01

51

Properties of magnesium alloys reinforced with nanoparticles and carbon nanotubes: a review  

Microsoft Academic Search

Magnesium alloys suffer from only moderate high-temperature strength and creep resistance. Aluminium-free magnesium alloys\\u000a for sand casting or alloys containing aluminium with expensive additional alloying elements may be in use, but only microparticle\\u000a or microfibre-reinforced magnesium alloys really exhibit satisfactory creep strengths at temperatures up to 250 °C. Reinforcing\\u000a magnesium alloys with ceramic nanoparticles could be a solution for preserving a

Hajo Dieringa

2011-01-01

52

New developments in assessing hot tearing in magnesium alloy castings  

Microsoft Academic Search

High performance magnesium parts produced by permanent mold casting often exhibit hot tear defects. Theoretical prediction of hot tears in magnesium alloys has reached only limited success and further research is necessary to enhance understanding of the fundamental mechanisms associated with the formation of this defect.In this research, numerical modeling of the casting process enabled identification of casting regions susceptible

L. Bichler; C. Ravindran

2010-01-01

53

Mechanoelectrochemical Behavior of Pure Magnesium and Magnesium Alloys Stressed in Aqueous Solutions  

Microsoft Academic Search

A new synergistic effect of corrosion and stress on the viscoelasticity of pure magnesium and magnesium alloys has been shown. This phenomenon named corrosion creep has been studied in 99.9653% Mg, die-cast AZ91D (Mg–9% Al–1% Zn), AM50 (Mg–5% Al–0.4% Mn), and AS21 (Mg–2.3% Al, 0.23% Mn, 1.10% Si) alloys. Creep tests were carried out at 25°C in air and in

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

2000-01-01

54

Behavior of stress corrosion cracking in a magnesium alloy  

Microsoft Academic Search

Slow strain rate testing (SSRT) was employed to study the stress corrosion cracking (SCC) behavior of ZE41 magnesium alloy\\u000a in 0.01 M NaCl solution. Smooth tensile specimens with different thicknesses were strained dynamically in both longitudinal\\u000a and transverse direction under permanent immersions at a strain rate of 10?6 s?1. It is found that ZE41 magnesium alloy is susceptible to SCC

Renguo Song; Fanger Yang; Carsten Blawert; Wolfgang Dietzel

2009-01-01

55

Influence of alloy elements and pouring temperature on the fluidity of cast magnesium alloy  

Microsoft Academic Search

The fluidity is one of the most important properties for cast alloy. The quality of castings is influenced by the fluidity of liquid metal, especially under gravity casting conditions. In this paper, the factors affecting the fluidity of cast magnesium alloy have been studied by vacuum suction method. The experimental data show that the relationship between the fluidity of magnesium

Qin Hua; Deming Gao; Hongjun Zhang; Yuhui Zhang; Qijie Zhai

2007-01-01

56

Enhanced Age-hardening in Aluminium-Magnesium Alloys  

Microsoft Academic Search

ALTHOUGH the solubility of magnesium in aluminium is as high as 16.8 per cent (alloy contents are expressed as atomic percentages) at 450° C (ref. 1), and decreases to an estimated value of 1 per cent at room temperature, the alloys show an abnormally small response to age-hardening. Furthermore, there is no evidence to indicate that the ageing characteristics of

I. J. Polmear; K. R. Sargant

1963-01-01

57

On the Modeling of Plastic Deformation of Magnesium Alloys  

NASA Astrophysics Data System (ADS)

Magnesium alloys are promising materials due to their low density and therefore high specific strength. However, the industrial application is not well established so far, especially for wrought products such as sheets or profiles. Due to its hexagonal crystallographic structure, deformation mechanisms observed in magnesium alloys are rather different from those in face centered cubic metals such as aluminum alloys. This leads not only to a mechanical anisotropy, but also to a tension-compression asymmetry, i.e. unequal compressive and tensile yield strength. The resulting complexity in the yielding behavior of such materials cannot be captured by conventional models of J2 plasticity. Cazacu and Barlat, therefore, proposed a phenomenological yield potential which accounts for the respective phenomena by introducing the third invariant of the stress tensor. Simulations based on this model are performed with ABAQUS/Explicit and a user defined routine VUMAT for validating the respective implementation. The application aims at simulating the extrusion process of magnesium alloys.

Ertürk, S.; Steglich, D.; Bohlen, J.; Letzig, D.; Brocks, W.

2007-05-01

58

Forming of magnesium alloys at 100 °C by hydrostatic extrusion  

NASA Astrophysics Data System (ADS)

Magnesium wrought alloys are of special interest for use as structural parts due to the possibility of obtaining improved and more homogeneous microstructure and mechanical properties compared with cast components. The market for magnesium wrought alloys is still relatively small, and they are only used for special applications due to the high cost of the feedstock. Currently, with the decreasing prices for the primary magnesium extrusion, magnesium has become competitive with aluminum, and is important for upcoming research and development activities. In this study hydrostatic extrusion, as a quite rarely applied technique, was used for deformation of commercial magnesium alloys at 100 °C, which is significantly below the temperature necessary for activation of new gliding systems. All experiments were carried out using typical industrial extrusion parameters like extrusion rate and extrusion ratio but with the objective of obtaining extremely fine-grained materials as are received typically from equal channel angular extrusion processing. These experiments show that the processing of magnesium alloys is possible even at a temperature of 100 °C. The limitations of this processing and the influence of process parameters on the microstructure and mechanical properties of extruded profiles will be discussed.

Swiostek, J.; Göken, J.; Letzig, D.; Kainer, K. U.

2006-12-01

59

THE DEVELOPMENT OF A NEW MANUFACTURING ROUTE FOR SUPERPLASTIC MAGNESIUM ALLOY SHEET EXPLOITING TWIN ROLL CASTING  

Microsoft Academic Search

Because of their propensity to dynamically recrystallise, superplastic behaviour can be obtained from magnesium alloys considerably more easily than from comparable aluminium alloys. In some cases even as cast magnesium alloys can exhibit reasonable superplasticity and there appears no need for the special alloying additions or complex thermomechanical treatments required by aluminium alloys such as AA2004 or AA7475. The paper

Richard Dashwood; Martin Jackson; David Klaumünzer; Zhongyun Fan; Roger Grimes

60

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

61

The effects of some elements on the igniting temperature of magnesium alloys  

Microsoft Academic Search

This paper studied the effects of some elements on the igniting temperature of the magnesium alloys. The main proposals of the study is to increase the igniting temperature by adding some elements to the magnesium alloys and make the magnesium alloys process easily like cast iron and aluminium without flux and gas cover. The results show that oxide film of

Zhao Weimin; Sun Yong; Li Haipeng; Liang Chunyong

2006-01-01

62

An investigation on the hot extrusion process of magnesium alloy sheet  

Microsoft Academic Search

This study investigates the hot extrusion of magnesium alloy sheets at various temperatures, material, speed and lubricant. A multi-speed method is applied to extrude a magnesium alloy sheet at a high extrusion ratio. The experimental results are analyzed to optimize the processing conditions, increase the tensile strength and reduce the extrusion load on the magnesium alloy thin sheet. Nowadays, most

Su-Hai Hsiang; Jer-Liang Kuo

2003-01-01

63

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

64

Crystallographic texture evolution of three wrought magnesium alloys during equal channel angular extrusion  

Microsoft Academic Search

Texture strongly impacts the plasticity of metals and the equal channel angular extrusion (ECAE) process has been demonstrated to induce unusual textures and enhance the room temperature ductility of magnesium alloys. This paper documents a wide range of textures that may be generated by ECAE of magnesium alloys. Considered broadly, the ECAE processing of magnesium alloys tends to produce ?0001?

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

2005-01-01

65

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

66

Magnesium alloys laser (Nd:YAG) cladding and alloying with side injection of aluminium powder  

NASA Astrophysics Data System (ADS)

The development of the high purity magnesium alloys (such as WE43) incites the designers to reconsider them, and the car industry appears, these days, the most interested to use this kind of alloy. However, due to their ignitability and tendency to oxidation, magnesium alloys require surface treatments. A series of experiments was carried out in order to improve the corrosion resistance of two types of magnesium alloys, WE43 and ZE41. In most cases, the substrate surface was treated before laser interaction. Side injection of aluminium powder under a 3 kW cw Nd:YAG laser was employed. The deposited layers present very good bond properties. The resulting microstructure was analysed and some mechanical properties determined, such as hardness, which is increased due to the Al 3Mg 2 and Al 12Mg 17 intermetallic formation. The results obtained represent an important step to achieve an enhanced corrosion resistance for magnesium alloys.

Ignat, Sorin; Sallamand, Pierre; Grevey, Dominique; Lambertin, Michel

2004-03-01

67

A Study on Factors Affecting the Degradation of Magnesium and a Magnesium-Yttrium Alloy for Biomedical Applications  

PubMed Central

Controlling degradation of magnesium or its alloys in physiological saline solutions is essential for their potential applications in clinically viable implants. Rapid degradation of magnesium-based materials reduces the mechanical properties of implants prematurely and severely increases alkalinity of the local environment. Therefore, the objective of this study is to investigate the effects of three interactive factors on magnesium degradation, specifically, the addition of yttrium to form a magnesium-yttrium alloy versus pure magnesium, the metallic versus oxide surfaces, and the presence versus absence of physiological salt ions in the immersion solution. In the immersion solution of phosphate buffered saline (PBS), the magnesium-yttrium alloy with metallic surface degraded the slowest, followed by pure magnesium with metallic or oxide surfaces, and the magnesium-yttrium alloy with oxide surface degraded the fastest. However, in deionized (DI) water, the degradation rate showed a different trend. Specifically, pure magnesium with metallic or oxide surfaces degraded the slowest, followed by the magnesium-yttrium alloy with oxide surface, and the magnesium-yttrium alloy with metallic surface degraded the fastest. Interestingly, only magnesium-yttrium alloy with metallic surface degraded slower in PBS than in DI water, while all the other samples degraded faster in PBS than in DI water. Clearly, the results showed that the alloy composition, presence or absence of surface oxide layer, and presence or absence of physiological salt ions in the immersion solution all influenced the degradation rate and mode. Moreover, these three factors showed statistically significant interactions. This study revealed the complex interrelationships among these factors and their respective contributions to degradation for the first time. The results of this study not only improved our understanding of magnesium degradation in physiological environment, but also presented the key factors to consider in order to satisfy the degradation requirements for next-generation biodegradable implants and devices. PMID:23799028

Johnson, Ian; Liu, Huinan

2013-01-01

68

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

69

The development of lightweight hydride alloys based on magnesium  

SciTech Connect

The development of a magnesium based hydride material is explored for use as a lightweight hydrogen storage medium. It is found that the vapor transport of magnesium during hydrogen uptake greatly influences the surface and hydride reactions in these alloys. This is exploited by purposely forming near-surface phases of Mg{sub 2}Ni on bulk Mg-Al-Zn alloys which result in improved hydrogen adsorption and desorption behavior. Conditions were found where these near-surface reactions yielded a complex and heterogeneous microstructure that coincided with excellent bulk hydride behavior. A Mg-Al alloy hydride is reported with near atmospheric plateau pressures at temperatures below 200{degrees}C. Additionally, a scheme is described for low temperature in-situ fabrication of Mg{sub 2}Ni single phase alloys utilizing the high vapor pressure of Mg.

Guthrie, S.E.; Thomas, G.J.; Yang, N.Y.C.; Bauer, W. [Sandia National Labs., Livermore, CA (United States)

1996-02-01

70

Design and microstructural analysis of magnesium alloys for dynamical applications  

Microsoft Academic Search

A microanalytical characterization of cast magnesium alloys of eutectic origin based on the Mg–Al–Ca ternary matrix system\\u000a has been carried out in order to investigate the influence of alloying elements on their microstructure as well as microchemistry-processing-microstructural\\u000a relations using structure-sensitive techniques of electron microscopy, mechanical spectroscopy (internal friction), X-ray\\u000a diffractometry, and advanced microanalytical methods including electron probe compositional analysis. Following

V. G. Tkachenko; K. H. Kim; B. G. Moon; A. S. Vovchok

2011-01-01

71

Magnesium alloys as implant materials--principles of property design for Mg-RE alloys.  

PubMed

Magnesium alloys have attracted increasing interest in the past years due to their potential as implant materials. This interest is based on the fact that magnesium and its alloys are degradable during their time of service in the human body. Moreover magnesium alloys offer a property profile that is very close or even similar to that of human bone. The chemical composition triggers the resulting microstructure and features of degradation. In addition, the entire manufacturing route has an influence on the morphology of the microstructure after processing. Therefore the composition and the manufacturing route have to be chosen carefully with regard to the requirements of an application. This paper discusses the influence of composition and heat treatments on the microstructure, mechanical properties and corrosion behaviour of cast Mg-Gd alloys. Recommendations are given for the design of future degradable magnesium based implant materials. PMID:19788945

Hort, N; Huang, Y; Fechner, D; Störmer, M; Blawert, C; Witte, F; Vogt, C; Drücker, H; Willumeit, R; Kainer, K U; Feyerabend, F

2010-05-01

72

Application of yttrium in AZ61 magnesium alloy and the semi-solid AZ61 alloy  

Microsoft Academic Search

The semi-solid magnesium alloy slurry was prepared by a newly self-developed mechanical stirring machine for preparing continuous semi-solid slurry, the effects of rare earth elements yttrium on the ignition point, the casting microstructure, the semi-solid microstructure and mechanical properties of AZ61 magnesium alloy were studied in this paper. The experimental results showed that increasing the Y content would increase the

Zhou Bingfeng; Yan Hong

2010-01-01

73

NUMERICAL SIMULATION OF NATURAL CONVECTION IN MAGNESIUM ALLOY SQUEEZE CASTING  

Microsoft Academic Search

Natural convection may play an important role in solidification due to its potential influence on solutes distribution in melts and grain structure. But, in fact, it has received less attention than conduction in metal solidification processes. To simulate the solidification phenomena of squeeze cast magnesium alloy, a coupled mathematical model has been developed. An analysis based on a Control-Volume Finite

Alfred Yu; Naiyi Li; Henry Hu

2003-01-01

74

Semisolid Twin-roll Casting Process of Magnesium Alloy Sheets  

Microsoft Academic Search

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.

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

2004-01-01

75

A Model for Gas Microporosity in Aluminum and Magnesium Alloys  

Microsoft Academic Search

A quantitative prediction of the amount of gas microporosity in aluminum and magnesium-alloy castings is performed with a continuum model of dendritic solidification. The distribution of the pore volume fraction and pore size is calculated from a set of conservation equations that solves the transport phenomena during solidification at the macroscale and the hydrogen diffusion into the pores at the

Sergio D. Felicelli; Liang Wang; Claudio M. Pita; Enrique Escobar de Obaldia

2009-01-01

76

Microstructure development during the deformation of aluminium-magnesium alloys  

Microsoft Academic Search

The conditions for serrated yielding in aluminium-magnesium alloys in temperature\\/strain rate space are reported. The microstructures of samples deformed just within and just outside the serrated regime are described. The differences in structure seen are relatively minor and do not seem to reflect the markedly different deformation behaviour. The conclusion is drawn that the deformed microstructures are formed, in part,

B. A. Parker; JangHo Lim

1996-01-01

77

QUENCHED-IN VACANCIES IN DILUTE ALUMINIUM-MAGNESIUM ALLOYS  

Microsoft Academic Search

Electron-microscope observations of the development of prismatic ; dislocation loops due to quenched-in vacancies in dilute aluminum-magnesium ; alloys were made in connection with measurements of the dimensional changes of ; quenched specimens. From this irformation direct evidence for the collapse of ; vacancy clusters into prismatic dislocation loops was obtained. The retardation ; of the development of prismatic loops

J. Takamura; K. Okazaki; I. G. Greenfield

1963-01-01

78

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

79

Theoretical risk assessment of magnesium alloys as degradable biomedical implants.  

PubMed

The theoretical tolerable implant masses for ten magnesium alloys as degradable biomedical implant materials are evaluated in this study. Dose-response assessment is conducted using toxicological data from authoritative public health agencies such as the US Agency for Toxic Substances and Disease Registry and the USEPA Integrated Risk Information System, and assuming 1 year of even corrosion. Uncertainty factors adopted by the agencies are used. The tolerable limits corresponding to various component elements in an alloy are considered separately, and the lowest tolerable limit is selected as the tolerable limit of the alloy. The results show that aluminum is usually the component element with the lowest tolerance, and the tolerable mass for Al-containing magnesium alloys fall to around or below 1g per person per year, while the limit for other magnesium alloys can well exceed 10 g. Deficits in the toxicological data of some component elements are noted. This study illustrates that toxicological calculations should be taken into consideration when developing novel degradable metallic implants. PMID:19969109

Yuen, C K; Ip, W Y

2010-05-01

80

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

81

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

82

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

83

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

84

Study of Forming of Magnesium Alloy by Explosive Energy  

NASA Astrophysics Data System (ADS)

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; Yahiro, Ititoku

2011-05-01

85

Corrosion behaviour of laser-melted magnesium alloys  

NASA Astrophysics Data System (ADS)

The present paper reports studies of the corrosion behaviour of magnesium alloys, AZ31, AZ61 and WE43 following laser surface melting (LSM) with a 2 kW continuous wave CO 2 laser to depth about 1 mm. The laser-melted samples were immersed in 5 wt.% sodium chloride solution of pH 10.5 for 10 days, with open circuit potential measurements recorded in the initial 24 h. LSM resulted in improvement of the corrosion resistance of the alloys, with weight losses reduced by about 30, 66 and 87% for the AZ31, AZ61 and WE43 alloys, respectively. Rutherford backscattering spectroscopy (RBS) and nuclear reaction analysis (NRA) revealed that the average compositions of the alloys, following removal of surface oxide, were relatively unaffected by laser melting, indicating that any losses of magnesium or gains of oxygen only affected superficial layers. The improved corrosion resistance following LSM is associated with refinement of the alloy microstructure due to the rapid cooling of the melted layer, which results in increased concentration of alloying elements in solid solution in matrix regions and more uniform distributions of the corrosion-resistant ?-phase that can accumulate as a protective layer.

Abbas, G.; Liu, Z.; Skeldon, P.

2005-07-01

86

The aluminium-scandium-lithium-magnesium system as a potential source of superplastically formable alloys  

Microsoft Academic Search

Alloys from the aluminum-lithium-scandium-magnesium system have been cast and rolled for study. The goal is to evaluate this system for the development of superplastically formable, high strength alloys. Aluminum-scandium-magnesium alloys have shown potential as superplastic alloys. These alloys rely on small AlâSc (ordered L1â) precipitates for grain structure stabilization and strengthening. Additional precipitation strengthening is required to raise their strength

Emigh

1990-01-01

87

A Model for Gas Microporosity in Aluminum and Magnesium Alloys  

Microsoft Academic Search

A quantitative prediction of the amount of gas microporosity in aluminum and magnesium-alloy castings is performed with a\\u000a continuum model of dendritic solidification. The distribution of the pore volume fraction and pore size is calculated from\\u000a a set of conservation equations that solves the transport phenomena during solidification at the macroscale and the hydrogen\\u000a diffusion into the pores at the

Sergio D. Felicelli; Liang Wang; Claudio M. Pita; Enrique Escobar De Obaldia

2009-01-01

88

Thermomechanical modelling of indirect extrusion process for magnesium alloys  

Microsoft Academic Search

The complexity of deformation phenomena observed in magnesium and its alloys originates from its hexagonal closed packed crystallographic\\u000a structure. Mechanical anisotropy and asymmetry in tension-compression are hence observed. A phenomenological model derived\\u000a by Cazacu and Barlat accounts for the respective phenomena. However, the capabilities of this model for simulation of extrusion\\u000a are limited since strain rate and temperature dependency on

S. Ertürk; D. Steglich; J. Bohlen; D. Letzig; W. Brocks

2009-01-01

89

Modelling and Simulation of Extrusion of Magnesium Alloys  

Microsoft Academic Search

Extrusion, as one of the bulk-metal forming processes, is of significant importance for the production of semi-finished components.\\u000a For magnesium and its alloys, the technology for processing is available today, but there is still a fundamental lack in understanding\\u000a the factors that determine the development of microstructure and mechanical properties during the process. Due to its hexagonal\\u000a crystallographic structure, deformation

S. Ertürk; D. Steglich; J. Bohlen; D. Letzig; W. Brocks

2008-01-01

90

Crystal Structure of beta-Aluminium-Magnesium Alloy  

Microsoft Academic Search

A PIECE of beta-aluminium-magnesium alloy of irregular shape, when examined by the Laue method, showed all the characteristics of the Laue symmetry m3m = 0h, which proves conclusively that beta Al-Mg is cubic and not hexagonal as assumed by K. Riederer1. By means of rotation photograms the length of the edge of the unit cube was determined to be a

Harald Perlitz

1944-01-01

91

Surface Analysis and Bonding of Aluminium-Magnesium Alloys  

Microsoft Academic Search

Previous work has used X-ray photoelectron spectroscopy to examine the surface compositions of aluminium-alloy substrates subjected to various surface pretreatments prior to bonding. It was proposed that the presence of magnesium in the oxide structure adversely affected the service-life of adhesive joints when they were exposed to aqueous environments. The present work further explores this correlation by examining a range

A. J. Kinloch; H. E. Bishop; N. R. Smart

1982-01-01

92

Thixotropic deformation behavior of semi-solid AZ61 magnesium alloy during compression process  

Microsoft Academic Search

Compression tests on semi-solid AZ61 magnesium alloy fabricated by strain-induced melt activation (SIMA) and the conventional as-casted were carried out using the Gleeble-1500 dynamic material testing machine. The relationships between stress and strain and the microstructural evolutions for AZ61 magnesium alloy were analyzed in different deformation conditions. The results show that the deformation resistance of semi-solid AZ61 magnesium alloy is

Hong Yan; Bingfen Zhou

2006-01-01

93

TEM investigations of Elektron 21 magnesium alloy after long-term annealing  

Microsoft Academic Search

The paper presents results of TEM investigations of Elektron 21 magnesium alloy in as cast condition and after long-term annealing.\\u000a Elektron 21 is magnesium based casting alloy containing rare earth (Nd and Gd) for used to at 200°C in aerospace application.\\u000a It has high strength, good corrosion resistance and excellent castability [1]. Magnesium alloys containing neodymium and gadolinium\\u000a are characterised

A. Kielbus

94

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

95

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 Mg–Zn–Zr alloys, i.e. ZK30 and ZK60, and a WE-type alloy (Mg–Y–RE–Zr) were investigated by means of long-term static immersion testing in Hank’s solution, non-static immersion testing in Hank’s 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 Hank’s 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 7 days, 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

96

MECHANICAL PROPERTIES OF A MAGNESIUM-ALUMINIUM-BERYLLIUM ALLOY USED FOR FUEL ELEMENT CLADDING  

Microsoft Academic Search

Possibilities of using magnesium alloys for fuel element cladding ; materials are evaluated. The main attention is given measurements of mechanical ; properties of a Mg-Al-Be alloy and to their evaluation. (auth);

Bartak

1963-01-01

97

Corrosion protection of aerospace grade magnesium alloy Elektron 43(TM) for use in aircraft cabin interiors  

NASA Astrophysics Data System (ADS)

Magnesium alloys exhibit desirable properties for use in transportation technology. In particular, the low density and high specific strength of these alloys is of interest to the aerospace community. However, the concerns of flammability and susceptibility to corrosion have limited the use of magnesium alloys within the aircraft cabin. This work studies a magnesium alloy containing rare earth elements designed to increase resistance to ignition while lowering rate of corrosion. The microstructure of the alloy was documented using scanning electron microscopy. Specimens underwent salt spray testing and the corrosion products were examined using energy dispersive spectroscopy.

Baillio, Sarah S.

98

Endothelial responses of magnesium and other alloying elements in magnesium-based stent materials.  

PubMed

Biodegradable tailored magnesium (Mg) alloys are some of the most promising scaffolds for cardiovascular stents. During the course of degradation after implantation, all the alloying elements in the scaffold will be released to the surrounding vascular tissues. However, fundamental questions regarding the toxicity of alloying elements towards vascular cells, the maximum amount of each element that could be used in alloy design, or how each of the alloying elements affects vascular cellular activity and gene expression, are still not fully answered. This work systematically addressed these questions by revealing how application of different alloying elements commonly used in Mg stent materials influences several indices of human endothelial cell health, i.e., viability, proliferations, cytoskeletal reorganizations, migration, and the gene expression profile. The overall cell viability and proliferation showed a decreasing trend with increasing concentrations of the ions, and the half maximal effective concentrations (EC50) for each element were determined. When applied at a low concentration of around 10 mM, Mg had no adverse effects but improved cell proliferation and migration instead. Mg ions also altered endothelial gene expression significantly in a dose dependent manner. Most of the changed genes are related to angiogenesis and the cell adhesion signaling pathways. Findings from this work provide useful information on maximum safe doses of these ions for endothelial cells, endothelial responses towards these metal ions, and some guidance for future Mg stent design. PMID:25363018

Zhao, Nan; Zhu, Donghui

2015-01-24

99

Elevated temperature behaviour of rapidly solidified magnesium alloys containing rare earths  

Microsoft Academic Search

The microstructure and mechanical properties of bars of six magnesium alloys (AZ91, AZ151, ACa54, ZE41, WE43 and WE54) extruded from melt spun ribbons, were investigated. At room temperature, the 0.2% proof stress of all the alloys (300–500 MPa) is much higher than that of commercial cast magnesium alloys. As far as the effect of temperature is concerned, the alloys can

C. Sanchez; G. Nussbaum; P. Azavant; H. Octor

1996-01-01

100

Numerical optimization of gating system parameters for a magnesium alloy casting with multiple performance characteristics  

Microsoft Academic Search

An optimization technique for design of gating system parameters of a cylindrical magnesium casting based on the Taguchi method with multiple performance characteristics was proposed in this paper. The various gating systems for a casting model of magnesium alloy were designed. Mold filling and solidification processes of the magnesium casting were simulated with the MAGMASOFT®. The simulation results indicated that

Zhizhong Sun; Henry Hu; Xiang Chen

2008-01-01

101

Effect of process parameters on density of magnesium alloy parts by low-pressure expendable pattern casting  

Microsoft Academic Search

The combination of magnesium alloys with the low-pressure expendable pattern casting (LP-EPC) process would bright future for application of magnesium alloys. The researches are focused on the effect of process parameters on the internal casting quality of magnesium alloy parts. AZ91D magnesium alloy castings were produced for different combinations of the LP-EPC process parameters. Specifically, pouring temperature, vacuum, filling velocity

LI Ji-qiang; DONG Xuan-pu

102

Dissimilar material laser welding between magnesium alloy AZ31B and aluminum alloy A5052-O  

Microsoft Academic Search

Joining technology of lightweight dissimilar metals between magnesium and aluminum alloys is essential for realizing hybrid structure cars and other engineering applications. In the present study, the normal center-line welding of lap joint was carried out by laser welding. It was found that the intermetallic layer formed near interface between two metals significantly degraded the joining strength. FEM heat transfer

Rattana Borrisutthekul; Yukio Miyashita; Yoshiharu Mutoh

2005-01-01

103

Characterization of fold defects in AZ91D and AE42 magnesium alloy permanent mold castings  

Microsoft Academic Search

Casting premium-quality magnesium alloy components for aerospace and automotive applications poses unique challenges. Magnesium alloys are known to freeze rapidly prior to filling a casting cavity, resulting in misruns and cold shuts. In addition, melt oxidation, solute segregation and turbulent metal flow during casting contribute to the formation of fold defects. In this research, formation of fold defects in AZ91D

L. Bichler; C. Ravindran

2010-01-01

104

Applying ANN to predict the forming load and mechanical property of magnesium alloy under hot extrusion  

Microsoft Academic Search

This study establishes the database concerning magnesium alloy hot extrusion, and uses it to conduct various investigations. Firstly, artificial neural networks (ANN) analysis is used to determine the die shapes of various extrusion ratios. Secondly, the process parameters for the hot extrusion of magnesium alloy are determined, and thirdly, the tensile strength and maximum extrusion load of the finished product

Su-Hai Hsiang; Jer-Liang Kuo

2005-01-01

105

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

Microsoft Academic Search

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

Mengwu Wu; Shoumei Xiong

2012-01-01

106

Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature  

Microsoft Academic Search

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

Jongshin Lee; Bongsun You; Seogou Choi; Youngsuk Kim

2007-01-01

107

Properties of magnesium alloy joints welded by a CO2 laser beam  

Microsoft Academic Search

Because of their specific gravity, magnesium alloys find increasing applications in the automotive industry. Safety and travelling comfort requirements, satisfied by the use of steel or aluminium parts, are responsible for the increase in the car weight and, therefore, in increased fuel consumption and consequent environmental pollution. Replacement of these materials by magnesium alloys satisfies the two requirements while not

W. Kalita; J. Hoffman; A. Kolasa; P. Kolodziejczyk

2005-01-01

108

Numerical simulation of AM50A magnesium alloy under large deformation  

Microsoft Academic Search

The present research concentrates on the development of a material model for the AM50A magnesium alloy, frequently used in the automotive industry. This computer model was developed and validated through experimental and numerical simulation of standardized charpy and tensile tests, and intensive microstructural analysis. The material model was further used to predict the behavior of an AM50A magnesium alloy steering

William Altenhof; Anna Raczy; Melissa Laframboise; Jennifer Loscher; Ahmet Alpas

2004-01-01

109

Effect of chemical structure of borates on the tribological characteristics of magnesium alloy during sliding  

Microsoft Academic Search

Effects of four borates with different chemical structure on the tribological properties of magnesium alloy in sliding contact with bearing steel were investigated under boundary lubrication using a Timken type tester. It was shown that the borate without active element is not effective at reducing the friction and wear of magnesium alloy, and the borates containing nitrogen, sulfur and chlorine

Weijiu Huang; Ya Fu; Jiu Wang; Zhaofeng Li; Ming Liu

2005-01-01

110

Effect of rare earths (Y, Ce) additions on the ignition points of magnesium alloys  

Microsoft Academic Search

Magnesium alloys with low density have considerable potential as light-weight structural materials for automobile and aircraft industry, but their extensive application has been limited due to the poor oxidation resistance. As is well known, it is impossible to melt magnesium alloys without any protection because of serious oxidation and even burning. Commonly fluxes or protective gases (CO2 ,S O 2,

J. F. Fan; G. C. Yang; S. L. Chen; H. Xie; M. Wang; Y. H. Zhou

2004-01-01

111

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

Microsoft Academic Search

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

Mahmoud A Rabah

2003-01-01

112

The Improvement of Tribological and Fatigue Properties of Casting Magnesium Alloy AZ91 Performed Diamond Like Carbon Coating  

Microsoft Academic Search

In recent years, magnesium alloy has been widely used because of its low weight and ease of recycling. However, because magnesium alloys provide inferior wear resistance, it is necessary to improve this property to use magnesium alloy for more machine parts. For this study, we produced a diamond like carbon (DLC) coating that has high hardness, low friction, and excellent

Hiroyuki Akebono; Hideto Suzuki

2008-01-01

113

Tensile behaviour of squeeze cast AM100 magnesium alloy and its Al 2O 3 fibre reinforced composites  

Microsoft Academic Search

Magnesium alloys are increasingly used in automotive and aerospace applications mainly due to their light weight combined with reasonably high tensile properties. In addition to providing a large reduction in weight, magnesium alloys exhibit excellent machinability and good damping capacity. However, their low mechanical properties when exposed to elevated temperatures limit their usage. Making composites out of these magnesium alloys

S Jayalakshmi; S. V Kailas; S Seshan

2002-01-01

114

Broadened X-ray-diffraction profile analysis of cold-rolled aluminium-magnesium alloys  

Microsoft Academic Search

A cold-rolled, commercial pure aluminium and three aluminium-magnesium alloys (containing, respectively, 1 wt%, 3 wt% and 5 wt% magnesium) were studied by X-ray-diffraction (XRD) profile analysis. The investigated equivalent plastic deformations of the materials were ranged between 0.1 and 5.0. With increases in the amounts of magnesium, the diffraction peaks widened. For each alloy, the peak width (which gives first

N. Ji; J. L. Lebrun; P. Sainfort

1994-01-01

115

Preparation, characterization and wear behavior of carbon coated magnesium alloy with electroless plating nickel interlayer  

NASA Astrophysics Data System (ADS)

Poor wear resistance of rare earth magnesium alloys has prevented them from wider application. In this study, composite coating (PVD carbon coating deposited on electroless plating nickel interlayer) is prepared to protect GW83 magnesium alloys against wear. The Ni + C composite coating has a dense microstructure, improved adhesion strength and hardness due to the effective support of Ni interlayer. The wear test result shows that the Ni + C composite coating can greatly prolong the wear life of the magnesium alloy. The wear track of the Ni + C coated magnesium alloy is obviously narrower and shows less abrasive particles as compared with the bare one. Abrasive wear is the wear mechanism of the coatings at the room temperature. In conclusion, the wear resistance of the GW83 magnesium alloy can be greatly improved by the Ni + C composite coating.

Mao, Yan; Li, Zhuguo; Feng, Kai; Guo, Xingwu; Zhou, Zhifeng; Dong, Jie; Wu, Yixiong

2015-02-01

116

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

117

General and localized corrosion of magnesium alloys: A critical review  

NASA Astrophysics Data System (ADS)

Magnesium (Mg) alloys as well as experimental alloys are emerging as light structural materials for current, new, and innovative applications. This paper describes the influence of the alloying elements and the different casting processes on the microstructure and performance of these alloys and corrosion. It gives a comprehensible approach for the resistance of these alloys to general, localized and metallurgically influenced corrosion, which are the main challenges for their use. Exposure to humid air with ˜65% relative humidity during 4 days gives 100-150 nm thickness. The film is amorphous and has an oxidation rate less than 0.01 µm/y. The pH values between 8.5 and 11.5 correspond to a relatively protective oxide or hydroxide film; however above 11.5 a passive stable layer is observed. The poor corrosion resistance of many Mg alloys can be due to the internal galvanic corrosion caused by second phases or impurities. Agitation or any other means of destroying or preventing the formation of a protective film leads to increasing corrosion kinetics. The pH changes during pitting corrosion can come from two different reduction reactions: reduction of dissolved oxygen (O) and that of hydrogen (H) ions. Filiform corrosion was observed in the uncoated AZ31, while general corrosion mainly occurred in some deposition coated alloys. Crevice corrosion can probably be initiated due to the hydrolysis reaction. Exfoliation can be considered as a type of intergranular attack, and this is observed in unalloyed Mg above a critical chloride concentration.

Ghali, Edward; Dietzel, Wolfgang; Kainer, Karl-Ulrich

2004-02-01

118

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

119

Stress corrosion cracking in magnesium alloys: Characterization and prevention  

NASA Astrophysics Data System (ADS)

The positive environmental influence of magnesium alloy usage in transportation applications could be compromised by catastrophic fast fracture caused by stress corrosion cracking (SCC). Transgranular stress corrosion cracking (TGSCC) of AZ91 has been evaluated using the linearly increasing stress test and the constant extension rate test. The TGSCC threshold stress was 55 75 MPa in distilled water and in 5 g/L NaCl. The TGSCC velocity was 7×10-10 m/s to 5×10-9 m/s. A delayed hydride-cracking model for TGSCC was implemented using a finite element script in MATLAB and the model predictions were compared with the experiment. A key outcome is that, during steady-state TGSCC propagation, a high dynamic hydrogen concentration is expected to build up behind the crack tip. In this paper, recommendations are given for preventing SCC of magnesium alloys in service. One of the most important recommendations might be that the total stress in service should be below a threshold level, which, in the absence of other data, could be estimated to be ˜50% of the tensile yield strength.

Winzer, N.; Atrens, A.; Dietzel, W.; Song, G.; Kainer, K. U.

2007-08-01

120

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

121

Microstructure development and thixoextrusion of magnesium alloy prepared by repetitive upsetting-extrusion  

Microsoft Academic Search

Thixoextrusion involves processing alloys with a spheroidal microstructure in the semi-solid state. Before thixoextrusion, repetitive upsetting-extrusion (RUE) is introduced into the strain induced metal activation (SIMA) process to predeform AZ80 magnesium alloy. Microstructure evolution of RUE formed AZ80 magnesium alloy during partial remelting is studied at temperatures for times. Tensile mechanical properties of thixoextruded components are determined and compared with

Qiang Chen; Zude Zhao; Zhixiang Zhao; Chuankai Hu; Dayu Shu

2011-01-01

122

Effect of Porosity on the High Cycle Fatigue Behavior of Casing AM60B Magnesium Alloy  

Microsoft Academic Search

The effect of casting defects on the high cycle fatigue property of magnesium alloy was investigated in this study. Two AM60B magnesium alloys were manufactured by high pressure die casting with different processing parameters such as die morphology, melt and die temperatures. One of AM60B alloys with relatively high porosity was called C1 (4.06%) and the other was called C2

K. S. Kim; J. C. Park; C. D. Yim; K. A. Lee

2011-01-01

123

Magnesium-based hydrogen storage materials modified by mechanical alloying  

SciTech Connect

The effects of mechanical alloying on microstructure and electrochemical performance of a Mg-Ni-Y-Al hydrogen storage alloy in 6 M KOH solution were studied. The ball-milled powders were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected-area electron diffraction (SED) and energy dispersion spectrometry (EDS). TEM and EDS results clearly reveal that the smaller nickel clusters or particles were well dispersed on the surface of larger magnesium alloy particles by mechanical grinding for 72 h. With an increase in milling time to 240 h, the nickel clusters or particles disappeared and a new monophase alloy with amorphous structure was formed. The electrochemical capacity of the modified material significantly increased with increasing milling time within 72 h and then dropped to nearly nil when the milling time reached 240 h. The capacity decay, however, was always improved with increasing grinding time. Further analysis and discussion were made based on d.c. polarization and a.c. impedance spectroscopy measurement results.

Cui, N.; He, P.; Luo, J.L.

1999-10-26

124

Intergranular corrosion of an aluminum-magnesium-silicon-copper alloy  

SciTech Connect

The intergranular (intercrystalline) corrosion (IGC) of a heat-treated aluminum-magnesium-silicon-copper alloy was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM revealed that tall chimneys of corrosion product formed on the surface above the pits during oxygenated salt water immersion. It was postulated that pitting corrosion occurred first and that the corrosion chimneys maintained the acidic, chloride pit environment that subsequently caused IGC (preferential dissolution of the region adjacent to the grain boundaries). TEM foils of the same alloy were immersed in a model pit solution (dilute hydrochloric acid) and showed IGC identical to the corrosion attack seen in the bulk samples. Potentiodynamic polarization in the dilute HCl solution verified that pure Al corroded many times faster than the bulk alloy. These results indicated IGC of this alloy occurred because the depleted region adjacent to the grain boundaries corroded rapidly in acidic solutions. The presence of pits with corrosion chimneys, or some type of occluded cells, must have maintained the acidic environment, which caused IGC.

Burleigh, T.D. [Univ. of Pittsburgh, PA (United States). Materials Science and Engineering Dept.; Ludwiczak, E.; Petri, R.A. [Alcoa Technical Center, Alcoa Center, PA (United States)

1995-01-01

125

Minimum quantity lubrication machining of aluminum and magnesium alloys  

NASA Astrophysics Data System (ADS)

The use of minimum quantity lubrication (MQL) machining, i.e. drilling and tapping of aluminum and magnesium alloys using very low quantities of cutting fluids was studied and the MQL machining performance was compared to dry and conventional flooded conditions. An experimental drilling station with an MQL system was built to measure torque and thrust force responses. Uncoated and diamond-like carbon (DLC) coated HSS drills were tested against 319 Al and AZ91 alloys using 10--50 ml/h of distilled water (H 2O-MQL) and a fatty acid based MQL agent (FA-MQL). The results indicated that H2O-MQL used in conjunction with non-hydrogenated DLC (NH-DLC) coatings reduced the average torque and thrust-force compared to dry cutting and achieved a performance comparable with conventional flooded drilling. At least 103 holes could be drilled using NH-DLC in H2O-MQL and uncoated HSS in FA-MQL in drilling of both 319 Al and AZ91. MQL drilling and tapping provided a stable machining performance, which was evident from the uniform torque and force patterns and also resulted in desirable hole surface, thread quality and chip segments. The maximum temperature generated in the workpiece during MQL machining was lower than that observed in dry drilling and tapping, and comparable to flooded conditions. The mechanical properties of the material adjacent to drilled holes, as evaluated through plastic strain and hardness measurements, revealed a notable softening in case of dry drilling, with magnesium alloys exhibiting a recrystallized grain zone, but not for MQL drilling. Softened aluminum and magnesium promoted adhesion to the tools resulted built-up edge formation and consequently high torques and thrust-forces were generated. NH-DLC coatings' low COF in H 2O-MQL against 319 Al (0.10) and AZ91 (0.12) compared to uncoated HSS (0.63 and 0.65) limited the temperature increase during NH-DLC in H2 O-MQL drilling and hence both torques and thrust forces were effectively reduced.

Bhowmick, Sukanta

2011-12-01

126

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

127

Friction behavior of laser cladding magnesium alloy against AISI 52100 steel  

Microsoft Academic Search

The use of magnesium alloys in engineering applications is becoming increasingly important as a relatively low density allows savings in energy consumption and therefore reduction in air pollution. An associated reduction in inertia makes these alloys potential candidates for friction components, but they suffer from poor wear resistance. Laser surface alloying with appropriate powder mixture is an innovative technique to

A. Fabre; J. E. Masse

128

Fatigue deformation in the interior of aged ternary aluminium-magnesium-zinc alloys  

Microsoft Academic Search

Metallographic observations have been made of deformation, associated with the fatigue process in the interior of several aged ternary aluminiumzinc-magnesium alloys. It has been found that the deformation occurring in these relatively complex alloys differs from that observed in pure metals.With alloys which had a high zinc content the fatigue process was essentially a grain boundary phenomenon and cracking was

I. J. Polmear; I. F. Bainbridge

1959-01-01

129

Microstructures in friction-stir welded dissimilar magnesium alloys and magnesium alloys to 6061-T6 aluminum alloy  

Microsoft Academic Search

Wrought Mg alloy AZ31B-H24 and semisolid-cast Mg alloy AZ91D (approximately 3% primary solid fraction) were friction-stir welded to Al alloy 6061-T6. Semisolid-cast (approximately 3% and approximately 20% primary solid fractions) Mg alloys AZ91D and AM60B were also joined using the same technique, with AZ91D on the advancing side. Numerous welds were made with the Mg alloys and the 6061-T6 Al

A. C Somasekharan; L. E Murr

2004-01-01

130

Binary Magnesium Alloys: Searching for Novel Compounds by Computational Thermodynamics  

NASA Astrophysics Data System (ADS)

Magnesium alloys are among the lightest structural materials and are of considerable technical interest. We use the high-throughput framework AFLOW to make T = 0 K ground state predictions by scanning a large set of known candidate structures for thermodynamic minima. The study presented here encompasses 34 Mg-X systems of interest (X=Al, Au, Ca, Cd, Cu, Fe, Ge, Hg, Ir, K, La, Pb, Pd, Pt, Mo, Na, Nb, Os, Rb, Re, Rh, Ru, Sc, Si, Sn, Sr, Ta, Tc, Ti, V, W, Y, Zn, Zr). Avenues for further investigation revealed by this study include stable phases found in addition to experimental phases and compound forming systems thought to be either immiscible or non-compound forming. The existence of potentially novel ordered phases presents new opportunities for materials design.

Taylor, Richard; Curtarolo, Stefano; Hart, Gus

2011-03-01

131

Evaluation of magnesium ions release, biocorrosion, and hemocompatibility of MAO/PLLA-modified magnesium alloy WE42.  

PubMed

Magnesium alloys may potentially be applied as biodegradable metallic materials in cardiovascular stent. However, the high corrosion rate hinders its clinical application. In this study, a new approach was adopted to control the corrosion rate by fabricating a biocompatible micro-arc oxidation/poly-L-lactic acid (MAO/PLLA) composite coating on the magnesium alloy WE42 substrate and the biocompatibility of the modified samples was investigated. The scanning electronic microscope (SEM) images were used to demonstrate the morphology of the samples before and after being submerged in hanks solution for 4 weeks. The degradation was evaluated through the magnesium ions release rate and electrochemical impedance spectroscopy (EIS) test. The biocompatibility of the samples was demonstrated by coagulation time and hemolysis behavior. The result shows that the poly-L-lactic acid (PLLA) effectively improved the corrosion resistance by sealing the microcracks and microholes on the surface of the MAO coating. The modified samples had good compatibility. PMID:21053265

Lu, Ping; Cao, Lu; Liu, Yin; Xu, Xinhua; Wu, Xiangfeng

2011-01-01

132

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

Microsoft Academic Search

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

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

2000-01-01

133

Effect of overageing temperature on the superplastic behaviour in magnesium alloys  

Microsoft Academic Search

An especially fine-grained structure d<10?m is necessary for superplastic forming. Conventional magnesium alloys in cast condition show only a very coarse-grained structure with an average grain size of d>100?m. Yet through overageing and successive warm extrusion moulding a sufficient number of recrystallization nuclei are formed in the magnesium alloys so that during the final recrystallization treatment a very fine microstructure

V. Wesling; T. Ryspaev; A. Schram

2007-01-01

134

Kinetics of recrystallization for twin-roll casting AZ31 magnesium alloy during homogenization  

Microsoft Academic Search

The kinetics of recrystallization for twin-roll casting AZ31 magnesium alloy with different thicknesses during homogenization was analyzed. It is shown that fine grains are first formed at the boundaries of deformed bands in the twin-roll casting slab. The recrystallized grains with no strain are gradually substituted for the deformed microstructure of twin-roll casting AZ31 magnesium alloy. The incubation temperature and

Hu Zhao; Pei-Jie Li; Liang-Ju He

2011-01-01

135

Mechanical behavior of cast and forged magnesium alloys and their microstructures  

Microsoft Academic Search

Effects of manufacturing processes on microstructure and mechanical properties of magnesium alloys AM60 and AZ31B were investigated. The magnesium alloy AM60 was produced by high-pressure die cast (HPDC) with two different casting processors but AZ31B was produced by forging. Casting defects were investigated with SEM observations for the specimens obtained from the two casting processors. The fatigue tests were conducted

Hong Tae Kang; Terry Ostrom

2008-01-01

136

Semisolid manufacturing process of magnesium alloys by twin-roll casting  

Microsoft Academic Search

An experimental approach has been employed to ascertain the effectiveness of semi-solid roll strip casting of magnesium alloys by a 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

H. Watari; K. Davey; M. T. Rasgado; T. Haga; S. Izawa

2004-01-01

137

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 415 °C for 2 h and an ageing

P.. Cavaliere; P. P. De Marco

2007-01-01

138

Microstructure and wear resistance of Al–SiC composites coatings on ZE41 magnesium alloy  

Microsoft Academic Search

Al and Al–SiC composites coatings were prepared by oxyacetylene flame spraying on ZE41 magnesium alloy substrates. Coatings with controlled reinforcement rate of up to 23vol.% were obtained by spraying mixtures containing aluminium powder with up to 50vol.% SiC particles. The coatings were sprayed on the magnesium alloy with minor degradation of its microstructure or mechanical properties. The coatings were compacted

P. Rodrigo; M. Campo; B. Torres; M. D. Escalera; E. Otero; J. Rams

2009-01-01

139

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 -30°C to 200°C 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

140

Facile formation of biomimetic color-tuned superhydrophobic magnesium alloy with corrosion resistance.  

PubMed

The design of color-tuned magnesium alloy with anticorrosive properties and damping capacity was created by means of a simple and inexpensive method. The vertically self-aligned nano- and microsheets were formed on magnesium alloy AZ31 by a chemical-free immersion process in ultrapure water at a temperature of 120 °C, resulting in the color expression. The color changed from silver with metallic luster to some specific colors such as orange, green, and orchid, depending on the immersion time. The color-tuned magnesium alloy showed anticorrosive performance and damping capacity. In addition, the colored surface with minute surface textures was modified with n-octadecyltrimethoxysilane (ODS), leading to the formation of color-tuned superhydrophobic surfaces. The corrosion resistance of the color-tuned superhydrophobic magnesium alloy was also investigated using electrochemical potentiodynamic measurements. Moreover, the color-tuned superhydrophobic magnesium alloy showed high hydrophobicity not just for pure water but also for corrosive liquids, such as acidic, basic, and some aqueous salt solutions. In addition, the American Society for Testing and Materials (ASTM) standard D 3359-02 cross cut tape test was performed to investigate the adhesion of the color-tuned superhydrophobic film to the magnesium alloy surface. PMID:21319782

Ishizaki, Takahiro; Sakamoto, Michiru

2011-03-15

141

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

142

Formation of an aluminum-alloyed coating on AZ91D magnesium alloy in molten salts at lower temperature  

Microsoft Academic Search

An aluminum-alloyed coating was formed on an AZ91D magnesium alloy in molten salts containing AlCl3 at a lower temperature of 380°C. The microstructure and phase constitution of the alloyed layer were investigated by optical microscopy, scanning electron microscopy, energy dispersive spectrum and X-ray diffraction. The nano-hardness of the coating was studied by nanoindentation associated with scanning probe microscopy. The corrosion

C. Zhong; M. F. He; L. Liu; Y. J. Chen; B. Shen; Y. T. Wu; Y. D. Deng; W. B. Hu

2010-01-01

143

Morphology of Corrosion Damage in Magnesium Alloys and Anion Effects on Passive Film Stability  

Microsoft Academic Search

The need for reduced weight in automotive applicati ons has lead directly to an increased interest in magne sium and its alloys. Magnesium has a very low specific gravity (1.74), but can have a reasonable stiffness compare d to aluminum, the other widely used lightweight metal. The materials properties of the alloys used are promisi ng. However, a major factor

Andrew Fones; Miguel Gonzalez Torreira

144

Corrosion fatigue behavior of die-cast and shot-blasted AM60 magnesium alloy  

Microsoft Academic Search

Magnesium (Mg) and its alloys have a long tradition of use as a lightweight material in the field of commercial and especially automotive construction. Unfortunately its poor corrosion resistance restricts its use under corrosive atmosphere. So far, most of the research works on corrosion fatigue properties of Mg alloys have dealt with effect of pre-existing pit or effect of pitting

Sabrina Alam Khan; Yukio Miyashita; Yoshiharu Mutoh; Toshikatsu Koike

2011-01-01

145

The Characteristic Electron Energy Loss Spectra of Aluminium-Magnesium and Aluminium-Copper Alloys  

Microsoft Academic Search

The characteristic electron energy loss spectra of 1500 . ev electrons ; scattered by aluminum-magnesium and aluminum-copper alloys were measured. A ; plasma and a lowered plasma energy loss were observed in the alloys, and it was ; found that surface oxidation caused the disappearance of the lowered plasma loss ; and the appearance of a new modified lowered plasma

C. J. Powell

1960-01-01

146

Development of Magnesium Powder Metallurgy AZ31 Alloy Using Commercially Available Powders  

NASA Astrophysics Data System (ADS)

Magnesium and its alloys are attractive materials for use in automotive and aerospace applications because of their low density and good mechanical properties. However, difficulty in forming magnesium and the limited number of available commercial alloys limit their use. The present work reviews the efforts to improve the attractiveness of magnesium through non-traditional processing, and presents the results of producing AZ31 magnesium alloy via powder metallurgy P/M. P/M can be used to alleviate the formability problem through near-net-shape processing, and also allows unique chemical compositions that can lead to the development of new alloys with novel properties. The feasibility of producing magnesium powder metallurgy products utilizing the industrially dominant process of mixed powder blending, uni-axial die compaction and controlled atmosphere sintering was investigated. An alloy composition based on the commercial Mg alloy AZ31 (3 mass % Al, 1 mass % Zn) was used to facilitate the comparison to similar wrought product. The optimal processing conditions (compaction pressure, sintering time and temperature) were found to maximize sintered density and mechanical properties. Results show that sintering temperature is one of the major variables that has an appreciable effect on the final properties of the samples, and that the effects of compaction pressure and sintering time were insignificant. The material showed poor tensile properties, with a maximum tensile strength of 32 MPa due to lack of sufficient densification. The latter was related to the lack of liquid phase formed during sintering of Al/Zn magnesium alloys and the barrier to diffusion due to the presence of the stable magnesium surface layer.

Burke, Paul; Kipouros, Georges J.

2011-04-01

147

Investigation of the antimicrobial activity and biocompatibility of magnesium alloy coated with HA and antimicrobial peptide.  

PubMed

Implant-associated infection is one of the biggest problems in orthopedic surgery. Antimicrobial peptides (AMPs) are well-known components of the innate immunity and less susceptible to the development of pathogen resistance compared to conventional antibiotics. Magnesium alloys as potential biodegradable bone implants have been received much attention in biomaterials field. This study investigated the deposition of calcium phosphate (CaP) coatings and loading of AMPs on the magnesium alloy surface by a biomimetic method. Scanning electron microscope (SEM) results presented that a microporous and plate-like CaP coating was processed on the magnesium alloy surface. X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis showed the main component of coating was hydroxyapatite (HA). Degradation assay in vitro showed that the HA coating deposited onto the magnesium alloy was corroded more slowly than the bare one. The amount of AMP loaded in the HA coating was 11.16 ± 1.99 ?g/cm(2). The AMP loaded onto HA coatings had slow release for 7 days. The AMP-loaded coating showed antimicrobial activity against Staphylococcus aureus. Its bacterial inhibition rate exceeded 50 % after 4 days and the antibacterial effect was sustained for 7 days. The coated magnesium alloys loaded with AMP could improve rat bone marrow mesenchymal stem cells (rBMMSCs) proliferation. Furthermore, it could also promote alkaline phosphatase (ALP) activity of rBMMSCs. Both radiographic evaluation and histopathology analysis demonstrated that implantation of the coated magnesium alloy into the rabbit femoral condyle had promoted bone repair and showed anti-inflammatory effect. The results showed that the AMP loaded onto HA coatings on the magnesium alloy surface could be considered an ideal orthopedic implant against S. aureus infection. PMID:25631264

Tian, Jinhuan; Shen, Si; Zhou, Changren; Dang, Xiangli; Jiao, Yanpeng; Li, Lihua; Ding, Shan; Li, Hong

2015-02-01

148

Biaxial Deformation of the Magnesium Alloy AZ80  

NASA Astrophysics Data System (ADS)

The multiaxial deformation of magnesium alloys is important for developing reliable, robust models for both the forming of components and also analysis of in-service performance of structures, for example, in the case of crash worthiness. The current study presents a combination of unique biaxial experimental tests and biaxial crystal plasticity simulations using a visco-plastic self-consistent (VPSC) formulation conducted on a relatively weak AZ80 cast texture. The experiments were conducted on tubular samples which are loaded in axial tension or compression along the tube and with internal pressure to generate hoop stresses orthogonal to the axial direction. The results were analyzed in stress and strain space and also in terms of the evolution of crystallographic texture. In general, it was found that the VPSC simulations matched well with the experiments. However, some differences were observed for cases where basal slip and \\{ {10bar{1}2} \\} extension twinning were in close competition such as in the biaxial tension quadrant of the plastic potential. The evolution of texture measured experimentally and predicted from the VPSC simulations was qualitatively in good agreement. Finally, experiments and VPSC simulations were conducted on a second AZ80 material which had a stronger initial texture and a higher level of mechanical anisotropy. In the previous case, the agreement between experiments and simulations was good, but a larger difference was observed in the biaxial tension quadrant of the plastic potential.

Tomlinson, P.; Azizi-Alizamini, H.; Poole, W. J.; Sinclair, C. W.; Gharghouri, M. A.

2013-07-01

149

Application of YAG Laser TIG Arc Hybrid Welding to Thin AZ31B Magnesium Alloy Sheet  

NASA Astrophysics Data System (ADS)

A magnesium alloy is said to be an ecological material with high ability of recycling and lightweight property. Especially, magnesium alloys are in great demand on account of outstanding material property as a structural material. Under these circumstances, research and development of welding process to join magnesium alloy plates are of great significance for wide industrial application of magnesium. In order to use it as a structure material, the welding technology is very important. TIG arc welding process is the most ordinary process to weld magnesium alloy plates. However, since the heat source by the arc welding process affects the magnesium alloy plates, HAZ of welded joint becomes wide and large distortion often occurs. On the other hand, a laser welding process that has small diameter of heat source seems to be one of the possible means to weld magnesium alloy in view of the qualitative improvement. However, the low boiling point of magnesium generates some weld defects, including porosity and solidification cracking. Furthermore, precise edge preparation is very important in butt-welding by the laser welding process, due to the small laser beam diameter. Laser/arc hybrid welding process that combines the laser beam and the arc is an effective welding process in which these two heat sources influence and assist each other. Using the hybrid welding, a synegistic effect is achievable and the disadvantages of the respective processes can be compensated. In this study, YAG laser/TIG arc hybrid welding of thin magnesium alloy (AZ31B) sheets was investigated. First of all, the effect of the irradiation point and the focal position of laser beam on the quality of a weld were discussed in hybrid welding. Then, it was confirmed that a sound weld bead with sufficient penetration is obtained using appropriate welding conditions. Furthermore, it was made clear that the heat absorption efficiency is improved with the hybrid welding process. Finally, the tensile tests of welded joints were performed, and it was confirmed that they have sufficient mechanical properties. As a result of this study, it is confirmed that, if the appropriate welding conditions are selected, sound welded joints of AZ31B magnesium alloy are obtainable by the YAG laser/TIG arc hybrid welding process.

Kim, Taewon; Kim, Jongcheol; Hasegawa, Yu; Suga, Yasuo

150

Microstructures and dislocations in the stressed AZ91D magnesium alloys  

Microsoft Academic Search

The microstructures and the dislocation arrangements in the die cast AZ91D magnesium alloy as well as the stressed alloys have been investigated using transmission electron microscopy, high-resolution transmission electron microscopy and energy dispersive X-ray (EDX) analysis. Besides the dominant ?-Mg and ?-Mg17Al12 phases, Al8Mn5 and Mg5Al phases have also been found and studied in the alloy. Dislocation pile-ups have been

R. M Wang; A Eliezer; E Gutman

2003-01-01

151

Excimer laser treatment of ZE41 magnesium alloy for corrosion resistance and microhardness improvement  

Microsoft Academic Search

A laser surface melting treatment (LSMT) was performed on a ZE41 Mg-alloy using an excimer KrF laser. The laser-melted layer depth depends on the laser scan speed. The morphology and the microstructure of the laser-melted surface were characterized, thanks to the scanning electron microscopy (SEM). The melted Mg-alloy presented a homogenous distribution of the alloying elements in the magnesium matrix.

Walid Khalfaoui; Eric Valerio; Jean Eric Masse; Michel Autric

2010-01-01

152

The effect of grain refining on the microsegregation of aluminium–magnesium alloy 5182  

Microsoft Academic Search

Aluminium alloy 5182 (AA5182) contains approximately 4.5%Mg as its principal alloying addition, and is most commonly used to make the lid of the aluminium can. With a view to the possible future development of a micro-macro model to describe the casting of this alloy, the effect of grain refinement on the microsegregation of magnesium in industrial rolling ingots of AA5182

A. M. Glenn; S. P. Russo; J. D. Gorman; P. J. K. Paterson

2001-01-01

153

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

154

Thermal Conductivity of Magnesium Alloys in the Temperature Range from -125 °C to 400 °C  

NASA Astrophysics Data System (ADS)

Magnesium alloys have been widely used in recent years as lightweight structural materials in the manufacturing of automobiles, airplanes, and portable computers. Magnesium alloys have extremely low density (as low as 1738 kg · m-3) and high rigidity, which makes them suitable for such applications. In this study, the thermal conductivity of two different magnesium alloys made by twin-roll casting was investigated using the laser-flash technique and differential scanning calorimetry for thermal diffusivity and specific heat capacity measurements, respectively. The thermal diffusivity of the magnesium alloys, AZ31 and AZ61, was measured over the temperature range from -125 °C to 400 °C. The alloys AZ31 and AZ61 are composed of magnesium, aluminum, and zinc. The thermal conductivity gradually increased with temperature. The densities of AZ31 and AZ61 were 1754 kg · m-3 and 1777 kg · m-3, respectively. The thermal conductivity of AZ31 was about 25 % higher than that of AZ61, and this is attributed to the amount of precipitation.

Lee, Sanghyun; Ham, Hye Jeong; Kwon, Su Yong; Kim, Sok Won; Suh, Chang Min

2013-12-01

155

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

156

CONSTITUTIONAL FACTORS AFFECTING THE TENSILE PROPERTIES OF WROUGHT ALUMINIUM-MAGNESIUM-SILICON-COPPER ALLOYS  

Microsoft Academic Search

S>The tensile properties of solution-treated and artificially aged ; alloys within the composition range 0.5 to 2.0% magnesium, 0.3 to 1.2% silicon, ; and 0 to 1.5% copper, have been investigated, and related to equilibrium ; reactions at the heat-treatment temperatures. An isotherm for the aluminum-- ; magnesium --silicon-- copper system at 520 deg C has been derived from published

D. L. W

1958-01-01

157

Characteristics of Fatigue-activated Creep in an Aluminium-Magnesium Alloy  

Microsoft Academic Search

EXPERIMENTS have been conducted on thin-walled tubes of an aluminium-magnesium alloy (3.08 per cent magnesium, 0.3 iron, 0.44 manganese, 0.18 silicon) under conditions of simple shear. Two tubes aligned on a common axis are used for each test, the torque being applied through a disk connected to both tubes. The assembly is mounted in a thermostatically controlled enclosure, and to

A. J. Kennedy

1962-01-01

158

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

159

Effect of magnesium content on the high temperature adhesion of Al–Mg alloys to steel surfaces  

Microsoft Academic Search

The transfer and adhesion of material to die surfaces during the rolling or stamping of aluminum alloy sheets reduce the surface quality of the finished product, particularly when these operations are conducted at elevated temperatures. This study investigates the effect of magnesium content on high-temperature adhesion between aluminum alloys containing different percentages of magnesium, and an AISI 52100 steel. 5000

A. R. Riahi; A. Edrisy; A. T. Alpas

2009-01-01

160

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

161

Numerical analysis of self-pierce riveting of AZ31 magnesium alloy sheets  

NASA Astrophysics Data System (ADS)

Magnesium alloy sheet has a broad development prospect for lightweight metal in automotive industry. Selfpierce Riveting (SPR) process is a suitable joining technology to fasten materials of different nature. This paper is concerned with the development of numerical models of the SPR process of AZ31 magnesium alloy sheet. Based on DEFORM-2D finite element software, a two-dimensional axisymmetric model has been built for the SPR process. Then the distribution of stress and strain, and the stroke-load curve are analyzed in the forming process of the riveting. After a 2D simulation of SPR process, the quality of riveted joint is evaluated in terms of joint cross-sectional shape. The results show a better understanding of mechanical properties of SPR joints of magnesium alloy sheets. As a sufficient interlock and bottom thickness leading to a reasonably good joint, the numerical simulation method plays a significant role to predict the final strength of the joint.

Han, S. L.; Wu, Y. W.; Zeng, Q. L.; Gao, Y.

2013-05-01

162

Warm deep drawing of wrought magnesium alloy sheets produced by semi-solid roll strip-casting process  

Microsoft Academic Search

This paper is concerned with the development of a continuous strip-casting technology to facilitate the manufacture of magnesium sheet alloys economically whilst maintaining high quality. Established in the paper is warm formability of cast magnesium alloy sheets after being hot rolled by semi-solid roll strip-casting process. It has been found that magnesium sheet with 2.0–4.0mm thickness could be produced at

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

2006-01-01

163

Design of experiment (DOE) study of biodegradable magnesium alloy synthesized by mechanical alloying using fractional factorial design  

NASA Astrophysics Data System (ADS)

The biodegradable nature of magnesium (Mg) makes it a most highlighted and attractive to be used as implant materials. However, rapid corrosion rate of Mg alloys especially in electrolytic aqueous environment limits its performance. In this study, Mg alloy was mechanically milled by incorporating manganese (Mn) as alloying element. An attempt was made to study both effect of mechanical alloying and subsequent consolidation processes on the bulk properties of Mg-Mn alloys. 2k-2 factorial design was employed to determine the significant factors in producing Mg alloy which has properties closes to that of human bones. The design considered six factors (i.e. milling time, milling speed, weight percentage of Mn, compaction pressure, sintering temperature and sintering time). Density and hardness were chosen as the responses for assessing the most significant parameters that affected the bulk properties of Mg-Mn alloys. The experimental variables were evaluated using ANOVA and regression model. The main parameter investigated was compaction pressure.

Salleh, Emee Marina; Ramakrishnan, Sivakumar; Hussain, Zuhailawati

2014-06-01

164

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

165

Modifying AM60B Magnesium Alloy Die Cast Surfaces by Friction Stir Processing  

Microsoft Academic Search

These experiments were done to evaluate the feasibility of locally modifying the surface properties of magnesium alloys with friction-stir processing. The magnesium alloy used for the study was high-pressure die-cast AM60B, nominally Mg-6Al-0.13 Mn (wt. %). Friction-stir passes were made with a translation speed of 1.7 mm\\/s using tool-rotation speeds of 1,250 rpm or 2,500 rpm. Stir passes with good

Michael L Santella; Zhili Feng; Cassandra Degen; Tsung-Yu Pan

2006-01-01

166

Microstructure and wear resistance of Al-SiC composites coatings on ZE41 magnesium alloy  

NASA Astrophysics Data System (ADS)

Al and Al-SiC composites coatings were prepared by oxyacetylene flame spraying on ZE41 magnesium alloy substrates. Coatings with controlled reinforcement rate of up to 23 vol.% were obtained by spraying mixtures containing aluminium powder with up to 50 vol.% SiC particles. The coatings were sprayed on the magnesium alloy with minor degradation of its microstructure or mechanical properties. The coatings were compacted to improve their microstructure and protective behaviour. The wear behaviour of these coatings has been tested using the pin-on-disk technique and the reinforced coatings provided 85% more wear resistance than uncoated ZE41 and 400% more than pure Al coatings.

Rodrigo, P.; Campo, M.; Torres, B.; Escalera, M. D.; Otero, E.; Rams, J.

2009-08-01

167

Excimer laser treatment of ZE41 magnesium alloy for corrosion resistance and microhardness improvement  

NASA Astrophysics Data System (ADS)

A laser surface melting treatment (LSMT) was performed on a ZE41 Mg-alloy using an excimer KrF laser. The laser-melted layer depth depends on the laser scan speed. The morphology and the microstructure of the laser-melted surface were characterized, thanks to the scanning electron microscopy (SEM). The melted Mg-alloy presented a homogenous distribution of the alloying elements in the magnesium matrix. The laser surface melting treatment increased the microhardness of the ZE41 Mg-alloy and improved its corrosion resistance.

Khalfaoui, Walid; Valerio, Eric; Masse, Jean Eric; Autric, Michel

2010-09-01

168

Characterization of fold defects in AZ91D and AE42 magnesium alloy permanent mold castings  

SciTech Connect

Casting premium-quality magnesium alloy components for aerospace and automotive applications poses unique challenges. Magnesium alloys are known to freeze rapidly prior to filling a casting cavity, resulting in misruns and cold shuts. In addition, melt oxidation, solute segregation and turbulent metal flow during casting contribute to the formation of fold defects. In this research, formation of fold defects in AZ91D and AE42 magnesium alloys cast via the permanent mold casting process was investigated. Computer simulations of the casting process predicted the development of a turbulent metal flow in a critical casting region with abrupt geometrical transitions. SEM and light optical microscopy examinations revealed the presence of folds in this region for both alloys. However, each alloy exhibited a unique mechanism responsible for fold formation. In the AZ91D alloy, melt oxidation and velocity gradients in the critical casting region prevented fusion of merging metal front streams. In the AE42 alloy, limited solubility of rare-earth intermetallic compounds in the {alpha}-Mg phase resulted in segregation of Al{sub 2}RE particles at the leading edge of a metal front and created microstructural inhomogeneity across the fold.

Bichler, L. [Centre for Near-net-shape Processing of Materials, Ryerson University, 101 Gerrard St. E., Toronto, M5B 2K3 (Canada); Ravindran, C., E-mail: rravindr@ryerson.ca [Centre for Near-net-shape Processing of Materials, Ryerson University, 101 Gerrard St. E., Toronto, M5B 2K3 (Canada)

2010-03-15

169

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 Jürgen; Kerber, Kai

2013-01-01

170

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

171

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

172

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

Microsoft Academic Search

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

Timothy Al Hosch

2010-01-01

173

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

174

Evaluation of tensile properties of 5052 type aluminum-magnesium alloy at warm temperatures  

Microsoft Academic Search

Purpose: The purpose of the paper is to evaluate the tensile properties of 5052 type aluminum-manganese alloy in warm temperatures. Design\\/methodology\\/approach: In this research, uniaxial tensile deformation behavior of 5052-H32 type aluminum magnesium alloy was studied range between room to 300°C and in the strain rate range of 0.0083-0.16 s-1. Findings: It was observed that the uniaxial tensile elongation of

F. Ozturk; S. Toros; S. Kilic

175

Soft X-ray emission spectra of non-dilute aluminium-magnesium alloys  

Microsoft Academic Search

Aluminium and magnesium LII, III emission spectra have been obtained from the inter-metallic compounds Al2Mg2 and Al12Mg17 and also from the pure metals. A progressive change of band shapes emerges. On alloying, the Al band develops a low energy hump, more prominent in the more dilute alloy, accompanied by a decline in the peak at the Fermi edge. With increasing

A. Appleton; C. Curry

1965-01-01

176

Influence of aggressive ions on the degradation behavior of biomedical magnesium alloy in physiological environment.  

PubMed

Various electrochemical approaches, including potentiodynamic polarization, open circuit potential evolution and electrochemical impedance spectroscopy (EIS), are employed to investigate the degradation behavior of biomedical magnesium alloy under the influence of aggressive ions, such as chloride, phosphate, carbonate and sulfate, in a physiological environment. The synergetic effects and mutual influence of these ions on the degradation behavior of Mg are revealed. Our results demonstrate that chloride ions can induce porous pitting corrosion. In the presence of phosphates, the corrosion rate decreases and the formation of pitting corrosion is significantly delayed due to precipitation of magnesium phosphate. Hydrogen carbonate ions are observed to stimulate the corrosion of magnesium alloy during the early immersion stage but they can also induce rapid passivation on the surface. This surface passivation behavior mainly results from the fast precipitation of magnesium carbonate in the corrosion product layer that can subsequently inhibit pitting corrosion completely. Sulfate ions are also found to stimulate magnesium dissolution. These results improve our understanding on the degradation mechanism of surgical magnesium in the physiological environment. PMID:18571486

Xin, Yunchang; Huo, Kaifu; Tao, Hu; Tang, Guoyi; Chu, Paul K

2008-11-01

177

Fast neutron activation analysis of oxide inclusions in magnesium alloy ingots  

NASA Astrophysics Data System (ADS)

Magnesium will have an increasingly important role to play in the automotive industry's materials strategy. In addition to its obvious use as a lightweight alternative, magnesium offers advantages in areas such as component integration and NVH (noise, vibration and harshness). Although the metallic composition of magnesium alloys has been carefully defined, there is no uniform industry standard for non-metallic inclusions, such as oxides, which are believed to adversely impact the material's strength. A definitive test has been needed, preferably one that provides a highly sensitive, calibrated, nondestructive evaluation of the metal's bulk oxide content. In response to this need, fast neutron activation analysis (FNAA) has emerged as an important tool for providing highly accurate quantitative information on the oxygen content in magnesium alloys. Oxygen levels from less than 50 to several thousand ppm have been observed in these alloys, with the highest levels concentrated at the top center of the ingot. Several operational procedures have been developed to optimize the analysis, including: a new automated, blank-free procedure which pneumatically transports machined magnesium cylinders between the irradiation and counting facilities; the use of an oxygen standard prepared from polyethylene and titanium dioxide, machined to match the sample dimensions; and implementation of new background subtraction software.

Fuerst, C. D.; James, W. D.

1999-06-01

178

Rapid coating of AZ31 magnesium alloy with calcium deficient hydroxyapatite using microwave energy.  

PubMed

Due to their unique biodegradability, magnesium alloys have been recognized as suitable metallic implant materials for degradable bone implants and bioresorbable cardiovascular stents. However, the extremely high degradation rate of magnesium alloys in physiological environment has restricted its practical application. This paper reports the use of a novel microwave assisted coating technology to improve the in vitro corrosion resistance and biocompatibility of Mg alloy AZ31. Results indicate that a dense calcium deficient hydroxyapatite (CDHA) layer was uniformly coated on a AZ31 substrate in less than 10min. Weight loss measurement and SEM were used to evaluate corrosion behaviors in vitro of coated samples and of non-coated samples. It was seen that CDHA coatings remarkably reduced the mass loss of AZ31 alloy after 7days of immersion in SBF. In addition, the prompt precipitation of bone-like apatite layer on the sample surface during immersion demonstrated a good bioactivity of the CDHA coatings. Proliferation of osteoblast cells was promoted in 5days of incubation, which indicated that the CDHA coatings could improve the cytocompatibility of the AZ31 alloy. All the results suggest that the CDHA coatings, serving as a protective layer, can enhance the corrosion resistance and biological response of magnesium alloys. Furthermore, this microwave assisted coating technology could be a promising method for rapid surface modification of biomedical materials. PMID:25686961

Ren, Yufu; Zhou, Huan; Nabiyouni, Maryam; Bhaduri, Sarit B

2015-04-01

179

Variability of skin thickness in an AM60B magnesium alloy die-casting  

Microsoft Academic Search

The skin thickness is investigated in regions of different solidification conditions in a die-cast AM60B magnesium alloy component. The results of several different techniques for determining the skin thickness in six different samples are compared. The hardness profile, the elemental aluminum and oxygen contents, the change in grain sizes, the change in eutectic percentage, and the onset of large ?-Mg

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

2006-01-01

180

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

181

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

Microsoft Academic Search

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

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

1999-01-01

182

Phase compositions in magnesium-rare earth alloys containing yttrium, gadolinium or dysprosium  

Microsoft Academic Search

Phase compositions have been investigated, using thin foil energy dispersive X-ray spectroscopy, in three magnesium-rare earth alloys, containing yttrium, gadolinium or dysprosium. Compositions are suggested for the as-cast eutectic and ? precipitate phases and possible compositions for the ?1 precipitate phases are discussed.

P. J. Apps; H. Karimzadeh; J. F. King; G. W. Lorimer

2003-01-01

183

Heat transfer characteristics of lost foam casting process of magnesium alloy  

Microsoft Academic Search

Effects of vacuum, pouring temperature and pattern thickness on the heat transfer of magnesium alloy lost foam casting(LFC) process were explored. The results indicate that without vacuum a positive thermal gradient from the gate to the end of the casting was formed immediately after the mold filling. The average temperature of the casting, the temperature gradient and solidification times increase

Zi-li LIU; Qing-lin PAN; Zhao-feng CHEN; Xi-qin LIU; Jie TAO

2006-01-01

184

The structure and formation of dislocation networks in aluminium-magnesium alloys  

Microsoft Academic Search

When investigating rapidly solidified aluminium—magnesium alloys by means of the thin foil technique, dislocation networks were abundantly revealed. It is shown that these are knitted on dislocation forests generated on contact boundaries of sub-dendrites or cells growing from the melt. Knitting occurs mainly by climb when ‘detached’ dislocations nucleating inside the cells during solidification and cooling are trapped by forests.

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

1967-01-01

185

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

186

Studies on influence of zinc immersion and fluoride on nickel electroplating on magnesium alloy AZ91D  

NASA Astrophysics Data System (ADS)

The effect of zinc immersion and the role of fluoride in nickel plating bath were mainly investigated in nickel electroplating on magnesium alloy AZ91D. The state of zinc immersion, the composition of zinc film and the role of fluoride in nickel plating bath were explored from the curves of open circuit potential (OCP) and potentiodynamic polarization, the images of scanning electron microscopy (SEM) and the patterns of energy dispersive X-ray (EDX). Results show that the optimum zinc film mixing small amount of Mg(OH) 2 and MgF 2 is obtained by zinc immersion for 30-90 s. The corrosion potential of magnesium alloy substrate attached zinc film will be increased in nickel plating bath and the quantity of MgF 2 sandwiched between magnesium alloy substrate and nickel coating will be reduced, which contributed to produce nickel coating with good performance. Fluoride in nickel plating bath serves as an activator of nickel anodic dissolution and corrosion inhibitor of magnesium alloy substrate. 1.0-1.5 mol dm -3 of F - is the optimum concentration range for dissolving nickel anode and protecting magnesium alloy substrate from over-corrosion in nickel plating bath. The nickel coating with good adhesion and high corrosion resistance on magnesium alloy AZ91D is obtained by the developed process of nickel electroplating. This nickel layer can be used as the rendering coating for further plating on magnesium alloys.

Zhang, Ziping; Yu, Gang; Ouyang, Yuejun; He, Xiaomei; Hu, Bonian; Zhang, Jun; Wu, Zhenjun

2009-06-01

187

LIQUID LITHIUM EXTRACTION OF THORIUM FROM THORIUM-MAGNESIUM ALLOY  

Microsoft Academic Search

A process for recovering Th from Th-Mg alloy, utilizing liquid Li ; extraction, was investigated. Dissolution of Th--Mg alloy in liquid Li metal ; resulted in the formation of a Li-Mg alloy solution and the precipitation of Th ; as a finely divided solid. Th separation was accomplished by filtration through ; stainless steel filters. Over 99.7% of the introduced

1962-01-01

188

Some Key Issues and Accesses to the Application of Magnesium Alloys  

NASA Astrophysics Data System (ADS)

The status of Mg alloy application, and then some key issues limiting their applications and the corresponding accesses were briefly discussed. It was supposed that development of new alloys with high performance and low cost, investigating advanced forming technology, and development of credible and effective surface modification technologies and related equipment were the urgent tasks in present. Correspondingly, three aspects of researches were carried out. (1) A new alloy with high strength and elongation, but low RE and Zn contents, named ZW21, was invented. (2) Semisolid ingots of AZ91D, AM60 and ZW21 alloys available for thixoforming were prepared. Thixoforming increased the ultimate tensile strength of AZ91D alloy by 20% compared with permanent mould casting. (3) A new kind of micro arc oxidation equipment with a capacity of treating 6m2 surface was developed and has been used to treating motorcycle hub of magnesium alloy.

Hao, Yuan; Chen, Tijun; Ma, Ying; Li, Yuandong; Yan, Fengyun; Huang, Xiaofeng

189

Biomimetic hydrophobic surface fabricated by chemical etching method from hierarchically structured magnesium alloy substrate  

NASA Astrophysics Data System (ADS)

As one of the lightest metal materials, magnesium alloy plays an important role in industry such as automobile, airplane and electronic product. However, magnesium alloy is hindered due to its high chemical activity and easily corroded. Here, inspired by typical plant surfaces such as lotus leaves and petals of red rose with super-hydrophobic character, the new hydrophobic surface is fabricated on magnesium alloy to improve anti-corrosion by two-step methodology. The procedure is that the samples are processed by laser first and then immersed and etched in the aqueous AgNO3 solution concentrations of 0.1 mol/L, 0.3 mol/L and 0.5 mol/L for different times of 15 s, 40 s and 60 s, respectively, finally modified by DTS (CH3(CH2)11Si(OCH3)3). The microstructure, chemical composition, wettability and anti-corrosion are characterized by means of SEM, XPS, water contact angle measurement and electrochemical method. The hydrophobic surfaces with microscale crater-like and nanoscale flower-like binary structure are obtained. The low-energy material is contained in surface after DTS treatment. The contact angles could reach up to 138.4 ± 2°, which hydrophobic property is both related to the micro-nano binary structure and chemical composition. The results of electrochemical measurements show that anti-corrosion property of magnesium alloy is improved. Furthermore, our research is expected to create some ideas from natural enlightenment to improve anti-corrosion property of magnesium alloy while this method can be easily extended to other metal materials.

Liu, Yan; Yin, Xiaoming; Zhang, Jijia; Wang, Yaming; Han, Zhiwu; Ren, Luquan

2013-09-01

190

Magnesium alloys (WE43 and ZE41) characterisation for laser applications  

NASA Astrophysics Data System (ADS)

One of the most important parameters in laser treatment is the quantity of beam energy absorbed by the substrate. Despite its important role played in laser processes, this factor is rarely available for the laser sources wavelengths and at high temperatures reached during such treatments. A series of experiments were carried out in order to characterise, from this point of view, two types of magnesium alloys, WE43 and ZE41, often used in laser applications (cladding, alloying, welding, etc.). The results represent an important step in order to understand Mg-alloys behaviour under laser beam action.

Ignat, Sorin; Sallamand, Pierre; Grevey, Dominique; Lambertin, Michel

2004-06-01

191

Corrosion and wear resistance improvement of magnesium alloys by laser cladding with Al-Si  

NASA Astrophysics Data System (ADS)

Laser cladding with Al-Si powders have been carried out on three different magnesium alloys (AZ61, ZK30 and WE54) in order to improve their wear and corrosion properties using Nd:YAG CW laser. Optimized parameters allow obtaining crack and pore free coatings with good metallurgical bonding. Special care in shielding atmosphere is required to avoid porosity and corrosion. The hardness of the coatings is higher (130-250 HV) than that of as-received alloys. Salt spray corrosion tests and pin on disc sliding wear tests were carried out confirming that Al-Si coatings improves the wear and corrosion resistance of the alloys.

Carcel, Bernabe; Sampedro, Jesus; Ruescas, Ana; Toneu, Xavier

192

Interactive effect of cerium and aluminum on the ignition point and the oxidation resistance of magnesium alloy  

Microsoft Academic Search

This paper focused on the interactive effect of cerium (Ce) addition and aluminum (Al) content in magnesium alloy on ignition point and oxidation resistance. Ce content played an important role in improving the oxidation resistance of Mg alloy. Ignition point ascended with increasing Ce content. 0.25wt% Ce content in Mg alloys could greatly improve tightness of the oxide film of

Peng-yu Lin; Hong Zhou; Wei Li; Wen-ping Li; Na Sun; Rong Yang

2008-01-01

193

Development of Forming Limit Diagrams of Aluminum and Magnesium Sheet Alloys at Elevated Temperatures  

NASA Astrophysics Data System (ADS)

Magnesium components are increasingly being considered for use in vehicle structures due to the potential for weight reduction, fuel economy improvement, and emission reduction. Apart from castings, magnesium sheet components can open an entirely new opportunity for mass reduction. Magnesium’s poor ductility at room temperature, however, requires sheet forming to be carried out at elevated temperatures. The forming limits of magnesium alloy AZ31B-O were measured with both in-plane (Marciniak) and out-of-plane (limiting dome height) test methods at 300 °C. Forming limits of aluminum alloys 5182-O and 5754-O were also measured at room temperature and compared with published forming limit diagram data to validate the test procedures. Differences between the in-plane and out-of-plane test methods are discussed along with a description of failure modes and experimental challenges in obtaining strain localization and fracture in the appropriate locations. The plane strain forming limit (FLDo) of AZ31B at 300 °C was on the order of 67% strain, which agrees well with published data.

Hsu, Emilie; Carsley, John E.; Verma, Ravi

2008-06-01

194

Corrosion inhibition of rapidly solidified Mg-3% Zn-15% Al magnesium alloy with sodium carboxylates  

SciTech Connect

The ability of sodium linear-saturated carboxylates to protect magnesium alloys against aqueous corrosion was characterized. Electrochemical measurements of polarization resistance and corrosion current showed the inhibition efficiency of these compounds is a function of their concentration and of the length of the aliphatic chain. In every case studied, the efficiency increased with immersion time. At pH 8, the best inhibiting behavior was observed with 0.05 M sodium undecanoate. The potential-pH diagram of magnesium in an aqueous solution containing undecanoate anions was generated based upon the solubility determined for magnesium undecanoate (Mg[CH{sub 3}(CH{sub 2}){sub 9}COO]{sub 2}). According to this diagram, the very low corrosion rate was suspected to result from formation of Mg(CH{sub 3}[CH{sub 2}]{sub 9}COO){sub 2}. Infrared spectrometry carried out on both the synthesized magnesium carboxylate and the product from the magnesium alloy surface after inhibitive treatment confirmed this hypothesis.

Daloz, D.; Michot, G. [Ecole des Mines, Nancy (France). Lab. de Metallurgie Physique and Sciences des Materiaux; Rapin, C.; Steinmetz, P. [Univ. Henri Poincare de Nancy, Vandoeuvre les Nancy (France). Lab. de Chimie du Solide Mineral

1998-06-01

195

Microstructure and Corrosion Characterization of Squeeze Cast AM50 Magnesium Alloys  

NASA Astrophysics Data System (ADS)

Squeeze casting of magnesium alloys potentially can be used in lightweight chassis components such as control arms and knuckles. This study documents the microstructural analysis and corrosion behavior of AM50 alloys squeeze cast at different pressures between 40 and 120 MPa and compares them with high-pressure die cast (HPDC) AM50 alloy castings and an AM50 squeeze cast prototype control arm. Although the corrosion rates of the squeeze cast samples are slightly higher than those observed for the HPDC AM50 alloy, the former does produce virtually porosity-free castings that are required for structural applications like control arms and wheels. This outcome is extremely encouraging as it provides an opportunity for additional alloy and process development by squeeze casting that has remained relatively unexplored for magnesium alloys compared with aluminum. Among the microstructural parameters analyzed, it seems that the ?-phase interfacial area, indicating a greater degree of ? network, leads to a lower corrosion rate. Weight loss was the better method for determining corrosion behavior in these alloys that contain a large fraction of second phase, which can cause perturbations to an overall uniform surface corrosion behavior.

Sachdeva, Deepika; Tiwari, Shashank; Sundarraj, Suresh; Luo, Alan A.

2010-12-01

196

Properties and microstructure of aluminum-copper-magnesium-lithium alloys  

Microsoft Academic Search

The microstructure and mechanical properties of Al?Cu?Mg?Li alloy extrusions prepared from both rapidly cooled powder flakes\\u000a and cast ingots have been determined. Embrittlement of the alloys by lithium was observed in both powder source and ingot\\u000a source metarial. Fracture in all the powder source alloys was partly transgranular and partly along the boundaries of the\\u000a original powder flakes. In the

Donald Webster

1979-01-01

197

Divorced eutectic in a HPDC magnesium–aluminum alloy  

Microsoft Academic Search

The morphology of the eutectic in a thin-wall high pressure die cast (HPDC) U-shape AM60 magnesium box was investigated by light microscope, SEM, TEM and EPMA. The extremely fast cooling rate taking place in the solidification process produces a highly segregated zone near the boundaries of small grains and a fine distribution of ? particles, which is typical of a

S. Barbagallo; H. I. Laukli; O. Lohne; E. Cerri

2004-01-01

198

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

199

Evaluation of magnesium alloys with alternative surface finishing for the proliferation and chondro-differentiation of human mesenchymal stem cells  

NASA Astrophysics Data System (ADS)

Articular cartilage has little capacity for self-repair. As a result, continuous mechanical stress can lead to the degradation of articular cartilage, culminating in progressive damage and joint degeneration. Tissue engineering has arisen as a promising therapeutic approach to cartilage repair. Magnesium alloys are one of the most important metallic biomaterials emerging in this area due to their biocompatibility, bio-absorbability and especially to their mechanical properties. These properties make magnesium alloys a promising biomaterial in the regeneration of cartilage tissue. Objective. This study was undertaken to analyze the influence of surface characteristics of magnesium alloys in the adhesion, proliferation and differentiation of human mesenchymal stem cells (MSCs). Methods. Two commercial magnesium alloys (AZ31B and ZM21) were subjected to different treatments in order to obtain four different surfaces in each alloy. Human MSCs were seeded into the magnesium alloys and analyzed for their proliferation and chondrogenesis differentiation ability. Results. Human MSCs showed a greater proliferation and chondro-differentiation when cultured in the ZM21 magnesium alloy with a surface finishing of fine sanding, polishing, and etching.

Trinidad, J.; Arruebarrena, G.; Sáenz De Argandoña, E.; Ruiz De Eguino, G.; Infante, A.; Rodríguez, C. I.

2010-11-01

200

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

201

Microstructure and mechanical property of ECAPed ZE41 magnesium alloy  

Microsoft Academic Search

A ZE41 alloy was processed by equal channel angular pressing (ECAP) at 320°C. The microstructure and tensile properties were investigated. It has been observed that ECAP refines both the grains and precipitates, thus modifies the strength and ductility of the alloy. The sample after 6-passes of ECAP processing has a yield stress of 230MPa and elongation of 20%, compared with

R G Ding; C W Chung; Y L Chiu

2010-01-01

202

Corrosion of heat treated magnesium alloy ZE41  

Microsoft Academic Search

This paper investigates the effect of heat treatment upon the corrosion morphology and mechanism of ZE41 alloy. The results of optical and scanning electron microscopy (SEM) together with potentiodynamic polarisation reveal the importance of the microstructure in the initiation and propagation of corrosion in an aqueous environment. The corrosion of the heat-treated alloy is significantly altered due to changes in

W. C. Neil; M. Forsyth; P. C. Howlett; C. R. Hutchinson; B. R. W. Hinton

2011-01-01

203

Temperature fuzzy control system in the processing of rheocasting-rolling on semi-solid magnesium alloy  

Microsoft Academic Search

Temperature is a very important parameter in the processing of semi-solid magnesium alloy. The accuracy of temperature controlling affects the quality of the magnesium strips directly, so it has a very important meaning to enhance the temperature controlling precision. But the resistant furnace, which is the object of the controlling, has the characteristics of nonlinearity, time varying, pure delaying and

Zhang Ying; Xu Jinhua; Zhao Haibo; Geng Maopeng; Guo Hongmin; Ma Qiang; Xie Shuisheng

2010-01-01

204

Creep and rupture behavior of a commercial aluminum–magnesium alloy A5083 at constant applied stress  

Microsoft Academic Search

Commercial aluminum–magnesium alloy was tested to examine the creep-rupture behavior at constant applied stress. At the initial stage, the alloy showed the inverse transition creep with the incubation time. The incubation time would be induced through the release of the free dislocations from the magnesium atmosphere or\\/and second particles. Minimum strain rate was observed instead of steady state creep rate.

Keisuke Ishikawa; Yasuo Kobayashi

2004-01-01

205

Effect of cooling rate on ignition point of AZ91D–0.98 wt.% Ce magnesium alloy  

Microsoft Academic Search

Influence of the cooling rate, Kp, on the ignition point of AZ91D–0.98 wt.% Ce magnesium alloy is investigated. To the AZ91D–0.98 wt.% Ce magnesium alloy, the cooling rate has a great effect on its microstructure and phase. XRD shows that it mainly consists of ?-Mg, Mg17Al12 and Ce phases with rapid solidification treatment, while ?-Mg, Mg17Al12 and Al11Ce3 phases are with air

W. Li; H. Zhou; W. Zhou; M. X. Wang

2007-01-01

206

Laser surface modification of Ti and TiC coatings on magnesium alloy  

NASA Astrophysics Data System (ADS)

In order to enhance the surface properties of magnesium alloy, a highly intense laser surface melting process following plasma spraying of Ti or TiC on AZ31 alloy were employed. When laser surface melting was applied to Ti coated magnesium alloy, the formation of fine Ti particle dispersed surface layer on the substrate occurred. The corrosion potential of the AZ31 alloy with Ti dispersed surface was significantly increased in 3.5 wt % NaCl solution. Additionally, an improved hardness was observed for the laser treated specimens as compared to the untreated AZ31 alloy. Laser melting process following plasma thermal deposition was also applied for obtaining in situ TiC coating layer on AZ31 alloy. The TiC coating layer could be successfully formed via in situ reaction between pure titanium and carbon powders. Incomplete TiC formation was observed in the plasma sprayed specimen, while completely transformed TiC layer was found after post laser melting process. It was also confirmed that the laser post treatment induced enhanced adhesion strength between the coating and the substrate.

Kim, J. M.; Lee, S. G.; Park, J. S.; Kim, H. G.

2014-12-01

207

Quality issues in laser welding of automotive aluminum and magnesium alloys  

NASA Astrophysics Data System (ADS)

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 porosity formation during laser welding. The instability of the keyhole was the main cause of macro-porosity formation during laser welding of thin plates of aluminum alloys 5182 and 5754. A computer model was developed to understand the formation and prevention of macroporosity. The stability of keyhole was not a major factor in pore formation during laser welding of die-cast magnesium alloy AM60B. Well controlled remelting of the welded metal led to the removal of gas bubbles and reduced porosity in the welded metal. Loss of alloying elements due to vaporization resulted in significant changes in the composition of the weld metal. Numerical computations of heat transfer and fluid flow and mass transfer were helpful in understanding and controlling compositional changes due to evaporation. Taken as a whole, the research to be presented is a contribution to the growing quantitative knowledge base in fusion welding. Expansion of this knowledge base is necessary, if not essential, to solve important quality problems in fusion welding based on scientific principles.

Zhao, Hailiang

208

In vitro degradation and mechanical integrity of calcium-containing magnesium alloys in modified-simulated body fluid.  

PubMed

The successful applications of magnesium-based alloys as degradable orthopaedic implants are mainly inhibited due to their high degradation rates in physiological environment and consequent loss in the mechanical integrity. This study examines the degradation behaviour and the mechanical integrity of calcium-containing magnesium alloys using electrochemical techniques and slow strain rate test (SSRT) method, respectively, in modified-simulated body fluid (m-SBF). Potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) results showed that calcium addition enhances the general and pitting corrosion resistances of magnesium alloys significantly. The corrosion current was significantly lower in AZ91Ca alloy than that in AZ91 alloy. Furthermore, AZ91Ca alloy exhibited a five-fold increase in the surface film resistance than AZ91 alloy. The SSRT results showed that the ultimate tensile strength and elongation to fracture of AZ91Ca alloy in m-SBF decreased only marginally (approximately 15% and 20%, respectively) in comparison with these properties in air. The fracture morphologies of the failed samples are discussed in the paper. The in vitro study suggests that calcium-containing magnesium alloys to be a promising candidate for their applications in degradable orthopaedic implants, and it is worthwhile to further investigate the in vivo corrosion behaviour of these alloys. PMID:18313746

Kannan, M Bobby; Raman, R K Singh

2008-05-01

209

Microstructure and mechanical property of ECAPed ZE41 magnesium alloy  

NASA Astrophysics Data System (ADS)

A ZE41 alloy was processed by equal channel angular pressing (ECAP) at 320°C. The microstructure and tensile properties were investigated. It has been observed that ECAP refines both the grains and precipitates, thus modifies the strength and ductility of the alloy. The sample after 6-passes of ECAP processing has a yield stress of 230MPa and elongation of 20%, compared with 160 MPa and 8% prior to the ECAP. The deformation of the alloy is predominated via dislocation slip with mechanical twinning.

Ding, R. G.; Chung, C. W.; Chiu, Y. L.

2010-07-01

210

Texture Control by Selective Deformation Mechanism Activation in Magnesium Alloy  

E-print Network

alloy. We accomplished these goals through the use of equal channel angular extrusion, rolling, and heat treatment coupled with microscopy, diffraction, and mechanical testing. Notable achievements include demonstration of tensile twin suppression...

Foley, David Christopher

2014-07-01

211

Modeling dynamic strain aging of aluminum-magnesium alloys  

Microsoft Academic Search

This thesis presents atomistic studies and continuum modeling of solute clustering and solute diffusion in Al-Mg alloys, which are considered elements of the mechanism of dynamic strain aging (DSA). Solute clustering in Al-Mg binary alloys is first studied by means of Monte-Carlo simulations. In the undistorted lattice, Mg has a tendency to form a coherent phase. The binding energy of

Dawei Zhang

2006-01-01

212

Electrochemical investigation of the influence of laser surface melting on the microstructure and corrosion behaviour of ZE41 magnesium alloy – An EIS based study  

Microsoft Academic Search

Surface melting of a magnesium alloy, ZE41 (4%-Zn, 1%-RE) was performed to achieve electrochemical homogeneity at the surface by microstructure refinement. Large secondary precipitates are particularly known to cause severe pitting in magnesium alloys. The corrosion resistance of the laser treated and untreated alloy was investigated by potentiodynamic polarisation and electrochemical impedance spectroscopy. Contrary to the reported behaviour of other

P. Chakraborty Banerjee; R. K. Singh Raman; Y. Durandet; G. McAdam

2011-01-01

213

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 545°C, 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 545°C 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 <450°C or oxide ligament formation at temperature >500°C 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

214

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

215

Preparation and characterization of graphite-dispersed styrene-acrylic emulsion composite coating on magnesium alloy  

NASA Astrophysics Data System (ADS)

In this work, an electrically conductive, corrosion resistant graphite-dispersed styrene-acrylic emulsion composite coating on AZ91D magnesium alloy was successfully produced by the method of anodic deposition. The microstructure, composition and conductivity of the composite coating were characterized using optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR) and four electrode volume resistivity instrument, respectively. The corrosion resistance of the coating was evaluated using potentiodynamic polarization measurements and salt spray tests. It is found that the graphite-dispersed styrene-acrylic emulsion composite coating was layered structure and displayed good electrical conductivity. The potentiodynamic polarization tests and salt spray tests reveal that the composite coating was successful in providing superior corrosion resistance to AZ91D magnesium alloy.

Zhang, Renhui; Liang, Jun; Wang, Qing

2012-03-01

216

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

SciTech Connect

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; Green, Robert [Center for Nondestructive Evaluation, 3400 N. Charles St., Baltimore, Maryland 21218 (United States); Martz, Harry; Dolan, Ken; Rikard, Derrill [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); Horstemeyer, Mark [Sandia National Laboratories, 7011 East Ave., Livermore, California 94550 (United States)

1999-12-02

217

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

218

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

219

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

220

Growth and characterization of Mg(OH) 2 film on magnesium alloy AZ31  

NASA Astrophysics Data System (ADS)

Magnesium-based biomaterials have been proposed as potential candidates for biodegradable implant materials, such as bone screws, bone plates, intraluminal stents and so on. However, the poor corrosion resistance inhibits their applications in surgery. They collapse before the injured tissues are healed. In this paper, Mg(OH) 2 nonstructural film was synthesized on the substrate of AZ31 magnesium alloy by hydrothermal method with NaOH solution as mineralizer to reduce the corrosion rate of magnesium-based materials. The obtained films were characterized by XRD, SEM, and XPS. The results showed that a Mg(OH) 2 film with nanostructure surface can be synthesized by hydrothermal method. It was observed that the thickness of film increased with the holding time. Corrosion rates of the films were studied by immersing the samples in Hank's solution (37 °C). Surface deposits of samples with films soaked in Hank's solution for 31 days were investigated by XRD, SEM, EDS, XPS, and FTIR. It verified that the corrosion rate of the magnesium alloy with grown film was slowed down in the Hank's solution and the behavior of corrosion was inhibited effectively. Amorphous calcium apatite precursor was observed to deposit on the surface of the film during corrosion experiments in Hank's solution. And the tape test revealed a strong adhesion between the film and the substrate.

Zhu, Yanying; Wu, Guangming; Zhang, Yun-Hong; Zhao, Qing

2011-05-01

221

Solution softening in magnesium alloys: the effect of solid solutions on the dislocation core structure and nonbasal slip.  

PubMed

There is a pressing need to improve the ductility of magnesium alloys so that they can be applied as lightweight structural materials. In this study, a mechanism for enhancing the ductility of magnesium alloys has been pursued using the atomistic method. The generalized stacking fault (GSF) energies for basal and prismatic planes in magnesium were calculated by using density functional theory, and the effect of the GSF energy on the dislocation core structures was examined using a semidiscrete variational Peierls-Nabarro model. Yttrium was found to have an anomalous influence on the solution softening owing to a reduction in the GSF energy gradient. PMID:23220883

Tsuru, T; Udagawa, Y; Yamaguchi, M; Itakura, M; Kaburaki, H; Kaji, Y

2013-01-16

222

Optimization of bead spacing during laser cladding of ZE41AT5 magnesium alloy castings  

Microsoft Academic Search

A 4kW Nd:YAG laser system was employed to clad 6.2-mm ZE41A-T5 aerospace magnesium alloy castings at various bead spacings using 1.5-mm filler. An operating window between the bead spacing and the elevated defocusing distance was determined based on theoretical analyses and experimental investigation. Based on the profile characteristics of single beads, this window can be used to determine the optimum

X. Cao; M. Jahazi; J. Fournier; M. Alain

2008-01-01

223

Electroless NiP deposition on magnesium alloy from a sulfate bath  

Microsoft Academic Search

A technology for electroless Ni-P deposition on AZ91D from a low cost plating bath containing sulfate nickel was proposed.\\u000a The seal pretreatment was employed before the electroless Ni-P deposition for the sake of occluding the micro holes of the\\u000a cast magnesium alloy and interdicting the bubble formation in the Ni-P coating during plating process. And pickling pretreatment\\u000a can provide a

Guangyu Li; Liyuan Niu; Qing Jiang; Zhonghao Jiang; Jianshe Lian

2008-01-01

224

Process Parameters Effect on a Rectangular Tube HydroForming with Magnesium Alloy  

Microsoft Academic Search

Due to the light weight and electromagnetic interference shielding capabilities in magnesium alloy material, it is widely\\u000a utilized in 3C electronic components and automobile parts. However, its formability is very poor due to the phenomenon of\\u000a negative strain hardening rate appearing in large strain deformation range, so it is usually formed as die casting or casting\\u000a styles leads to much

S. Y. Lin; C. M. Chang; S. S. Chi

225

Electroless nickel-plating on die cast magnesium alloy AZ91D  

Microsoft Academic Search

Electroless nickel-plating on die cast magnesium alloy AZ91D was investigated. Growth of the electroless nickel-plating coating was characterized using scanning electron microscopy. Corrosion resistance of the coating was evaluated by open circuit potential and potentiodynamic polarization curves in 3.5% (mass fraction) NaCl solution. The results show that plating deposition is initiated on the crevices and then spread onto primary ?

JIA Su-qiu; JIA Shu-sheng; YAO Jun

226

Reliability of Laser Welding Process for ZE41AT5 Magnesium Alloy Sand Castings  

Microsoft Academic Search

Laser welding is a promising joining method for magnesium alloys. The process reliability of 2-mm ZE41A-T5 butt joints welded by a 4 kW Nd:YAG laser was investigated from weld geometries, defects and mechanical properties using Weibull statistical distribution. Smooth, geometrically regular and macroscopically defect-free sound joints were obtained. However, sag, undercut, surface misalignment, and some variations in weld width and

Haider Al-Kazzaz; Xinjin Cao; Mohammad Jahazi; Mamoun Medraj

2008-01-01

227

Influence of temperature on oxidation behaviour of ZE41 magnesium alloy  

Microsoft Academic Search

The influence of temperature on the oxidation behaviour of commercial ZE41 magnesium alloy has been studied. Thermogravimetric tests were carried out to determine the oxidation kinetics in the 350–500°C range. Morphology and growth of the oxidation films were analysed by Scanning Electronic Microscopy (SEM), Energy Dispersive X-Ray Spectrometry (EDS) and X-Ray Diffraction (XRD). It was found that the oxidation kinetics

M. D. López; C. J. Múnez; M. Carboneras; P. Rodrigo; M. D. Escalera; E. Otero

2010-01-01

228

Corrosion of magnesium alloy ZE41 – The role of microstructural features  

Microsoft Academic Search

Magnesium alloy ZE41, used extensively in the aerospace industry, possesses excellent mechanical properties albeit poor corrosion resistance. This paper investigates the mechanism of corrosion and the interaction between the grain boundary intermetallic phases, the Zr-rich regions within the grains and the bulk Mg-rich matrix. The results of optical and scanning electron microscopy (SEM) together with energy-dispersive X-ray (EDX) and atomic

W. C. Neil; M. Forsyth; P. C. Howlett; C. R. Hutchinson; B. R. W. Hinton

2009-01-01

229

Sol–gel coatings of low sintering temperature for corrosion protection of ZE41 magnesium alloy  

Microsoft Academic Search

Silica coatings have been obtained through the organic sol–gel route on magnesium–zinc alloys (ZE41) using low sintering temperatures for their corrosion protection. Tetraethoxysilane (TEOS) was used as alkoxide precursor, and the coatings, monolayer and 3-layers, were deposited by dip-coating technique at a controlled extraction speed of 35cm\\/min. Temperatures of 135°C were applied for several hours for coating densification avoiding mechanical

A. J. López; J. Rams; A. Ureña

2011-01-01

230

Sol–gel silica coatings on ZE41 magnesium alloy for corrosion protection  

Microsoft Academic Search

Silica coatings have been applied on the surface of ZE41 magnesium alloy following the organic sol–gel route and the dip-coating technique. Three different concentrations of sol solution and two densification temperatures of the coating (400°C and 500°C) were used to optimize the compaction of the coatings and as a result reach the corrosion protection of the metallic substrate tests in

A. J. López; E. Otero; J. Rams

2010-01-01

231

Microstructure and mechanical properties of AZ80 magnesium alloy sheet processed by differential speed rolling  

Microsoft Academic Search

A heat-treatable AZ80 magnesium alloy has been subjected to differential speed rolling (DSR) at a large thickness reduction per pass of 33%, and microstructure, texture, mechanical properties, stretch formability as well as texture evolution during stretch forming have been investigated. The basal pole of the DSR-processed sheet tilts toward the rolling direction at 15°. The as-rolled sheet exhibits a combination

Xinsheng Huang; Kazutaka Suzuki; Naobumi Saito

2009-01-01

232

Basal plane texture and flow pattern in friction stir weld of a magnesium alloy  

Microsoft Academic Search

The microtextures in a friction-stir-welded magnesium (Mg) alloy, AZ61, with a nugget-shaped stir zone were analyzed by orientation\\u000a imaging microscopy (OIM). The base material had a (0002) ?uvi0? texture ((0002) parallel to the sheet plane, ?uvi0? parallel to the welding direction). Friction stir welding produced texture components different from those of the base material\\u000a in the stir zone. Except for

Seung Hwan C. Park; Yutaka S. Sato; Hiroyuki Kokawa

2003-01-01

233

Characterization of ceramic PVD thin films on AZ31 magnesium alloys  

Microsoft Academic Search

Ceramic thin films have been widely used to protect the metal substrate as coatings in the past years. In order to improve the poor corrosion resistance of AZ31 magnesium alloy, the study in this paper used the electron beam evaporation method to prepare ceramic PVD films on its surface with TiO2 and Al2O3 as donors, respectively. Atomic force microscopy (AFM),

Guosong Wu; Xiaoqin Zeng; Wenbin Ding; Xingwu Guo; Shoushan Yao

2006-01-01

234

Tribological characteristics of magnesium alloy using N-containing compounds as lubricating additives during sliding  

Microsoft Academic Search

The tribological characteristics of a magnesium alloy, AZ91D, were investigated in a sliding lubricating system using various N-containing compounds as lubricating additives on a Timken type tester against a bearing steel (AISI52100) ring. Results indicated that a significant improvement in the tribological performance exists using N-containing compounds as additives. The characteristics of anti-wear, anti friction and load-carrying capacity increased with

Weijiu Huang; Changhua Du; Zhaofeng Li; Ming Liu; Weiming Liu

2006-01-01

235

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

236

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

Microsoft Academic Search

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

W. Duffy; S. Dalal

1996-01-01

237

Fatigue Crack Growth Mechanisms in High-Pressure Die-Cast Magnesium Alloys  

NASA Astrophysics Data System (ADS)

Microstructure-affected micromechanisms of fatigue crack growth operating near the limit plasticity regime were experimentally identified for the four main commercial high-pressure die-cast (HPDC) magnesium alloys: AM50, AM60, AZ91, and AE44. These fatigue micromechanisms manifested by the concomitant effects of casting pores, interdendritic Al-rich solid solution layer, ?-phase particles, Mn-rich inclusions, rare earth-rich intermetallics, dendrite cell size, and surface segregation phenomena. These concomitant mechanisms clearly delineated the fatigue durability observed for the AM50, AM60, AZ91, and AE44 Mg alloys in both the low- and high-cycle fatigue regimes.

El Kadiri, Haitham; Horstemeyer, M. F.; Jordon, J. B.; Xue, Yibin

2008-01-01

238

Modelling and Design of Magnesium and High Entropy Alloys Through Combining Statistical and Physical Models  

NASA Astrophysics Data System (ADS)

Physical and statistical models are combined to describe and design magnesium and high entropy alloys. A principal component analysis is applied to merge material datasets, and it is shown that limits in properties can be envisaged. Extrapolation techniques can be employed to devise properties of non-existing alloys, such as specific heat capacity, melting point and Young's modulus. These in turn can be input to physical models to predict, for example, yield strength and modulus of toughness. The tools described herein can readily be used for materials discovery, and are being implemented in the Accelerated Metallurgy project.

Toda-Caraballo, Isaac; Rivera-Díaz-del-Castillo, Pedro E. J.

2015-01-01

239

Modelling and Design of Magnesium and High Entropy Alloys Through Combining Statistical and Physical Models  

NASA Astrophysics Data System (ADS)

Physical and statistical models are combined to describe and design magnesium and high entropy alloys. A principal component analysis is applied to merge material datasets, and it is shown that limits in properties can be envisaged. Extrapolation techniques can be employed to devise properties of non-existing alloys, such as specific heat capacity, melting point and Young's modulus. These in turn can be input to physical models to predict, for example, yield strength and modulus of toughness. The tools described herein can readily be used for materials discovery, and are being implemented in the Accelerated Metallurgy project.

Toda-Caraballo, Isaac; Rivera-Díaz-del-Castillo, Pedro E. J.

2014-12-01

240

Susceptibility of rare-earth-magnesium alloys to micro-galvanic corrosion  

Microsoft Academic Search

Four commercially produced rare-earth-magnesium alloys, as-cast ZE41, sand-cast WE43-T6, and wrought WE43-T6 and WE54-T6, were studied by scanning Kelvin probe force microscopy (SKPFM) in order to evaluate the role of their micro-constituent phases on potential galvanic interactions. Such interactions were then examined by immersion of the alloys in 3.5wt% NaCl solution. The results confirmed that SKPFM was a powerful tool

A. E. Coy; F. Viejo; P. Skeldon; G. E. Thompson

2010-01-01

241

Formation of intermetallic phases in diffusion-welded joints of aluminium and magnesium alloys  

Microsoft Academic Search

Basic research has been done on diffusion-welded joints with the overall aim of an adjusted interface design. The phase formation\\u000a of aluminium alloy\\/magnesium alloy bonds has been revealed by X-ray diffraction, energy-dispersive spectroscopy and electron\\u000a back-scatter diffraction. The presence of Al12Mg17 and Al3Mg2 phases in a bi-layer has been confirmed. The distribution and microstructure of the formed intermetallics and the

D. Dietrich; D. Nickel; M. Krause; T. Lampke; M. P. Coleman; V. Randle

2011-01-01

242

On the use of magnesium alloys for aerospace and defense mirrors  

NASA Astrophysics Data System (ADS)

Extreme light-weighting is important in many aerospace and defense applications but the cost associated with beryllium or other exotic materials can be prohibitive. The current standard for producing cost effective, high performance mirrors is to diamond machine mirror blanks from aluminum alloy stock. About 80% material removal is the limit for geometrical lightweighting while still retaining the structural integrity required for optical fabrication. To reduce weight further requires alternative materials. This paper summarizes the status of diamond machined finishing and coating of magnesium alloys to produce cost effective, lightweight mirrors with high, broadband reflectivity and low scatter finish.

Woodard, Kenneth S.; Comstock, Lovell E.; Wamboldt, Leonard; Crifasi, Joseph C.

2014-06-01

243

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

244

Biodegradable poly(lactide-co-glycolide) coatings on magnesium alloys for orthopedic applications.  

PubMed

Polymeric film coatings were applied by dip coating on two magnesium alloy systems, AZ31 and Mg4Y, in an attempt to slow the degradation of these alloys under in vitro conditions. Poly(lactic-co-glycolic acid) polymer in solution was explored at various concentrations, yielding coatings of varying thicknesses on the alloy substrates. Electrochemical corrosion studies indicate that the coatings initially provide some corrosion protection. Degradation studies showed reduced degradation over 3 days, but beyond this time point however, do not maintain a reduction in corrosion rate. Scanning electron microscopy indicates inhomogeneous coating durability, with gas pocket formation in the polymer coating, resulting in eventual detachment from the alloy surface. In vitro studies of cell viability utilizing mouse osteoblast cells showed improved biocompatibility of polymer coated substrates over the bare AZ31 and Mg4Y substrates. Results demonstrate that while challenges remain for long term degradation control, the developed polymeric coatings nevertheless provide short term corrosion protection and improved biocompatibility of magnesium alloys for possible use in orthopedic applications. PMID:23053803

Ostrowski, Nicole J; Lee, Boeun; Roy, Abhijit; Ramanathan, Madhumati; Kumta, Prashant N

2013-01-01

245

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

246

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

247

Biocorrosion of magnesium alloys: a new principle in cardiovascular implant technology?  

PubMed Central

Objectives: To develop and test a new concept of the degradation kinetics of newly developed coronary stents consisting of magnesium alloys. Methods: Design of a coronary stent prototype consisting of the non-commercial magnesium based alloy AE21 (containing 2% aluminium and 1% rare earths) with an expected 50% loss of mass within six months. Eleven domestic pigs underwent coronary implantation of 20 stents (overstretch injury). Results: No stent caused major problems during implantation or showed signs of initial breakage in the histological evaluation. There were no thromboembolic events. Quantitative angiography at follow up showed a significant (p < 0.01) 40% loss of perfused lumen diameter between days 10 and 35, corresponding to neointima formation seen on histological analysis, and a 25% re-enlargement (p < 0.05) between days 35 and 56 caused by vascular remodelling (based on intravascular ultrasound) resulting from the loss of mechanical integrity of the stent. Inflammation (p < 0.001) and neointimal plaque area (p < 0.05) depended significantly on injury score. Planimetric degradation correlated with time (r = 0.67, p < 0.01). Conclusion: Vascular implants consisting of magnesium alloy degradable by biocorrosion seem to be a realistic alternative to permanent implants. PMID:12748224

Heublein, B; Rohde, R; Kaese, V; Niemeyer, M; Hartung, W; Haverich, A

2003-01-01

248

Effect of Ca and Rare Earth Elements on Impression Creep Properties of AZ91 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Creep properties of AZ91 magnesium alloy and AZRC91 (AZ91 + 1 wt pct RE + 1.2 wt pct Ca) alloy were investigated using the impression creep method. It was shown that the creep properties of AZ91 alloy are significantly improved by adding Ca and rare earth (RE) elements. The improvement in creep resistance is mainly attributed to the reduction in the amount and continuity of eutectic ?(Mg17Al12) phase as well as the formation of new Al11RE3 and Al2Ca intermetallic compounds at interdendritic regions. It was found that the stress exponent of minimum creep rate, n, varies between 5.69 and 6 for AZ91 alloy and varies between 5.81 and 6.46 for AZRC91 alloy. Activation energies of 120.9 ± 8.9 kJ/mol and 100.6 ± 7.1 kJ/mol were obtained for AZ91 and AZRC91 alloys, respectively. It was shown that the lattice and pipe-diffusion-controlled dislocation climb are the dominant creep mechanisms for AZ91 and AZRC91 alloys, respectively. The constitutive equations, correlating the minimum creep rate with temperature and stress, were also developed for both alloys.

Nami, B.; Razavi, H.; Mirdamadi, S.; Shabestari, S. G.; Miresmaeili, S. M.

2010-08-01

249

Double Oxide Film Defects in Cast Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Castings were made in an unfluxed commercial purity Mg alloy in plate molds with both well-designed and poorly designed running system features. The poor running system design was associated with more entrainment of the surface oxide film during mold filling and produced a greater spread in ultimate tensile strength (UTS) and pct elongation values than the castings produced with the good running system design. This is also an effect found in Al alloys where it has also been associated with entrainment of the surface oxide film during mold filling. Scanning electron microscopy of the fracture surfaces of tensile test bars cut from the cast plates revealed oxide film defects comprised of folded over and symmetrical MgO films, similar in form and structure to the double oxide film defects found in Al alloys.

Griffiths, W. D.; Lai, N.-W.

2007-01-01

250

Textures, microstructures, anisotropy and formability of aluminum-manganese-magnesium and aluminum-magnesium alloys  

NASA Astrophysics Data System (ADS)

In this dissertation work, the microstructure and texture evolution of continuous cast (CC) and direct chill (DC) cast Al-Mn-Mg (AA 3105 and AA 3015) and Al-Mg (AA 5052) alloys during cold rolling and annealing are systematically investigated. Macrotexture analyses were based on three-dimensional orientation distribution functions (ODFs) calculated from incomplete pole figures from X-ray diffraction by using arbitrarily defined cell (ADC) and series expansion methods. A new technique, electron backscatter diffraction (EBSD), was adopted for microtexture and mesotexture investigation. The anisotropy and formability of Al-Mn-Mg and Al-Mg alloys are correlated to the texture results. For aluminum alloys studied in this work, a stronger Cube orientation is observed in DC hot band than in CC hot band after complete recrystallization. alpha and beta fibers become well developed beyond 50% cold rolling in both CC and DC aluminum alloys. The highest intensity along the beta fiber (skeleton line) is located between the Copper and the S orientations in both materials after high cold rolling reductions. In both CC and DC aluminum alloys, a cell structure develops with the indication of increasing CSL Sigma1 boundaries during the early stages of cold rolling. There is no evidence of the development of twin boundaries (Sigma3, Sigma9, Sigma27a & 27b) in either CC or DC aluminum alloys when the cold rolling reductions are less than 40%. The R and Cube textures are dominant recrystallization texture components in CC and DC AA 5052 alloys. The volume fraction of the Cube component is increased by increasing cold rolling reduction and annealing temperature but not by increasing annealing time while the volume fraction of the R component is only increased by increasing cold rolling reduction. Stronger Cube and R orientations are found at the surface layer than at half-thickness layer of cold rolled hot bands after annealing. The Cube and P textures are dominant recrystallization texture components in DC AA 3105 and CC AA 3015 alloys, respectively. When the hot bands of CC AA 3015 alloy were directly cold rolled followed by annealing the P orientation {011}<566>, accompanied by the R-CubeND orientation {001}<130>, was found to be the major recrystallization texture component for CC AA 3015 alloy. The Brass orientation {011}<112> transforms to the P orientation along the alpha fiber during annealing. The intensity of the P orientation increases with increasing cold rolling reduction and the highest intensity is obtained utilizing a 450°C anneal. The Zener drag mechanism appears to be responsible for the formation of the highly RD-elongated recrystallized grain structure. For CC AA3015 alloy, the yield strength and ultimate strength of cold rolled hot bands at O-temper condition can be significantly increased by solid solution annealing of hot bands before cold rolling.

Liu, Jiantao

251

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

252

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

253

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

254

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

255

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

256

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

257

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

SciTech Connect

The superplastic behavior of a fine-grained AZ91 alloy, processed by equal channel angular extrusion, has been investigated in a low temperature range of 423--523 K. 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 superplastic elongation than the alloy with equilibrium grain boundaries. Furthermore, the strain rate for superplastic flow of the former was lower than that of the latter. These differences probably arise because the accommodation process for grain boundary sliding is hampered by the long-range stresses associated with the non-equilibrium grain boundaries.

Mabuchi, M. [National Industrial Research Inst. of Nagoya (Japan)] [National Industrial Research Inst. of Nagoya (Japan); Ameyama, K. [Ritsumeikan Univ., Noji-Higashi, Shiga (Japan). Dept. of Mechanical Engineering] [Ritsumeikan Univ., Noji-Higashi, Shiga (Japan). Dept. of Mechanical Engineering; Iwasaki, H. [Himeji Inst. of Tech., Hyogo (Japan). Dept. of Materials Science and Engineering] [Himeji Inst. of Tech., Hyogo (Japan). Dept. of Materials Science and Engineering; 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

1999-05-28

258

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

259

One-step electrodeposition process to fabricate corrosion-resistant superhydrophobic surface on magnesium alloy.  

PubMed

A simple, one-step method has been developed to construct a superhydrophobic surface by electrodepositing Mg-Mn-Ce magnesium plate in an ethanol solution containing cerium nitrate hexahydrate and myristic acid. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were employed to characterize the surfaces. The shortest electrodeposition time to obtain a superhydrophobic surface was about 1 min, and the as-prepared superhydrophobic surfaces had a maximum contact angle of 159.8° and a sliding angle of less than 2°. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements demonstrated that the superhydrophobic surface greatly improved the corrosion properties of magnesium alloy in 3.5 wt % aqueous solutions of NaCl, Na2SO4, NaClO3, and NaNO3. Besides, the chemical stability and mechanical durability of the as-prepared superhydrophobic surface were also examined. The presented method is rapid, low-cost, and environmentally friendly and thus should be of significant value for the industrial fabrication of anticorrosive superhydrophobic surfaces and should have a promising future in expanding the applications of magnesium alloys. PMID:25559356

Liu, Qin; Chen, Dexin; Kang, Zhixin

2015-01-28

260

Modifying AM60B Magnesium Alloy Die Cast Surfaces by Friction Stir Processing  

SciTech Connect

These experiments were done to evaluate the feasibility of locally modifying the surface properties of magnesium alloys with friction-stir processing. The magnesium alloy used for the study was high-pressure die-cast AM60B, nominally Mg-6Al-0.13 Mn (wt. %). Friction-stir passes were made with a translation speed of 1.7 mm/s using tool-rotation speeds of 1,250 rpm or 2,500 rpm. Stir passes with good appearance were obtained under both conditions. In some cases up to five passes were overlapped on a single bar to produce stir zones with cross-sectional dimensions of about 1.5 mm x 10 mm. Metallographic examinations indicated that the stir zones were largely comprised of a magnesium solid solution with equiaxed grains on the order of 5-10 {micro}m in size. Hardness mapping showed that the stir zones experienced increases of 16-25% compared to the as-cast metal. Room-temperature testing showed that, compared to the cast metal, the stir zones had flow stresses nearly 20% higher with about twice the tensile elongation.

Santella, Michael L [ORNL; Feng, Zhili [ORNL; Degen, Cassandra [South Dakota School of Mines and Technology; Pan, Dr. Tsung-Yu [Ford Motor Company

2006-01-01

261

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

262

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

263

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

NASA Astrophysics Data System (ADS)

The plastic deformation of AZ31 magnesium alloy under tension at temperatures of 4.2-295K 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 becomes unstable (serrated) at temperatures of 4.2-25K and more stress jerks occur in the SPD polycrystal than in the SC alloy. The temperature dependence of the yield stress of the alloy is typical of thermally activated unpinning of dislocations from short-range barriers. The ratio of the yield stresses for the SPD and SC alloys at a given temperature is explained by hardening owing to a reduction in grain size and softening owing to a favorable texture. As the grain size is reduced, the rate of strain hardening of the alloy falls off, but its ductility (strain to fracture) increases because of the texture. The strain rate sensitivity of the alloy for T ?100K is independent of microstructure and is determined by intersections with forest dislocations. As the temperature is raised over 150-295K the strain rate sensitivity becomes greater owing to activation of dynamic recovery and an enhanced contribution from diffusion processes during plastic deformation of micrograined materials.

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

2010-12-01

264

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

265

Bioresorbable drug-eluting magnesium-alloy scaffold for treatment of coronary artery disease.  

PubMed

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

266

Investigating the characteristics of AZ61 magnesium alloy on the hot and semi-solid compression test  

Microsoft Academic Search

The characteristics of magnesium AZ61 in semi-solid state have been investigated to understand the changes in its stress-strain\\u000a in the compression process, the effects on its strain under different processing temperatures, and the consequence of the\\u000a change of peak stress. First, the AZ61 magnesium alloy is heated to 660 C and sustained at that temperature for 5 min. Then\\u000a by natural cooling,

Jer-Liang Kuo; Sumio Sugiyama; Su-Hai Hsiang; Jun Yanagimoto

2006-01-01

267

On the Possibility of using Alluminium-Magnesium Alloys with Improved Mechanical Characteristics for Body Elements of Zenit-2S Launch Vehicle Propellant Tanks  

Microsoft Academic Search

Yuzhnoye SDO developed several generations of launch vehicles and spacecraft that are characterized by weight perfection, optimal cost, accuracy of output geometrical characteristics, stable strength characteristics, high tightness. The main structural material of launch vehicles are thermally welded non-strengthened aluminium- magnesium alloys. The aluminium-magnesium alloys in the annealed state have insufficiently high strength characteristics. Considerable increase of yield strength of

V. Sitalo; T. Lytvyshko

2002-01-01

268

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 550°C 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

269

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.

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

2013-11-01

270

The corrosion performance of magnesium alloy AM-SC1 in automotive engine block applications  

Microsoft Academic Search

The magnesium alloy AM-SC1 has been developed as a creep-resistant automotive engine block material. This paper outlines its\\u000a corrosion performance under laboratory test conditions, considering corrosion on both the external and internal surfaces.\\u000a This study found that AM-SC1 has a corrosion performance comparable to AZ91 when subjected to an aggressive salt-spray environment\\u000a or in galvanic-coupling environments. This article further demonstrates

Guangling Song; David Stjohn; Colleen Bettles; Gordon Dunlop

2005-01-01

271

Study on the anodizing of AZ31 magnesium alloys in alkaline borate solutions  

NASA Astrophysics Data System (ADS)

A kind of environmentally friendly anodizing route for magnesium alloys, based on a new kind of organic additive (AA) contained traditional alkaline borate solution and 50 Hz civil ac current, has been studied. It is found that the formation of the anodic films is always coupled with the additive depended sparking and oxygen evolution, and the optimized ivory-white smooth anodic film possesses high corrosion resistance and excellent binding strength to AZ31 substrate. Meanwhile, The results also show that the structure, the corrosion resistance and the morphology of the anodic films are mainly dependent on the anodizing voltage, time and additives.

Wu, C. S.; Zhang, Z.; Cao, F. H.; Zhang, L. J.; Zhang, J. Q.; Cao, C. N.

2007-02-01

272

Fabrication of biomimetic hydrophobic films with corrosion resistance on magnesium alloy by immersion process  

NASA Astrophysics Data System (ADS)

Biomimetic hydrophobic films of crystalline CeO2 were prepared on magnesium alloy by an immersion process with cerium nitrate solution and then modified with DTS (CH3(CH2)11Si(OCH3)3). The CeO2 films fabricated with 20-min immersion yield a water contact angle of 137.5 ± 2°, while 20-min DTS treatment on top of CeO2 can further enhance the water contact angle to 146.7 ± 2°. Then corrosion-resistant property of these prepared films against NaCl solution was investigated and elucidated using electrochemical measurements.

Liu, Yan; Lu, Guolong; Liu, Jindan; Han, Zhiwu; Liu, Zhenning

2013-01-01

273

High Cycle Fatigue of Cast Mg-3Nd-0.2Zn Magnesium Alloys  

NASA Astrophysics Data System (ADS)

This paper investigates the high cycle fatigue properties of a recently developed high-strength cast magnesium alloy [Mg-3Nd-0.2Zn (all compositions in wt pct except when otherwise stated)] with varied Zr contents for grain refinement (NZ30K) and the influence of heat treatment conditions. The NZ30K alloy containing 0.45Zr and heat treated to the peak-aged T6 condition [14 hours at 473 K (200 °C)] shows the highest fatigue strength, about 100 MPa, which is about 25 pct higher than that of commercial AZ91D-T6 alloy. In the absence of casting flaws, the high cycle fatigue properties of the NZ30K alloy strongly depend on its grain size and heat treatment conditions. The dependency of fatigue strength on grain sizes follows the Hall-Petch relationship. The NZ30K alloy also shows a significant response to heat treatments. The fatigue strength increases in a near linear fashion with increasing yield strength of the material through heat treatment.

Li, Zhenming; Wang, Qigui; Luo, Alan A.; Fu, Penghuai; Peng, Liming; Wang, Yingxin; Wu, Guohua

2013-11-01

274

Surface characteristics and corrosion behaviour of WE43 magnesium alloy coated by SiC film  

NASA Astrophysics Data System (ADS)

Amorphous SiC film has been successfully fabricated on the surface of WE43 magnesium alloy by plasma enhanced chemical vapour deposition (PECVD) technique. The microstructure and elemental composition were analyzed by transmission electron microscopy (TEM), glancing angle X-ray diffraction (GAXRD) and X-ray photoelectron spectroscopy (XPS), respectively. The immersion test indicated that SiC film could efficiently slow down the degradation rate of WE43 alloy in simulated body fluid (SBF) at 37 ± 1 °C. The indirect toxicity experiment was conducted using L929 cell line and the results showed that the extraction medium of SiC coated WE43 alloys exhibited no inhibitory effect on L929 cell growth. The in vitro hemocompatibility of the samples was investigated by hemolysis test and blood platelets adhesion test, and it was found that the hemolysis rate of the coated WE43 alloy decreased greatly, and the platelets attached on the SiC film were slightly activated with a round shape. It could be concluded that SiC film prepared by PECVD made WE43 alloy more appropriate to biomedical application.

Li, M.; Cheng, Y.; Zheng, Y. F.; Zhang, X.; Xi, T. F.; Wei, S. C.

2012-01-01

275

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

276

Structural homogeneity and low-temperature micromechanical properties of ultrafine-grained AZ31 magnesium alloy  

NASA Astrophysics Data System (ADS)

The degree of microstructural homogeneity of ultrafine-grained (UFG) AZ31 magnesium alloy produced by a special thermomechanical process including four cycles of equal-channel angular pressing (ECAP, route Bc) is studied by the microindentation method. The defect structure of the UFG alloy is quite homogeneous. Texture owing to ECAP showed up as a lower average microhardness measured in a plane perpendicular to the extrusion axis than that measured in a plane containing that axis, and in a slight dependence of the microhardness on the location of the indent on the billet surface. The microhardness of the initial coarse-grained alloy is close to that of the UFG samples measured in a plane perpendicular to the extrusion axis. Tensile deformation of the samples over a wide temperature range of 4.2-295 K increased the microhardness in the region of the neck by more than 30%. The temperature dependence of the microhardness over 77-295 K is indicative of thermally activated plastic deformation in AZ31 alloy. The mechanism for deformation of the alloy appears to be interactions between dislocations and local defects of impurity origin.

Estrin, Y. Z.; Fomenko, L. S.; Lubenets, S. V.; Rusakova, A. V.

2011-06-01

277

Analytical Method for Forming Limit Diagram Prediction with Application to a Magnesium ZEK100-O Alloy  

NASA Astrophysics Data System (ADS)

A significant barrier to broader implementation of magnesium alloys is their poor room temperature formability, a consequence of the anisotropic response of the Mg hexagonal closed-packed (hcp) crystal structure. Additions of rare earth (RE) elements, such as in the ZEK100 alloys, weaken the texture and improve formability. Room temperature forming limit analyses of RE-containing Mg alloys, particularly Mg ZEK100, have not been explored to any significant extent in the literature. In this paper, strain-based forming limit diagrams (FLDs) are derived for an Mg ZEK100-O alloy (Zn1.34Zr0.23Nd0.182, wt.%) using an analytical method that combines the vertex theory of Storen and Rice (J Mech Phys Solids, 23:421-441, 1979), the anisotropic yield criterion of Barlat and Lian (Int J Plast, 5:51-66, 1989), and a hardening law. The method does not rely on assumptions about pre-existing defects, is broadly applicable to sheet alloys exhibiting in-plane anisotropy requiring a higher-order yield criterion, and requires only minimal experimental inputs. Results from the analytical method are compared with experimentally derived FLDs based upon the well-known Nakajima test and tensile deformation, and with predictions from an existing analytical method for FLDs. Close agreement between the experimentally derived FLDs and the present theoretical method was obtained. Sheet materials where the theoretical method does not apply are also discussed.

Min, Junying; Hector, Louis G.; Lin, Jianping; Carter, Jon T.

2013-11-01

278

Research on microstructures of sub-rapidly solidified AZ61 Magnesium Alloy  

SciTech Connect

AZ61 magnesium alloy foils of 0.5-3.0 mm thick were successfully produced by using sub-rapid solidification technique. Microstructures of conventionally solidified (CS) and sub-rapidly solidified (sub-RS) alloys were examined by optical microscope (OM) and scanning electron microscope (SEM). The results showed that the cellular grain of 1.8-13.5 {mu}m can be obtained during sub-rapid solidification process. Phase compositions and microdistribution of the alloying elements in the foils were analyzed by X-ray diffraction (XRD) and electron probe microanalyzer (EPMA), respectively. The eutectic transformation L {yields} {alpha}-Mg + {beta}-Mg{sub 17}Al{sub 12} and microsegregation in conventionally solidified AZ61 alloy were remarkably suppressed in sub-rapid solidification process. As a consequence, the alloying elements Al, Zn, Mn showed much higher solid solubility and the sub-rapid solidification microstructures dominantly consisted of supersaturated {alpha}-Mg solid solution. Meanwhile, the {beta}-Mg{sub 17}Al{sub 12} phases located in the {alpha}-Mg grain boundaries are largely decreased due to high solidification cooling rate.

Teng Haitao, E-mail: seantht@yahoo.com.cna [Key Laboratory for Materials Modification by Laser, Ion and Electron Beams, Ministry of Education (China); School of Materials Science and Engineering, Dalian University of Technology, Dalian 116085 (China); Zhang Xiaoli; Zhang Zhongtao [Key Laboratory for Materials Modification by Laser, Ion and Electron Beams, Ministry of Education (China); School of Materials Science and Engineering, Dalian University of Technology, Dalian 116085 (China); Li Tingju, E-mail: tjuli@dlut.edu.cn [Key Laboratory for Materials Modification by Laser, Ion and Electron Beams, Ministry of Education (China); School of Materials Science and Engineering, Dalian University of Technology, Dalian 116085 (China); Cockcroft, Steve [Department of Materials Engineering, University of British Columbia, Vancouver (Canada)

2009-06-15

279

Magnesium alloys: predicting in vivo corrosion with in vitro immersion testing.  

PubMed

Magnesium (Mg) and its alloys have been proposed as degradable replacements to commonly used orthopedic biomaterials such as titanium alloys and stainless steel. However, the corrosion of Mg in a physiological environment remains a difficult characteristic to accurately assess with in vitro methods. The aim of this study was to identify a simple in vitro immersion test that could provide corrosion rates similar to those observed in vivo. Pure Mg and five alloys (AZ31, Mg-0.8Ca, Mg-1Zn, Mg-1Mn, Mg-1.34Ca-3Zn) were immersed in either Earle's balanced salt solution (EBSS), minimum essential medium (MEM), or MEM-containing 40 g/L bovine serum albumin (MEMp) for 7, 14, or 21 days before removal and assessment of corrosion by weight loss. This in vitro data was compared to in vivo corrosion rates of the same materials implanted in a subcutaneous environment in Lewis rats for equivalent time points. The results suggested that, for the alloys investigated, the EBSS buffered with sodium bicarbonate provides a rate of degradation comparable to those observed in vivo. In contrast, the addition of components such as (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) (HEPES), vitamins, amino acids, and albumin significantly increased corrosion rates. Based on these findings, it is proposed that with this in vitro protocol, immersion of Mg alloys in EBSS can be used as a predictor of in vivo corrosion. PMID:22331609

Walker, Jemimah; Shadanbaz, Shaylin; Kirkland, Nicholas T; Stace, Edward; Woodfield, Tim; Staiger, Mark P; Dias, George J

2012-05-01

280

Effects of sealing treatment on corrosion resistance and degradation behavior of micro-arc oxidized magnesium alloy wires  

NASA Astrophysics Data System (ADS)

The effects of three different sealing treatments on micro-arc oxidized (MAO) medical magnesium alloy wires using boiling water, zirconia sol-gel, and organic gelatin-hydroxyapatite (HA) coatings on the surface morphology, corrosion resistance, and degradation behavior in simulated body fluid (SBF) and simulated intestinal fluid (SIF) are investigated. The treatments involving boiling water or gelatin-HA coating can effectively seal the discharge channels making the surface pores less and smaller. The treatments also improve the corrosion resistance of the MAO magnesium alloy wires, especially the samples with the gelatin-HA coatings which also exhibit reduced degradation in both simulated physiological environments.

Chu, C. L.; Han, X.; Xue, F.; Bai, J.; Chu, P. K.

2013-04-01

281

Optimization of laser beam welding process parameters to attain maximum tensile strength in AZ31B magnesium alloy  

NASA Astrophysics Data System (ADS)

An empirical relationship is developed to predict tensile strength of the laser beam welded AZ31B magnesium alloy by incorporating process parameters such as laser power, welding speed and focal position. The experiments were conducted based on a three factor, three level, central composite face centered design matrix with full replications technique. The empirical relationship can be used to predict the tensile strength of laser beam welded AZ31B magnesium alloy joints at 95% confidence level. The results indicate that the welding speed has the greatest influence on tensile strength, followed by laser power and focal position.

Padmanaban, G.; Balasubramanian, V.

2010-11-01

282

Microstructural characterization of ultrasonic impact treated aluminum-magnesium alloy  

NASA Astrophysics Data System (ADS)

Aluminum 5456-H116 has high as-welded strength, is formable, and highly corrosion resistant, however, it can become sensitized when exposed to elevated temperatures for a prolonged time. Sensitization results in the formation of a continuous ? phase at the grain boundaries that is anodic to the matrix. Thus the grain boundaries become susceptible to stress corrosion cracking (SCC) and intergranular corrosion cracking (IGC). Cracking issues on aluminum superstructures have prompted the use of a severe plastic deformation processes, such as ultrasonic impact treatment (UIT), to improve SCC resistance. This study correlated the effects of UIT on the properties of 5456-H116 alloy to the microstructural evolution of the alloy and helped develop a fundamental understanding of the mechanisms that cause the microstructural evolution. Ultrasonic impact treatment produces a deformed layer at the surface ˜ 10 to 18 µm thick that is characterized by micro-cracks, tears, and voids. Ultrasonic impact treatment results in grain refinement within the deformation layer and extending below the deformed layer. The microstructure exhibits weak crystallographic texture with larger fraction of high angle grain boundaries. Nanocrystalline grains within the deformation layer vary in size from 2 to 200 nm in diameter and exhibit curved or wavy grain boundaries. The nanocrystalline grains are thermally stable up to 300°C. Above 300°C, grain growth occurs with an activation energy of ˜ 32 kJ/mol. Below the deformation layer, the microstructure is characterized by submicron grains, complex structure of dislocations, sub-boundaries, and Moiré fringes depicting overlapping grains. The deformation layer does not exhibit the presence of a continuous ? phase, however below the deformation layer; a continuous ? phase along the grain boundaries is present. In general the highest hardness and yield strength is at the UIT surface which is attributed to the formation of nanocrystalline grains. Although the highest hardness and yield strength was observed at the UIT surface, the results were mixed with some lower values. The lower hardness and yield strength values at the UIT surface are attributed to the voids and micro cracking/micro voids observed in the deformation layer. The fracture mode was transgranular ductile fracture with micro void coalescence and dimples. Both UIT and untreated material exhibit similar levels of intergranular corrosion susceptibility. Corrosive attack was intergranular with slightly deeper attack in the untreated material. Numerical simulation modeling showed that the calculated residual stress under the tool, ˜80 MPa, is of the same order of magnitude as the compressive residual stresses measured by XRD measurements near the surface. Modeling also showed that high effective strains were induced almost immediately. The UIT process also resulted in rapid localized heating to a maximum temperature of ˜32°C during the first eleven pin tool cycles. The model also showed that during UIT processing, the material undulates as the pin tool impacts and retracts from the surface of the material. The undulations represent the elastic response of the surface to the compressive stresses built up during a pin tool cycle.

Tran, Kim Ngoc Thi

283

Femtosecond laser-induced iridescent effect on AZ31B magnesium alloy surface  

NASA Astrophysics Data System (ADS)

Both micro-ripples and nano-ripples were firstly reported at AZ31B magnesium alloy surface irradiated by femtosecond laser in atmospheric environment. Iridescent effect was also demonstrated over a large area of the irradiated surface induced by scanning laser beam. Results revealed that the colour effect was mainly attributed to the nano-ripples with broad distribution of periods acting as diffraction gratings, and intensity of the structural colour was greatly influenced by morphology evolution of the micro-ripples with laser processing. It was suggested that near-field interference between surface plasmons polaritons and incident laser light determined the formation of the nano-ripples, and initial surface roughness combing with such interference lead to the formation of the micro-ripples. Potential applications of such effect on Mg alloys and how to apply the technique to other materials with different properties was further proposed.

Guan, Y. C.; Zhou, W.; Li, Z. L.; Zheng, H. Y.

2013-10-01

284

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

SciTech Connect

Lawrence Livermore National Lab and Sandia National Laboratories, CA 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. The authors concentrate on characterizing monotonically loaded Mg alloy specimens using CT. 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, A.; Green, R.E.; Martz, H.; Dolan, K.; Horstemeyer, M.; Derrill, R.

1999-06-16

285

Wear Behavior Characterization for the Screening of Magnesium-based Alloys  

NASA Astrophysics Data System (ADS)

This research is focused on the development of a systematic approach to evaluate the selection of materials for Mg-based alloys under wear conditions for biomedical applications. A pilot study was carried out in order to establish an accurate and reliable wear testing technique for magnesium and its alloys. This pilot study was conducted on aluminum (Al) and pure Mg, and showed that aluminum has a lower wear rate compared to Mg. The technique displayed good repeatability and high precision. For the main study, an ERC Mg-based alloy was to be compared with pure Mg. The same technique, when applied to pure Mg from a different vendor, produced up to 90% scatter in the data. Microstructure was studied to see if it had any correlation with the scatter. It was discovered that Mg ingot from the second vendor had outsized grains that contributed to the disproportional scatter in the wear data. Increasing the stroke length during wear testing was required so that the wear data would be averaged over multiple grains and reduces the variation in computed wear rates. In the main study, wear behavior and friction properties were analyzed using microtribometery, mechanical stylus profilometry, and microindentation. Surface morphology and microstructure were characterized using optical microscopy, scanning electron microscopy, and optical profilometry. For the main study, pure Mg and the ERC alloy as-cast and extruded conditions were compared. Pure Mg and MZCR alloys were extruded at 350°C and 400°C, respectively. Mg and MZCR alloy were cast at 350°C and heat treated at 510°C. The extruded specimens were divided into two sections, cross-section and longitudinal section. Wear tests were carried out under the applied normal load 0.5 N - 2.5 N in 0.5 N increments sliding at a rate of 0.2 Hz for 240 passes. The results show that the alloying and extrusion processes increase the hardness of the MZCR alloy significantly up to 80%. The as-cast MZCR has a lower resistance to wear compared to as-cast pure Mg. However, the extrusion process enhances the alloy wear resistance as the extrusion ratio increases. On the other hand, the extrusion process on Mg decreases its wear resistance and hardness properties. The wear resistance was greater in the cross-section for the pure Mg with extrusion ratio of 10 and for the MZCR alloy extruded at ratios of 10 and 50. The cross-section of the MZCR alloys had the lowest amount of wear compared to the longitudinal section.

McGhee, Paul R.

286

Texture Control of Aluminum, Iron, and Magnesium Alloy Sheets to Increase Their Plastic Strain Ratios  

NASA Astrophysics Data System (ADS)

It is known that the limiting drawing ratio of sheet metals is proportional to their plastic strain ratios, and the plastic strain ratios of fcc and bcc metal sheets increase with increasing <111>//ND component in their textures. Conventional cold rolling and subsequent annealing of fcc metals cannot give rise to the <111>//ND component. Specifically, the cold rolling texture of polycrystalline fcc metals is characterized by the fiber connecting the {112}<111>, {123}<634>, and {011}<211> orientations in the Euler space, which is often called the ?-fiber. The density of each component in the fiber depends on the stacking fault energy of metals. The {112}<111> and {123}<634> textured Al alloy sheets evolve the {001}<100> texture, when recrystallized. The low plastic strain ratios of the Al alloy sheets are attributed to the {001}<100> texture. The <111>//ND texture can be obtained in shear deformed fcc sheets. Bcc steels develop the <111>//ND texture when cold rolled and recrystallized. However, the density of <111>//ND depends on the content of dissolved interstitial elements such as carbon and nitrogen. The density of the <111>//ND component decreases with increasing concentration of the dissolved interstitial elements. For a given steel, the density of the <111>//ND component can vary with varying thermomechanical treatment. Magnesium alloy sheets are subjected to sheet forming processes at temperatures of 200 °C or higher because of their basal plane texture, or the <0002>//ND orientation. Many studies have been made to alleviate the component so that the magnesium alloy sheets can have better formability. In this article, the above issues are briefly reviewed and discussed.

Lee, Dong Nyung; Han, Heung Nam

2011-08-01

287

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

288

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 300°C 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

289

Studies of the AZ91 magnesium alloy / SiO2-coated carbon fibres composite microstructure  

NASA Astrophysics Data System (ADS)

The microstructure of magnesium matrix composite reinforced with SiO2nano-layer coated carbon fibres, deposited by sol-gel method was characterized. The composite was obtained by infiltration method and the effect of SiO2 on the composite microstructure was analyzed by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM+EDS) and transmission electron microscopy combined with energy-dispersive X-ray spectroscopy (TEM+EDS) methods. Good wettability of fibres by the magnesium alloy AZ91 (Al 9 wt%, Zn 0.3 wt%) was confirmed since fibres were closely surrounded with alloy and pulling-out effect was not visible. The interface region was evidently with aluminium enriched. Near carbon fibre surface a regular layer of SiOX oxide enriched with Al was detected by high angle annular dark field image (HAADF) combined with energy-dispersive X-ray spectroscopy (EDS). The plate or needle shaped very fine particles of Al12Mg17 were identified near the AZ91 matrix zone by bright field (BF) and selected area electron diffraction (SADP).

Olszówka-Myalska, A.; Botor-Probierz, A.

2010-02-01

290

Study on Pressurized Solidification Behavior and Microstructure Characteristics of Squeeze Casting Magnesium Alloy AZ91D  

NASA Astrophysics Data System (ADS)

Squeeze casting technology for magnesium alloys has a great application potential in automobile manufacturing and has received increasing attention from both academic and industrial communities. In this study, the pressurized solidification behavior of magnesium alloy AZ91D in squeeze casting process was investigated using computer-aided cooling curve analysis (CA-CCA). It was found that the applied pressure increased both the start and end temperatures of primary ?-Mg formation but had little effect on the sizes of temperature ranges. Moreover, the applied pressure increased the start temperature and decreased the end temperature of eutectic reaction during the solidification, resulting in a larger temperature range of eutectic reaction compared with solidification under atmospheric pressure. The grains were remarkably refined, and the eutectic fraction increased with increasing applied pressure. The dendritic microstructure with a larger secondary dendrite arm spacing (SDAS) was observed under a higher applied pressure at the central part of the experimental casting. By correlating the CA-CCA and SDAS data, it was found that SDAS and the cooling rate at the maximum ?-Mg growth could be fit into the power law equation in classic solidification theories.

Han, Zhiqiang; Pan, Haowei; Li, Yanda; Luo, Alan A.; Sachdev, Anil K.

2015-02-01

291

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

292

Identification of an advanced constitutive model of Magnesium alloy AZ31B  

NASA Astrophysics Data System (ADS)

The main aim of this paper is to study the flow behavior of the AZ31B magnesium alloy by means of tensile tests performed in extended ranges of temperature and strain rates. The flow stress-strain curves analyzed by power law type constitutive equation [1] can only fit well with experimental curves at the work-hardening stage. A new mathematical model is studied to describe the softening behavior of material based on tensile experiments. The relative parameters are obtained by fitting the equation with the experimental data. The genetic algorithm has been used to obtain the global optimal fitting parameters. The comparison between the fitted and experimental data proves the effectiveness of the model. The results indicate that this model leads to a better simulation of the flow stress during the softening stage than that of the power law equation. Based on this model, the deep drawing process has been simulated with the commercial finite element code FORGE®. The punch load and thickness distribution of AZ31 sheet have been studied. The study of the results is helpful to the application of the stamping technology for the magnesium alloy sheet.

Liu, Z. G.; Massoni, E.

2011-05-01

293

Creep behavior of an AZ91 magnesium alloy reinforced with alumina fibers  

SciTech Connect

Creep tests were conducted at elevated temperatures on an AZ91 alloy reinforced with 20 vol pct Al{sub 2}O{sub 3} fibers. When the creep data are interpreted by incorporating a threshold stress into the analysis, it is shown that the true stress exponent, n, is {approximately}3 at the lower stress levels and increases to >3 at the higher stresses. The true activation energy for creep is close to the value anticipated for interdiffusion of aluminum in magnesium. This behavior is interpreted in terms of a viscous glide process with n = 3 and a breakaway of the dislocations from their solute atom atmospheres at the higher stress levels. The threshold stresses in this composite appear to arise from an attractive interaction between mobile dislocations in the matrix alloy and Mg{sub 17}Al{sub 12} precipitates. The experimental results reveal several important similarities between the creep behavior of this magnesium-based composite and the well-documented creep properties of aluminum-based composites.

Li, Y.; Langdon, T.G. [Univ. of Southern California, Los Angeles, CA (United States)

1999-08-01

294

Solidification, growth mechanisms, and associated properties of Al-Si and magnesium lightweight casting alloys  

SciTech Connect

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 magnesium-based 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

2010-05-16

295

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.

Minárik, P.; Král, R.; Jane?ek, M.

2013-09-01

296

Corrosion behavior of magnesium alloy AZ91 and its MMC in NaCl solution  

SciTech Connect

The corrosion behaviors of magnesium alloy AZ91C and its Al{sub 2}O{sub 3}(short fiber)-reinforced metal matrix composite (MMC) in alkaline solutions (pH 10.5) containing chloride were compared using potentiodynamic polarization measurements, electrochemical impedance spectroscopy (EIS) and immersion tests. Dependence of polarization characteristics (corrosion potential and corrosion current density) on chloride concentration was similar for both materials. The corrosion potential E{sub corr} decreased linearly with the logarithm of chloride concentration, while the corrosion current density i{sub corr} increased rapidly at chloride concentrations larger than 0.1%, with the i{sub corr} for the MMC consistently higher than that for AZ91C, reaching a factor of about 3 in3.5% sodium chloride solution. EIS data indicated that the protective film on the MMC was inferior to that on the matrix alloy. With stirring and at frequencies higher than 5 Hz, the electrode/electrolyte interface might be described by the simplified Randles model for both materials. Immersion tests showed that the corrosion rate of the MMC, in terms of weight loss, was about 7 times that of the matrix alloy. Thus the present investigation indicated that in alkaline solutions containing chloride ions, the presence of Al{sub 2}O{sub 3} short fibers in the alloy did not drastically alter the corrosion behavior, but significantly reduced its corrosion resistance.

Chan, W.M.; Cheng, F.T.; Leung, L.K.; Horylev, R.J.; Yue, T.M. [Hong Kong Polytechnic Univ., Hunghom (Hong Kong)

1997-12-01

297

Effect of Sb on the microstructure and mechanical properties of AZ91 magnesium alloy  

NASA Astrophysics Data System (ADS)

Effects of Sb addition on the microstructure, mechanical properties, and fracture behaviors of AZ91 magnesium alloy, as well as the sensitivity to section thickness of the structure and mechanical properties, have been studied. The results show that when Sb is added into the AZ91 alloy, the grain is refined, the Mg17Al12 phase is refined and granulated, and a new Mg3Sb2 phase is formed and becomes coarse needle-shaped as Sb content increases. The room-temperature tensile strength, elongation, and impact toughness increase first, and then decrease with increasing Sb content. The study on sensitivity to section thickness shows that, when composition is constant, the room-temperature tensile strength and elongation increase with the reduction of section thickness; when section thickness is constant, the room-temperature tensile strength and elongation increase first, and then decrease with increasing Sb content. Additionally, the Sb addition improves the tensile strength of the AZ91 alloy at 100°C and 150°C. The room-temperature tensile and impact fractographs of the AZ91 alloy show intergranular fracture. With increasing Sb content, the tearing deformation zones on the both fractographs enlarge at first, and then diminish, which is consistent with the change of tensile strength, elongation, and impact toughness increasing first, and then reducing with increasing Sb content.

Wang, Qudong; Chen, Wenzhou; Ding, Wenjiang; Zhu, Yanping; Mabuchi, M.

2001-03-01

298

Fatigue properties of magnesium alloy AZ91 processed by severe plastic deformation.  

PubMed

Fatigue properties of cast AZ91 magnesium alloy processed by severe plastic deformation were investigated and compared with the properties of the initial cast state. The severe plastic deformation was carried out by equal channel angular pressing (ECAP). The ECAP treatment resulted in a bimodal structure. The bimodality consists in a coexistence of fine grained areas with higher content of Mg17Al12 particles and areas exhibiting larger grains and lower density of Mg17Al12 particles. Improvement of the basic mechanical properties of AZ91 (yield stress, tensile strength and ductility) by ECAP was significant. Also the improvement of the fatigue life in the low-cycle fatigue region was substantial. However the improvement of the fatigue strength in the high-cycle fatigue region was found to be negligible. The endurance limit based on 10(7) cycles for the cast alloy was 80MPa and for the alloy processed by ECAP 85MPa. The cyclic plastic response in both states was qualitatively similar; initial softening was followed by a long cyclic hardening. Fatigue cracks in cast alloy initiate in cyclic slip bands which were formed in areas of solid solution. In the case of severe plastic deformed material with bimodal structure two substantially different mechanisms of crack initiation were observed. Crack initiation in slip bands was a preferred process in the areas with large grains whereas the grain boundaries cracking was a characteristic mechanism in the fine grained regions. PMID:25498295

Fintová, Stanislava; Kunz, Ludvík

2015-02-01

299

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

NASA Astrophysics Data System (ADS)

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 included the FSW of AZ91D with AM60, and the FSW of AZ91D with AZ31B-H24. Both Mg AZ91D and AZ31B-H24 alloys were welded to 6061-T6 Al. Dissimilar Al alloy welds included the FSW of Al 6061-T6 to Al 5052-H34. Dynamic recrystallization was observed in the weld region as well as in the transition region (HAZ), with a clear decrease in the grain size from the base material through the transition zone and into the FSW zone. The welds were free of porosities. The FSW zone in the welds of Mg alloys (AZ31B and AZ91D) to 6061-T6 A1 showed unique dissimilar-weld characteristics such as complex intercalated microstructures with lamellar-like bands of Mg-rich and Al-rich regions. EDX analysis of the weld zones revealed bands with equal parts of Mg and Al, as well as unique recrystallized bands with predominance of either material were observed. The transition from the HAZ to the FSW zone consistently shows a sharp demarcation on either side of the weld. The transition from the Mg AZ31B HAZ to the FSW zone reveals a demarcation band region that uniquely characterizes all Mg AZ31B-Al 6061-T6 welds. In the case of the FSW of Mg AZ91D-Al 6061-T6, the demarcation band was revealed to form in the retreating side of the weld. Vickers microhardness testing performed on the weld cross-sections provided microhardness profiles that revealed the compensation of the normal degradation of 6061-T6 Al in the HAZ. It was also noticed that all the Mg-AI welds showed very high and erratic microhardness values in the weld zone, in comparison to the base material. The dissimilar Mg alloy welds revealed a homogenous, equi-axed, fine-grain structure in the FSW zone, along with complex intercalated microstructures. A sharp demarcation was seen on the advancing side (AZ91D) and a fairly diffuse flow was observed on the retreating side (AM60B) for both sets of solid fractions. Vickers microhardness testing on the dissimilar Mg alloy systems revealed no degradation of residual microhardness of the material in the FSW zone or the transition zone. Limited TEM studies of these welds revealed dense dislocation structures. Considering the Hall-Petch relationship, both the presence of dense dislocation structures and the decrease in weld zone grain sizes might be contributing to the lack of degradation observed in the weld region. The FSW of dissimilar Al alloys show a sharp advancing side demarcation, a rather diffuse retreating side, and an intercalated weld zone microstructure. The interfaces within this weld system are also unique in that a very fine boundary layer demarcates the lamellar bands of recrystallized material within the weld zone. The transitioning of the elongated grains into the weld zone, and the widely varying grain structures across the advancing side interface are also confirmations of general weld characteristics.

Somasekharan, Anand Chandrika

2005-11-01

300

Calibrating material parameters to model the thin-walled components made of die cast AM60B magnesium alloy  

Microsoft Academic Search

As a novel lightweight metal, die cast AM60B magnesium alloy continues to be considered as a potential replacement for steel in certain automotive components. However, proper numerical model representing this alloy has not yet been fully explored. Thus, an optimisation methodology was developed to calibrate the material parameters needed for four available material laws, namely, MAT_99, MAT_81, MAT_24 and MAT_107

Feng Zhu; Clifford C. Chou; King H. Yang; Xiaoming Chen; David Wagner; Sukhi Bilkhu; Alan Luo

2012-01-01

301

Effect of high-intensity ultrasonic field on process of semi-continuous casting for AZ80 magnesium alloy billets  

Microsoft Academic Search

Under the high-intensity ultrasonic field, AZ80 magnesium alloy was semi-continuously cast. The effects of ultrasonic intensity on the as-cast microstructures and mechanical properties were investigated. The results show that the microstructures of the alloy cast under high-intensity ultrasonic field are fine and uniform, and the grains are equiaxed, rose-shaped or globular with an average size of 257 ?m. High-intensity field

Zhi-qiang ZHANG; Qi-chi LE; Jian-zhong CUI

2010-01-01

302

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

303

Electrochemical properties of magnesium-based hydrogen storage alloys improved by transition metal boride and silicide additives  

Microsoft Academic Search

Transition metal borides and silicides prepared by mechanical alloying (MA) and chemical reduction methods (CR) were introduced to improve the corrosion resistance of magnesium-based hydrogen storage alloys. The additive of FeB prepared by MA can remarkably enhance the discharge capacity and cycling stability which has initial discharge capacity of 355.9mAhg?1 and keeps 224mAhg?1 after 100 cycles, and the exchange density

Li-Fang Jiao; Hua-Tang Yuan; Yi-Jing Wang; Yong-Mei Wang

2009-01-01

304

Quenching of vacancies in pure aluminium and in dilute aluminium-indium and aluminium-magnesium alloys  

Microsoft Academic Search

The increase in resistivity due to quenched-in vacancies was measured for zone-refined aluminium and two aluminium alloys based upon zone-refined aluminium containing indium and magnesium respectively. The alloys were made by levitation melting to minimize pick-up of other impurities. For the pure metal E? , the activation energy for the formation of a vacancy, was found to be 0·76±0·02 ev,

F. C. Duckworth; J. Burke

1966-01-01

305

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 515°C, 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

306

THE SPECTROCHEMICAL ANALYSIS OF MAGNESIUM AND ITS ALLOYS FOR BERYLLIUM, LEAD, AND OTHER TRACE ELEMENTS BY SOLUTION AND SALTCAP TECHNIQUES  

Microsoft Academic Search

Spectrographic solution and salt-cap techniques are described for the ; determination of beryllium, lead, and other trace elements in magnesium alloys in ; the range within plus or minus 4% between 0.0001 and 0.01% with a high voltage ; spark source and a rotating disk electrode method. Comparative sensitivity and ; precision results are given for Al, Ca, Cu, Fe,

R. E. Mansell

1961-01-01

307

A Crystalline Plasticity Finite Element Method for Simulation of the Plastic Deformation of AZ31 Magnesium Alloys  

Microsoft Academic Search

In this paper, a constitutive framework based on a crystalline plasticity model is employed to simulate the plastic deformation of AZ31 magnesium alloy, which posses the hexagonal close packed (HCP) crystal structure. Dislocation slip and mechanical twinning are taken into account in the model. The successive integration method is used to determine the active slip systems, and the contribution of

Dayong Li; Shaorui Zhang; Weiqin Tang; Shiyao Huang; Yinghong Peng

2010-01-01

308

Effects of humidity and contact material on fretting fatigue behavior of an extruded AZ61 magnesium alloy  

Microsoft Academic Search

Fretting fatigue tests of the extruded AZ61 magnesium alloy with the same contact material under low and high humidity were carried out to investigate basic fretting fatigue characteristics and effect of humidity on fretting fatigue behavior. Influence of contact material was also studied by using JIS S45C carbon steel contact material. Degradation of fatigue strength due to fretting was much

Anchalee Saengsai; Yukio Miyashita; Yoshiharu Mutoh

2009-01-01

309

Mössbauer and X-ray diffraction study of an aluminium-magnesium-silicon alloy containing Pb and Sn  

Microsoft Academic Search

The Mössbauer parameters of tin in aluminium matrix were studied and published in an earlier paper1. The aim of this work was to carry out investigations on tin in an aluminium alloy containing magnesium, silicon and lead beside the Mössbauer active tin. The effect of heat treatments on the formation of intermetallic compounds was studied by X-ray diffraction and by

A. Vértes; T. Turmezey; Á. Griger; M. Z. Awad; S. Nagy

1984-01-01

310

Numerical simulation of early stages of oxide formation in molten aluminium–magnesium alloys in a reverberatory furnace  

Microsoft Academic Search

A significant amount of aluminium is processed by melting aluminium scrap that contains small amounts of magnesium. A major drawback of aluminium production in secondary melt furnaces is the formation of dross or aluminium oxide by the oxidation of the molten metal. Since aluminium scrap forms a major source of the metal in secondary aluminium processing, the presence of alloying

Anindya Kanti De; Achintya Mukhopadhyay; Swarnendu Sen; Ishwar K Puri

2004-01-01

311

Systematic understanding of corrosion behavior of plasma electrolytic oxidation treated AZ31 magnesium alloy using a mouse model of subcutaneous implant.  

PubMed

This study was conducted to identify the differences between corrosion rates, corrosion types, and corrosion products in different physiological environments for AZ31 magnesium alloy and plasma electrolytic oxidation (PEO) treated AZ31 magnesium alloy. In vitro and in vivo tests were performed in Hank's Balanced Salt Solution (HBSS) and mice for 12 weeks, respectively. The corrosion rates of both AZ31 magnesium alloy and PEO treated AZ31 magnesium alloy were calculated based on DC polarization curves, volume of hydrogen evolution, and the thickness of corrosion products formed on the surface. Micro X-ray computed tomography (Micro-CT), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were used to analyze morphological and chemical characterizations of corrosion products. The results show that there is more severe localized corrosion after in vitro test in HBSS; however, the thicknesses of corrosion products formed on the surface for AZ31 magnesium alloy and PEO treated AZ31 magnesium alloy in vivo were about 40% thicker than the thickness of corrosion products generated in vitro. The ratio of Ca and P (Ca/P) in the corrosion products also differed. The Ca deficient region and higher content of Al in corrosion product than AZ31 magnesium alloy were identified after in vivo test in contrast with the result of in vitro test. PMID:25491800

Jang, Yongseok; Tan, Zongqing; Jurey, Chris; Collins, Boyce; Badve, Aditya; Dong, Zhongyun; Park, Chanhee; Kim, Cheol Sang; Sankar, Jagannathan; Yun, Yeoheung

2014-12-01

312

Comparative biomechanical and radiological characterization of osseointegration of a biodegradable magnesium alloy pin and a copolymeric control for osteosynthesis.  

PubMed

Magnesium alloys offer great advantages as degradable implant material for pediatric fracture fixation and hold the potential to overcome certain critical shortcomings inherent to currently used degradable (co)polymers. Besides good biocompatibility and appropriate degradation kinetics, sufficient implant anchorage in host bone is critical to prevent implant failure. Bone-implant anchorage of biodegradable magnesium alloys, however, has not yet been related and compared to that of copolymers, their degradable counterparts currently in clinical use. The aim of this study, therefore, was to comparatively assess bone-implant interface strength and the amount of peri-implant bone of a biodegradable magnesium alloy pin (Mg-Y-Nd-HRE) and a self-reinforced copolymeric control (85/15 poly(l-lactic-co-glycolic acid)). To this purpose, push-out testing, microfocus computed tomography (?CT), histological and scanning electron microscopic examination was performed after 4, 12 and 24 weeks of transcortical implantation in 72 rats. Biomechanical testing revealed significantly higher ultimate shear strength for the magnesium alloy pins than for the copolymeric controls at all 3 timepoints (P?0.001 for all comparisons). As evaluated by ?CT, the amount of bone present near the interface and in a wider radius (up to 0.5mm) around it was higher in the magnesium alloy implants at 4 weeks, without significant differences at 12 and 24 weeks. Histological examination confirmed direct bone-to-implant contact for both implant types. In vivo degradation of implants did not induce any noticeable local or systemic inflammation. This data suggests that the investigated degradable magnesium alloy rod exhibits markedly superior bone-implant interface strength and a greater amount of peri-implant bone than a self-reinforced copolymeric control currently in use; thus it fulfills a crucial prerequisite for its successful clinical deployment as an alternative degradable orthopedic implant material. Further studies, however, are warranted to evaluate the long-term degradation behavior and biocompatibility of the investigated degradable magnesium-based alloy. PMID:24001403

Lindtner, Richard A; Castellani, Christoph; Tangl, Stefan; Zanoni, Gerald; Hausbrandt, Peter; Tschegg, Elmar K; Stanzl-Tschegg, Stefanie E; Weinberg, Annelie-Martina

2013-12-01

313

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

314

Dissimilar friction stir welding between 5052 aluminum alloy and AZ31 magnesium alloy  

Microsoft Academic Search

Dissimilar friction stir welding between 5052 Al alloy and AZ31 Mg alloy with the plate thickness of 6 mm was investigated. Sound weld was obtained at rotation speed of 600 r\\/min and welding speed of 40 mm\\/min. Compared with the base materials, the microstructure of the stir zone is greatly refined. Complex flow pattern characterized by intercalation lamellae is formed

Yong YAN; Da-tong ZHANG; Cheng QIU; Wen ZHANG

2010-01-01

315

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

316

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 300°C. 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

317

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

318

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

319

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

320

Influence of Laser Processing Parameters on Microstructure and Corrosion Kinetics of Laser-Treated ZE41 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

In the present study, surface melting of a magnesium alloy, ZE41, was performed with an Nd:YAG laser using different laser parameters. The microstructure of the laser-treated and untreated specimens was analyzed by optical and scanning electron microscopy and X-ray diffraction. Corrosion resistance of the different laser-treated specimens along with the untreated alloy was characterized using electrochemical impedance spectroscopy and weight loss measurements in 0.001 M sodium chloride solution. Although the laser processing parameters influenced the microstructure and the melt depth of the laser-treated zone, these had little effect on the corrosion resistance of the alloy.

Chakraborty Banerjee, P.; Singh Raman, R. K.; Durandet, Y.; McAdam, G.

2013-05-01

321

Zirconium, calcium, and strontium contents in magnesium based biodegradable alloys modulate the efficiency of implant-induced osseointegration  

PubMed Central

Development of new biodegradable implants and devices is necessary to meet the increasing needs of regenerative orthopedic procedures. An important consideration while formulating new implant materials is that they should physicochemically and biologically mimic bone-like properties. In earlier studies, we have developed and characterized magnesium based biodegradable alloys, in particular magnesium-zirconium (Mg-Zr) alloys. Here we have reported the biological properties of four Mg-Zr alloys containing different quantities of strontium or calcium. The alloys were implanted in small cavities made in femur bones of New Zealand White rabbits, and the quantitative and qualitative assessments of newly induced bone tissue were carried out. A total of 30 experimental animals, three for each implant type, were studied, and bone induction was assessed by histological, immunohistochemical and radiological methods; cavities in the femurs with no implants and observed for the same period of time were kept as controls. Our results showed that Mg-Zr alloys containing appropriate quantities of strontium were more efficient in inducing good quality mineralized bone than other alloys. Our results have been discussed in the context of physicochemical and biological properties of the alloys, and they could be very useful in determining the nature of future generations of biodegradable orthopedic implants. PMID:23976848

Mushahary, Dolly; Sravanthi, Ragamouni; Li, Yuncang; Kumar, Mahesh J; Harishankar, Nemani; Hodgson, Peter D; Wen, Cuie; Pande, Gopal

2013-01-01

322

Zirconium, calcium, and strontium contents in magnesium based biodegradable alloys modulate the efficiency of implant-induced osseointegration.  

PubMed

Development of new biodegradable implants and devices is necessary to meet the increasing needs of regenerative orthopedic procedures. An important consideration while formulating new implant materials is that they should physicochemically and biologically mimic bone-like properties. In earlier studies, we have developed and characterized magnesium based biodegradable alloys, in particular magnesium-zirconium (Mg-Zr) alloys. Here we have reported the biological properties of four Mg-Zr alloys containing different quantities of strontium or calcium. The alloys were implanted in small cavities made in femur bones of New Zealand White rabbits, and the quantitative and qualitative assessments of newly induced bone tissue were carried out. A total of 30 experimental animals, three for each implant type, were studied, and bone induction was assessed by histological, immunohistochemical and radiological methods; cavities in the femurs with no implants and observed for the same period of time were kept as controls. Our results showed that Mg-Zr alloys containing appropriate quantities of strontium were more efficient in inducing good quality mineralized bone than other alloys. Our results have been discussed in the context of physicochemical and biological properties of the alloys, and they could be very useful in determining the nature of future generations of biodegradable orthopedic implants. PMID:23976848

Mushahary, Dolly; Sravanthi, Ragamouni; Li, Yuncang; Kumar, Mahesh J; Harishankar, Nemani; Hodgson, Peter D; Wen, Cuie; Pande, Gopal

2013-01-01

323

Evolution of stress in individual grains and twins in a magnesium alloy aggregate.  

SciTech Connect

This is an in situ measurement of the full stress tensor and its evolution in a growing deformation twin and, simultaneously, in the grain where the twin forms. The combined information provides a detailed picture of the grain-twin interaction. The three-dimensional x-ray diffraction method using 80.7 keV synchrotron x rays allows us to in situ investigate a grain within the bulk of a magnesium alloy (AZ31) sample that is compressed to activate the {l_brace}10{bar 1}2{r_brace} <{bar 1}011> tensile twin system. We observe that the stress state of the twin is drastically different from the one of the grain in which it is embedded. We analyze such result in terms of the shear transformation associated with twinning and the dimensional constraints imposed by the surrounding aggregate.

Aydiner, C. C.; Bernier, J. V.; Clausen, B.; Lienert, U.; Tome, C. N.; Brown, D. W.; X-Ray Science Division; LANL; LLNL

2009-07-01

324

The corrosion performance of magnesium alloy AM-SC1 in automotive engine block applications  

NASA Astrophysics Data System (ADS)

The magnesium alloy AM-SC1 has been developed as a creep-resistant automotive engine block material. This paper outlines its corrosion performance under laboratory test conditions, considering corrosion on both the external and internal surfaces. This study found that AM-SC1 has a corrosion performance comparable to AZ91 when subjected to an aggressive salt-spray environment or in galvanic-coupling environments. This article further demonstrates that, with the appropriate selection of a commercially available engine coolant, the internal corrosion of AM-SC1 can be maintained at a tolerable level. In addition, internal corrosion resistance can be significantly improved by the addition of fluorides to the coolant solution. It is concluded that AM-SC1 can be successfully used in an engine environment provided that some simple corrosion-prevention strategies are adopted.

Song, Guangling; Stjohn, David; Bettles, Colleen; Dunlop, Gordon

2005-05-01

325

The Influence of Strain Path on Biaxial Compressive Behavior of AZ31 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The strain path dependence of the compressive flow behavior of cast AZ31 magnesium alloy was investigated. Biaxial compression tests with linear strain paths were conducted using a unique biaxial compression device. It was found that the equivalent stress-strain relations varied according to the strain paths. The work contour for linear strain paths was well described by the Logan-Hosford yield criterion. Biaxial compressions with abrupt strain path change were also carried out to investigate the influences of the prestrain amplitude and angular relation of the sequential strain paths on the flow behavior. Rapid increase in the equivalent stress was observed just after the abrupt strain path change. These specific flow behaviors were discussed with regard to the plastic anisotropy, which showed rapid evolution in the early stage of the biaxial compressions.

Shimizu, Ichiro; Tada, Naoya; Nakayama, Kosuke

326

Punchless Drawing of Magnesium Alloy Sheet under Cold Condition and its Computation  

NASA Astrophysics Data System (ADS)

The punchless drawing with Maslennikov's technique was applied to the circular cup drawing of magnesium alloy AZ31B sheet under cold condition. The elastic rubber ring was used instead of the `hard' punch, where the compressed ring dragged the sheet inward the die cavity. Attainable circumferential strain of the blank was increased by this technique with repetitive drawing operation. Thickness of the rubber pad affected little the attainable strain. The shape appearance became better when a harder rubber was used. The cup forming by single drawing operation was also tested using a small die shoulder radius. The LDR of 1.250 was obtained with the straight cup wall. Further, the computation of the punchless drawing was also conducted for the single drawing operation. The computed deformation pattern was well consistent with the corresponding experimental result.

Yamashita, Minoru; Hattori, Toshio; Sato, Joji

2011-01-01

327

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

328

Achieving High Strength and High Ductility in Friction Stir-Processed Cast Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Friction stir processing (FSP) is emerging as an effective tool for microstructural modification and property enhancement. As-cast AZ91 magnesium alloy was friction stir processed with one-pass and two-pass to examine the influence of processing conditions on microstructural evolution and corresponding mechanical properties. Grain refinement accompanied with development of strong basal texture was observed for both processing conditions. Ultrafine-grained (UFG) AZ91 was achieved under two-pass FSP with fine precipitates distributed on the grain boundary. The processed UFG AZ91 exhibited a high tensile strength of ~435 MPa (117 pct improvement) and tensile fracture elongation of ~23 pct. The promising combination of strength and ductility is attributed to the elimination of casting porosity, and high density of fine precipitates in an UFG structure with quite low dislocation density. The effects of grain size, precipitate, and texture on deformation behavior have been discussed.

Yuan, Wei; Panigrahi, Sushanta K.; Mishra, Rajiv S.

2013-08-01

329

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

330

Electrochemical behaviors of the magnesium alloy substrates in various pretreatment solutions  

NASA Astrophysics Data System (ADS)

Interface reactions and film features of AZ91D magnesium alloy in pickling, activation and zinc immersion solutions have been investigated. The surface morphologies of the specimens were observed with scanning electron microscope (SEM). Electrochemical behaviors of AZ91D magnesium alloy in the baths of pickling, activation and zinc immersion were analyzed based on the open circuit potential (OCP) - time curves in various solutions. The results show that the corrosive rate in HNO 3 + CrO 3 or HNO 3 + H 3PO 4 pickling solution was more rapid than in KMnO 4 pickling-activation solution. Both ? phase and ? phase of the substrates were uniformly corroded in HNO 3 + CrO 3 or HNO 3 + H 3PO 4 pickling solution, the coarse surface can augment the mechanical occlusive force between the subsequent coatings and the substrates, so coatings with good adhesion can be obtained. In HF activation solution, the chromic compound formed via HNO 3 + CrO 3 pickling was removed and a compact MgF 2 film was formed on the substrate surface. In K 4P 2O 7 activation solution, the corrosion products formed via HNO 3 + H 3PO 4 pickling were removed, a new thin film of oxides and hydroxides was formed on the substrate surface. In KMnO 4 pickling-activation solution, a film of manganic oxides and phosphates was adhered on the substrate surface. Zinc film was symmetrically produced via K 4P 2O 7 activation or KMnO 4 pickling-activation, so it was good interlayer for Ni or Cu electroplating. Asymmetrical zinc film was produced because the MgF 2 film obtained in the HF activation solution had strong adhesive attraction and it was not suitable for interlayer for electroplating. However, the substrate containing compact MgF 2 film without zinc immersion was fit for direct electroless Ni-P plating.

Zhu, Yanping; Yu, Gang; Hu, Bonian; Lei, Xiping; Yi, Haibo; Zhang, Jun

2010-02-01

331

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

332

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

333

Finite-Element Damage Analysis for Failure Prediction of Warm Hydroforming Tubular Magnesium Alloy Sheets  

NASA Astrophysics Data System (ADS)

Bursting has been recognized by many researchers as a common failure mode in the tube hydroforming (THF) process. Therefore, the prediction of the bursting that occurs during the THF process has received much attention in the manufacturing industry and research institutions. Effective prediction of failure can reduce significantly the number of practical trials required to obtain the desired products. However, the prediction of such bursting for magnesium-based (Mg-based) alloy can be a rather difficult issue due to the nonlinear nature of the model used to describe the deformation process at elevated temperatures. This article proposes the failure prediction of Mg-based alloy during the THF process at elevated temperatures by using the Marciniak and Kuczynski (M-K) model. In the study, numerical simulation was performed by the finite-element (FE) analysis commercial software ABAQUS, with the material model assumed to be elastic-plastic. The constitutive model of Mg-based alloy (AZ31B) tube at different elevated temperatures, for instance at 493 K, 523 K, and 553 K, was represented by the Fields-Backofen constitutive equation, with material parameters collected from relevant literature. Accordingly, THF experiments were conducted by a self-developed thermal hydroforming attachment coping with an existing hydraulic power press to validate the prediction of the numerical results. The geometrical parameters for the specimen tubes used in the experiment were Ø22 × 150 mm, and 1.5 mm wall thickness. The numerical and the experimental results were demonstrated to have good agreement. The results of the simulation and the THF experiments imply that the model proposed in this study can provide a reliable prediction of the failure analysis of the Mg-based alloy tube during the THF process.

Chan, L. C.

2014-11-01

334

Analysis of Solid State Bonding in the Extrusion Process of Magnesium Alloys --Numerical Prediction and Experimental Verification  

NASA Astrophysics Data System (ADS)

The automotive industry developments focused on increasing fuel efficiency are accomplished by weight reduction of vehicles, which consequently results in less negative environmental impact. Usage of low density materials such as Magnesium alloys is an approach to replace heavier structural components. One of the challenges in deformation processing of Magnesium is its low formability attributed to the hexagonal close packed (hcp) crystal structure. The extrusion process is one of the most promising forming processes for Magnesium because it applies a hydrostatic compression state of stress during deformation resulting in improved workability. Many researchers have attempted to fully understand solid state bonding during deformation in different structural materials such as Aluminum, Copper and other metals and alloys. There is a lack of sufficient understanding of the extrusion welding in these materials as well as very limited knowledge on this subject for hollow profiles made from Magnesium alloys. The weld integrity and the characteristic of the welding microstructure are generally unknown. In this dissertation three related research projects are investigated by using different tools such as microstructure characterization, mechanical testing, thermo-mechanical physical simulation and finite element numerical modeling. Project 1: Microstructure characterization supported by mechanical testing of the extrusion welding regions in Magnesium alloy AM30 extrudate. The microstructure characterization was conducted using Light Optical Microscopy (LOM), in addition to LOM the electron backscattered diffraction (EBSD) technique was implemented to characterize in depth the deformed and welded microstructure. Project 2: Finite element numerical simulation of AM30 extrudate to model different process parameters and their influence on localized state variables such as strain, strain rate, temperature and normal pressure within the weld zone. Project 3: Physical simulation of the extrusion welding by using Gleeble 3500 thermo-mechanical simulator to create deformation welds in Magnesium alloy AM30 samples in compression test under various temperatures and strain rates conditions. Based on the obtained results from the performed research projects and literature review, a new qualitative criterion of extrusion welding has been introduced as contribution to the field. The criterion and its analysis have provided better understanding of material response to processing parameters and assisted in selecting the processing windows for good practices in the extrusion process. In addition, the new approach contributed to better understanding and evaluating the quality of the solid state bonding of Mg alloy. Accordingly, the criteria help to avoiding formation of potential mechanical and metallurgical imperfections.

Alharthi, Nabeel H.

335

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

336

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

337

Investigation of susceptibility to hot cracking of MSR-B magnesium alloy  

NASA Astrophysics Data System (ADS)

In castings of magnesium alloys defects or inconsistencies often appear (like casting misrun, porosities and cracks) particularly in the huge dimensional castings. Such defects are mended with the use of padding and welding. This work in combination with industrial tests of casting welding shows that the causes of high-temperature brittleness are the partial tears of the structure and the hot of both the castings and the welded and padded joints. Such phenomena should treat the cracks as irreversible failures caused by the process of crystallisation that is in the area of co-existence of the solid and liquid structural constituent. The assessment of the resistance to hot fractures was conducted on the basis of the transvarestriant trial. The transvarestriant trial consists of changing of strain during welding. It was stated that the range of the high-temperature brittleness is very broad, which significantly limits the application of the welding techniques to join or mend the elements made of alloy MSR-B. The brittleness is caused mainly by metallurgical factors, i.e., precipitation of inter-metallic phases from the solid solution. Essential differences of fracture morphology type in brittle temperature range were observed and described.

Adamiec, J.; Mucha, S.

2010-02-01

338

Atomistic analysis of short range interaction and local chemical order in LPSO structures of Magnesium alloys  

NASA Astrophysics Data System (ADS)

Magnesium alloys have been object of interest as lightweight material with high strength weight ratio. In particular Long Period Stacking Ordered (LPSO) structure phases show to have a strong influence in enhancing mechanical properties of such kind alloys. However the chemical order of the interacting atomic species in the Mg lattice has not been fully understood. We perform first principles Density Functional Theory (DFT) calculation to compute formation energies as well as interaction energies of the doping atoms in both Faced Centered Cubic (FCC) and Hexagonal Close Packed (HCP) Mg lattices. In particular we consider the Mg-Al-Gd and Mg-Zn-Y ternary systems. We also calculate activation energies for vacancy assisted doping atoms diffusion in order to perform a further analysis of the kinetics of the process. In order to describe short range interaction and cluster formation in the Mg matrix, we build an on lattice potential based on first principles DFT interaction energies. By means of these inter-atomic potentials, we perform Monte Carlo simulations to analyze the chemical order occurring in LPSO Mg-Al-Gd structures.

Fronzi, Marco; Kimizuka, Hajime; Matsubara, Kazuki; Ogata, Shigenobu

2013-03-01

339

PHB, crystalline and amorphous magnesium alloys: promising candidates for bioresorbable osteosynthesis implants?  

PubMed

In this study various biodegradable materials were tested for their suitability for use in osteosynthesis implants, in particular as elastically stable intramedullary nails for fracture treatment in paediatric orthopaedics. The materials investigated comprise polyhydroxybutyrate (PHB), which belongs to the polyester family and is produced by microorganisms, with additions of ZrO2 and a bone graft substitute; two crystalline magnesium alloys with significantly different degradation rates ZX50 (MgZnCa, fast) and WZ21 (MgYZnCa, slow); and MgZnCa bulk metallic glasses (BMG). Push-out tests were conducted after various implantation times in rat femur meta-diaphysis to evaluate the shear forces between the implant material and the bone. The most promising materials are WZ21 and BMG, which exhibit high shear forces and push-out energies. The degradation rate of ZX50 is too fast and thus the alloy does not maintain its mechanical stability long enough during the fracture-healing period. PHB exhibits insufficient mechanical properties: it degrades very slowly and the respective low shear forces and push-out energy levels are unsatisfactory. PMID:24364952

Celarek, Anna; Kraus, Tanja; Tschegg, Elmar K; Fischerauer, Stefan F; Stanzl-Tschegg, Stefanie; Uggowitzer, Peter J; Weinberg, Annelie M

2012-08-01

340

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

341

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

342

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

343

A Crystalline Plasticity Finite Element Method for Simulation of the Plastic Deformation of AZ31 Magnesium Alloys  

NASA Astrophysics Data System (ADS)

In this paper, a constitutive framework based on a crystalline plasticity model is employed to simulate the plastic deformation of AZ31 magnesium alloy, which posses the hexagonal close packed (HCP) crystal structure. Dislocation slip and mechanical twinning are taken into account in the model. The successive integration method is used to determine the active slip systems, and the contribution of twinning to the grain reorientation is treated by the PTR method. The FE model is introduced into ABAQUS/Explicit through a user material subroutine (VUMAT). Three deformation processes of AZ31 magnesium alloy, including tension, compression and a stamping process, are simulated with the present method. The simulation results are compared with experiment and those presented in the literature.

Li, Dayong; Zhang, Shaorui; Tang, Weiqin; Huang, Shiyao; Peng, Yinghong

2010-06-01

344

Using Artificial Neural Networks to Investigate the Influence of Temperature on Hot Extrusion of AZ61 Magnesium Alloy  

Microsoft Academic Search

The hot extrusion process of magnesium alloy involves many processing parameters, billet temperature is one of the parameters\\u000a that directly affect the tensile strength of finished product. Hot extrusion experiments of involving rectangular tubes are\\u000a conducted at selected billet temperatures of 320, 350, 380 and 400 C. Artificial neural networks (ANN) analysis then is performed\\u000a at increments of 10 C each time

Su-Hai Hsiang; Jer-Liang Kuo; Fu-Yuan Yang

2006-01-01

345

Influence of twin roll casting and differential speed rolling on microstructure and tensile properties in magnesium alloy sheets  

Microsoft Academic Search

Twin-roll casting (TRC) process combines casting and hot rolling into a single step, having an advantage of one-step processing of flat rolled products. Besides being such a cost-effective process, TRC also has a beneficial effect on microstructure such as reducing segregation, improving inclusion size distribution, refining microstructural and textural homogeneity. However, conventional equal speed rolling (ESR) of TRC magnesium alloy

Suk Bong Kang; Jaehyung Cho; Lili Chang; Yinong Wang

2011-01-01

346

Optimization of Processing Parameters During Laser Cladding of ZE41AT5 Magnesium Alloy Castings Using Taguchi Method  

Microsoft Academic Search

A continuous wave 4 kW Nd:YAG laser welding system was employed to clad single beads on machined 6.2-mm thick ZE41A-T5 aerospace magnesium alloy sand castings using nominal 1.6-mm filler rods of the parent metal. Based on the quality criterion of minimum dilution ratio, the Taguchi experimental method was used to optimize different process parameters and to identify the dominating factors. It

X. Cao; M. Xiao; M. Jahazi; J. Fournier; M. Alain

2008-01-01

347

Observation of Micro-scale Surface Morphology with Microtexture Development During Plane Strain Tensile Deformation in AZ31 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The change of microstructure including microtexture and surface morphology in AZ31 magnesium alloy under plane strain tension was investigated by 3D observation combined confocal microscope and high-resolution electron backscattered diffraction. Micro-scale changes in the surface morphology were observed on the area including tensile twin bands. The mechanism for surface morphology variation was discussed with the nucleation of tensile twinning and the strain partitioning caused by continuing deformation after the nucleation of the twins.

Lee, Keunho; Kim, Kyung Il; Kim, Se-Jong; Suh, Dong-Woo; Oh, Kyu Hwan; Han, Heung Nam

2015-01-01

348

Combined kinematic\\/isotropic hardening behavior study for magnesium alloy sheets to predict ductile fracture of rotational incremental forming  

Microsoft Academic Search

In order to predict the ductile fracture of rotational incremental forming for magnesium alloy sheet , a combination of kinematic\\u000a and isotropic hardening law is implemented and ev aluated from the histories of ductile fracture value (I) by means of finite\\u000a element analysis. Here, the criterion for a ductile fracture, as developed by OYANE, [J. Mech. Work. Tech. 4 (1980),

Nguyen Duc-Toan; Park Jin-Gee; Kim Young-Suk

2010-01-01

349

Validation and generalisation of hybrid models for flow stress and recrystallisation behaviour of aluminium–magnesium alloys  

Microsoft Academic Search

Numerical models for materials properties prediction require validation to assure the developer and the user that the mechanics and numerical algorithms implemented in the model are correct and consistent with the experimental information available in the literature. Validation of computer models for hot deformation of aluminium–magnesium alloys is described in this paper. The models utilise data-driven neuro-fuzzy models, which describe

M. F. Abbod; C. M. Sellars; D. A. Linkens; Q. Zhu; M. Mahfouf

2005-01-01

350

Stress-induced knitting of dislocation networks with four-fold nodes in an aluminium-magnesium alloy  

Microsoft Academic Search

Two-dimensional dislocation networks were studied in an aluminium-magnesium alloy slightly strained at 500°c after liquid quench, looking especially for four-fold nodes. The condition for the stress-induced knitting of networks with four-fold nodes was found to be that the knitting is performed by two different sets of dislocations, one of which has a Burgers vector perpendicular to that of the forest

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

1969-01-01

351

Bond strength and interfacial structure of silicon nitride joints brazed with aluminium-silicon and aluminium-magnesium alloys  

Microsoft Academic Search

From the results of the bending strength and Weibull modulus of the joints of silicon nitride ceramics brazed using aluminium-silicon and aluminium-magnesium alloy filler metals at a temperature of 1073 K for 0.9 ksec in a vacuum of 1.3 × 10-3 Pa, silicon, especially, present in a small amount in the filler metals, was found to be effective in improving

X. S. Ning; T. Okamoto; Y. Miyamoto; A. Koreeda; K. Suganuma; S. Goda

1991-01-01

352

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 300°C 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

353

The effect of sintering pressure on the microstructure and properties of a nanocrystalline magnesium alloy in spark plasma sintering  

NASA Astrophysics Data System (ADS)

Many studies have shown that particle boundaries in spark plasma sintering (SPS) can be easily removed by using a combination of sintering temperature and pressure. We already reported that a degassing treatment prior to sintering by SPS was a critical step to remove particle-particle boundaries effectively and to obtain a magnesium alloy having high strength and high ductility. In this study, the microstructural evolution and the mechanical properties of nanocrystalline Mg-6%Al alloys were investigated to determine the effect of sintering pressure combined with an appropriate degassing treatment.

Kim, Ka Ram; Kim, Hye Sung; Kwon, Soon Hong; Hwang, Dae-Youn

2014-11-01

354

Creation of an internal state variable plasticity-damage-corrosion model validated by experiments with Magnesium alloys  

NASA Astrophysics Data System (ADS)

In this study, a new consistent formulation coupling kinematics, thermodynamics, and kinetics with damage using an extended multiplicative decomposition of the deformation gradient that accounts for corrosion effects is presented. The technical approach used for modeling the corrosion behavior of magnesium alloys was divided into three primary steps. First, a predictive corrosion model was developed based on experimental corrosion observations. The experimentally-observed corrosion mechanisms of pitting, intergranular, and general corrosion on the AZ31 magnesium alloy were quantified in 3.5 wt.% NaCl immersion and salt spray environments using optical microscopy and laser profilometry to document the changes in the pit characteristics. Although both environments showed similar trends, the immersion environment was more deleterious with respect to intergranular and general corrosion. On the other hand, the salt-spray environment allowed deeper pits to form throughout the entirety of the experiments, which led to a substantial thickness drop (general corrosion) compared with the immersion environment. Next, the complete corrosion model based upon the internal state variable theory was formulated to capture the effects of pit nucleation, pit growth, pit coalescence, and general corrosion. Different rate equations were given for each mechanism. Following the formulation of the model, the aforementioned experimental work and experimental work on four other magnesium alloys (AZ61, AM30, AM60, and AE44), was used to validate the model.

Walton, Christopher Avery

355

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

356

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.

357

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

358

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 ~125-150°C. Elevated temperature bending-under-tension (BUT) friction tests were conducted at 350°C 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

359

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)2·4H2O (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

360

Investigation of Carboxylic Acid-Neodymium Conversion Films on Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The new carboxylic acid-neodymium anhydrous conversion films were successfully prepared and applied on the AZ91D magnesium alloy surface by taking absolute ethyl alcohol as solvent and four kinds of soluble carboxylic acid as activators. The corrosion resistance of the coating was measured by potentiodynamic polarization test in 3.5 wt.% NaCl solution in pH 7.0. The morphology, structure, and constituents of the coating were observed by scanning electron microscope, energy dispersivespectrum, x-ray photoelectron spectrum, and Fourier infrared spectrometer. Results show that corrosion resistance properties of samples coated with four different anhydrous conversion films were improved obviously. The corrosion potential increased, corrosion current density decreased, and polarization resistance increased. Among these four kinds of conversion films the one added with phytic exhibits the best corrosion resistant property. The mechanism of anhydrous-neodymium conversion film formation is also analyzed in this paper. It reveals that the gadolinium conversion coating is mainly composed of stable Nd2O3, MgO, Mg(OH)2, and carboxylate of Nd. And that the sample surface is rich in organic functional groups.

Cui, Xiufang; Liu, Zhe; Lin, Lili; Jin, Guo; Wang, Haidou; Xu, Binshi

2015-01-01

361

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

362

Inverse Identification of the Dynamic Recrystallization Parameters for AZ31 Magnesium Alloy Using BP Neural Network  

NASA Astrophysics Data System (ADS)

The effect of the dynamic recrystallization (DRX) parameters are of prime importance to improve the accuracy of the numerical simulation of hot forming processes for metals. However, it is difficult to determine the values of DRX parameters from experiments because of the influence of various factors, such as temperature, etc. In the present study, the DRX parameters for AZ31 magnesium alloy are identified by using the method of inverse analysis based on measured stress, BP neural network algorithm, genetic algorithm (GA), orthogonal experiment, and numerical simulation. Then, by applying the identified parameters in finite element analysis, the comparison between the numerically calculated and the experimental results is made to verify the correctness of the method. The results show that the numerically calculated stress, strain, recrystallized fraction, and average grain size valus are in good agreement with the experimental ones. These results demonstrate that the method of inverse analysis is a feasible and an effective tool for determination of the AZ31 DRX parameters.

Lou, Yan; Wu, Wenhua; Li, Luoxing

2012-07-01

363

Effects of heat input on microstructure and tensile properties of laser welded magnesium alloy AZ31  

SciTech Connect

A 3 kW CO{sub 2} laser beam was used to join wrought magnesium alloy AZ31 sheets, and the effects of heat input on the quality of butt welding joints were studied. By macro and microanalysis, it is found that the welding heat input plays an important role in laser welding process for AZ31 wrought sheets. After welding, the grains far from the weld centre present the typical rolled structure. But the microstructure out of the fusion zone gradually changes to complete equiaxed crystals as the distance from the weld centre decreases. Adjacent to the fusion boundary, there is a band region with columnar grains, and its growth direction is obviously perpendicular to the solid/liquid line. The microstructure in fusion centre consists of fine equiaxed grains and the many precipitated particles are brittle phase Mg{sub 17}Al{sub 12} or Mg{sub 17}(Al,Zn){sub 12}. With increasing the heat input, the band width of columnar grains varies, the grains in fusion zone get coarser, and the distribution of precipitates changes from intragranularly scattered particles to intergranularly packed ones. The results of tensile test show that the change trend of ultimate tensile strength (UTS) and elongation of the welded joints is to increase at first and then decrease with the heat input increasing. When the heat input reaches 24 J mm{sup -1}, the maximum value of the UTS is up to 96.8% of the base metal.

Quan, Y.J. [School of Materials Science and Engineering, Hunan University, Changsha 410082 (China)], E-mail: quanyj_2006@yahoo.com.cn; Chen, Z.H.; Gong, X.S.; Yu, Z.H. [School of Materials Science and Engineering, Hunan University, Changsha 410082 (China)

2008-10-15

364

Spectroscopic study of plasma during electrolytic oxidation of magnesium-aluminium alloys  

NASA Astrophysics Data System (ADS)

Plasma during Electrolytic Oxidation (PEO) of magnesium-aluminium alloys is studied in this work by means of Optical Emission Spectroscopy (OES). Spectral line shapes of the H?, Al II 704.21 nm and Mg II 448.11 nm line are analyzed to measure plasma electron number density Ne. From the H? line profile, two PEO processes characterized by relatively low electron number densities Ne ? 1015 cm?3 and Ne ? 2 × 1016 cm?3 were discovered while the shape and shift of Al II and Mg II lines revealed the third process characterized by large electron density Ne = (1-2) × 1017 cm?3. Low Ne processes, related with breakdown in gas bubbles and on oxide surface, are not influenced by anode material or electrolyte composition. The ejection of evaporated anode material through oxide layer is designated here as third PEO process. Using the Boltzmann plot technique, electron temperature of 4000 K and 33000 K is determined from relative intensities of Mg I and O II lines, respectively. Several difficulties in the analysis of spectral line shapes are met during this study and the ways to overcome some of the obstacles are demonstrated.

Jovovi?, J.

2014-12-01

365

Stress corrosion cracking of rare-earth containing magnesium alloys ZE41, QE22 and Elektron 21 (EV31A) compared with AZ80  

Microsoft Academic Search

Stress corrosion cracking (SCC) of the high-performance rare-earth containing magnesium alloys ZE41, QE22 and Elektron 21 (EV31A) was studied using slow strain rate test (SSRT) method in air, distilled water and 0.5wt.% NaCl solution. For comparison, the well-known AZ80 alloy was also studied. All alloys were susceptible to SCC in 0.5wt.% NaCl solution and distilled water to some extent. AZ80

M. Bobby Kannan; W. Dietzel; C. Blawert; A. Atrens; P. Lyon

2008-01-01

366

The surface reactivity of a magnesium-aluminium alloy in acidic fluoride solutions studied by electrochemical techniques and XPS  

NASA Astrophysics Data System (ADS)

The behaviour of the 6% Al magnesium alloy AM60 in aqueous acid fluoride solutions was studied in situ by electrochemical techniques and the surface chemistry of the resulting film was examined by monochromatized XPS. The evolution of the corrosion potential and cyclic voltammograms showed that the aggressiveness of the solutions is mainly driven by their fluoride concentration, the pH having almost no detectable influence. The more concentrated and acidic fluoride solutions led to a higher degree of fluoride coverage of the surface. The surface film is composed of magnesium hydroxide and hydroxyfluoride Mg(OH) 2- xF x which approaches MgF 2 with increasing fluoride concentration in the film. The parameters governing the film evolution and their relation to surface reactions are discussed.

Verdier, S.; van der Laak, N.; Delalande, S.; Metson, J.; Dalard, F.

2004-08-01

367

A study of thermally induced segregation of magnesium in aluminium-magnesium alloys by means of AES  

Microsoft Academic Search

The thermally induced segregation of Mg in a 1% Mg\\/Al alloy in the temperature range 225 to 350 degrees C has been studied by means of Auger electron depth profiling. An activation energy for the process has been determined and a linear relationship was found between the amount of Mg enrichment in the surface region and temperature. The results suggest

S. O. Saied; J. L. Sullivan

1993-01-01

368

Reactive sputter deposition of alumina films on magnesium alloy by double cathode glow-discharge plasma technique  

SciTech Connect

In order to overcome the problem of the corrosion resistance of AZ31 magnesium alloy, the nanocrystalline Al{sub 2}O{sub 3} film was deposited on AZ31 magnesium alloy by double cathode glow-discharge plasma technique. The microstructure, chemical composition and elemental chemical state of the sputter-deposited nanocrystalline Al{sub 2}O{sub 3} film were analyzed by means of scanning electron microscopy equipped with an energy dispersive spectroscope, X-ray diffraction), transmission electron microscope and X-ray photoelectron spectroscopy. The results indicated that the sputter-deposited nanocrystalline Al{sub 2}O{sub 3} film consisted of single {theta}-Al{sub 2}O{sub 3} phase with average grain size about 60 nm. The hardness and the elastic modulus of the as-deposited nanocrystalline Al{sub 2}O{sub 3} film were about 17.21 GPa and 217 GPa measured by nanoindentation instrument, respectively. The corrosion behavior of the sputter-deposited nanocrystalline Al{sub 2}O{sub 3} film in 3.5%NaCl solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. The amount of porosity for the sputter-deposited nanocrystalline Al{sub 2}O{sub 3} film calculated by two electrochemical methods was equal to 0.0086% and 0.168%, respectively. The sputter-deposited nanocrystalline Al{sub 2}O{sub 3} film exhibited excellent corrosion resistance, which was attributed to its dense enough structure to prevent magnesium alloy from corrosion in aggressive solutions.

Zhou Chenghou, E-mail: zhouchenghoujiayou@163.com [Department of Material Science and Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016 (China); Xu Jiang, E-mail: xujiang73@nuaa.edu.cn [Department of Material Science and Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016 (China); Jiang Shuyun, E-mail: jiangshy@seu.edu.cn [Department of Mechanical Engineering, Southeast University, 2 Si Pai Lou, Nanjing 210096 (China)

2010-02-15

369

Cryogenic machining and burnishing of AZ31B magnesium alloy for enhanced surface integrity and functional performance  

NASA Astrophysics Data System (ADS)

Surface integrity of manufactured components has a critical impact on their functional performance. Magnesium alloys are lightweight materials used in the transportation industry and are also emerging as a potential material for biodegradable medical implants. However, the unsatisfactory corrosion performance of Mg alloys limits their application to a great extent. Surface integrity factors, such as grain size, crystallographic orientation and residual stress, have been proved to remarkably influence the functional performance of magnesium alloys, including corrosion resistance, wear resistance and fatigue life. In this dissertation, the influence of machining conditions, including dry and cryogenic cooling (liquid nitrogen was sprayed to the machined surface during machining), cutting edge radius, cutting speed and feed rate, on the surface integrity of AZ31B Mg alloy was investigated. Cryogenic machining led to the formation of a "featureless layer" on the machined surface where significant grain refinement from 12 microm to 31 nm occurred due to dynamic recrystallization (DRX), as well as increased intensity of basal plane on the surface and more compressive residual stresses. Dry and cryogenic burnishing experiments of the same material were conducted using a fixed roller setup. The thickness of the processed-influenced layer, where remarkable microstructural changes occurred, was dramatically increased from the maximum value of 20 microm during machining to 3.4 mm during burnishing. The burnishing process also produced a stronger basal texture on the surface than the machining process. Preliminary corrosion tests were conducted to evaluate the corrosion performance of selected machined and burnished AZ31B Mg samples in 5% NaCl solution and simulated body fluid (SBF ). Cryogenic cooling and large edge radius tools were found to significantly improve the corrosion performance of machined samples in both solutions. The largest improvement in the material's corrosion performance was achieved by burnishing. A finite element study was conducted for machining of AZ31B Mg alloy and calibrated using the experimental data. A user subroutine was developed and incorporated to predict the grain size changes induced by machining. Good agreements between the predicted and measured grain size as well as thickness of featureless layers were achieved. Numerical studies were extended to include the influence of rake angle, feed rate and cutting speed on the featureless layer formation. KEYWORDS: Surface Integrity, Cryogenic Machining/Burnishing, Corrosion Resistance, Finite Element Analysis, Magnesium Alloys.

Pu, Zhengwen

370

XPS study of the surface chemistry on AZ31 and AZ91 magnesium alloys in dilute NaCl solution  

NASA Astrophysics Data System (ADS)

The surface chemistry on AZ31 and AZ91 magnesium alloys was characterized by X-ray photoelectron spectroscopy (XPS) in the corrosion and the passivation zones. In the corrosion zone, the presence of Mg(OH) 2 and MgCO 3 species was found in the outer surface, whereas, in the inner layer, the co-existence of Mg(OH) 2, MgO and MgCO 3 species was observed for both alloys. The presence of Al 3+ in the surface electrolyte to form Al 2O 3/Al(OH) 3 and the formation of carbonate product provide a better passivation on the surfaces and retard the chloride-induced corrosion on the materials in the passivation zone.

Wang, Lei; Shinohara, Tadashi; Zhang, Bo-Ping

2010-08-01

371

Phase Transformation Behavior of Porous TiNi Alloys Produced by Powder Metallurgy Using Magnesium as a Space Holder  

NASA Astrophysics Data System (ADS)

Porous TiNi alloys with porosities in the range of 51 to 73 pct were prepared successfully applying a new powder metallurgy fabrication route in which magnesium was used as a space holder, resulting in either single austenite phase or a mixture of austenite and martensite phases dictated by the composition of the starting powders, but entirely free from secondary brittle intermetallics, oxides, nitrides, and carbonitrides. Since transformation temperatures are very sensitive to composition, deformation, and oxidation, for the first time, transformation temperatures of porous TiNi alloys were investigated using chemically homogeneous specimens in as-sintered and aged conditions eliminating secondary phase, contamination, and deformation effects. It was found that the porosity content of the foams has no influence on the phase transformation temperatures both in as-sintered and aged conditions, while deformation, oxidation, and aging treatment are severely influential.

Aydo?mu?, Tarik; Bor, Elif Tarhan; Bor, ?akir

2011-09-01

372

Evaluation of short-term effects of rare earth and other elements used in magnesium alloys on primary cells and cell lines.  

PubMed

Degradable magnesium alloys for biomedical application are on the verge of being used clinically. Rare earth elements (REEs) are used to improve the mechanical properties of the alloys, but in more or less undefined mixtures. For some elements of this group, data on toxicity and influence on cells are sparse. Therefore in this study the in vitro cytotoxicity of the elements yttrium (Y), neodymium (Nd), dysprosium (Dy), praseodymium (Pr), gadolinium (Gd), lanthanum (La), cerium (Ce), europium (Eu), lithium (Li) and zirconium (Zr) was evaluated by incubation with the chlorides (10-2000 microM); magnesium (Mg) and calcium (Ca) were tested at higher concentrations (200 and 50mM, respectively). The influence on viability of human osteosarcoma cell line MG63, human umbilical cord perivascular (HUCPV) cells and mouse macrophages (RAW 264.7) was determined, as well as the induction of apoptosis and the expression of inflammatory factors (TNF-alpha, IL-1alpha). Significant differences between the applied cells could be observed. RAW exhibited the highest and HUCPV the lowest sensitivity. La and Ce showed the highest cytotoxicity of the analysed elements. Of the elements with high solubility in magnesium alloys, Gd and Dy seem to be more suitable than Y. The focus of magnesium alloy development for biomedical applications should include most defined alloy compositions with well-known tissue-specific and systemic effects. PMID:19800429

Feyerabend, Frank; Fischer, Janine; Holtz, Jakob; Witte, Frank; Willumeit, Regine; Drücker, Heiko; Vogt, Carla; Hort, Norbert

2010-05-01

373

A study of aluminum-lithium alloys: Strength profile in 2090 aluminum-lithium-copper-magnesium-zirconium alloy  

Microsoft Academic Search

Aluminum-containing lithium alloys are undergoing intensive development as replacements for conventional aluminum alloys 2024 and 7075 in aircraft structural applications. Lithium is a very reactive metal so that an elevated temperature heat treatments can cause lithium diffusion to the surface and reaction with the atmosphere. Solid state diffusion of lithium within the 2090 alloy and subsequent surface oxidation during solution

Soepriyanto

1991-01-01

374

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

375

Characterization of microarc oxidation coatings formed on AM60B magnesium alloy in silicate and phosphate electrolytes  

NASA Astrophysics Data System (ADS)

Microarc oxidation coatings on AM60B magnesium alloy were prepared in silicate and phosphate electrolytes. Structure, composition, mechanical property, tribological, and corrosion resistant characteristics of the coatings was studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and microhardness analyses, and by ball-on-disc friction and potentiodynamic corrosion testing. It is found that the coating produced from the silicate electrolyte is compact and uniform and is mainly composed of MgO and forsterite Mg 2SiO 4 phases, while the one formed in phosphate electrolyte is relatively porous and is mainly composed of MgO phase. The thick coating produced from a silicate electrolyte possesses a high hardness and provides a low wear rate (3.55 × 10 -5 mm 3/Nm) but a high friction coefficient against Si 3N 4 ball. A relatively low hardness and friction coefficient while a high wear rate (8.65 × 10 -5 mm 3/Nm) is recorded during the testing of the thick coating produced from a phosphate electrolyte. Both of these types of coatings provide effective protection for the corrosion resistance compared with the uncoated magnesium alloy. The coating prepared from the silicate electrolyte demonstrates better corrosion behavior due to the compacter microstructure.

Liang, Jun; Hu, Litian; Hao, Jingcheng

2007-03-01

376

A New Constitutive Model for AZ31B Magnesium Alloy Sheet Deformed at Elevated Temperatures and Various Strain Rates  

NASA Astrophysics Data System (ADS)

In this study, a new constitutive model is established for AZ31B magnesium alloy sheet at elevated temperatures and strain rates in order to describe two competing mechanisms for deformation, i.e. both work-hardening and softening stage of AZ31B magnesium alloy sheet. Stress-strain curves obtained by conducting uni-axial tensile tests at elevated and strain rates were first separated at the maximum stress and corresponding strain values. Voce's law [25] was then employed to fit separated hardening and softening stage. A MATLAB tool is used to determine material parameters by using least square fitting method at various temperatures and strain rate. The mergence of separated work-hardening and softening equations is in good agreement with experimental data. The parameters of fitting curves are utilized to determine them as a function of temperature and strain rate using a surface fitting method. The final equation is then implemented to predict stress-strain curves at various temperatures and strain rates. The proposed equation showed the good comparability between the simulation results and the corresponding experiments.

Nguyen, Duc-Toan

2014-12-01

377

Mold-filling characteristics of AZ91 magnesium alloy in the low-pressure expendable pattern casting process  

NASA Astrophysics Data System (ADS)

The magnesium (Mg) alloy low-pressure expendable pattern casting (EPC) process is a newly developed casting technique combining the advantages of both EPC and low-pressure casting. In this article, metal filling and the effect of the flow quantity of inert gas on the filling rate in the low-pressure EPC process are investigated. The results showed that the molten Mg alloy filled the mold cavity with a convex front laminar flow and the metal-filling rate increased significantly with increasing flow quantity when flow quantity was below a critical value. However, once the flow quantity exceeded a critical value, the filling rate increased slightly. The influence of the flow quantity of inert gas on melt-filling rate reveals that the mold fill is controlled by flow quantity for a lower filling rate, and, subsequently, controlled by the evaporation of polystyrene and the evaporation products for higher metal velocity. Meanwhile, the experimental results showed that the melt-filling rate significantly affected the flow profile, and the filling procedure for the Mg alloy in the low-pressure EPC process. A slower melt-filling rate could lead to misrun defects, whereas a higher filling rate results in folds, blisters, and porosity. The optimized filling rate with Mg alloy casting is 140 to 170 mm/s in low-pressure EPC.

Wu, H. B.; Fan, Z. T.; Huang, N. Y.; Dong, X. P.; Tian, X. F.

2005-02-01

378

Electrochemical impedance spectroscopic investigation of the role of alkaline pre-treatment in corrosion resistance of a silane coating on magnesium alloy, ZE41  

Microsoft Academic Search

The protective performance of the coatings of bis-1,2-(triethoxysilyl) ethane (BTSE) on ZE41 magnesium alloy with different surface pre-treatments were evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 0.1M sodium chloride solution. Electrical equivalent circuits were developed based upon hypothetical corrosion mechanisms and simulated to correspond to the experimental data. The morphology and cross section of the alloy subjected

P. Chakraborty Banerjee; R. K. Singh Raman

2011-01-01

379

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

380

Modeling and analyzing the effects of heat treatment on the characteristics of magnesium alloy joint welded by the tungsten-arc inert gas welding  

Microsoft Academic Search

The objective of this paper is to present the mathematical models for modeling and analysis of the effects of heat treatment on the characteristics of magnesium alloy joint welded by the tungsten-arc inert gas (TIG) welding. The process of heat treatment adopts the tempering process with varying processing parameters, including tempering temperature and tempering time. The microstructure and mechanical properties

Te-Chang Tsai; Chih-Chung Chou; Deng-Maw Tsai; Ko-Ta Chiang

2011-01-01

381

Ultra Fine-Grained AZ31 Magnesium Alloy Obtained by a Combination of Grain Refinement and Equal Channel Angular Pressing  

NASA Astrophysics Data System (ADS)

Different amounts of Al-5Ti-1B master alloy (TiBAl) were added to the AZ31 magnesium alloy (Mg-3Al-1Zn-0.2Mn) as grain refiner and the resulting microstructure and grain size distributions were studied after extrusion and equal channel angular pressing (ECAP). Results showed that the addition of 0.6% TiBAl had the strongest grain refinement effect, reducing the grain sizes by 54.5 and 48.5% in the extruded and ECAPed conditions, respectively. The observed grain refinement was partly due to the presence of the thermally-stable micron- and submicron-sized particles in the melt which act as nucleation sites during solidification. During the high-temperature extrusion and ECAP processes, dynamic recrystallization (DRX) and grain growth are likely to occur. However, the mentioned particles will help in reducing the grain size by the particle stimulated nucleation (PSN) mechanism. Furthermore, the pinning effect of these particles can oppose grain growth by reducing the grain boundary migration. These two phenomena together with the partitioning of the grains imposed by the severe plastic deformation in the ECAP process have all contributed to the achieved ultrafine-grained structure in the AZ31 alloy.

Torbati-Sarraf, S. A.; Mahmudi, R.

382

Constitutive Behavior of Commercial Grade ZEK100 Magnesium Alloy Sheet over a Wide Range of Strain Rates  

NASA Astrophysics Data System (ADS)

The constitutive behavior of a rare-earth magnesium alloy ZEK100 rolled sheet is studied at room temperature over a wide range of strain rates. This alloy displays a weakened basal texture compared to conventional AZ31B sheet which leads to increased ductility; however, a strong orientation dependency persists. An interesting feature of the ZEK100 behavior is twinning at first yield under transverse direction (TD) tensile loading that is not seen in AZ31B. The subsequent work hardening behavior is shown to be stronger in the TD when compared to the rolling and 45 deg directions. One particularly striking feature of this alloy is a significant dependency of the strain rate sensitivity on orientation. The yield strength under compressive loading in all directions and under tensile loading in the TD direction is controlled by twinning and is rate insensitive. In contrast, the yield strength under rolling direction tensile loading is controlled by non-basal slip and is strongly rate sensitive. The cause of the in-plane anisotropy in terms of both strength and strain rate sensitivity is attributed to the initial crystallographic texture and operative deformation mechanisms as confirmed by measurements of deformed texture. Rate-sensitive constitutive fits are provided of the tensile stress-strain curves to the Zerilli-Armstrong[1] hcp material model and of the compressive response to a new constitutive equation due to Kurukuri et al.[2

Kurukuri, Srihari; Worswick, Michael J.; Bardelcik, Alexander; Mishra, Raja K.; Carter, Jon T.

2014-07-01

383

A study of aluminum-lithium alloys: Strength profile in 2090 aluminum-lithium-copper-magnesium-zirconium alloy  

SciTech Connect

Aluminum-containing lithium alloys are undergoing intensive development as replacements for conventional aluminum alloys 2024 and 7075 in aircraft structural applications. Lithium is a very reactive metal so that an elevated temperature heat treatments can cause lithium diffusion to the surface and reaction with the atmosphere. Solid state diffusion of lithium within the 2090 alloy and subsequent surface oxidation during solution heat treatment were investigated. Thermodynamic and kinetic analyses were used to evaluate the alloy's thermal oxidation behavior. A mathematical model based on simultaneous diffusion and surface oxidation of lithium was developed to predict lithium concentration profiles across the specimen. Agreement was obtained between the predicted lithium concentration profiles and their corresponding experimental results. Microhardness and yield strength profiles were found also to follow the corresponding lithium concentration profiles. Various heat treatment procedures were studied on this 2090 alloy to give a greater understanding of precipitate strengthening.

Soepriyanto, S.

1991-01-01

384

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

2011-12-01

385

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-Lücke-Stüwe) 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

386

Effect of ECAP on microstructure and mechanical properties of ZE41 magnesium alloy  

Microsoft Academic Search

A ZE41 alloy was processed by equal channel angular pressing (ECAP) at 320°C and its microstructure and tensile properties were evaluated. It has been observed that the ECAP refines both the grains and precipitates, thus modifying the strength and ductility of the alloy. The sample after 6 passes of ECAP processing has a yield stress of 230MPa and elongation of

Rengen Ding; Chuanwei Chung; Yulung Chiu; Paul Lyon

2010-01-01

387

Extraction of second phases from magnesium and aluminum alloys for analytical electron microscopy.  

PubMed

Techniques are described for the extraction onto carbon replicas of precipitates and inclusions from Mg and Al-based alloys for analytical transmission electron microscopy. EDX analysis of Mn precipitates from a Mg-Mn alloy illustrates the problems that can arise from spurious X-rays, caused by the use of a 3mm disc specimen. PMID:7919529

Carpenter, G J; Ng-Yelim, J; Phaneuf, M W

1994-08-01

388

Reactivities of aluminium and aluminium-magnesium alloy powders in polymeric composites  

Microsoft Academic Search

Polymeric compositions containing Al-Mg alloys show higher reactivities, in comparison with similar compositions containing aluminium. This is observed irrespective of the amount of oxidizer, type of oxidizer used, type of polymeric binder, and over a range of the particle sizes of the metal additive. This is evident from the higher calorimetric values obtained for compositions containing the alloy, in comparison

S. Deevi

1996-01-01

389

Immobilised molten salt membrane based magnesium sensor for aluminium-magnesium melts  

Microsoft Academic Search

Magnesium sensitive probes were constructed and tested in different melts of commercial aluminium-magnesium alloys. The probes\\u000a were composed of a porous magnesium oxide one closed end tube or thimble to which a magnesium conducting salt is impregnated.\\u000a The activity of magnesium in the aluminium-magnesium melt was determined with report to a pure magnesium reference contained\\u000a in the inside of the

J. Vangrunderbeek; J. Luyten; R. Stephen; F. De Schutter; L. Zhang; D. Fray

1995-01-01

390

Corrosion rate of magnesium and its alloys in buffered chloride solutions  

Microsoft Academic Search

The effect of the buffer capacity of test solution on the corrosion rate of cast pure (>99.95 mass%) and high-purity (>99.9999 mass%) magnesium, and AZ31 and AZ91E has been studied. Their corrosion rates were measured gravimetrically in a pH 6.5 and a pH 9 borate buffer including chloride ions, and in a conventional chloride solution. Except for the AZ91E in

H Inoue; K Sugahara; A Yamamoto; H Tsubakino

2002-01-01

391

The Effect of Thermomechanical Processing on the Tensile, Fatigue, and Creep Behavior of Magnesium Alloy AM60  

NASA Astrophysics Data System (ADS)

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 ( ? f ). The as-molded material exhibited the lowest strength, while the annealed material exhibited an intermediate strength but the highest ? 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, Z.; Huang, J.; Decker, R. F.; Lebeau, S. E.; Walker, L. R.; Cavin, O. B.; Watkins, T. R.; Boehlert, C. J.

2011-05-01

392

The Role of Microstructure on Ductility of Die-Cast AM50 and AM60 Magnesium Alloys  

NASA Astrophysics Data System (ADS)

Die-cast AM50 and AM60 magnesium alloys have been examined to determine the fracture processes in bending and tension and to elucidate the influences of microstructure and porosity distribution on mechanical properties. The effect of section thickness has been explored using 2-, 6-, and 10-mm-thick die-cast plates. The processes of damage accumulation in terms of crack initiation, growth, and linkage leading to eventual failure have been studied qualitatively using progressive tensile straining experiments and three-point bend studies. The presence of a heterogeneous distribution of porosity played a critical role in the observed differences between strains to fracture in tension and in bending. More rapid damage accumulation at lower strains was observed in the high porosity regions with the rate of damage accumulation strongly dependent on the loading mode. Fracture processes at the microstructural level were characterized by scanning electron microscopy using an in-situ bending fixture. Crack initiation and growth occurred predominantly in the interdendritic eutectic regions, both in the presence of porosity and, to a lesser extent, in pore-free regions. The role of porosity volume fraction and distribution on ductility in these alloys has been examined using a modified Brown-Embury model. This model allows the prediction of fracture location in either loading mode by predicting the critical strains for the onset of cracking in differently strained regions of the test samples.

Chadha, Gurjeev; Allison, John E.; Jones, J. Wayne

2007-02-01

393

Fatigue characterization of high pressure die-cast magnesium AM60B alloy using experimental and computational investigations  

NASA Astrophysics Data System (ADS)

The object of the current dissertation is to foster fundamental advances in microstructure-fatigue characteristics of a high pressure die cast magnesium AM60B alloy. First, high cycle fatigue staircase experiments were conducted on specimens extracted from automobile instrument panels. The resulting fracture surfaces were then examined with scanning electron microscopic imaging to elucidate the fatigue crack initiation sites and propagation paths at different stages of the fatigue life. Due to the fact that the qualification of the crack initiation and propagation mechanisms through experiment alone is difficult, complementary micromechanical finite element simulations were conducted. Particularly, the effects of different applied loading conditions and the porosity morphology (e.g. pore shape, pore size, pore spacing, proximity to the free surface) on the maximum plastic shear strain range, as a driving force for crack initiation, were analyzed. Moreover, at the microstructually small crack (MSC) propagation stage, the shielding effects of beta-phase Mg17Al12 particles were systematically studied. Based on the distribution of the maximum principal stress within the particles and the maximum hydrostatic stress along the particle/matrix interfaces, the relative influence of the pre-damaged (fractured or debonded) particles and various particle cluster morphologies were carefully investigated. In the finite element simulations, the constitutive behaviours of AM60B alloy and the alpha-matrix were simulated by the advanced kinematic hardening law tuned with experimentally determined material parameters under cyclic loading.

Lu, You

394

Potentiostatic pulse-deposition of calcium phosphate on magnesium alloy for temporary implant applications - An in vitro corrosion study.  

PubMed

In this study, a magnesium alloy (AZ91) was coated with calcium phosphate using potentiostatic pulse-potential and constant-potential methods and the in vitro corrosion behaviour of the coated samples was compared with the bare metal. In vitro corrosion studies were carried out using electrochemical impedance spectroscopy and potentiodynamic polarization in simulated body fluid (SBF) at 37°C. Calcium phosphate coatings enhanced the corrosion resistance of the alloy, however, the pulse-potential coating performed better than the constant-potential coating. The pulse-potential coating exhibited ~3 times higher polarization resistance than that of the constant-potential coating. The corrosion current density obtained from the potentiodynamic polarization curves was significantly less (~60%) for the pulse-deposition coating as compared to the constant-potential coating. Post-corrosion analysis revealed only slight corrosion on the pulse-potential coating, whereas the constant-potential coating exhibited a large number of corrosion particles attached to the coating. The better in vitro corrosion performance of the pulse-potential coating can be attributed to the closely packed calcium phosphate particles. PMID:25427473

Kannan, M Bobby; Wallipa, O

2013-03-01

395

Effect of laser power and specimen temperature on atom probe analyses of magnesium alloys.  

PubMed

The influence of laser power, wave length, and specimen temperature on laser assisted atom probe analyses for Mg alloys was investigated. Higher laser power and lower specimen temperature led to improved mass and spatial resolutions. Background noise and mass resolutions were degraded with lower laser power and higher specimen temperature. By adjusting the conditions for laser assisted atom probe analyses, atom probe results with atomic layer resolutions were obtained from all the Mg alloys so far investigated. Laser assisted atom probe investigations revealed detailed chemical information on Guinier-Preston zones in Mg alloys. PMID:21269771

Oh-ishi, K; Mendis, C L; Ohkubo, T; Hono, K

2011-05-01

396

MICROSTRUCTURAL AND CHEMICAL MICROANALYSIS STUDIES OF RARE EARTH-TRANSITION METAL-ALUMINIUM-MAGNESIUM ALLOYS  

Microsoft Academic Search

This paper presents details of a study to determine the microstructure and chemical composition of some cast alloys represented by the general formula: La0.7-xPrxMg0.3Al0.3Mn0.4Co0.5Ni3.8, (0 ? x ? 0.7). These hydrogen storage alloys are candidate material for negative electrodes in nickel metal-hydride (Ni\\/MH) batteries. The effects of substituting La with Pr, on the composition of various phases in the alloys

L. M. C. Zarpelon; E. Galego; H. Takiishi; R. N. Faria

397

Reduction mechanism of surface oxide in aluminum alloy powders containing magnesium studied by x-ray photoelectron spectroscopy using synchrotron radiation  

SciTech Connect

We investigated the reduction mechanism of surface oxide on aluminum alloy powders containing magnesium, by x-ray photoelectron spectroscopy using synchrotron radiation (SR-XPS). The reduction is the initial reaction in a new aluminum nitridation method developed by one of the authors. In heating the powders to 823 K, magnesium soluted in the powders moves from the inner region to the surface at temperatures below 573 K, and finally, above 773 K, the magnesium reduces the aluminum oxide of powder surfaces by chemical reaction, which breaks the surface oxide films, and metallic aluminum appears on the topmost surface of the powders. These results suggest that the SR-XPS system is very useful for dynamic chemical reaction analysis of the surface via {ital in situ} measurement. {copyright} {ital 1997 American Institute of Physics.}

Kimura, A.; Shibata, M. [Analytical Characterization Center, Sumitomo Electric Industries, Ltd. 1-1-3 Shimaya, Konohana-ku, Osaka 554 (Japan)] [Analytical Characterization Center, Sumitomo Electric Industries, Ltd. 1-1-3 Shimaya, Konohana-ku, Osaka 554 (Japan); Kondoh, K.; Takeda, Y. [Itami Research Laboratories, Sumitomo Electric Industries, Ltd. 1-1-1 Koyakita, Itami 664 (Japan)] [Itami Research Laboratories, Sumitomo Electric Industries, Ltd. 1-1-1 Koyakita, Itami 664 (Japan); Katayama, M.; Kanie, T.; Takada, H. [Harima Research Laboratories, Sumitomo Electric Industries, Ltd. Harima Science Garden City, Kamigori Hyogo 678-12 (Japan)] [Harima Research Laboratories, Sumitomo Electric Industries, Ltd. Harima Science Garden City, Kamigori Hyogo 678-12 (Japan)

1997-06-01

398

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

399

Formation of intermetallic compound coating on magnesium AZ91 cast alloy  

NASA Astrophysics Data System (ADS)

This study describes an intermetallic compound coating formed on AZ91 Mg cast alloy. The Al sputtered on AZ91 cast alloy reacted with substrate during a short period of heat treatment at 435°C, resulting in the formation of a continuous intermetallic compound layer. The short period treatment has the advantage of minimizing the negative effect on the microstructure of substrate and the mechanical properties, comparing with the reported diffusion coatings. DSC measurement and examination on the cross-section of Al sputtered samples show that local melting occurred along the Al/substrate interface at the temperature range between 430~435°C. The formation mechanism of intermetallic compound coating is proposed in terms of the local melting at Al/substrate interface. The salt water immersion test showed significant improvement in corrosion resistance of the intermetallic compound coated AZ91 cast alloy compared with the as-cast alloys.

Zhu, Tianping; Gao, Wei

2009-08-01

400

Effect of Carbon Nanotube on High-Temperature Formability of AZ31 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Room-temperature tensile properties of AZ31 alloy have significantly been improved when reinforced with carbon nanotube via ingot metallurgy process. However, high-temperature (up to 250 °C) elongation-to-failure tensile test of the developed nanocomposite revealed a considerable softening in the AZ31 alloy matrix accompanied by an incredible ductility increment (up to 132%). Microstructural characterization of the fractured samples revealed that the dynamic recrystallization process has induced a complete recrystallization in the AZ31 alloy at a lower temperature (150 °C) followed by substantial grain growth at a higher temperature used in this study. Fractography on the fractured surfaces revealed that the room-temperature mixed brittle-ductile modes of fracture behavior of AZ31 alloy have transformed into a complete ductile mode of fracture at high temperature.

Hassan, S. Fida; Paramsothy, M.; Gasem, Z. M.; Patel, F.; Gupta, M.

2014-08-01

401

Effect of temperature on synthesis and properties of aluminum–magnesium mechanical alloys  

Microsoft Academic Search

The synthesis of an Al0.7Mg0.3 mechanical alloy was studied using a planetary mill. Several distinct temperature regimes of mechanical alloying were achieved using milling jars equipped with finned heat sinks and an external air conditioner installed to cool the entire milling chamber. Wireless temperature sensors were attached to the milling jars to monitor the process temperature. Intermediate and final products

Swati M. Umbrajkar; Mirko Schoenitz; Steven R. Jones; Edward L. Dreizin

2005-01-01

402

Hydrogen-environment-assisted cracking of an aluminum-zinc-magnesium(copper) alloy  

Microsoft Academic Search

There is strong evidence to indicate that hydrogen embrittlement plays a significant, if not controlling, role in the environmentally assisted cracking of 7XXX series aluminum alloys. In order to better understand hydrogen environment assisted cracking (HEAC), crack growth rate tests in the K-independent stage II crack growth regime were conducted on fracture mechanics specimens of an Al-6.09Zn-2.14Mg-2.19Cu alloy (AA 7050)

George Aloysius Young Jr.

1999-01-01

403

Deformation Behavior of AZ80 Wrought Magnesium Alloy at Cryogenic Temperatures  

SciTech Connect

The influence of temperature on the deformation and failure behavior of AZ80 wrought Mg alloy has been examined from 77K to 298K. It is found that the yield strength (YS) and ultimate strength (UTS) are increasing with the temperature decreasing, while the elongation is decreasing especial between 213K and 143K. Based on the mechanical tests, observation of environmental scanning electron microscope (ESEM) and transmission electron microscope (TEM), it is proposed that the alloy deforms mainly by slips and twins, but undergoes different mechanism of cleavage in the range of testing temperature. At T>213K, the alloy ductility is higher because the dislocations could pass through twins but pile up at precipitate phase: Mg17Al12, which causes the crack nucleate. At T<143K, the alloy ductility is lower because the dislocation slip are suppressed greatly and dislocations pile up at twins, and cause crack nucleate and expand along twins quickly. At 143Kalloy ductility drops sharply with decreasing temperature. The twins play an important role in deformation and failure of Mg alloys at cryogenic temperature.

Tang Wei; Li Xiuyan; Han Enhou; Xu Yongbo; Li Yiyi [Institute of Metal Research, Chinese Academy of Science, Shenyang, Liaoning, 110016 (China)

2006-03-31

404

Abrasion Resistance of Al-Ni-Mm-Fe Amorphous and Nanocrystalline Composite Coating on the Surface of AZ91 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

An Al-Ni-Mm-Fe amorphous and nanocrystalline composite coating was prepared onto the surface of AZ91 magnesium alloy by high velocity arc spraying process. And the microstructure of the coating was analyzed by scanning electron microscope (TEM) and X-ray diffraction (XRD). The analysis results indicated that the coating consists of amorphous, nanocrystalline and crystalline phases. It has a dense structure with a low porosity of about 2.0%. Its average micro Vickers hardness value is about 330 HV0.1, which is five times than that of AZ91 magnesium alloy (62 HV0.1) and four times than that of pure Al coating (71 HV0.1). The abrasion tests showed that the Al-Ni-Mm-Fe coating exhibits a good abrasion resistance.

Zhang, Z. B.; Liang, X. B.; Chen, Y. X.; Xu, B. S.

405

Cyclic Deformation Behavior of a Rare-Earth Containing Extruded Magnesium Alloy: Effect of Heat Treatment  

NASA Astrophysics Data System (ADS)

The present study was aimed at evaluating strain-controlled cyclic deformation behavior of a rare-earth (RE) element containing Mg-10Gd-3Y-0.5Zr (GW103K) alloy in different states (as-extruded, peak-aged (T5), and solution-treated and peak-aged (T6)). The addition of RE elements led to an effective grain refinement and weak texture in the as-extruded alloy. While heat treatment resulted in a grain growth modestly in the T5 state and significantly in the T6 state, a high density of nano-sized and bamboo-leaf/plate-shaped ?' (Mg7(Gd,Y)) precipitates was observed to distribute uniformly in the ?-Mg matrix. The yield strength and ultimate tensile strength, as well as the maximum and minimum peak stresses during cyclic deformation in the T5 and T6 states were significantly higher than those in the as-extruded state. Unlike RE-free extruded Mg alloys, symmetrical hysteresis loops in tension and compression and cyclic stabilization were present in the GW103K alloy in different states. The fatigue life of this alloy in the three conditions, which could be well described by the Coffin-Manson law and Basquin's equation, was equivalent within the experimental scatter and was longer than that of RE-free extruded Mg alloys. This was predominantly attributed to the presence of the relatively weak texture and the suppression of twinning activities stemming from the fine grain sizes and especially RE-containing ?' precipitates. Fatigue crack was observed to initiate from the specimen surface in all the three alloy states and the initiation site contained some cleavage-like facets after T6 heat treatment. Crack propagation was characterized mainly by the characteristic fatigue striations.

Mirza, F. A.; Chen, D. L.; Li, D. J.; Zeng, X. Q.

2014-12-01

406

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

407

Corrosion behaviour of thermally sprayed Al and Al\\/SiCp composite coatings on ZE41 magnesium alloy in chloride medium  

Microsoft Academic Search

Thermally sprayed Al and Al\\/SiCp composite coatings have been deposited on ZE41 magnesium alloy and mechanical compaction at room temperature was applied to the Al and Al\\/SiCp coatings to reduce their porosity. Corrosion behaviour of coated samples was evaluated and compared to that of uncoated substrate in 3.5wt.% NaCl solution using electrochemical measurements. Al and Al\\/SiCp composite coatings reduced the

M. Carboneras; M. D. López; P. Rodrigo; M. Campo; B. Torres; E. Otero; J. Rams

2010-01-01

408

The synergistic inhibition effect of organic silicate and inorganic Zn salt on corrosion of Mg10Gd3Y magnesium alloy  

Microsoft Academic Search

The inhibition effects of organic sodium aminopropyltriethoxysilicate (APTS–Na) and inorganic zinc nitrate on the corrosion of Mg-10Gd-3Y magnesium alloy (GW103) in ASTM D1384-87 corrosive water are investigated by electrochemical techniques and immersion test. The results show that individual organic or inorganic inhibitor has low inhibition efficiency. However, when these organic and inorganic inhibitors are used together, a synergistic inhibition behavior

Junying Hu; Daobing Huang; Guang-Ling Song; Xingpeng Guo

2011-01-01

409

Organosilane self-assembled layers (SAMs) and hybrid silicate magnesium-rich primers for the corrosion protection of aluminum alloy 2024 T3  

NASA Astrophysics Data System (ADS)

Although current chromate coatings function very well in corrosion protection for aircraft alloys, such as aluminum alloy 2024 T3, the U.S. Environmental Protection Agency is planning to totally ban the use of chromates as coating materials in the next decade or so because of their extremely toxic effect. For this purpose, both self-assembled layers and silicate magnesium-rich primers were tested to provide the corrosion protection for aluminum alloy. The long-term goal of this research is to develop a coating system to replace the current chromate coating for aircraft corrosion protection. Aluminum alloy 2024 T3 substrates were modified with self-assembled monolayer or multilayer thin films from different alkylsilane compounds. Mono-functional silanes, such as octadecyltrichlorosilane (C18SiCl3), can form a mixed hydrophobic monolayer or multilayer thin film on the aluminum oxide surface to provide a barrier to water and other electrolytes, so the corrosion resistance of the SAMs modified surface was increased significantly. On the other hand, the bi-functional silane self-assembly could attach the aluminum surface through the silicon headgroup while using its functional tailgroup to chemically bond the polymer coating, thus improving the adhesion between the aluminum substrate and coating substantially, and seems to contribute more to corrosion protection of aluminum substrate. Organosilanes were also combined with tetraethyl orthosilicate (TEOS) in propel ratios to form a sol-gel binder to make silicate magnesium-rich primers. Analogue to the inorganic zinc-rich coatings, the silicate magnesium-rich primers also showed excellent adhesion and solvent resistance. The sacrificial magnesium pigments and the chemically inert silicate binder both contribute to the anti-corrosion properties. Future studies will be focused on the formula optimization for better toughness, chemical resistance and anticorrosion performance.

Wang, Duhua

410

The development and characterization of a novel aluminum-copper-magnesium P/M alloy  

NASA Astrophysics Data System (ADS)

Powder metallurgy (P/M) is a metal fabrication process that is characterized by high yield and ability to be automated, as well as the resultant part complexity and reproducibility. This press and sinter process is favoured by the automotive industry. Aluminum alloy P/M parts are particularly attractive because they have a high strength to weight ratio and they can be made to have high corrosion and wear resistance. There are few commercial Al P/M alloys currently in use and they occupy a small portion of the market. To expand the use of aluminum in the industry a new alloy was created, modeled after the wrought AC2024 family of alloys. P/M 2324, with a nominal composition of Al-4.4Cu-1.5Mg, was assessed using physical, chemical and mechanical methods to help maximize alloy properties through processing. The objective of this work was to develop a viable industrial alloy. The investigation of 2324 included the evaluation of starting powders, starting composition, processing methods, secondary treatments, and industrial response. All blending and compacting was completed at Dalhousie University, while sintering was undertaken at Dalhousie and GKN Sinter Metals. The green alloy was assessed for best compaction pressure using green density and strength. The sintered alloy was assessed to determine the best press and sinter variables, using dimensional change, sintered density, apparent hardness, tensile properties and microscopy. These same sintered properties were tested to determine if sintering done on a laboratory scale could be replicated industrially. The viability of heat treatment was tested using differential scanning calorimetry, hardness and tensile properties. The alloy was also subject to modifications of Cu and Mg amounts, as well as to the addition of tin to the base composition. It was determined that compaction at 400MPa and sintering at 600°C for 20min produced the best properties for the sintered bodies. The resultant mechanical properties were attributed to a high sintered density (2.68g/cm 3 or 97% of theoretical) and strengthening mechanisms present in the Al-Cu-Mg system. These mechanisms included possible secondary phases formed in the alloy seen using microscopy and differential scanning calorimetry analyses. A T6 heat treatment of solutionizing at 495°C for 1.5h, water quench and aging for 10h was found to improve the properties of 2324. Modifications to Cu and Mg alloying additions produced few gains. However, the presence of 0.2Sn (w/o) was found to enhance the alloy. Resultant properties of the optimal alloy included an apparent hardness of 76.6HRE and an ultimate tensile strength of 367MPa. Also studied was the discrepancy observed in sintering at GKN and Dalhousie and the mechanisms at work with the addition of Sn. 2324 was adapted successfully to P/M applications. It was capable of performing against an established Al P/M industry standard, and with further testing its uses can undoubtedly be expanded.

Boland, Christopher Daniel

411

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 Bénard, Agustín Eduardo; Martínez Hernández, David; González Reyes, José Gonzalo; Ortiz Prado, Armando; Schouwenaars Franssens, Rafael

2014-02-01

412

Effect of Na2SiO3 solution concentration of micro-arc oxidation process on lap-shear strength of adhesive-bonded magnesium alloys  

NASA Astrophysics Data System (ADS)

Micro-arc oxidation films are fabricated on the surface of AZ31B magnesium alloy in the Na2SiO3 electrolyte. The mechanical performance of magnesium alloy bonding with the adhesive is examined by single lap-shear test, and the morphology and composition of the oxidation film are characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The data indicate that the increase of Na2SiO3 solution concentration results in the decrease of bonding strength of magnesium alloy joints, while the porosity has no directly relation with the variation of the lap-shear strength. The results also show that Na2SiO3 participates into the film formation and the fabricated film is mainly composed of MgO and Mg2SiO4. In particular, with the increase of Na2SiO3 solution concentration, the content of MgO decreased while that of Mg2SiO4 increased. Moreover, MgO could initiate the formation of the hydroxyl group, which potentially enhances surface wettability and hydrogen bonding with the adhesive. This rationale is strongly supported by the results of Fourier Transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle measuring.

Gao, Haitao; Zhang, Meng; Yang, Xin; Huang, Ping; Xu, Kewei

2014-09-01

413

Cyclic deformation of extruded AM30 magnesium alloy in the transverse direction  

NASA Astrophysics Data System (ADS)

Cyclic deformation characteristics of a recently developed AM30 Mg extrusion alloy in the transverse direction were evaluated under strain-controlled tests at different strain amplitudes. The alloy exhibited strong cyclic hardening especially at higher strain amplitudes. While the initial tensile Young's modulus was essentially the same in both transverse and longitudinal directions, the hysteresis loops were asymmetric in the longitudinal direction, but nearly symmetric in the transverse direction. This tension-compression asymmetry was associated with the presence of strong texture in the extruded Mg alloy. With increasing strain amplitude the mid-life hysteresis loops showed a clockwise rotation which was related to nonlinear or pseudoelastic deformation behavior. Fatigue crack initiation occurred at the specimen surface, and multiple initiation sites were observed at higher strain amplitudes. Crack propagation was basically characterized by the formation of characteristic fatigue striations.

Chen, D. L.; Emami, A. R.; Luo, A. A.

2010-07-01

414

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

415

Explosion bonding: aluminum-magnesium alloys bonded to austenitic stainless steel  

SciTech Connect

The explosion bonding of 5000 series aluminum alloys to 300 series stainless steel alloys is summarized. The process technique involves a parallel gap arrangement with copper or aluminum bonding aids. Successful bonds have been achieved using either a single shot process for joining the trilayer clad or a sequential shot technique for each metal component. Bond success is monitored through a combined metallographic and tensile strength evaluation. Tensile properties are shown to be strongly dependent upon process parameters and the amount of intermetallic formation at the aluminum bond interface. Empirical data has been compared with experimental and destructive test results to determine the optimum procedures.

Patterson, R.A.

1982-01-01

416

Solidification modeling and experimental investigation of aluminum-rich aluminum-copper-magnesium-zinc alloys  

Microsoft Academic Search

The microstructure and microsegregation of two ternary Al-rich alloys, Al-3.9Cu-0.9Mg and Al-15Cu-1Mg, and a quaternary Al-rich Al-3.86Cu-0.89Mg-0.99Zn alloy were studied by using microscopic modeling coupled with the information of real phase diagram. The microscopic model calculations include Scheil conditions, back diffusion in the solid, dendrite arm coarsening, and undercoolings of dendrite tip and the formation of eutectic mixture. The modeling

Fanyou Xie

1999-01-01

417

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

418

Concurrent Integration of Science-Based Mechanistic Relationships with Computational Thermodynamics and Kinetic Simulations for Strengthening Magnesium Alloys at Elevated Temperatures  

NASA Astrophysics Data System (ADS)

Integrated computational materials engineering approaches to alloy development leverage the hierarchical, interconnected nature of materials systems to rapidly optimize material performance. Particular emphasis is placed on the use of predictive models and simulation tools to elucidate fundamental relationships within the processing-structure-processing materials paradigm. For the current work, computational simulation results were used in combination with mechanistic, science-based models to assist alloy design. Two case studies are presented as illustrative examples that focus on high-temperature magnesium (Mg) alloy development. Solid solution strengthening potency and solute-based effects on creep rate were discussed in the first case study to guide strategies for solute selection in alloy development. This analysis was completed through the identification of composition-sensitive microstructural parameters that were subsequently evaluated in a predictive fashion. The second case study used computational thermo-kinetic simulations to evaluate Mg alloy precipitate systems for their ability to nucleate a high number density of coarsening-resistant particles. This nucleation and growth analysis was then applied to a Mg-Sn-Al alloy to highlight the utility of the current methodology in predicting multicomponent alloy precipitation behavior. This paper ultimately seeks to provide insight into an integrative approach that captures the important underlying material physics through relationships parameterized by descriptive thermodynamic and kinetic factors, where these factors can be readily calculated with a commercially available suite of computational tools in concert with accessible data in the literature.

Bryan, Z. L.; Manuel, M. V.

2015-01-01

419

Energy-Saving Melting and Revert Reduction Technology (E-SMARRT): Lost Foam Thin Wall - Feasibility of Producing Lost Foam Castings in Aluminum and Magnesium Based Alloys  

SciTech Connect

With the increased emphasis on vehicle weight reduction, production of near-net shape components by lost foam casting will make significant inroad into the next-generation of engineering component designs. The lost foam casting process is a cost effective method for producing complex castings using an expandable polystyrene pattern and un-bonded sand. The use of un-bonded molding media in the lost foam process will impose less constraint on the solidifying casting, making hot tearing less prevalent. This is especially true in Al-Mg and Al-Cu alloy systems that are prone to hot tearing when poured in rigid molds partially due to their long freezing range. Some of the unique advantages of using the lost foam casting process are closer dimensional tolerance, higher casting yield, and the elimination of sand cores and binders. Most of the aluminum alloys poured using the lost foam process are based on the Al-Si system. Very limited research work has been performed with Al-Mg and Al-Cu type alloys. With the increased emphasis on vehicle weight reduction, and given the high-strength-to-weight-ratio of magnesium, significant weight savings can be achieved by casting thin-wall (? 3 mm) engineering components from both aluminum- and magnesium-base alloys.

Fasoyinu, Yemi [CanmetMATERIALS] [CanmetMATERIALS; Griffin, John A. [University of Alabama - Birmingham] [University of Alabama - Birmingham

2014-03-31

420

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

421

Prediction of Yield Loci for a Magnesium Alloy Sheet using Crystal-Plasticity Finite-Element Method  

NASA Astrophysics Data System (ADS)

This paper presents the prediction of yield loci for an AZ31 magnesium alloy sheet using a rate-dependent crystal-plasticity finite-element method. A differential work-hardening behavior was clearly observed; the contour of plastic work was initially rather flattened in the vicinity of equi-biaxial tension, but thereafter severely bulged. The variation of the relative activity of each family of slip systems was examined to investigate the mechanism of the differential work-hardening behavior. During uniaxial tension, the work hardening was determined mainly by the basal slip in the very beginning, while by both the prismatic slip and the basal slip in the subsequent deformation. On the other hand, during equi-biaxial tension, the activity of the basal slip systems was predominant throughout the deformation, while the relative activity of the prismatic slip systems was smaller than that in the uniaxial tension. We concluded that this difference in the relative activities of the slip systems depending on the biaxial-stress ratio eventually resulted in the differential work-hardening behavior of the contour of plastic work. The mechanism that the activity of the prismatic slip systems decreased as the biaxial-stress ratio approached to one was also discussed using a simple analytical model.

Hama, Takayuki; Fujimoto, Hitoshi; Takuda, Hirohiko

2011-08-01

422

Corrosion of Magnesium-Aluminum Alloys with Al-11Si/SiC Thermal Spray Composite Coatings in Chloride Solution  

NASA Astrophysics Data System (ADS)

Depositions of Al-11Si coatings reinforced with 5, 15, and 30 vol.% SiC particles (SiCp) were performed onto AZ31, AZ80, and AZ91D magnesium alloys. The influence of substrate composition and SiCp proportion on the anti-corrosion properties of composite coatings was evaluated using DC and AC electrochemical measurements in 3.5 wt.% NaCl solution at 22 °C. The as-sprayed coatings were permeable to the saline solution, and galvanic corrosion occurred at the substrate/coating interface after immersion in the saline solution for a few hours. The addition of SiCp yielded coatings with higher porosity and less effectiveness against corrosion. The application of a cold-pressing post-treatment produced denser coatings with reduced surface roughness, improved hardness, and superior corrosion resistance. However, galvanic corrosion was observed after several days of immersion because of penetration of the 3.5 wt.% NaCl solution through the remaining pores in the coatings.

Arrabal, R.; Pardo, A.; Merino, M. C.; Mohedano, M.; Casajús, P.; Matykina, E.

2011-03-01

423

Cyclic-Tension Fatigue Behavior in a Rolled AZ31B Magnesium Alloy Studied Using Ultrasonic Shear Waves  

NASA Astrophysics Data System (ADS)

Nondestructive evaluation of cyclic-tension fatigue in a rolled magnesium alloy, Mg-3Al-1Zn, was performed using vertically polarized shear wave (SV) reflection and shear horizontal wave (SH) transmission methods. Internal friction measured by SV reflection increased rapidly in the early stages of the fatigue and finally saturated, showing dominating interactions of movable dislocations and twinning boundaries with the waves as acoustic nonlinearities. The propagation time and logarithmic damping ratio in the SH transmission method followed a repeated increase and subsequent sudden decrease pattern, and finally converged toward fatigue failure due to acoustoelasticity, which represents the interaction with residual stresses. The wave and phase data were determined using an optical microscope, a scanning electron microscope, a surface roughness tester, and X-ray diffraction. The results demonstrated that during the fatigue process, residual stress accumulated on the compressive side of the specimen, despite the applied cyclic-tension loading. Brittle cracks that originated in inclusions provided sudden relief from the residual stress.

Yamagishi, Hideki; Fukuhara, Mikio; Matsumoto, Hiroaki; Chiba, Akihiko

2010-08-01

424

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

425

Effect of potassium fluoride in electrolytic solution on the structure and properties of microarc oxidation coatings on magnesium alloy  

NASA Astrophysics Data System (ADS)

Oxide coatings were produced on AM60B magnesium alloy substrate making use of microarc oxidation (MAO) technique. The effect of KF addition in the Na 2SiO 3-KOH electrolytic solution on the microarc oxidation process and the structure, composition, and properties of the oxide coatings was investigated. It was found that the addition of KF into the Na 2SiO 3-KOH electrolytic solution caused increase in the electrolyte conductivity and decrease in the work voltage and final voltage in the MAO process. Subsequently, the pore diameter and surface roughness of the microarc oxidation coating were decreased by the addition of KF, while the coating compactness was increased. At the same time, the phase compositions of the coatings also varied after the addition of KF in the electrolytic solution, owing to the participation of KF in the reaction and its incorporation into the oxide coating. Moreover, the coating formed in the electrolytic solution with KF had a higher surface hardness and better wear-resistance than that formed in the solution without KF, which was attributed to the changes in the spark discharge characteristics and the compositions and structures of the oxide coatings after the addition of KF.

Liang, Jun; Guo, Baogang; Tian, Jun; Liu, Huiwen; Zhou, Jinfang; Xu, Tao

2005-10-01

426

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

427

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

428

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

429

Producing Nanocomposite Layer on the Surface of As-Cast AZ91 Magnesium Alloy by Friction Stir Processing  

NASA Astrophysics Data System (ADS)

Friction stir processing (FSP) is an effective tool to produce a surface composite layer with enhanced mechanical properties and modified microstructure of as-cast and sheet metals. In the present work, the mechanical and microstructural properties of as-cast AZ91 magnesium alloy were enhanced by FSP and an AZ91/SiC surface nanocomposite layer has been produced using 30 nm SiC particles. Effect of the FSP pass number on the microstructure, grain size, microhardness, and powder distributing pattern of the surface developed has been investigated. The developed surface nanocomposite layer presents a higher hardness, an ultra fine grain size and a better homogeneity. Results show that, increasing the number of FSP passes enhances distribution of nano-sized SiC particles in the AZ91 matrix, decreases the grain size, and increases the hardness significantly. Also, changing of the tool rotating direction results much uniform distribution of the SiC particles, finer grains, and a little higher hardness.

Asadi, P.; Besharati Givi, M. K.; Faraji, G.

430

Fusion cutting of aluminum, magnesium, and titanium alloys using high-power fiber laser  

NASA Astrophysics Data System (ADS)

The effects of cutting speed and assist gas pressure on laser cutting of 1-mm thick Al 1050, AZ31, and Ti6Al4V lightweight alloys are experimentally investigated. Fiber laser cutting of these materials is not broadly investigated and the acquisition of a new level of knowledge is of fundamental importance for applications like sheet metal trimming in automotive industry. The main process outputs are in depth compared with results reported in literature and obtained by cutting with CO2 and Nd?YAG lasers. The good cut quality, the high productivity, and the easy delivery of the beam obtained at the same time, corroborate the advantage of using fiber lasers for thin sheets lightweight alloys cutting.

Scintilla, Leonardo Daniele; Tricarico, Luigi

2013-07-01

431

Surface characterization and cytocompatibility evaluation of silanized magnesium alloy AZ91 for biomedical applications  

NASA Astrophysics Data System (ADS)

Mg alloys with high Al contents have superior corrosion resistance in aqueous environments, but poor cytocompatibility compared to that of pure Mg. We have silanized the cast AZ91 alloy to improve its cytocompatibility using five different silanes: ethyltriethoxysilane (S1), 3-aminopropyltriethoxysilane (S2), 3-isocyanatopyltriethoxysilane (S3), phenyltriethoxysilane (S4) and octadecyltriethoxysilane (S5). The surface hydrophilicity/hydrophobicity was evaluated by water contact angle measurements. X-ray photoelectron analysis was performed to investigate the changes in surface states and chemical composition. All silane reagents increased adsorption of the albumin to the modified surface. In vitro cytocompatibility evaluation revealed that silanization improved cell growth on AZ91 modified by silane S1. Measurement of the concentration of Mg2+ ions released during the cell culture indicated that silanization does not affect substrate degradation.

Witecka, Agnieszka; Yamamoto, Akiko; Dybiec, Henryk; Swieszkowski, Wojciech

2012-12-01

432

Repair of magnesium alloy castings by means of welding and pad welding  

Microsoft Academic Search

Purpose: Attempts were carried out at pad welding and welding of castings made of alloy AZ91D. Technologies were developed to repair such castings by means of welding methods encompassing the choice of weld deposit, welding parameters, heating parameters and the technique of welding. Design\\/methodology\\/approach: The research were focus on encompassed: pad welding and welding tests on flat plates cut out

J. Adamiec; S. Roskosz; R. Jarosz

433

Enhanced formability at elevated temperature of a cross-rolled magnesium alloy sheet  

Microsoft Academic Search

Relationship between texture and press formability of AZ31 Mg alloy sheets processed by cross-roll rolling was investigated. The Erichsen values of the cross-rolled specimens showed superior press formability compared with those of the specimens by normal-roll rolling. The superior press formability was related to a reduction in directional dependence of the thickness-direction strain and width-direction strain normalized by the tensile-direction

Yasumasa Chino; Kensuke Sassa; Akira Kamiya; Mamoru Mabuchi

2006-01-01

434

Thermochemical computations and experimentation on deposition of aluminum and zinc on magnesium alloy  

Microsoft Academic Search

The feasibility of Al and Zn deposition on Mg alloys by means of thermal deposition and diffusion process is evaluated by means of thermochemical computations and experimentation. For the thermodynamic analysis, a closed system consisting of Al2O3 as filler, Al as donor, halide or halide compound as process activator and argon as inert gas was considered. ZnCl2 as activator was

He Meifeng; Wu Yating; Tang Zhixin; Hu Wenbin

2009-01-01

435

Chemistry and electrochemistry of environment-assisted cracking of an aluminum-zinc-magnesium-copper alloy  

Microsoft Academic Search

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

Kevin Richard Cooper

2001-01-01

436

Copper(aluminum, Magnesium and Tantalum) Bilayer and Alloy Metallization for Ulsi  

Microsoft Academic Search

In this thesis, studies are reported on how to passivate the surface of Cu, and how to improve the adhesion of Cu to SiO_2\\/Si substrates while at the same time maintaining the low resistivity of Cu. Also reported in the thesis are investigations of the thin film reactions of Mg, Cu(Mg) bilayers and alloy films with SiO _2\\/Si substrates. Studies

Wei Wang

1996-01-01

437

New Thermodynamic Data for Liquid Aluminum-Magnesium Alloys from emf, Vapor Pressures, and Calorimetric Studies  

Microsoft Academic Search

Experimental thermodynamic studies of liquid Al-Mg alloys have been performed by several methods resulting in: (1) Mg activities\\u000a from galvanic cells with liquid electrolytes at temperatures from\\u000a 910 to 1070 K, at XMg = 0.1 to 0.7 and for the dilute range when XMg = 0.0126 to 0.1430 at 927 K; (2) Mg activities from the emf method with solid

Z. Moser; W. Zakulski; K. Rzyman; W. Gasior; Z. Panek; I. Katayama; T. Matsuda; Y. Fukuda; T. Iida; Z. Zajaczkowski; J. Botor

1998-01-01

438

Friction stir welding of AZ-91 and AM-Lite magnesium alloys  

Microsoft Academic Search

The objective of this paper was to report the results of butt joint quality of friction stir welding (FSW) of samples of alloys of MgAlZn group. Welding has been carried out with the FSW tool of welding speed ranging from 140 to 355 mm\\/min. In the stir zone and the surrounding, neither porosity nor cracks have been obtained. Microhardness in the

Lechos?aw Tuz; Pawe? Ko?odziejczak; Andrzej Kolasa

2011-01-01

439

A predictive mechanism for dynamic strain ageing in aluminium-magnesium alloys  

Microsoft Academic Search

Dynamic strain ageing (DSA) is the phenomenon in which solute atoms diffuse around dislocations and retard dislocation motion, leading to negative strain-rate sensitivity (nSRS) and thus to material instabilities during processing, an important issue in commercial metal alloys. Here, we show the mechanism of DSA and nSRS on experimental strain-rate, temperature and stress scales for Al-Mg to be single-atomic-hop motion

William A. Curtin; David L. Olmsted; Louis G. Hector

2006-01-01

440

A predictive mechanism for dynamic strain ageing in aluminium–magnesium alloys  

Microsoft Academic Search

Dynamic strain ageing (DSA) is the phenomenon in which solute atoms diffuse around dislocations and retard dislocation motion, leading to negative strain-rate sensitivity (nSRS) and thus to material instabilities during processing, an important issue in commercial metal alloys. Here, we show the mechanism of DSA and nSRS on experimental strain-rate, temperature and stress scales for Al–Mg to be single-atomic-hop motion

David L. Olmsted; Louis G. Hector; William A. Curtin

2006-01-01