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1

Influence of impurities on damping properties of ZK60 magnesium alloy  

Microsoft Academic Search

The influence of impurities on damping capacities of ZK60 magnesium alloys in the as-cast, as-extruded and T4-treated states was investigated by dynamically mechanical analyzer at room temperature. Granato and Lucke dislocation pinning model was employed to explain damping properties of the alloys. It is found that reducing impurity content can decrease the amount of second-phase particles, increase grain size and

Xian-hua CHEN; Jian-jun MAO; Fu-sheng PAN; Jian PENG; Jing-feng WANG

2010-01-01

2

Enhanced electromagnetic interference shielding in ZK60 magnesium alloy by aging precipitation  

NASA Astrophysics Data System (ADS)

Electromagnetic interference shielding, hardness, and electrical conductivity measurements were employed to evaluate the effect of aging precipitation on shielding characteristics of ZK60 magnesium alloy. During artificial aging MgZn2 phase precipitates occurred and the age hardening peak happened at 150 °C for 15 h. Aging precipitation induced enhanced shielding effectiveness as well as tensile strength in the alloy. It is interesting to note that the shielding effectiveness exhibited a rapid increase with increase in aging time until 15 h, but for longer aging time it tended to remain largely unchanged. Artificial aging at 150 °C for 15 h can thus be considered as the optimum heat treatment condition. In this condition, the good combination of superior shielding effectiveness greater than 70 dB and high mechanical properties was achieved. The origin of the attractive electromagnetic interference shielding properties is discussed based on second phase precipitation in the alloy.

Chen, Xianhua; Liu, Juan; Pan, Fusheng

2013-06-01

3

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

4

Tensile properties of extruded ZK60–RE alloys  

Microsoft Academic Search

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

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

2003-01-01

5

Enhanced mechanical response of magnesium alloy ZK60A containing Si 3N 4 nanoparticles  

Microsoft Academic Search

ZK60A Nanocomposite containing Si3N4 nanoparticles was fabricated using solidification processing followed by hot extrusion. The ZK60A nanocomposite exhibited smaller grain size than monolithic ZK60A, significantly reduced presence of intermetallic phase, reasonable Si3N4 nanoparticle distribution, non-dominant (0002) texture in the longitudinal direction, and 12% lower hardness than monolithic ZK60A. Compared to monolithic ZK60A (in tension), the ZK60A nanocomposite simultaneously exhibited higher

M. Paramsothy; J. Chan; R. Kwok; M. Gupta

2011-01-01

6

Microstructure characterization of ZK60 magnesium alloys using TEM and HR-EBSD.  

PubMed

ZK60 (Mg-Zn-Zr) alloys exhibited a variation in precipitates with aging, and their mechanical properties also changed. Microindentation tests were carried out on two types of ZK60 alloys of solid solution (T4) and peak aging (T6). Microstructure and texture evolution during indentation was investigated using electron backscatter diffraction. Twinning occurred near the indentation marks in most grains. It was found that tensile twinning was dominant, and two twin variants were usually observed. Texture and microstructure evolution by twinning and slip activation was further examined by uniaxial compression test with strain. The initial random orientation gradually changed into basal fibers with strain. Some grains with nonbasal orientations aligned with the loading direction easily underwent twinning followed by slip deformation. Other grains near basal orientations revealed only slip deformation. PMID:23920164

Cho, Jae-Hyung; Kim, Soo-Hyun; Han, Sang-Ho; Kang, Suk-Bong

2013-08-01

7

Effect of rolling temperature on microstructure and texture of twin roll cast ZK60 magnesium alloy  

Microsoft Academic Search

Twin roll cast ZK60 alloy strip\\/sheet with final thickness of 0.5 mm was prepared, and effect of rolling temperature on microstructure and texture development was investigated using OM and XRD technique, microstructure and texture were measured on specimens subjected to rolling experiment at different rolling temperature, and macrotexture was also evaluated by X-ray diffraction method. In addition, the (100) and

Hong-mei CHEN; Hua-shun YU; Suk-bong KANG; Guang-hui MIN; Yun-xue JIN

2010-01-01

8

Microstructure, in vitro corrosion and cytotoxicity of Ca-P coatings on ZK60 magnesium alloy prepared by simple chemical conversion and heat treatment.  

PubMed

Magnesium alloys are potential biodegradable materials for biomedical application. But their poor corrosion resistance may result in premature failure of implants. In this study, to solve this problem, Ca-P coatings were prepared on ZK60 magnesium alloy by a simple chemical conversion process and heat treatment. Surface characterization showed that a flake-like Dicalcium phosphate dihydrate (DCPD) (CaHPO?·2H?O) coating was formed on ZK60 alloy by the chemical conversion process. DCPD transformed into Dicalcium phosphate anhydrous (DCPa) (CaHPO?) and Ca?P?O? after heat treatment. Results of potentiodynamic polarization showed the corrosion potential of ZK60 was increased from -1666?mV to -1566?mV with DCPD coating, while -1515?mV was obtained after heat treatment. The corrosion current density of ZK60 was measured to be reduced from 35?µA/cm² to 3.5?µA/cm² with DCPD coating, while a further reduction to 1?µA/cm² was observed after heat treatment. This indicated that the coatings improved the substrate corrosion resistance significantly, and apparently, the heat-treated coating had a higher corrosion resistance. Immersion test demonstrated that both the coatings could provide protection for the substrate and the heat-treated coating could induce deposition of bone-like apatite. Cytotoxicity evaluation revealed that none of the samples induced toxicity to L-929 cells after 1- and 3-day culture. The cytocompatibility of ZK60 was improved by the coatings, with the following sequence: uncoated ZK60?ZK60?

Li, Kaikai; Wang, Bing; Yan, Biao; Lu, Wei

2012-07-17

9

The in vitro degradation process and biocompatibility of a ZK60 magnesium alloy with a forsterite-containing micro-arc oxidation coating.  

PubMed

Magnesium has attracted much attention as a class of biodegradable metallic biomaterials. In this study, a silicate electrolyte-based micro-arc oxidation (MAO) treatment was adopted to prepare forsterite-containing MAO coatings on a ZK60 magnesium alloy in order to decrease the degradation rate and increase the biological property of the alloy. Four anodization voltages were chosen to prepare the MAO coatings. The cell experiment showed a cytotoxicity of grade 0 for the MAO-coated alloy to L929 cells and the hemolytic ratio was dramatically decreased for the MAO-coated alloy compared with the bare one. The corrosion resistance and the degradation behavior of the MAO-coated ZK60 alloy were studied using drop tests, electrochemical measurements and immersion tests. The results indicate that the MAO coating could effectively decrease the initial degradation rate of the alloy. The corrosion resistance of MAO coating was increased with the elevation of the preparation voltage. A degradation model for ZK60 alloy with a forsterite-containing MAO coating was proposed. Based on the model, the MAO-coated alloy experiences destruction and restoration simultaneously, and the coating fails in a peeling-off mode. PMID:23261923

Lin, Xiao; Tan, Lili; Zhang, Qiang; Yang, Ke; Hu, Zhuangqi; Qiu, Jianhong; Cai, Yong

2012-12-20

10

The Effects of Forging on the Microstructure and Tensile Properties of Magnesium Alloys AZ31 and ZK60  

Microsoft Academic Search

Magnesium alloys have gained considerable attention in the last fifteen years for application in electronic and automotive applications due to their high strength to weight ratio. High-pressure die casting is currently the predominant production technique with over 90% of magnesium products produced by casting. Forging provides many performance advantages over cast parts due to increased strength but the metal is

David Poerschke

11

Effects of heat treatment on microstructure and mechanical properties of ZK60 Mg alloy  

Microsoft Academic Search

The microstructure and mechanical properties of ZK60 Mg alloy were investigated under different solution treatments and artificial aging conditions. When as-cast ZK60 alloy was solution treated at 400 °C for 10 h and artificially aged at 150 °C, the volume fraction of precipitates increased with the aging time up to 30 h. When the as-cast ZK60 alloy was solution treated

Xian-hua CHEN; Xiao-wang HUANG; Fu-sheng PAN; Ai-tao TANG; Jing-feng WANG; Ding-fei ZHANG

2011-01-01

12

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

SciTech Connect

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 other materials, especially, in wet and salt-laden environments. The corrosion is enhanced when an additional phase is added to magnesium alloys because most of the magnesium/reinforcement systems are electrochemically unstable. Previous investigations have revealed that high power laser surface treatment is an efficient way to improve the corrosion resistance of magnesium alloys and their composite materials, without resulting in significant adverse effects on the properties of the bulk materials. In the present study, laser cladding of an Al-Si eutectic alloy on magnesium ZK60/SiC composite was performed using a multiwave Nd:YAG laser. In order to avoid excessive oxidation, argon shielding gas was blown directly into the laser-generated molten pool instead of using a vacuum condition.

Yue, T.M.; Wang, A.H.; Man, H.C. [Hong Kong Polytechnic Univ., Kowloon (Hong Kong). Dept. of Mfg. Engineering

1999-01-08

13

Effects of cathode current density on structure and corrosion resistance of plasma electrolytic oxidation coatings formed on ZK60 Mg alloy  

Microsoft Academic Search

Current density is a key factor in plasma electrolytic oxidation (PEO) process. The aim of this paper is to study the effects of cathode current density on the composition, morphology, and corrosion resistance of ceramic coatings on ZK60 magnesium alloy prepared through bi-polar plasma electrolytic oxidation in Na3PO4 solution. The phase composition, morphology, and corrosion resistance were studied by X-ray

Peibo Su; Xiaohong Wu; Yun Guo; Zhaohua Jiang

2009-01-01

14

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

15

Deformation behavior and microstructure evolution of wrought magnesium alloys  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

16

Mechanical properties and damping capacity of (SiC{sub w}+B{sub 4}C{sub p})/ZK60A Mg alloy matrix composite  

SciTech Connect

Mg alloys possess the advantages of low density and high damping capacity and they are conventionally used in the aerospace and aviation industries. The mechanical properties of Mg alloy matrix composites reinforced with continuous fibers, short fibers or whiskers and particles are improved over those of unreinforced Mg alloys. The hybrid composite, that means its reinforcements are produced by an appropriate combination of short fibers (or whiskers) and particles, can satisfy the demands for reducing cost and improving properties. So the interest in Mg alloy matrix hybrid composites is increasing recently. In order to gain more data of this new kind of composites and to search for a better combination of different reinforcements, a Mg alloy matrix composite reinforced by hybrid SiC whiskers and B{sub 4}C particles was fabricated and its mechanical properties and damping capacity were studied in this paper.

Zhang Xiaonong; Zhang Di; Wu Renjie [Shanghai Jiao Tong Univ. (China). State Key Lab. of Metal Matrix Composites; Zhu Zhengang; Wang Can [Chinese Academy of Sciences, Hefei (China). Lab. of Internal Friction and Defect in Solids

1997-12-01

17

Effects of Titanium Nitride Surface Coating on High Speed Impact Induced Damage of Magnesium Alloys at Cryogenic Temperature  

Microsoft Academic Search

This reports a summary of our recent high speed impact tests aiming to clarify the impact characteristic of magnesium alloy with titanium nitride coating. We placed 100 mm x 100 mm and 3 mm thick magnesium alloy plates, ZK60A-T5 at 298 K, 223 K and 153 K, which were coated with 1 micron thick titanium nitride layer based on a

K. Takayama; D. Numata; R. Kubota; A. Shimamoto

2009-01-01

18

STATIC AND DYNAMIC CORROSION FATIGUE OF Mg ALLOYS USED IN AUTOMOTIVE INDUSTRY  

Microsoft Academic Search

Corrosion fatigue tests were carried out on die-cast and extruded magnesium alloys AZ91D, AZ80, AM50, and ZK60 in air, and NaCl-based and borate solutions. Nsol\\/Nair ratios (the relative fatigue life) were used for analysis of the corrosion fatigue behavior of Mg alloys in various environments, where Nsol and Nair are the numbers of cycles to failure in the solution and

A. Eliezer; J. Haddad; Y. Unigovski; E. M. Gutman

2005-01-01

19

Effects of Titanium Nitride Surface Coating on High Speed Impact Induced Damage of Magnesium Alloys at Cryogenic Temperature  

NASA Astrophysics Data System (ADS)

This reports a summary of our recent high speed impact tests aiming to clarify the impact characteristic of magnesium alloy with titanium nitride coating. We placed 100 mm x 100 mm and 3 mm thick magnesium alloy plates, ZK60A-T5 at 298 K, 223 K and 153 K, which were coated with 1 micron thick titanium nitride layer based on a hollow cathode discharge method. We also tested with uncoated magnesium plates. The plates were impinged by 8 mm diameter aluminum alloy (Al2017-T4) spheres at impact speeds of 0.5 to 1.7 km/s in a two-stage light gas gun in the SWRC, IFS, Tohoku Univ. Two specimens were installed at 100 mm interval vertically to the spheres in a cryogenic test chamber [1]. Impact phenomena were visualized with shadowgraph arrangements and recorded with ImaCon 200. As a result, the effect of surface coating on surface fracture was examined. We found the increase of hole areas in proportional to the impact speed and a clear difference of penetration hole and fracture patterns between impact speed of 0.5 km/s and higher impact speeds. The titanium nitride coating was effective to favorably control the damage process. [1] Numata,D. et al., Shock Waves (2008), 18:169-183.

Takayama, K.; Numata, D.; Kubota, R.; Shimamoto, A.

2009-06-01

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

Stress Drop LED by Twinning during Initial Stage of Hot Compression of Twin-Roll Cast Mg-5.51%Zn-0.49%Zr Alloy  

NASA Astrophysics Data System (ADS)

Flow stress behavior during initial stage of hot compression of twin-roll cast ZK60 magnesium alloy was characterized by employing deformation temperature of 300°C and 400°C, and a given strain rate of 10-2s-1. A stress drop during initial stage of hot compression at 300°C, generally led by dynamic recrystallization, was found to be attributed to twinning, correspondingly to dynamic recrystallization as deformation temperature was raised to 400°C.

Liu, Zhiyi; Xu, Jing; Hou, Yanhui; Kang, Sukbong

2012-12-01

22

THE HYDRIDING OF CERIUM-MAGNESIUM ALLOYS  

Microsoft Academic Search

Cerium-magnesium alloys containing from 0 to 75 at% Mg were subjected to ; hydriding at room temperature at a Hâ pressure of 0.5 to l.0 atm. The ; hydrogen content of the hydrogenated alloy was determined by measuring the ; evolved Hâ on adding HCl to the sample. In alloys containing up to 5 at.% ; Mg a small constant

V. I. Mikheeva; Z. K. Sterlyadkina

1961-01-01

23

Investment Casting of Magnesium-Lithium Alloys.  

National Technical Information Service (NTIS)

A method was developed for investment casting magnesium-lithium alloys into inhibited gypsum-bonded molds. Both prototype castings and separately cast test bars (0.252 inch) were produced. Visual and metallographic examination showed no evidence of metal-...

A. Saia R. E. Edelman

1966-01-01

24

LOST FOAM CASTING OF MAGNESIUM ALLOYS  

SciTech Connect

The lost foam casting process has been successfully used for making aluminum and cast iron thin walled castings of complex geometries. Little work has been carried out on cast magnesium alloys using the lost foam process. The article describes the research activities at Oak Ridge National Laboratory and Tennessee Technological University on lost foam casting of magnesium alloys. The work was focused on castings of simple geometries such as plate castings and window castings. The plate castings were designed to investigate the mold filling characteristics of magnesium and aluminum alloys using an infrared camera. The pate castings were then characterized for porosity distribution. The window castings were made to test the castability of the alloys under lost foam conditions. Significant differences between lost foam aluminum casting and lost foam magnesium casting have been observed.

Han, Qingyou [ORNL; Dinwiddie, Ralph Barton [ORNL; Sklad, Philip S [ORNL; Currie, Kenneth [Tennessee Technological University; Abdelrahman, Mohamed [Tennessee Technological University; Vondra, Fred [Tennessee Technological University; Walford, Graham [Walford Technologies; Nolan, Dennis J [Foseco-Morval

2007-01-01

25

In vitro and in vivo corrosion measurements of magnesium alloys  

Microsoft Academic Search

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

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

2006-01-01

26

Anticorrosive magnesium hydroxide coating on AZ31 magnesium alloy by hydrothermal method  

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

27

Constitutive Modeling of Magnesium Alloy Sheets  

SciTech Connect

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

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

2007-05-17

28

Application of the Diffraction Model to Amorphous Magnesium Zinc Alloys.  

National Technical Information Service (NTIS)

Amorphous magnesium-zinc (a-MgZn) alloys comprise the best system available for testing the diffraction model for electron transport in non-crystalline alloys. They are simple metal binary alloys. Conventional methods exist for determining electronic para...

P. J. Cote L. V. Meisel

1984-01-01

29

Dendritic solidification of magnesium alloy AZ91  

Microsoft Academic Search

The magnesium alloy AZ91 has been studied under different solidification conditions, to establish the details of the as-cast\\u000a structure. The electron backscattered pattern (EBSP) technique has been used to determine the crystallographic directions\\u000a of the dendrite stem and the secondary arms. Under unidirectional solidification conditions, two different stem directions\\u000a were found: at a low temperature gradient and high growth velocity,

K. Pettersen; O. Lohne; N. Ryum

1990-01-01

30

Investment casting of AZ91HP magnesium alloy  

Microsoft Academic Search

This paper describes AZ91HP magnesium alloy investment casting. The aim of this study is to optimize the process for magnesium\\u000a investment casting. Special attention was given to evaluating the thermal stability of oxides against molten AZ91HP magnesium\\u000a alloy. The oxides examined included CaO, CaZr03, and silica bonded A1203 and ZrSi04. Also, the microstructural features of the as-cast alloy were investigated,

Shaekwang Kim; Myounggyun Kim; Taewhan Hong; Heekook Kim; Youngjig Kim

2000-01-01

31

Pressurized solidification of magnesium alloy AM50A  

Microsoft Academic Search

Following the success in squeeze casting aluminum components in the automotive industry, squeeze casting of magnesium alloys is yet to be developed for further improvement on vehicles’ fuel economy. It is essential to have a scientific understanding of solidification phenomena taking place in squeeze casting of magnesium alloys for innovative product development and process control. This paper describes a systematic

Alfred Yu; Shuping Wang; Naiyi Li; Henry Hu

2007-01-01

32

IMPROVEMENTS IN OR RELATING TO MAGNESIUM BASE ALLOYS  

Microsoft Academic Search

It was found possible to incorporate both zirconium and aluminum in the ; same magnesium-base alloy in such a manner as to obtain a fine grain size even ; with less than 2~ aluminum present and to produce wrought anticles which are ; resistant to grain growth at elevated temperatures. The alloy consists of ; magnesium plus 0.25 to 10%

P. A. Fisher; E. F. Emley

1962-01-01

33

[Research on bioactivity of magnesium and its alloys].  

PubMed

Magnesium is an essential microelement which is not harmful to human body. As a light-weight metal with properties similar to natural bone, magnesium material possesses the characteristics of its degradability, little biotoxicity, as well as its regulatory strength and controllable degradation-speed. After the tissue has healed sufficiently, the burden of a second surgical procedure can be avoided. Therefore, there is need of investigation on the possible use of magnesium and its alloys as medical biomaterials, and the study of its bioactivity is the foundation of further application. This article reviews the bioactivity of magnesium and its alloys. PMID:19634698

Liu, Kui; Guo, Lei

2009-06-01

34

Potential automotive uses of wrought magnesium alloys  

SciTech Connect

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

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

1996-06-01

35

Aluminium-scandium-lithium-magnesium system as a potential source of superplastically formable alloys.  

National Technical Information Service (NTIS)

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 poten...

R. A. Emigh

1990-01-01

36

Ignition of Magnesium and Magnox Alloys. A Review of Data.  

National Technical Information Service (NTIS)

Available data on the ignition temperatures of magnesium and the Magnox alloys of interest in CEGB Magnox reactor operations have been reviewed. Two basic ignition modes, instantaneous where a continuing and high rate of temperature rise is applied to the...

R. J. Pearce

1987-01-01

37

Corrosion Protection of Magnesium Alloy AZ31B.  

National Technical Information Service (NTIS)

Corrosion rates for bare and coated Magnesium alloy AZ31B have been measured. Two coatings, Dow-23(Trademark) and Tagnite(Trademark), have been tested by electrochemical methods and their effectiveness determined. Electrochemical methods employed were the...

M. D. Danford M. J. Mendrek M. L. Mitchell P. D. Torres

1997-01-01

38

Molten Salt Electrowinning of Magnesium-Yttrium Alloys.  

National Technical Information Service (NTIS)

Preparation of high-purity magnesium-yttrium alloys by electroreduction of Y2O3 dissolved in a YF3-LiF bath and the subsequent deposition of yttrium in a molten magnesium cathode was investigated in laboratory-scale apparatus. Parameters such as temperatu...

D. G. Kesterke D. J. MacDonald E. Aamland

1973-01-01

39

Combustion Mechanism of Particles of Aluminum-Magnesium Alloys.  

National Technical Information Service (NTIS)

The authors have studied the combustion process of individual particles of aluminum-magnesium alloys under atmospheric pressure. The particles contained 5, 10, 20, 50, 70, 90, and 95% magnesium and were prepared in the form of spheres measuring from 100 t...

E. I. Popov L. Y. Kashporov V. M. Maltsev A. L. Breiter

1974-01-01

40

Discussions on grain refinement of magnesium alloys by carbon inoculation  

Microsoft Academic Search

Carbon inoculation has no effect on magnesium alloys that do not contain aluminium. The hypothesis proposed in a recent article [Scripta Materialia 49 (2003) 1129] that segregation of carbon plays a major role in the grain refinement of magnesium alloys by carbon inoculation is inconsistent with many of the observed facts. The Al4C3 or Al–C–O hypothesis, which is supported by

Ma Qian; P. Cao

2005-01-01

41

Modelling of CO 2 laser welding of magnesium alloys  

Microsoft Academic Search

Laser welding is an important joining process for magnesium alloys. These materials are being increasingly used in different applications such as in aerospace, aircraft, automotive, electronics, etc. To date, carbon dioxide (CO2) neodymium-doped yttrium aluminum garnet (Nd:YAG) and the high power diode laser have been extensively used to investigate the weldability of magnesium alloys. The present work describes an analytical

Kamel Abderrazak; Wacef Ben Salem; Hatem Mhiri; Georges Lepalec; Michel Autric

2008-01-01

42

Interfacial tension between magnesium alloys and chloride-fluoride melts  

Microsoft Academic Search

The authors use the method of maximum pressure in a gas bubble for investigating interfacial and surface tension of magnesium alloys in relation to their contents of such additives as aluminum, zinc, and manganese, and also of rare earth metals -- cerium and neodymium. Tables present data on the surface properties of alloys with two separate melt systems. Analyzing their

B. V. Patrov; I. A. Barannik; V. A. Polous

1985-01-01

43

Biocorrosion of a magnesium alloy with different processing histories  

Microsoft Academic Search

High rates of degradation in corrosive media represent the Achilles heel of Mg alloys, which hinders their applications in various areas, particularly in prosthetics. We present an investigation of the degradation behaviour of magnesium alloy AZ31 in Hank's solution that simulates bodily fluids. The degradation rate is shown to be significantly reduced by grain refinement produced by mechanical processing. In

H. Wang; Y. Estrin; Z. Zúberová

2008-01-01

44

IMPROVEMENTS IN OR RELATING TO MAGNESIUM BASE ALLOYS  

Microsoft Academic Search

A method was developed for incorporating both zirconium and aluminum in ; a magnesium alloy in such a manner as to obtain a fine grain size even with less ; than 2% aluminum present. Wrought articles were produced from this alloy that ; are resistant to grain growth at elevated temperatures. It was found possible to ; include other zirconium

P. A. Fisher; E. F. Emley

1962-01-01

45

On the Modeling of Plastic Deformation of Magnesium Alloys  

SciTech Connect

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.

Ertuerk, S.; Steglich, D.; Bohlen, J.; Letzig, D.; Brocks, W. [GKSS Research Center, Institute of Materials Research, Max-Plank-Str., D-21502 Geesthacht (Germany)

2007-05-17

46

Interfacial tension between magnesium alloys and chloride-fluoride melts  

SciTech Connect

The authors use the method of maximum pressure in a gas bubble for investigating interfacial and surface tension of magnesium alloys in relation to their contents of such additives as aluminum, zinc, and manganese, and also of rare earth metals -- cerium and neodymium. Tables present data on the surface properties of alloys with two separate melt systems. Analyzing their results, the authors obtain a series of equations for finding the extremal point -alloy composition with the minimal or maximal spreading coefficient.

Patrov, B.V.; Barannik, I.A.; Polous, V.A.

1985-04-20

47

The relation between mechanical properties and structure of aluminum and magnesium cast alloys at low temperatures  

Microsoft Academic Search

Conclusions 1.The following cast alloys have the best combination of properties in the temperature range 293–20°K: A119 aluminum and VM12 magnesium alloys.2.A satisfactory level of properties is observed down to a temperature of 77°K in the case of alloys VAl5 and Ml10 alloys.3.The use of cast aluminum-magnesium alloys Al27-1 and Al8M and the magnesium alloy M15 is permissible down to

R. I. Il'ina; N. G. Sidorov; B. S. Morozov; M. F. Nikitina; P. F. Koshelev

1970-01-01

48

In vitro decomposition study of coated magnesium alloys  

NASA Astrophysics Data System (ADS)

In the last decade, magnesium has resurged as an important biomaterial. It's mechanical properties are very similar to natural bone, and it degrades in vivo to non toxic substances. Unfortunately, corrosion of pure magnesium in vivo is rapid, thus coated alloys that decrease it's corrosion could be used as implants in orthopedics. This presentation will describe the degradation results in a simulated body fluid (SBF).

Piersma, Tyler; White, Desiree; Cheng, Xinggou; Rabago-Smith, Montserrat; Lecronier, David

2010-04-01

49

In vivo decomposition study of coated magnesium alloys  

NASA Astrophysics Data System (ADS)

In the last decade, magnesium has resurged as an important biomaterial. Its mechanical properties are very similar to natural bone, and it degrades in vivo to non toxic substances. Unfortunately, corrosion of pure magnesium in vivo is rapid, thus coated alloys that decrease its corrosion could be used as implants in orthopedics. This presentation will describe the degradation results in cell cultures and in rats.

White, Desiree; Piersma, Tyler; Lecronier, David; Cheng, Xingguo; Rabago-Smith, Montserrat

2010-04-01

50

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

51

Thermodynamics of Magnesium--Bismuth Alloys.  

National Technical Information Service (NTIS)

Results of a study of magnesium--bismuth system are reported. These results explain the differences in the activity values of magnesium as reported by Egan (Acta Met., 7, 560(1959)) and Vetter and Kubaschewski (Z. Electrochem. 57, 243(1953)), and give mor...

R. Prasad V. Venugopal P. N. Iyer D. D. Sood

1975-01-01

52

Characterization and Degradation Study of Calcium Phosphate Coating on Magnesium Alloy Bone Implant In Vitro  

Microsoft Academic Search

Magnesium alloys have similar mechanical properties with natural bone, and they degrade within a certain time span. Therefore, magnesium alloys are suitable to be made as bone screws or plates. However, high susceptibility to corrosion has limited their applications in the orthopedic field. They would possess great medical functions if the degradation rates of magnesium alloys could be reduced. This

J. X. Yang; F. Z. Cui; Q. S. Yin; Y. Zhang; T. Zhang; X. M. Wang

2009-01-01

53

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

54

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

55

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

56

Surface Modifications of Magnesium Alloys for Biomedical Applications  

Microsoft Academic Search

In recent years, research on magnesium (Mg) alloys had increased significantly for hard tissue replacement and stent application\\u000a due to their outstanding advantages. Firstly, Mg alloys have mechanical properties similar to bone which avoid stress shielding.\\u000a Secondly, they are biocompatible essential to the human metabolism as a factor for many enzymes. In addition, main degradation\\u000a product Mg is an essential

Jingxin Yang; Fuzhai Cui; In Seop. Lee

2011-01-01

57

Optimization of Heat Treatment Conditions of Magnesium Cast Alloys  

Microsoft Academic Search

In this paper there are presented results of the optimization of heat treatment conditions, which are temperature and heating time during solution heat treatment or ageing as well the cooling rate after solution treatment for MCMgAl12Zn1, MCMgAl9Zn1, MCMgAl6Zn1, MCMgAl3Zn1 cast magnesium alloys. A casting cycle of alloys has been carried out in an induction crucible furnace using a protective salt

Leszek A. Dobrza?ski; Tomasz Ta?ski; Jacek Trzaska

2010-01-01

58

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

Microsoft Academic Search

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

Hongyang ZHAO; Pei BIAN; Dongying JU

2009-01-01

59

Microstructure characteristics and mechanical properties of laser weld bonding of magnesium alloy to aluminum alloy  

Microsoft Academic Search

Weldability of magnesium alloy to aluminum alloy in laser weld bonded (LWB) joints was investigated. Results showed that magnesium\\/aluminum\\u000a could be easily joined by LWB under proper technological parameters. The weld was characterized by complex vortex flow at\\u000a the bottom, and there existed intermetallic compound layer between weld pool and lower sheet metal, which was composed of\\u000a the brittle phases

Liming Liu; Heng Wang; Gang Song; Jia’nan Ye

2007-01-01

60

Crashworthiness optimisation of vehicle structures with magnesium alloy parts  

Microsoft Academic Search

This paper explores the effects of replacing the baseline steel with lightweight magnesium alloy parts on crashworthiness characteristics and optimum design of a full-vehicle model. Full frontal, offset frontal and side crash simulations are performed on a validated 1996 Dodge Neon model using explicit nonlinear transient dynamic finite element analyses in LS-DYNA to obtain vehicle responses such as crash pulse,

Andrew Parrish; Masoud Rais-Rohani; Ali Najafi

2012-01-01

61

Precision forging technologies for magnesium alloy bracket and wheel  

Microsoft Academic Search

Fundamental investigations on precision forging technology of magnesium alloys were studied. As-cast billet prestraining and a new concept of hollow billet were proposed in order to reduce the maximum forming load. A scheme of isothermal forming and the use of combined female dies were adopted, which can improve the die filling capacity and ensure the manufacture of high quality forgings.

Qiang WANG; Zhi-min ZHANG; Xing ZHANG; Jian-min YU

2008-01-01

62

Fatigue crack propagation of magnesium alloy in biaxial stress fields  

NASA Astrophysics Data System (ADS)

Fatigue crack propagation tests of magnesium alloy were conducted under conditions of biaxial and uniaxial loading by using a cruciform specimen in a biaxial fatigue machine, in order to investigate the effect of non-singular stress cycling on the fatigue crack growth properties ?KI -da/dN. The Magnesium alloys (AZ31B-O) used for this research are 2.5mm thickness plates. There are four different kinds of plates due to their heat treatment conditions. These conditions are (a) with no heat treatments (AZ31B-O), (b) 200-degree 2 hours (AZ31B-200), (c) 350-degree 2 hours (AZ31B-350), and (d) 430-degree 2 hours (AZ31B-430). From these comprehensive experiments, the remarkable effect was found in the specific biaxial load stress ratio ?x0/?y0 on ?KI -da/dN relation. When biaxial load stress ratio was 0.5, it turned out that the fatigue crack propagation rate of a magnesium alloy becomes very slow. Of course, in other biaxial load stress ratios, fatigue crack propagation velocity was influenced to some extent. It turned out that fatigue crack propagation rate becomes fast when a biaxial load stress ratio is minus, and it becomes slow when a biaxial load stress ratio is plus. Some discussion is made on the effect of microstructure on fatigue crack propagation of magnesium alloy in a biaxial stress field.

Itoh, Yasumi; Shimamoto, Akira

2005-05-01

63

NEW FORGE WELDING OF ALUMINUM AND MAGNESIUM ALLOYS  

Microsoft Academic Search

A new forge-welding process for weldng high-strength aluminum and ; magnesium alloys has been developed. This forge welding consists of heating the ; parts to be welded to a temperature which is high enough to allow good uniform ; flow of the materials without cracking and yet the temperature is sufficiently ; low that the samples are not overaged or

L. A. Cook; D. G. Shafer

1958-01-01

64

Magnesium alloy ingots: Chemical and metallographic analyses  

NASA Astrophysics Data System (ADS)

The quality of a magnesium die casting is likely dependent on the quality of the feed stockingot material. Therefore, both Daimler-Chrysler and General Motors have established quality assurance measures that include analysis of magnesium ingots. These processes include chemical analysis, corrosion testing, fast neutron activation analysis, and metallography. Optical emission spectroscopy, inductively coupled plasma spectroscopy, and gravimetric analysis are several methods for determining the chemical composition of the material. Fast neutron activation analysis, image analysis and energy dispersive X-ray spectroscopy are used to quantify ingot cleanliness. These experimental techniques are described and discussed in this paper, and example case studies are presented for illustration.

Tartaglia, John M.; Swartz, Robert E.; Bentz, Rodney L.; Howard, Jane H.

2001-11-01

65

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

66

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

67

Study of Forming of Magnesium Alloy by Explosive Energy  

SciTech Connect

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

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

2011-05-04

68

Warm formability of aluminum-magnesium alloys  

SciTech Connect

Manufacturers have become increasingly interested in near-net-shape forming of aluminum alloys as a means to reduce production costs and the weight of aircraft and automotive structures. To achieve the ductilities required for this process, we have examined extended ductility of Al-Mg alloys in the warm forming, or Class I creep, regime. We have studied a high-purity, binary alloy of Al-2.8Mg and ternary alloys of Al-xMg-0.5Mn with Mg concentrations from 1.0 to 6.6 wt. %. Tensile tests, including strain rates-change tests, have been performed with these materials at temperatures of 300 and 400C over a range 10{sup {minus}4} to 2 {times} 10{sup {minus}2} s{sup {minus}1}. A maximum tensile failure strain of 325% for the binary alloy and a maximum of 125% in the ternary alloys have been measured. The experimental results have been used to evaluate the effects of solute concentration, microstructure, temperature, and strain rate on flow stress ({sigma}), elongation to failure (e{sub f}), and strain-rate sensitivity (m) of these alloys.

Taleff, E.M. [Stanford Univ., CA (United States). Dept. of Mechanical Engineering; Henshall, G.A.; Lesuer, D.R.; Nieh, T.G. [Lawrence Livermore National Lab., CA (United States)

1994-05-27

69

THE ANALYSIS OF THORIUM-MAGNESIUM BINARY ALLOYS  

Microsoft Academic Search

Procedures are presented for the determination of thorium and magneisum ; in their binary alloys. Thorium is detemined by direct titration with EDTA at pH ; 2.5 to 3 using xylenol orange as indicator. Magnesium is also titrated directly ; with EDTA at pH 10.3 after precipitating the thorium as its peroxide in acid ; solution Solochrome black 6B (C.I.

G. W. C. Milner; J. W. Edwards

1958-01-01

70

Electroless Ni–P coating of different magnesium alloys  

Microsoft Academic Search

Coating of AZ31B, AE 42 and ZRE1 wrought magnesium alloys was carried out using electroless Ni plating technique in a solution of nickel sulphate, sodium hypophosphite, ammonium hydrogen fluoride and glycine with a zinc immersion pre-treatment.The results of SEM\\/EDX investigations and X-ray diffraction indicate that the coat exhibit a typical surface morphology with compact nodules with good adherence to the

N. El Mahallawy; A. Bakkar; M. Shoeib; H. Palkowski; V. Neubert

2008-01-01

71

Dynamic behavior of electroless nickel plating reaction on magnesium alloys  

Microsoft Academic Search

In order to obtain better control over the quality of electroless nickel–phosphorous (EN) coatings on magnesium AZ91D alloy,\\u000a the effects of metal salt concentrations, reducing agent, pH, and temperature on deposition rate were studied. The reaction\\u000a orders and activation energy of the deposition were determined. The results show that the apparent activation energy (E\\u000a a) in the EN plating reaction

Zhihui Xie; Gang Yu; Tingjing Li; Zhenjun Wu; Bonian Hu

72

Multiaxial fatigue of extruded AZ61A magnesium alloy  

Microsoft Academic Search

Strain-controlled multiaxial fatigue experiments were conducted on extruded AZ61A magnesium alloy using thin-walled tubular specimens in ambient air. The experiments included fully reversed tension–compression, cyclic torsion, proportional axial-torsion, and 90° out-of-phase axial-torsion. For the same equivalent strain amplitude, fatigue life under proportional loading was the highest and the nonproportional loading resulted in the shortest fatigue life. Detectable kinks were identified

Qin Yu; Jixi Zhang; Yanyao Jiang; Qizhen Li

2011-01-01

73

Microstructure analysis of magnesium alloy melted by laser irradiation  

NASA Astrophysics Data System (ADS)

The effects of laser surface melting (LSM) on microstructure of magnesium alloy containing Al8.57%, Zn 0.68%, Mn0.15%, Ce0.52% were investigated. In the present work, a pulsed Nd:YAG laser was used to melt and rapidly solidify the surface of the magnesium alloy with the objective of changing microstructure and improving the corrosion resistance. The results indicate that laser-melted layer contains the finer dendrites and behaviors good resistance corrosion compared with the untreated layer. Furthermore, the absorption coefficient of the magnesium alloy has been estimated according to the numeral simulation of the thermal conditions. The formation process of fine microstructure in melted layers was investigated based on the experimental observation and the theoretical analysis. Some simulation results such as the re-solidification velocities are obtained. The phase constitutions of the melted layers determined by X-ray diffraction were ?-Mg17Al12 and ?-Mg as well as some phases unidentified.

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

2005-12-01

74

Synthesis of highly stable magnesium fluoride suspensions and their application in the corrosion protection of a Magnesium alloy  

Microsoft Academic Search

This study presents a new approach to enhance the corrosion resistance of tungsten inert gas (TIG) welded AZ31 magnesium alloys\\u000a by using nanocrystalline magnesium fluoride suspensions in a suspension plasma spray (SPS) process. We have developed a synthesis\\u000a for the preparation of nanocrystalline magnesium fluoride suspensions, which delivers nearly monodisperse nanoparticles in\\u000a a gram scale yield. The particles were analyzed

Florian Waltz; Mark A. Swider; Petra Hoyer; Thomas Hassel; Martin Erne; Kai Möhwald; Matthias Adlung; Armin Feldhoff; Claudia Wickleder; Friedrich-Wilhelm Bach; Peter Behrens

75

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

NASA Astrophysics Data System (ADS)

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

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

2004-06-01

76

On the shock response of the magnesium alloy elektron 675  

NASA Astrophysics Data System (ADS)

Alloying elements such as aluminum, zinc or rare-earths allow precipitation hardening of magnesium (Mg). The low densities of such strengthened Mg alloys have led to their adoption as aerospace materials and (more recently) they are being considered as armor materials. Consequently, understanding their response to high strain-rate loading is becoming increasingly important. Here, the plate-impact technique was employed to measure longitudinal stress evolution in armor-grade wrought Mg-alloy Elektron 675 under 1D shock loading. The spall behavior was interrogated using a Heterodyne velocimeter (Het-v) system, with an estimate made of the material's Hugoniot elastic limit for both aged and un-aged materials.

Hazell, Paul; Appleby-Thomas, Gareth James; Wielewski, Euan; Siviour, Clive Richard; Stennett, Chris

2012-03-01

77

Hot rolling characteristics of spray-formed AZ91 magnesium alloy  

Microsoft Academic Search

AZ91 magnesium alloy was prepared by spray forming. The spray-deposited alloy was subsequently hot-rolled with a 80% reduction at 350 °C. The microstructural features of the as-spray-deposited and hot-rolled alloy were examined by optical microscopy, scanning electron microscopy and X-ray diffractometry. The results show that the spray-formed AZ91 magnesium alloy has, compared with the as-cast ingot, a finer microstructure with

Xiao-feng WANG; Jiu-zhou ZHAO; Jie HE; Zhuang-qi HU

2007-01-01

78

Corrosion behavior of rapidly solidified magnesium-aluminium-zinc alloys  

SciTech Connect

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

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

1997-12-01

79

Recycling of magnesium alloys: Chemical equilibria between magnesium-lithium-based melts and salt melts  

Microsoft Academic Search

Magnesium-lithium alloys have been equilibrated with chloride melts at 700 C in iron crucibles. After quenching, the compositions\\u000a of the metal and salt phases were determined by chemical analyses. The obtained data were evaluated according to thermodynamic\\u000a principles. The following reactions were investigated: MgCl2+2Li=2LiCl+Mg (Reaction [1]), CaCl2+2Li=2LiCl+Ca (Reaction [2]), and BaCl2+2Li=2LiCl+Ba (Reaction [3]). The equilibrium of Reaction [1] is much

Klaus Schwerdtfeger; André Ditze; Christian-Thalès Mutale

2002-01-01

80

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

81

Electrochemical noise analysis of the corrosion of AZ91D magnesium alloy in alkaline chloride solution  

Microsoft Academic Search

The corrosion behavior of AZ91D magnesium alloy in alkaline chloride solution was investigated by electrochemical noise (EN). The wavelet transform, as well as noise resistance (Rn) and power spectral density (PSD), had been employed to analyze the EN data. It was revealed that there exist three different stages of corrosion for AZ91D magnesium alloy in alkaline chloride solution, including an

Tao Zhang; Yawei Shao; Guozhe Meng; Fuhui Wang

2007-01-01

82

Magnesium alloys: Corrosion properties. (Latest citations from the NTIS Bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning the corrosion of alloys containing magnesium. References examine the effects of stress corrosion and metal fatigue. Hydrogen embrittlement of aircraft structural components and reactors is also discussed. Particular emphasis is placed upon the magnesium-aluminum alloys. (Contains 250 citations and includes a subject term index and title list.)

Not Available

1993-12-01

83

Magnesium alloys: Corrosion properties. (Latest citations from the NTIS bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning the corrosion of alloys containing magnesium. References examine the effects of stress corrosion and metal fatigue. Hydrogen embrittlement of aircraft structural components and reactors is also discussed. Particular emphasis is placed upon the magnesium-aluminum alloys. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1995-11-01

84

Recent progress in corrosion protection of magnesium alloys by organic coatings  

Microsoft Academic Search

The excellent properties of magnesium alloys, especially the high strength\\/weight ratio, make them desirable materials in the automotive industry. However, their high corrosion susceptibility has greatly limited or even prevented their larger scale use for various applications. Organic coating is one of the most effective ways to prevent magnesium alloys from corrosion. In this report, the recent progress of organic

Rong-Gang Hu; Su Zhang; Jun-Fu Bu; Chang-Jian Lin; Guang-Ling Song

85

Influence of Cutting Speed on Flank Temperature during Face Milling of Magnesium Alloy  

Microsoft Academic Search

Chip ignition is one of the important problems in cutting magnesium alloy due to cutting temperature rise which is mainly caused by the increase of cutting speed. In this paper, we measured the mean flank temperature through mounting two K-type thermocouples in workpiece of AM50A magnesium alloy. Effect of cutting speed on the temperature rise of tool flank was analyzed.

Junzhan Hou; Ning Zhao; Shaoli Zhu

2011-01-01

86

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

Microsoft Academic Search

Microstructural evolution of AZ31 magnesium alloy welds without and with the addition of titanium powders during resistance spot welding was studied using optical microscopy, scanning electron microscopy, and transmission electron microscopy (TEM). The fusion zone of AZ31 magnesium alloy welds could be divided into columnar dendritic zone (CDZ) and equiaxed dendritic zone (EDZ). The well-developed CDZ in the vicinity of

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

2011-01-01

87

Toward Solid-State Switchable Mirror Devices Using Magnesium-Rich Magnesium-Nickel Alloy Thin Films  

Microsoft Academic Search

All-solid-state devices with switchable mirror properties based on magnesium-rich magnesium-nickel alloy thin films have been prepared using magnetron sputtering. The structure of the devices was a Mg-Ni alloy (40 nm)\\/Pd (4 nm)\\/Ta2O5 (200 nm)\\/HxWO3 (500 nm)\\/ITO on a glass. The composition of the alloy was Mg5Ni. In the initial state, the devices showed a shiny metallic front side and a

Yasusei Yamada; Kazuki Tajima; Shanhu Bao; Masahisa Okada; Kazuki Yoshimura

2007-01-01

88

Modelling of Superplastic Forming of AZ31 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

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

Giuliano, G.

2011-01-01

89

Modelling of Superplastic Forming of AZ31 Magnesium Alloy  

SciTech Connect

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

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

2011-01-17

90

Laser Surface Engineering of Magnesium Alloys: A Review  

NASA Astrophysics Data System (ADS)

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

Singh, Ashish; Harimkar, Sandip P.

2012-06-01

91

Plasma electrolytic oxidation coating on AZ91 magnesium alloy modified by neodymium and its corrosion resistance  

Microsoft Academic Search

Ceramic coatings on the surfaces of Mg-9Al-1Zn (AZ91) magnesium alloy and Mg-9Al-1Zn-1Nd magnesium alloy (AZ91 magnesium alloy modified by neodymium, named as AZ91Nd in this paper) are synthesized in aluminate electrolyte by plasma electrolytic oxidation (PEO) process, respectively. X-ray diffraction and X-ray photoelectron spectroscopy analyses show the PEO coating on the Mg-9Al-1Zn-1Nd alloy comprises not only MgO and Al2O3, which

Y. L. Song; Y. H. Liu; S. R. Yu; X. Y. Zhu; Q. Wang

2008-01-01

92

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

93

Microstructure and texture studies on magnesium sheet alloys  

NASA Astrophysics Data System (ADS)

The AZ3, the most common Mg sheet alloy, is currently produced by hot rolling of the DC cast ingot. Mg wrought alloys, in general have limited formability due to hexagonal close-packed structure and preferred orientation (texture). In order to improve magnesium sheet formability, a good understanding of microstructure and texture evolution in twin-roll casting is necessary. The objectives of this research are to study the microstructural and texture evolution in twin-roll cast AZ31 Mg sheet alloy and to develop/modify alloy compositions with improved mechanical properties (weakened texture). In the first part of study, the influence of cooling rate (CR) on the casting structure of AZ31 magnesium alloy has been investigated, as a background to understand microstructural development in TRC AZ31, using different moulds to obtain slow to moderate cooling rates. It was found that grain size and secondary dendrite arm spacing (SDAS) reduces as the cooling rate increases. Moreover, it was observed that with an increase in cooling rate the fraction of second phase particles increases and the second phase particles become finer. The second part focused on the microstructure and texture study of the twin-roll cast (TRC) AZ31 (Mg-3wt.%Al-1wt.%Zn) sheet. The results indicate that TRC AZ31 exhibits a dendritic microstructure with columnar and equiaxed grains. It was noted that the amount of these second phases in the TRC alloy is greater than the conventionally cast AZ31. Recrystallization at 420 °C leads to a bimodal grain-size distribution, while a fine-grain structure is obtained after rolling and annealing. The TRC AZ31 sheet exhibits basal textures in the (i) as-received, (ii) rolled and (iii) rolled-annealed conditions. However, post-annealing of the TRC AZ31 at 420 °C produces a relatively random texture that has not been previously observed in the conventional AZ31 sheet. The texture randomization is attributed to the particle-stimulated nucleation (PSN) of new grains in the TRC structure. The preliminary evaluation of mechanical properties indicates that such annealing treatment slightly increases the ultimate tensile strength (UTS), but significantly improves elongation. In the final of part of the study, the microstructures and textures of rolled and rolled/annealed Mg-1wt.%Mn-based and Mg-1wt.%Zn-Based alloys containing different levels of Ce and Sr were examined. The Ce addition refines the as-cast and rolled/annealed grain structure of Mg-1wt.%Mn (M1) alloy. Moreover, the overall texture intensity of basal pole was weakened for rolled as well as rolled/annealed Mg-Mn-Ce alloys compared to the M1 alloy. The texture weakening was attributed to the solid solubility of Ce in Mg rather than PSN or c/a ratio alteration. The Sr addition refined the as-cast and rolled/annealed grain structure of Mg-1wt.%Mn-Sr (MJ) and Mg-1wt.%Zn (Z1) alloy. Moreover, the overall texture intensity of basal pole was weakened for rolled as well as rolled/annealed Mg-Zn-Sr (ZJ) alloys compared to the Z1 alloy. The texture weakening is attributed to the PSN of new grains with random orientations.

Masoumi, Mohsen

94

Formability study of magnesium alloy AZ31B  

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

95

Microstructural development of diffusion-brazed austenitic stainless steel to magnesium alloy using a nickel interlayer  

Microsoft Academic Search

The differences in physical and metallurgical properties of stainless steels and magnesium alloys make them difficult to join using conventional fusion welding processes. Therefore, the diffusion brazing of 316L steel to magnesium alloy (AZ31) was performed using a double stage bonding process. To join these dissimilar alloys, the solid-state diffusion bonding of 316L steel to a Ni interlayer was carried

Waled M. Elthalabawy; Tahir I. Khan

2010-01-01

96

Electroless deposition of Ni–W–P coating on AZ91D magnesium alloy  

Microsoft Academic Search

Ternary Ni–W–P alloy coating was deposited directly on AZ91D magnesium alloy by using an alkaline-citrate-based baths. Nickel sulfate and sodium tungstate were used as metal ion sources, respectively, and sodium hypophosphite was used as a reducing agent. The pH value of the electroless bath was tailored for magnesium alloy. The coating was characterized for its structure, morphology, microhardness and the

W. X. Zhang; N. Huang; J. G. He; Z. H. Jiang; Q. Jiang; J. S. Lian

2007-01-01

97

Biofunctionalized anti-corrosive silane coatings for magnesium alloys.  

PubMed

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

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

2013-01-11

98

Quality issues in laser welding of automotive aluminum and magnesium alloys  

Microsoft Academic Search

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

Hailiang Zhao

2001-01-01

99

Microstructure and corrosion characteristics of laser-alloyed magnesium alloy AZ91D with Al Si powder  

Microsoft Academic Search

Blown-powder laser surface alloying was performed on the magnesium alloy AZ91D with Al-Si alloy powder to improve corrosion resistance. Characterization by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD) analysis revealed that intermetallic compounds (IMCs) of Mg2Si, Al12Mg17 and Al3Mg2 were formed in the matrix of alpha-Mg and Al solid solutions in Al-Si alloyed layers. The

Ming Qian; Da Li; Chang Jin

2008-01-01

100

Cyclic deformation and twinning in a semi-solid processed AZ91D magnesium alloy  

Microsoft Academic Search

To improve fuel economy and reduce greenhouse gas emissions, magnesium alloys are being considered for automotive and aerospace applications because of their high strength-to-weight ratio. The structural applications of magnesium components require understanding of low cycle fatigue (LCF) behavior, since cyclic or thermal stresses are frequently encountered in many structural applications. The objective of this study was to examine LCF

H. A. Patel; D. L. Chen; S. D. Bhole; K. Sadayappan

2010-01-01

101

Effect of Cryogenic Treatment on the Microstructure and Mechanical Properties of AZ31 Magnesium Alloy  

Microsoft Academic Search

The effect of cryogenic treatment (77 K) on the microstructure and mechanical properties of magnesium and AZ31 magnesium alloy has been investigated in this article. The results show that tensile stress and the hardness of the samples treated in a cryogenic environment are higher than those of the untreated samples. The improvement of mechanical properties is highly dependent on the soaking

Yong Jiang; Ding Chen; Zhenhua Chen; Junwei Liu

2010-01-01

102

Calcium phosphate coating on magnesium alloy by biomimetic method: Investigation of morphology, composition and formation process  

Microsoft Academic Search

Magnesium alloy has similar mechanical properties with natural bone and can degrade via corrosion in the electrolytic environment\\u000a of the human body. Calcium phosphate has been proven to possess bioactivity and bone inductivity. In order to integrate both\\u000a advantages, calcium phosphate coating was fabricated on magnesium alloy by a biomimetic method. Supersaturated calcification\\u000a solutions (SCSs) with different Ca\\/P ratio and

Jing-xin Yang; Yan-peng Jiao; Qing-shui Yin; Yu Zhang; Tao Zhang

2008-01-01

103

Tribological behavior of plasma electrolytic oxidation coating on magnesium alloy with oil lubrication at elevated temperatures  

Microsoft Academic Search

The ceramic coating with micro-pores structure on AM60B magnesium alloy was prepared in silicate electrolyte by plasma electrolytic oxidation (PEO) method. The PEO coating is mainly composed of percales MgO and forsterite Mg2SiO4 phases. The tribological performance of the PEO coatings and uncoated magnesium alloys under oil-lubricated wear conditions at different loads and elevated temperatures (80–120°C) was comparatively investigated. Results

Jie Guo; Liping Wang; J. Liang; Qunji Xue; Fengyuan Yan

2009-01-01

104

A study on stress corrosion cracking and hydrogen embrittlement of AZ31 magnesium alloy  

Microsoft Academic Search

The stress corrosion cracking (SCC) behavior and pre-exposure embrittlement of AZ31 magnesium alloy have been studied by slow strain rate tensile (SSRT) tests in this paper. It is showed that AZ31 sheet material is susceptible to SCC in distilled water, ASTM D1387 solution, 0.01M NaCl and 0.1M NaCl solution. The AZ31 magnesium alloy also becomes embrittled if pre-exposed to 0.01M

R. G. Song; C. Blawert; W. Dietzel; A. Atrens

2005-01-01

105

Calcium phosphate coating on magnesium alloy for modification of degradation behavior  

Microsoft Academic Search

Magnesium alloy has similar mechanical properties with natural bone, but its high susceptibility to corrosion has limited\\u000a its application in orthopedics. In this study, a calcium phosphate coating is formed on magnesium alloy (AZ31) to control\\u000a its degradation rate and enhance its bioactivity and bone inductivity. Samples of AZ31 plate were placed in the supersaturated\\u000a calcification solution prepared with Ca(NO3)2,

Fu-zhai Cui; Jing-xin Yang; Yan-peng Jiao; Qing-shui Yin; Yu Zhang; In-Seop Lee

2008-01-01

106

Microstructure and texture evolution of AZ31 magnesium alloy during rolling  

Microsoft Academic Search

The production of magnesium alloy sheets normally involves several processing stages including hot rolling, cold rolling and intermediate annealing. The microstructure and texture evolution of AZ31 magnesium alloy sheets in different processing states were investigated by optical microscopy and X-ray diffraction technique. It is found that the microstructure of hot-rolled sheets is dominated by recrystallized equiaxed grains, while that of

Guang-jie HUANG; Qing LIU; Ling-yun WANG; Ren-long XIN; Xing-pin CHEN; Fu-sheng PAN

2008-01-01

107

Corrosion action and passivation mechanism of magnesium alloy in fluoride solution  

Microsoft Academic Search

Corrosion action and passive mechanism of magnesium alloy in the fluoride solution were studied by means of scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDS), and electrochemistry methods. The results show that an insoluble MgF2 film is generated on the surface of magnesium alloy activated in the hydrofluoric acid. And the mass of the deposited MgF2 film may reach a constant

Jian-zhong LI; Jiu-gui HUANG; Yan-wen TIAN; Chang-sheng LIU

2009-01-01

108

Electroless Ni–P deposition plus zinc phosphate coating on AZ91D magnesium alloy  

Microsoft Academic Search

An electroless Ni–P deposition process has been developed to treat the AZ91D magnesium alloy surfaces against corrosion. Magnesium alloy AZ91D was first phosphatized in a zinc phosphating bath containing molybdate. Then an electroless Ni–P deposition was carried out on the phosphate coating from a sulfate solution. The phases in the phosphate coatings were analyzed by XRD. Microstructures of phosphate coatings

J. S. Lian; G. Y. Li; L. Y. Niu; C. D. Gu; Z. H. Jiang; Q. Jiang

2006-01-01

109

Preparation and corrosion resistance studies of zirconia coating on fluorinated AZ91D magnesium alloy  

Microsoft Academic Search

Novel anti-corrosion zirconia coating was prepared via the sol–gel method for AZ91D magnesium alloy using zirconium nitrate hydrate as a precursor modified with acetylacetone (AcAc). Magnesium alloy substrates were first fluorinated in 20% HF aqueous solution at room temperature for 20h, then, the zirconia coating was deposited on the fluorinated sample by dip coating. Basing on the sol–gel process, a

Qing Li; Xiankang Zhong; Junying Hu; Wei Kang

2008-01-01

110

Oxide Film and Porosity Defects in Magnesium Alloy AZ91  

SciTech Connect

Porosity is a major concern in the production of light metal parts. This work aims to identify some of the mechanisms of microporosity formation in magnesium alloy AZ91. Microstructure analysis was performed on several samples obtained from gravity-poured ingots in graphite plate molds. Temperature data during cooling was acquired with type K thermocouples at 60 Hz at three locations of each casting. The microstructure of samples extracted from the regions of measured temperature was then characterized with optical metallography. Tensile tests and conventional four point bend tests were also conducted on specimens cut from the cast plates. Scanning electron microscopy was then used to observe the microstructure on the fracture surface of the specimens. The results of this study revealed the existence of abundant oxide film defects, similar to those observed in aluminum alloys. Remnants of oxide films were detected on some pore surfaces, and folded oxides were observed in fracture surfaces indicating the presence of double oxides entrained during pouring.

Wang, Liang [Mississippi State University (MSU); Rhee, Hongjoo [Mississippi State University (MSU); Felicelli, Sergio D. [Mississippi State University (MSU); Sabau, Adrian S [ORNL; Berry, John T. [Mississippi State University (MSU)

2009-01-01

111

Magnetic properties of alloys containing mischmetal, cobalt, copper, iron, and magnesium. Report of investigations\\/1981  

Microsoft Academic Search

The Bureau of Mines investigated alloys containing mischmetal (MM), cobalt, copper, magnesium, and iron for use in permanent magnets in place of the scarce samarium-cobalt alloys. The magnetic properties of MM-Co, MM-Co-Cu, MM-Co-Cu-Mg, and MM-Co-Cu-Fe-Mg alloys were evaluated. Magnets were fabricated by powder metallurgy consisting of arc-melting the metals, crushing and grinding the resultant alloys, alining and compacting the powder,

J. W. Walkiewicz; J. S. Winston; M. M. Wong

1981-01-01

112

Electroless deposition of Ni W P coating on AZ91D magnesium alloy  

NASA Astrophysics Data System (ADS)

Ternary Ni W P alloy coating was deposited directly on AZ91D magnesium alloy by using an alkaline-citrate-based baths. Nickel sulfate and sodium tungstate were used as metal ion sources, respectively, and sodium hypophosphite was used as a reducing agent. The pH value of the electroless bath was tailored for magnesium alloy. The coating was characterized for its structure, morphology, microhardness and the corrosion properties. SEM observation showed the presence of dense and coarse nodules in the ternary coating. EDS analysis showed that the content of tungsten in the Ni W P alloy was 4.5 wt.%. Both the electrochemical analysis and the immersion test in 10% HCl solution revealed that the ternary Ni W P coating exhibited good corrosion resistance properties in protecting the AZ91D magnesium alloy.

Zhang, W. X.; Huang, N.; He, J. G.; Jiang, Z. H.; Jiang, Q.; Lian, J. S.

2007-03-01

113

Dry sliding wear behaviour of plasma electrolytic oxidation coated AZ91 cast magnesium alloy  

Microsoft Academic Search

A cast AZ91 magnesium alloy was plasma electrolytic oxidation (PEO) coated using a pulsed unipolar power source in a silicate based electrolyte. Constant processing conditions for two different durations were chosen to obtain coatings of 10 and 20?m thickness. The dry sliding wear studies performed on this alloy with and without PEO coatings against an AISI 52100 steel ball counterpart

P. Bala Srinivasan; C. Blawert; W. Dietzel

2009-01-01

114

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

115

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

116

Corrosion resistance of aged die cast magnesium alloy AZ91D  

Microsoft Academic Search

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

Guangling Song; Amanda L Bowles; David H StJohn

2004-01-01

117

Effect of fetal calf serum on the corrosion behaviour of magnesium alloys  

Microsoft Academic Search

The corrosion behaviour of WE43 magnesium alloys using the mini cell system was studied. Voltammetry and impedance spectroscopy were applied to study on the one hand the effect of microstructure of the working electrode and on the other hand the effect of proteins in the electrolyte. Two types of alloy samples were produced (i) by permanent mould casting and (ii)

H. Hornberger; F. Witte; N. Hort; W.-D. Mueller

2011-01-01

118

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

Microsoft Academic Search

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

Shaohui Yin; Takeo Shinmura

2004-01-01

119

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

PubMed

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

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

2011-09-06

120

Analysis of anisotropy of extruded magnesium alloy AZ31 bar  

NASA Astrophysics Data System (ADS)

The large strain Elastic Visco-Plastic Self-Consistent (EVPSC) model, with the recently developed Twinning and De-Twinning (TDT) description, is applied to study the mechanical behavior of magnesium alloy AZ31 extrusion. Five different specimen orientations with tilt angles of ? of 0°, 22.5°, 45°, 67.5° and 90° between extrusion direction and longitudinal specimen axis are used to study the mechanical anisotropy under both uniaxial tension and compression. It is found that the uniform strain under tension is sensitive to the tilt angle and the maximum uniform strain is found at ? = 45°. The effect of pre-strain in uniaxial compression along the extrusion direction on subsequent uniaxial tension and compression along different directions with respect to the extrusion direction is also investigated. It is demonstrated that the influence of the twinning during pre-strain in compression and the detwinning in the subsequent uniaxial tension on the uniaxial tension response depends significantly on the tilt angle. By comparing the differences in the flow stress vs. orientation curves between the as-received and pre-strained samples, the effect of pre-straining on material anisotropy is investigated. It is found that the pre-compression lowers the uniform strain regardless of the tilt angle ?.

Qiao, H.; Wang, H.; Wu, P. D.

2013-05-01

121

Warm Deep Drawing Of Rectangular Cups With Magnesium Alloy AZ31 Sheets  

SciTech Connect

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

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

2007-05-17

122

Phase diagrams of advanced magnesium alloys containing Al, Ca, Sn, Sr, and Mn  

NASA Astrophysics Data System (ADS)

In this paper an overview of the most relevant phase diagrams is given comprising the unconventional alloying elements Sn, Ca, and Sr, in reasonable combinations with Al and Mn in Mg alloys as a basis for advanced applications. The focus is on magnesium-rich partial projections of the liquidus surface of five ternary systems, relevant to technological applications for lightweight materials. All phase diagrams are calculated from a coherent thermodynamic multicomponent database for magnesium alloys. These calculations are validated by key samples in the pertinent subsystems, including extensive ternary assessments and also quaternary work. Isothermal sections of magnesium-rich phase diagrams of alloys with constant aluminum and manganese content at 500°C and 550°C are given for the two five-component systems: Mg-Al-Mn-Ca-Sr and Mg-Al-Mn-Ca-Sn.

Gröbner, Joachim; Janz, Andres; Kozlov, Artem; Mirkovi?, Djordje; Schmid-Fetzer, Rainer

2008-12-01

123

Toward Solid-State Switchable Mirror Devices Using Magnesium-Rich Magnesium-Nickel Alloy Thin Films  

NASA Astrophysics Data System (ADS)

All-solid-state devices with switchable mirror properties based on magnesium-rich magnesium-nickel alloy thin films have been prepared using magnetron sputtering. The structure of the devices was a Mg-Ni alloy (40 nm)/Pd (4 nm)/Ta2O5 (200 nm)/HxWO3 (500 nm)/ITO on a glass. The composition of the alloy was Mg5Ni. In the initial state, the devices showed a shiny metallic front side and a deep blue back side, namely, in a reflective state. The optical transmittance of the devices at a wavelength of 670 nm was modulated between ˜0.3% (the reflective state) and ˜40% (the transparent state) by applying a voltage of ± 5 V between the ITO and the Mg-Ni alloy layer. The color of the portion changed to the transparent state was relatively neutral. The transition from the reflective state to the transparent state started from the fringe of the electric contact on the Mg-Ni alloy side, and the transparent region spread gradually.

Yamada, Yasusei; Tajima, Kazuki; Bao, Shanhu; Okada, Masahisa; Yoshimura, Kazuki

2007-08-01

124

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

2012-01-01

125

Numerical Modeling of Magnesium Alloy Sheet Metal Forming at Elevated Temperature  

NASA Astrophysics Data System (ADS)

The development of light-weight vehicle is in great demand for enhancement of fuel efficiency and dynamic performance. The vehicle weight can be reduced effectively by using lightweight materials such as magnesium alloys. However, the use of magnesium alloys in sheet forming processes is still limited because of their low formability at room temperature and the lack of understanding of the forming process of magnesium alloys at elevated temperatures. In this study, uniaxial tensile tests of the magnesium alloy AZ31B-O at various temperatures were performed to evaluate the mechanical properties of this alloy relevant for forming of magnesium sheets. To construct a FLD (forming limit diagram), a forming limit test were conducted at temperature of 100 and 200 °C. For the evaluation of the effects of the punch temperature on the formability of a rectangular cup drawing with AZ31B-O, numerical modelling was conducted. The experiment results indicate that the stresses and possible strains of AZ31B-O sheets largely depend on the temperature. The stress decreases with temperature increase. Also, the strain increase with temperature increase. The numerical modelling results indicate that formability increases with the decrease in the punch temperature at the constant temperature of the die and holder.

Lee, Myeong-Han; Kim, Heon-Young; Kim, Hyung-Jong; Choi, Yi-Chun; Oh, Soo-Ik

2007-05-01

126

Determination of oxygen content in magnesium and its alloys by inert gas fusion-infrared absorptiometry.  

PubMed

A method for the determination of the oxygen content in magnesium and magnesium alloys has been developed. Inert gas fusion-infrared absorptiometry was modified by introducing a multistep heating process; a sample containing oxygen is fused with tin to form an eutectic mixture at 900°C in a graphite crucible, followed by a subsequent gradual temperature increase of up to 2000°C, which enables the evaporation of magnesium from the mixture, and subsequent solidification at the rim of the crucible. Residual tin including magnesium oxide remained at the bottom of the crucible. The oxygen in the tin is measured by a conventional inert gas fusion (IGF) method. From a comparison with the results of charged particle activation analysis, the IGF method is considered to be an attractive candidate for measuring the oxygen content in Mg and its alloys. PMID:21747180

Tsuge, Akira; Achiwa, Hatsumi; Morikawa, Hisashi; Uemoto, Michihisa; Kanematsu, Wataru

2011-01-01

127

A new technology for the joining by forming of magnesium alloys  

Microsoft Academic Search

Joining by forming of magnesium alloys is restricted by the limited forming capability of magnesium at room temperature. To\\u000a form acceptable joints without cracks usually heating of the parts to temperatures of 220?C or more is required. The application\\u000a of state-of-the-art joining by forming methods (such as self-pierce-riveting or clinching with a contoured die) implicates\\u000a pre-heating times of at least

Reimund Neugebauer; Reinhard Mauermann; Stephan Dietrich; Christian Kraus

2007-01-01

128

Capacitance–voltage, current–voltage, and thermal stability of copper alloyed with aluminium or magnesium  

Microsoft Academic Search

Copper alloyed with small amounts of aluminium or magnesium has recently been suggested as a promising material for interconnect applications in silicon integrated circuits. This work reports the results of the investigation of the electrical (capacitance–voltage and current–voltage) stability of the metal–oxide–semiconductor capacitor made with copper–0.5 at.% aluminium and copper–2 at.% magnesium as metal, deposited on thermally oxidized silicon substrates.

T Suwwan de Felipe; S. P Murarka; S Bedell; W. A Lanford

1998-01-01

129

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

130

Formation mechanism of an aluminium-based chemical conversion coating on AZ91D magnesium alloy  

Microsoft Academic Search

An environmentally clean aluminium-based conversion coating on AZ91D magnesium alloy was studied in aluminium nitrate solutions.\\u000a The morphology, composition, structure, and formation mechanism of the coating were investigated in detail using scanning\\u000a electron microscopy\\/energy dispersion spectrometry, X-ray diffraction, transmission electron microscopy, and electrochemical\\u000a corrosion tests. The results show that the conversion coating is composed of magnesium, aluminium, and oxygen, and

Wei-Ping Li; Xi-Mei Wang; Li-Qun Zhu; Wen Li

2010-01-01

131

Impression Creep Behavior of a Cast AZ91 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The creep behavior of the cast AZ91 magnesium alloy was investigated by impression testing. The tests were carried out under constant punching stress in the range 100 to 650 MPa, corresponding to 0.007 ? ? imp/ G ? 0.044, at temperatures in the range 425 to 570 K. Assuming a power-law relationship between the impression velocity and stress, depending on the testing temperature, stress exponents of 4.2 to 6.0 were obtained. When the experimental creep rates were normalized to the grain size and effective diffusion coefficient, a stress exponent of approximately 5 was obtained, which is in complete agreement with stress exponents determined by the conventional creep testing of the same material reported in the literature. Calculation of the activation energy showed a slight decrease in the activation energy with increasing stress such that the creep-activation energy of 122.9 kJ/mol at ? imp/ G = 0.020 decreases to 94.0 kJ/mol at ? imp/ G = 0.040. Based on the obtained stress exponents and activation energy data, it is proposed that dislocation climb is the controlling creep mechanism. However, due to the decreasing trend of creep-activation energy with stress, it is suggested that two parallel mechanisms of lattice and pipe-diffusion-controlled dislocation climb are competing. To elucidate the contribution of each mechanism to the overall creep deformation, the creep rates were calculated based on the effective activation energy. This yielded a criterion that showed that, in the high-stress regimes, the experimental activation energies fall in the range in which the operative creep mechanism is dislocation climb controlled by dislocation pipe diffusion. In the low-stress regime, however, the lattice-diffusion dislocation climb is dominant.

Kabirian, F.; Mahmudi, R.

2009-01-01

132

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

Microsoft Academic Search

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

He Yang; Liang Huang; Mei Zhan

2010-01-01

133

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

Microsoft Academic Search

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

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

134

Corrosion resistance of a composite polymeric coating applied on biodegradable AZ31 magnesium alloy.  

PubMed

The high corrosion rate of magnesium alloys is the main drawback to their widespread use, especially in biomedical applications. There is a need for developing new coatings that provide simultaneously corrosion resistance and enhanced biocompatibility. In this work, a composite coating containing polyether imide, with several diethylene triamine and hydroxyapatite contents, was applied on AZ31 magnesium alloys pre-treated with hydrofluoric acid by dip coating. The coated samples were immersed in Hank's solution and the coating performance was studied by electrochemical impedance spectroscopy and scanning electron microscopy. In addition, the behavior of MG63 osteoblastic cells on coated samples was investigated. The results confirmed that the new coatings not only slow down the corrosion rate of AZ31 magnesium alloys in Hank's solution, but also enhance the adhesion and proliferation of MG63 osteoblastic cells, especially when hydroxyapatite nanoparticles were introduced in the coating formulation. PMID:23454214

Zomorodian, A; Garcia, M P; Moura E Silva, T; Fernandes, J C S; Fernandes, M H; Montemor, M F

2013-02-28

135

An organic chromium-free conversion coating on AZ91D magnesium alloy  

NASA Astrophysics Data System (ADS)

Traditional conversion coatings on magnesium alloys are usually immersed in a solution containing hexavalent chromium compounds. However, the replacement treatments have been proposed by the present environmental driving to eliminate hexavalent chromium. In this work, a tannic acid based conversion coating on AZ91D magnesium alloy was obtained by treatment in a solution containing tannic acid and ammonium metavanadate. SEM, XPS and IR were used to determine the morphology and structure of the conversion coatings. Continuous and uniform conversion coating was deposited on AZ91D alloy and the main components of the coatings were Al 2O 3, MgF 2 and penta-hydroxy benzamide-magnesium complex. The formation mechanism of the coating was discussed. Polarization measurement and salt spray test showed that the corrosion resistance of the conversion coating was much higher than that of traditional chromate conversion coating.

Chen, Xiaoming; Li, Guangyu; Lian, Jianshe; Jiang, Qing

2008-12-01

136

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

137

Growth of zinc phosphate coatings on AZ91D magnesium alloy  

Microsoft Academic Search

Zinc phosphate coating was formed on AZ91D magnesium alloy through a phosphating bath where H3PO4, ZnO, Zn(NO3)2 and NaF were applied. Chlorate (NaClO3) was used as an accelerator of phosphatization to replace nitrite. The coating compositions were hopeite (Zn3(PO4)2·4H2O) and Zn. The growth process of the phosphate film on the magnesium alloy substrate was investigated by SEM observation and XRD

G. Y. Li; J. S. Lian; L. Y. Niu; Z. H. Jiang; Q. Jiang

2006-01-01

138

Corrosion behaviors in physiological solution of cerium conversion coatings on AZ31 magnesium alloy  

NASA Astrophysics Data System (ADS)

We obtained the compact cerium conversion coating with tiny and thick cracks on biomaterial AZ31 magnesium alloys. The coating is made of CeO 2 , CeO, Ce 2 O 3 , MgO, Mg(OH) 2 and Al 2 O 3 . The conversion coating can slow down the degradation of magnesium alloys immersed in Hank's solution for 24 h. The degradation elements were the essential element and a platform for forming a natural bone. Cerium conversion coating had better corrosion resistance than bare sample via electrochemical tests in Hank's solution.

Cui, Xiufang; Yang, Yuyun; Liu, Erbao; Jin, Guo; Zhong, Jinggao; Li, Qingfen

2011-09-01

139

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

SciTech Connect

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 Al{sub 3}Sc (ordered L1{sub 2}) precipitates for grain structure stabilization and strengthening. Additional precipitation strengthening is required to raise their strength to levels sufficient for aircraft applications. The addition of lithium provides this additional strengthening through the formation of Al{sub 3}Li({delta}{prime}). To produce the alloys studied in this research, a unique induction melting furnace was constructed that incorporates special features to produce aluminum-lithium alloys with low hydrogen content. The furnace also features a water cooled, copper casting mold to achieve a moderately rapid solidification rate. This is because the amount of scandium used (0.5 wt %) is in excess of the solubility limit and Al{sub 3}Sc cannot be re-solutionized to any extent. It is therefore desired to super-saturate the matrix with as much scandium as possible for later precipitation. Two high lithium alloys were produced, ALS2 (nominal composition Al-2.2Li-O.5 Sc) and AlS4 (nominal composition Al-2.0Li-2.2Mg-0.5Sc) that were strengthened with {delta}{prime} (Al{sub 3}Li). These alloys exhibited strength and ductility superior to those of aluminum-lithium-(magnesium)-zirconium alloys. This is because the scandium containing alloys have developed a finer grain structure and the Al{sub 3}Sc precipitates contribute to the alloys strength. 41 refs., 29 figs.

Emigh, R.A.

1990-07-01

140

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

Microsoft Academic Search

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

Guangling Song; Birgir Johannesson; Sarath Hapugoda; David StJohn

2004-01-01

141

Mathematical modeling and experimental study of squeeze casting of magnesium alloy AM50A and aluminum alloy A356  

Microsoft Academic Search

In recent years, the squeeze casting process has been widely used with various aluminum alloys to manufacture near-net shape automotive components. Preliminary research has also demonstrated technical feasibility potential of squeeze casting for magnesium. A better understanding of squeeze casting process is essential for applying the process for the production of large automotive components, such as engine block, using aluminum

Fang Yu

2006-01-01

142

An Investigation to Double Hit Deformation Behavior of AZ31 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

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

Shamsi, M.; Hanzaki, A. Zarei; Naei, H.

2007-04-01

143

Evaluation of sliding wear behaviour of feldspar particle-reinforced magnesium alloy composites  

Microsoft Academic Search

The unlubricated sliding wear behavior of magnesium alloy AZ91 composites reinforced with feldspar particles of size 30–50 ?m was evaluated. The content of feldspar in the alloy was varied from 1% to 5% in steps of 2-wt.%. Liquid metallurgy technique was used to fabricate the composites. A pin-on-disc wear-testing machine was used to evaluate the wear rate, in which an

S. C Sharma; B Anand; M Krishna

2000-01-01

144

Eutectic bonding of austenitic stainless steel 316L to magnesium alloy AZ31 using copper interlayer  

Microsoft Academic Search

The eutectic bonding of magnesium alloy (AZ31) to austenitic stainless steel alloy (316L) was performed using pure Cu interlayers.\\u000a The effect of hold time on the microstructural developments across the joint region and the related effect on bond shear strength\\u000a were studied at a bonding temperature of 530°C. The bonding process took place through a sequential occurrence of solid-state\\u000a diffusion

Waled M. Elthalabawy; Tahir I. Khan

2011-01-01

145

Formability of AZ31 magnesium alloy sheets at warm working conditions  

Microsoft Academic Search

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

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

2006-01-01

146

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

147

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

148

Laser beam welding of AZ31B-H24 magnesium alloy.  

SciTech Connect

The laser beam weldability of AZ31B magnesium alloy was examined with high power CW CO{sub 2} and pulsed Nd:YAG lasers. The low viscosity and surface tension of the melt pool make magnesium more difficult to weld than steel. Welding parameters necessary to obtain good welds were determined for both CW CO{sub 2} and pulsed Nd:YAG lasers. The weldability of the magnesium alloy was significantly better with the Nd:YAG laser. The cause of this improvement was attributed to the higher absorption of the Nd:YAG beam. A lower threshold beam irradiance was required for welding, and a more stable weldpool was obtained.

Leong, K. H.

1998-09-29

149

Forming Prediction of Magnesium Alloy Sheets using a Continuum Damage Mechanics Multistep Inverse Approach  

SciTech Connect

This paper applies multistep inverse approach using a new method to generate the intermediate configurations to analyze the press forming of magnesium alloys. The developed approach considers a final configuration to be formed from a flat blank sheet. It accounts for a series of intermediate configurations that are estimated based on the initial and final configurations as well as tooling conditions using optimization techniques. The approach is based on the concept of minimization of the surface area of the sheet metal subject to the constraints that the punch and die surfaces are not penetrated. Due to the limited formability of magnesium alloys, it is important to realistically estimate the intermediate configurations so that a damage mechanics approach can be explored to predict damage accumulations that can cause rupture of the sheet during forming. Elastic-plastic constitutive laws are used with the modified Hill’s criterion and deformation theory of plasticity to describe the behavior of AZ31 magnesium alloys. Damage is captured by a damage variable that governs the equivalent stress. A damage-plasticity coupled approach is employed for the integration of the constitutive equations. The computed strain increment from two consecutive intermediate configurations is used to predict the resulting damage accumulations during forming. The continuum damage mechanics multistep inverse approach is applied to predict forming of AZ31 magnesium alloys.

Bapanapalli, Satish K.; Nguyen, Ba Nghiep

2008-06-30

150

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

SciTech Connect

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

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

2007-05-17

151

Study on DC Double Pulse Metal Inert Gas (MIG) Welding of Magnesium Alloy  

Microsoft Academic Search

This article gives a preliminary research on direct current (DC) double pulse metal inert gas (MIG) welding of magnesium alloys. It will be an effort for broadening the application of this new MIG welding process. The unique parameters of DC double pulse MIG welding are selected to investigate their effects on weld bead geometry size and appearance of AZ31B Mg

Zhaodong Zhang; Xiangyu Kong

2012-01-01

152

Evaluation of low cycle fatigue life in AZ31 magnesium alloy  

Microsoft Academic Search

Magnesium alloys are attracting engineers for their practical application to structural components. Here fatigue properties, which is essential for structural use, have been examined on extruded AZ31 bar under uniaxial cyclic loading by both strain and stress controlled conditions. Adding fatigue tests with mean stresses under stress controlling conditions, fatigue life evaluation method has been discussed along with the analysis

S. Hasegawa; Y. Tsuchida; H. Yano; M. Matsui

2007-01-01

153

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

154

Texture and microstructure changes in asymmetrically hot rolled AZ31 magnesium alloy sheets  

Microsoft Academic Search

Asymmetrically hot rolled AZ31 magnesium alloy sheets exhibited a texture gradient, where the intensity of {0002} basal textures decreased from the upper surface through the center to the lower surface. After subsequent annealing, the intensity of {0002} components was reduced significantly throughout the thickness and the grains were refined possibly by discontinuous recrystallization.

Su-Hyeon Kim; Bong-Sun You; Chang Dong Yim; Young-Myoung Seo

2005-01-01

155

Influence of process parameters on fluidity of investment-cast AZ91D magnesium alloy  

Microsoft Academic Search

Investment casting is a versatile and precise process, which allows the fabrication of components requiring intricate shapes, the filling of thin sections and the reproduction of fine details. It is also useful for casting magnesium alloy prototypes but little quantitative information is available about the relationships between process parameters and fluidity, which plays an important role in the successful production

S. Lun Sin; D. Dubé

2004-01-01

156

Press Forging of Magnesium-Alloy Notebook Case with Complex Geometry  

Microsoft Academic Search

Press forging is a process for forming bosses with thin sheet metals. In this work, press forging has been applied to manufacture magnesium-alloy notebook computer case with complex geometry, such as sidewalls, bosses, and hooks. Forming characteristics, influence of process parameters on metal flow, and forming defect are investigated by using both experimental approach and the finite element method (FEM).

Cheng Sun; Shi-hong Zhang; Wei-dong Tang; Zhong-tang Wang

2010-01-01

157

Microstructures and mechanical properties of resistance spot welded magnesium alloy joints  

Microsoft Academic Search

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

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

2007-01-01

158

Design factors influencing weldability of the Mg4Y-3RE cast magnesium alloy  

Microsoft Academic Search

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

A. Kierzek; J. Adamiec

2011-01-01

159

Tensile properties and microstructure of AZ31B magnesium alloy sheet processed by repeated unidirectional bending  

Microsoft Academic Search

The mechanical properties of the AZ31B magnesium alloy sheet processed by repeated unidirectional bending (RUB) with a basal pole tilted in the rolling direction were systematically investigated at different temperatures. Compared with the as-received sheet exhibiting approximately the same average grain size, the fracture elongation increased while the proof stress decreased at room temperature. The initial texture had a significant

Guang-sheng HUANG; Hong-cheng LI; Bo SONG; Lei ZHANG

2010-01-01

160

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

161

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

162

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

163

Magnesium  

MedlinePLUS

... is it? Magnesium is the fourth most abundant mineral in the body and is essential to good ... the water supply. Water that naturally contains more minerals is described as "hard". "Hard" water contains more ...

164

In vivo degradation of magnesium alloy LA63 scaffolds for temporary stabilization of biological myocardial grafts in a swine model.  

PubMed

Abstract Synthetic or biological patch materials used for surgical myocardial reconstruction are often fragile. Therefore, a transient support by degradable magnesium scaffolds can reduce the risk of dilation or rupture of the patch until physiological remodeling has led to a sufficient mechanical durability. However, there is evidence that magnesium implants can influence the growth and physiological behavior of the host's cells and tissue. Hence, we epicardially implanted scaffolds of the magnesium fluoride-coated magnesium alloy LA63 in a swine model to assess biocompatibility and degradation kinetics. Chemical analysis of the pigs' organs revealed no toxic accumulation of magnesium ions in the skeletal muscle, myocardium, liver, kidney, and bone of the pigs 1, 3, and 6 months postimplantation. The implants were surrounded by a fibrous granulation tissue, but no signs of necrosis were histologically evaluable. A sufficiently slow degradation rate of the magnesium alloy scaffold can be demonstrated via micro-computed tomography investigation. We conclude that stabilizing scaffolds of the magnesium fluoride-coated magnesium alloy LA63 can be used for epicardial application because no significant adverse effects to myocardial tissue were noted. Thus, degradable stabilizing scaffolds of this magnesium alloy with a slow degradation rate can extend the indication of innovative biological and synthetic patch materials. PMID:23989110

Schilling, Tobias; Brandes, Gudrun; Tudorache, Igor; Cebotari, Serghei; Hilfiker, Andres; Meyer, Tanja; Biskup, Christian; Bauer, Michael; Waldmann, Karl-Heinz; Bach, Friedrich-Wilhelm; Haverich, Axel; Hassel, Thomas

2013-10-01

165

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

166

Protective Coatings for Magnesium Alloys. Part 3. Coordination Chemistry of the Magnesium Ion.  

National Technical Information Service (NTIS)

The coordination chemistry of magnesium ions was studied with respect to neutral, but polar, unidentate ligands in the presence of various donor anions. Complexes of the type (MgLn)A2 were prepared. Chemical analysis, infrared spectral data, and electrica...

D. L. Venezky

1967-01-01

167

Microstructural development of diffusion-brazed austenitic stainless steel to magnesium alloy using a nickel interlayer  

SciTech Connect

The differences in physical and metallurgical properties of stainless steels and magnesium alloys make them difficult to join using conventional fusion welding processes. Therefore, the diffusion brazing of 316L steel to magnesium alloy (AZ31) was performed using a double stage bonding process. To join these dissimilar alloys, the solid-state diffusion bonding of 316L steel to a Ni interlayer was carried out at 900 deg. C followed by diffusion brazing to AZ31 at 510 deg. C. Metallographic and compositional analyses show that a metallurgical bond was achieved with a shear strength of 54 MPa. However, during the diffusion brazing stage B{sub 2} intermetallic compounds form within the joint and these intermetallics are pushed ahead of the solid/liquid interface during isothermal solidification of the joint. These intermetallics had a detrimental effect on joint strengths when the joint was held at the diffusion brazing temperature for longer than 20 min.

Elthalabawy, Waled M., E-mail: elthalabawy@hotmail.com [Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N1N4 (Canada); Khan, Tahir I. [Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N1N4 (Canada)

2010-07-15

168

The effect of PVD coatings on the wear behaviour of magnesium alloys  

SciTech Connect

In this study, AlN/TiN was coated on magnesium alloys using physical vapour deposition (PVD) technique of DC magnetron sputtering, and the influence of the coating on the wear behaviour of the alloys was examined. A physical vapour deposition system for coating processes, a reciprocating wear system for wear tests, a universal hardness equipment for hardness measurement, a X-ray diffractometer (XRD) for compositional analysis of the coating, and a scanning electron microscopy (SEM) for surface examinations were used. It was determined that the wear resistance of the magnesium alloys can be increased by PVD coatings. However, small structural defects which could arise from the coating process or substrate were observed in the coating layers.

Altun, Hikmet [Department of Mechanical Engineering, Ataturk University, 25240, Erzurum (Turkey)], E-mail: haltun@atauni.edu.tr; Sen, Sadri [Department of Mechanical Engineering, Ataturk University, 25240, Erzurum (Turkey)

2007-10-15

169

Research activities of biomedical magnesium alloys in China  

NASA Astrophysics Data System (ADS)

The potential application of Mg alloys as bioabsorable/biodegradable implants have attracted much recent attention in China. Advances in the design and biocompatibility evaluation of bio-Mg alloys in China are reviewed in this paper. Bio-Mg alloys have been developed by alloying with the trace elements existing in human body, such as Mg-Ca, Mg-Zn and Mg-Si based systems. Additionally, novel structured Mg alloys such as porous, composited, nanocrystalline and bulk metallic glass alloys were tried. To control the biocorrosion rate of bio-Mg implant to match the self-healing/regeneration rate of the surrounding tissue in vivo, surface modification layers were coated with physical and chemical methods.

Zheng, Yufeng; Gu, Xuenan

2011-04-01

170

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

PubMed

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

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

2013-01-01

171

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

172

Biocompatibility of rapidly solidified magnesium alloy RS66 as a temporary biodegradable metal.  

PubMed

Biodegradable magnesium-based alloys are very promising materials for temporary implants. However, the clinical use of magnesium-based alloys is often limited by rapid corrosion and by insufficient mechanical stability. Here we investigated RS66, a magnesium-based alloy with extraordinary physicochemical properties of high tensile strength combined with a high ductility and a homogeneous grain size of ?1?m which was obtained by rapid solidification processing and reciprocal extrusion. Using a series of in vitro and in vivo experiments, we analyzed the biodegradation behavior and the biocompatibility of this alloy. In vitro, RS66 had no cytotoxic effects in physiological concentrations on the viability and the proliferation of primary human osteoblasts. In vivo, RS66 cylinders were implanted into femur condyles, under the skin and in the muscle of adult rabbits and were monitored for 1, 2, 3, 4 and 8weeks. After explantation, the RS66 cylinders were first analyzed by microtomography to determine the remaining RS66 alloy and calculate the corrosion rates. Then, the implantation sites were examined histologically for healing processes and foreign body reactions. We found that RS66 was corroded fastest subcutaneously followed by intramuscular and bony implantation of the samples. No clinical harm with transient gas cavities during the first 6weeks in subcutaneous and intramuscular implantation sites was observed. No gas cavities were formed around the implantation site in bone. The corrosion rates in the different anatomical locations correlated well with the local blood flow prior to implantation. A normal foreign body reaction occurred in all tissues. Interestingly, no enhanced bone formation could be observed around the corroding samples in the condyles. These data show that RS66 is biocompatible, and due to its interesting physicochemical properties, this magnesium alloy is a promising material for biodegradable implants. PMID:23416472

Willbold, Elmar; Kalla, Katharina; Bartsch, Ivonne; Bobe, Katharina; Brauneis, Maria; Remennik, Sergei; Shechtman, Dan; Nellesen, Jens; Tillmann, Wolfgang; Vogt, Carla; Witte, Frank

2013-02-14

173

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

174

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

175

HYDRIDATION OF CERIUM ALLOYS WITH MAGNESIUM AND ALUMINUM  

Microsoft Academic Search

Hydridation of Ce - Mg- Al alloy at room temperature and normal pressure ; was studied with an alloy containing 70 to 90 wt% Ce. Maximum of hydrogen ; absorption was in the region of 5 to 10% Al and 35 to 80% Mg. An increased ; amount of Al in the Ce-- Mg system contributes to increased hydrogen absorption.

V. I. Mikheeva; Z. K. Sterlyadkina; A. A. CHertkov

1963-01-01

176

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

177

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

178

Comparison of corrosion pitting under immersion and salt-spray environments on an as-cast AE44 magnesium alloy  

Microsoft Academic Search

The corrosion mechanisms of pitting, intergranular corrosion, and general corrosion were examined on an AE44 magnesium alloy subjected to immersion and salt-spray environments. The two environments show similar trends with respect to weight loss and thickness loss, although the immersion environment induces greater amounts of weight loss of magnesium. With respect to the corrosion mechanisms, the two environments show definitive

Holly J. Martin; M. F. Horstemeyer; Paul T. Wang

2010-01-01

179

Corrosion relationships as a function of time and surface roughness on a structural AE44 magnesium alloy  

Microsoft Academic Search

Pit initiation, growth, and coalescence corrosion mechanisms of an AE44 magnesium alloy subjected to a salt-water environment were quantified. Stereological quantities were evaluated using optical microscopy, scanning electron microscopy, and laser beam profilometry. Three corrosion mechanisms clearly arose: pitting, intergranular, and general. Pitting began as the result of localized galvanic dissolution between the intermetallics and magnesium matrix. Intergranular corrosion arose

Roxanna B. Alvarez; Holly J. Martin; M. F. Horstemeyer; Mei. Q. Chandler; Neil Williams; Paul T. Wang; Augusto Ruiz

2010-01-01

180

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

181

Magnesium alloys as body implants: fracture mechanism under dynamic and static loadings in a physiological environment.  

PubMed

It is essential that a metallic implant material possesses adequate resistance to cracking/fracture under the synergistic action of a corrosive physiological environment and mechanical loading (i.e. stress corrosion cracking (SCC)), before the implant can be put to actual use. This paper presents a critique of the fundamental issues with an assessment of SCC of a rapidly corroding material such as magnesium alloys, and describes an investigation into the mechanism of SCC of a magnesium alloy in a physiological environment. The SCC susceptibility of the alloy in a simulated human body fluid was established by slow strain rate tensile (SSRT) testing using smooth specimens under different electrochemical conditions for understanding the mechanism of SCC. However, to assess the life of the implant devices that often possess fine micro-cracks, SCC susceptibility of notched specimens was investigated by circumferential notch tensile (CNT) testing. CNT tests also produced important design data, i.e. threshold stress intensity for SCC (KISCC) and SCC crack growth rate. Fractographic features of SCC were examined using scanning electron microscopy. The SSRT and CNT results, together with fractographic evidence, confirmed the SCC susceptibility of both smooth and notched specimens of a magnesium alloy in the physiological environment. PMID:22075121

Choudhary, Lokesh; Raman, R K Singh

2011-10-31

182

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

183

Magnesium–titanium alloy thin-film switchable mirrors  

Microsoft Academic Search

In this paper, we show gasochromic and electrochromic switching properties of Pd top capped magnesium–titanium (Mg–Ti) thin films prepared by DC magnetron sputtering. These films show excellent switchable mirror properties. By exposing to 4% H2 in Ar, Pd (4nm)\\/Mg0.82Ti0.18 (40nm) film changed from the metallic state to the transparent state drastically within 5s. By exposing to air, it goes back

S. Bao; K. Tajima; Y. Yamada; M. Okada; K. Yoshimura

2008-01-01

184

Correlation between the surface chemistry and the atmospheric corrosion of AZ31, AZ80 and AZ91D magnesium alloys  

NASA Astrophysics Data System (ADS)

X-ray photoelectron spectroscopy (XPS) was used in order to investigate the correlation between the surface chemistry and the atmospheric corrosion of AZ31, AZ80 and AZ91D magnesium alloys exposed to 98% relative humidity at 50 °C. Commercially pure magnesium, used as the reference material, revealed MgO, Mg(OH) 2 and tracers of magnesium carbonate in the air-formed film. For the AZ80 and AZ91D alloys, the amount of magnesium carbonate formed on the surface reached similar values to those of MgO and Mg(OH) 2. A linear relation between the amount of magnesium carbonate formed on the surface and the subsequent corrosion behaviour in the humid environment was found. The AZ80 alloy revealed the highest amount of magnesium carbonate in the air-formed film and the highest atmospheric corrosion resistance, even higher than the AZ91D alloy, indicating that aluminium distribution in the alloy microstructure influenced the amount of magnesium carbonate formed.

Feliu, S., Jr.; Pardo, A.; Merino, M. C.; Coy, A. E.; Viejo, F.; Arrabal, R.

2009-01-01

185

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

Microsoft Academic Search

In order to overcome the problem of the corrosion resistance of AZ31 magnesium alloy, the nanocrystalline Al2O3 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 Al2O3 film were analyzed by means of scanning electron microscopy equipped with an energy dispersive spectroscope, X-ray diffraction),

Chenghou Zhou; Jiang Xu; Shuyun Jiang

2010-01-01

186

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

2008-03-03

187

Synthesis and Characterization of Magnesium-Alloyed Hematite Thin Films  

NASA Astrophysics Data System (ADS)

We have synthesized pure and Mg-alloyed hematite thin films on F-doped, SnO2-coated glass substrates by radiofrequency magnetron cosputtering of iron oxide with and without MgO sources in mixed Ar/O2 and mixed N2/O2 ambient. We found that hematite films deposited in N2/O2 ambient exhibited much poorer crystallinity than those deposited in Ar/O2 ambient. We determined that Mg alloying led to increased crystallinity and bandgap. Furthermore, we found that Mg alloying inverted the type of conductivity of the thin films: pure hematite thin films exhibited n-type conductivity, whereas Mg-alloyed hematite thin films exhibited p-type conductivity.

Tang, Houwen; Matin, M. A.; Wang, Heli; Al-Jassim, Mowafak; Turner, John; Yan, Yanfa

2012-11-01

188

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

Microsoft Academic Search

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

Choong Do Lee; Choon Sik Kang; Kwang Seon Shin

2000-01-01

189

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

190

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

NASA Astrophysics Data System (ADS)

Thermal barrier coatings (TBCs) of zirconia stabilized by 8 wt.% yttria (8YSZ) on top of rare earth-magnesium alloy were fabricated by atmospheric plasma spraying. Three coatings were prepared by controlling the substrate temperature with different cooling media including cold water, compressed air, and natural cooling during deposition. The phase compositions, mechanical properties, and thermal shock resistance of these coatings were investigated. These coatings are very helpful to the improvement of corrosion and wear resistances and thermal protection of magnesium alloy. During plasma spraying, the substrate temperature affects the microstructure of substrate and the bonding strength between the coating and the substrate. The coating whose substrate was cooled by compressed air during plasma spraying has a good thermal shock resistance. The coating failure is mainly induced by the substrate oxidation and thermal expansion mismatch between the coating and the substrate.

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

2011-06-01

191

Biodegradation behavior of micro-arc oxidized AZ31 magnesium alloys formed in two different electrolytes  

NASA Astrophysics Data System (ADS)

Degradation behavior of coated magnesium alloys is among most prominent factors for their biomedical applications. In this study, bio-corrosion behavior of micro-arc oxidized magnesium AZ31 alloys formed in silicate and phosphate baths was investigated in r-SBF medium. For this purpose polarization behavior and open circuit profile of the coated samples were achieved by electrochemical and immersion tests, respectively. Moreover, the morphology and composition of the coatings were evaluated before and after immersion test using scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The results showed that the phosphate film had better corrosion resistance and greater thickness than silicate film and, in turn, the lesser degradability in SBF solution, so that Ca2+ and PO43- containing compounds were more abundant on silicate film than phosphate film. Moreover phosphate film had greater surface roughness and lesser hydrophilic nature.

Seyfoori, A.; Mirdamadi, Sh.; Khavandi, A.; Raufi, Z. Seyed

2012-11-01

192

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

193

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

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

194

Mechanism and Microstructure of Oxide Fluxes for Gas Tungsten Arc Welding of Magnesium Alloy  

Microsoft Academic Search

Five single oxide fluxes---MgO, CaO, TiO2, MnO2, and Cr2O3---were used to investigate the effect of active flux on the depth\\/width ratio in AZ31B magnesium alloy. The microstructure and mechanical property of the tungsten inert gas (TIG) welding seam were studied. The oxygen content in the weld seam and the arc images during the TIG welding process were analyzed. A series

L. M. Liu; Z. D. Zhang; G. Song; L. Wang

2007-01-01

195

Die design for stamping a notebook case with magnesium alloy sheets  

Microsoft Academic Search

In the present study, the stamping process for manufacturing a notebook top cover case with LZ91 magnesium–lithium alloy sheet at room temperature was examined using both the experimental approach and the finite element analysis. A four-operation stamping process was developed to eliminate both the fracture and wrinkle defects occurred in the stamping process of the top cover case. In order

Heng-Kuang Tsai; Chien-Chin Liao; Fuh-Kuo Chen

2008-01-01

196

Formation process of composite plasma electrolytic oxidation coating containing zirconium oxides on AM50 magnesium alloy  

Microsoft Academic Search

The formation processes of a composite ceramic coating on AM50 magnesium alloy prepared by plasma electrolytic oxidation (PEO) in a K2ZrF6 electrolyte solution were studied by scanning electron microscope (SEM) and energy dispersive X-ray spectroscope (EDX). Electrochemical impedance spectroscopy (EIS) tests were used to study the variation of the corrosion resistance of the coating during the PEO treatment. The results

Feng LIU; Da-yong SHAN; Ying-wei SONG; En-hou HAN

2011-01-01

197

Investigation of plasma electrolytic oxidation process on AZ91D magnesium alloy  

Microsoft Academic Search

Ceramic coatings oxidized for different time periods were prepared to characterize the plasma electrolytic oxidation (PEO) process of AZ91D magnesium alloy. The coatings were analyzed using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscope and potentiodynamic polarization measurement. The results show that the PEO coatings perform different growth behaviors at different PEO stages, and different morphologies are exhibited on ?-

Guo-Hua Lv; Huan Chen; L. Li; Er-Wu Niu; Huan Pang; Bin Zou; Si-Ze Yang

2009-01-01

198

Corrosion performance of plasma electrolytic oxidized AZ31 magnesium alloy in silicate solutions with different additives  

Microsoft Academic Search

In this work, plasma electrolytic oxidation coatings were produced on AZ31 magnesium alloy. The electrolytes used were mainly composed of silicate, silicate with addition of phosphate or fluoride, respectively. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and potentiodynamic polarization tests were carried out to investigate the microstructure, element composition, phase composition and corrosion resistance of

Huan Chen; GuoHua Lv; GuLing Zhang; Hua Pang; XingQuan Wang; HeonJu Lee; SiZe Yang

2010-01-01

199

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

200

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

201

Shot peening on the high-strength wrought magnesium alloy AZ80—Effect of peening media  

Microsoft Academic Search

Influence of shot peening media on fatigue performance of the high-strength wrought magnesium alloy AZ80 has been investigated at Almen intensities ranging from 0.04 to 0.4mmN. By the use of different peening media (including glass beads, Zirblast B30 and Ce-ZrO2 (ZrO2 beads stabilized by Ce)), the improvement of about 60–75% in fatigue strength was achieved at optimum conditions. Peening AZ80

P. Zhang; J. Lindemann; C. Leyens

2010-01-01

202

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

203

Fatigue strength of a magnesium MA2-1 alloy after equal-channel angular pressing  

NASA Astrophysics Data System (ADS)

The fatigue strength of a magnesium MA2-1 alloy is studied after annealing and equal-channel angular pressing (ECAP). The ultrafine-grained structure formed upon ECAP is shown to increase the plasticity of the material during static tension, to decrease the cyclic life to failure, and not to decrease the fatigue limit. The mechanisms of crack nucleation and growth during cyclic deformation are investigated.

Terent'ev, V. F.; Dobatkin, S. V.; Prosvirnin, D. V.; Bannykh, I. O.; Kopylov, V. I.; Serebryany, V. N.

2010-09-01

204

Surface analysis of the injection molded magnesium alloy using GD-OES  

Microsoft Academic Search

Glow Discharge Optical Emission Spectroscopy (GD-OES) was applied to analyze the surface structure of injection-molded AZ91D magnesium alloy products. The thickness of surface layer containing mold lubricant is approximately 300 nm. H and C elements are good indicators for monitoring the presence of mold lubricant. A chemical cleaning system based on acid etching, desmutting and neutralizing steps can provide the

Isao Nakatsugawa; Katsuyuki Araki; Hidenori Takayasu; Ken Saito; Kikuo Matsusaka; Toshio Endou; Azusa Shida

2003-01-01

205

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

206

The semi-solid tensile deformation behavior of wrought AZ31 magnesium alloy  

Microsoft Academic Search

The semi-solid tensile deformation behavior of wrought AZ31 magnesium alloy has been studied through applying a set of low strain rate (0.001s?1) hot tension tests at temperature range of 300–500°C. The results indicated a ductility drop at ?450±25°C. This was attributed to the occurrence of eutectic reaction (L??+?) and the partial melting of intermetallic ? phase. The ductility was started

H. R. Abedi; A. Zarei-Hanzaki; S. M. Fatemi-Varzaneh; Ali A. Roostaei

2010-01-01

207

Compressive strain-rate sensitivity of magnesium–aluminum die casting alloys  

Microsoft Academic Search

Compressive properties of three die cast magnesium alloys (AM20, AM50, and AM60) have been investigated at a nominal strain rate range from 0.001s?1 to approximately 1700s?1. The high strain rate experiments were conducted using a Split Hopkinson Bar apparatus. The strain rate sensitivity decreased with increasing Al content at the low strain rates. At strain rates above 1500s?1 there was

Wei Qian Song; Peter Beggs; Mark Easton

2009-01-01

208

OPTIMIZATION OF THE EXTRUSION PROCESS FOR MAGNESIUM ALLOY SHEETS USING THE FUZZY BASED TAGUCHI METHOD  

Microsoft Academic Search

By combining the fuzzy-logic method and Taguchi method, this study investigates the optimum parameters for the multiple performance characteristics index (MPCI) of the hot-extrusion process for magnesium alloy sheets of AZ31 and AZ61. Process parameters include billet heating temperature, initial extrusion speed, container temperature, and lubricant. Depending on individual quality characteristics, the optimal parameter combination for the Taguchi method would

Su-Hai Hsiang; Yi-Wei Lin

209

Effect of laser offsets on joint performance of laser penetration brazing for magnesium alloy and steel  

Microsoft Academic Search

The experiments of laser penetration brazing for magnesium alloy and steel were carried out, and the effect of laser offsets on mechanical properties and microstructure of the welds was investigated. In the range of 0.4–0.8mm, with the increase of laser offset, the tensile strength of the joints increased firstly and reduced afterward. In particular, at 0.6mm laser offset, the average

Yugang Miao; Duanfeng Han; Jingzheng Yao; Feng Li

2010-01-01

210

Influence of processing and reinforcement on microstructure and impact behaviour of magnesium alloy AM100  

Microsoft Academic Search

Reinforcing magnesium alloys with a discontinuously dispersed ceramic phase has engineered a new family of materials that\\u000a are marketed under the trade name “metal-matrix composites”. Continuous research efforts in the processing of these materials\\u000a have provided the necessary impetus for their emergence and use in structural, automotive and even aerospace-related components.\\u000a In this paper we report the results of a

S. Jayalakshmi; S. Seshan; S. V. Kailas; K. Kumar; S. Srivatsan

2004-01-01

211

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

Microsoft Academic Search

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

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

2010-01-01

212

Twinning effects in a rod-textured AM30 Magnesium alloy  

Microsoft Academic Search

We experimentally and numerically investigated the effect of twinning on plasticity using an extruded rod-textured magnesium alloy. The rod-texture is a ?101¯0?-axis fiber texture that presents a fundamentally different anisotropy correlated to twinning with respect to the widely discussed c-axis fiber texture generated by clock rolling. We quantified a profuse {101¯2}?101¯1? extension twinning along the extrusion direction (ED) that consumed

Q. Ma; H. El Kadiri; A. L. Oppedal; J. C. Baird; B. Li; M. F. Horstemeyer; S. C. Vogel

213

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

Microsoft Academic Search

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

Edward Ghali; Wolfgang Dietzel; Karl-Ulrich Kainer

2004-01-01

214

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

Microsoft Academic Search

Different types of PVD coatings and plasma treatments were applied for the surface treatment of magnesium die cast alloy AZ91 specimens. The different types of surface treatment were all developed by the authors and the fundamental properties are described elsewhere. The coating systems were:•9 ?m CrN hard coating•3 ?m TiN coating•0.5 ?m plasma anodisation layer and 3 ?m Al2O3 coatingThe

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

2005-01-01

215

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

216

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

217

Evaluation of corrosion resistance of casting magnesium alloy AZ31 in NaCl solutions  

NASA Astrophysics Data System (ADS)

The results of tests of corrosion resistance of casting magnesium alloy AZ31 in NaCl solutions of 0,01÷2 M concentration have been presented. Electrochemical measurements were carried out with application of VoltaLab®PGP201 system by Radiometer. On the ground of registered polarisation curves, typical features characterising alloy resistance to electrochemical corrosion, i.e. corrosion potential, polarisation resistance, corrosion current density and corrosion rate, were determined. Electrochemical impedance spectroscopy was applied for evaluation of phenomena that occurred on the surface of the tested alloy. Resistance to corrosion was tested by means of immersion method for 1÷5 days. By means of scanning electron microscope with field emission FE SEM S-4200 Hitachi in cooperation with spectrometer EDS Voyager 3500 Noran Instruments, quantitative and qualitative analysis of chemical composition in micro-zones was made. The study also presents the results of measurements of geometrical features of AZ31 alloy surface after corrosion tests. The results of the tests show undoubtedly deterioration of corrosion properties of magnesium alloy AZ31 together with the increase in molar concentration of NaCl solution.

Przondziono, J.; Walke, W.; Szala, J.; Hadasik, E.; Wieczorek, J.

2011-05-01

218

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

2012-10-10

219

Improvement on Magnesium Alloy Sheet Forming at Warm Temperatures by Computer Simulation and Experiment  

NASA Astrophysics Data System (ADS)

A proper forming temperature range was determined, and the effects of blank holding forces on the workpiece quality were analyzed by warm deep drawing of cups in magnesium alloy sheets. The conditions of process defects as flange wrinkling and ruptures were analyzed by computer simulation with explicit finite element method to optimize the process parameters. Therefore, appropriate process parameters were selected to avoid forming defects effectively. In the paper, a rigid blank holder was used to adjust blank holding forces. A special liquid lubricant PTFE was used on the tool surfaces. Efforts were made to optimize process parameters by analyzing the causes of defects in order to improve the Limit Drawing Ratio of magnesium alloy workpieces. It is found that rolled magnesium alloy sheets are of good deep drawing formability at a forming temperature range of 105-170°C with the higher Limit Drawing Ratio up to 2.44. It is also necessary to control the time of heating blanks. The formability will be reduced severely by excessive heating time.

Zhang, S. H.; Zhang, K.; Xu, Y. C.; Wang, Z. T.; Xu, Y.; Wang, Z. G.

2004-06-01

220

Lap Fillet Welding of Thin Sheet AZ31 Magnesium Alloy with Pulsed Nd:YAG Laser  

NASA Astrophysics Data System (ADS)

In recent years, reducing the size and weight of consumer products requires the joining of thin sheets of magnesium alloys with both thickness and joining area of less than 1mm, especially for packaging purposes. Conventional welding processes are difficult to joint a thin sheet magnesium alloy because of high heat input, which in turns leads to various problems such as burn through and cracks. In this study, lap fillet welding of thin sheet magnesium alloy AZ31B with a thickness of 0.3 mm has been carried out using a pulsed Nd:YAG laser beam. The influences of gap, laser beam center location and scan speed on joint appearances have been investigated. It was found that defects were significantly reduced when the gap width was less than 35 µm when the laser beam center was located just on the edge of the upper specimen (x=0), and scan speed was varied from 400 to 450 m/min. Wider bond width at average value of 300 µm was achieved when the beam center was at x=0 with a wide range of scan speeds from 250 to 450 mm/min compared with the cases at x=-0.1 and -0.2 mm from edge. Increases in bond width and minimal defects at x=0 improve fracture load by 68% compared with those at x=-0.1 mm.

Ishak, Mahadzir; Yamasaki, Kazuhiko; Maekawa, Katsuhiro

221

Strain-Controlled Low-Cycle Fatigue Properties of a Newly Developed Extruded Magnesium Alloy  

NASA Astrophysics Data System (ADS)

To reduce fuel consumption and greenhouse gas emissions, magnesium alloys are being considered for automotive and aerospace applications due to their low density, high specific strength and stiffness, and other attractive traits. Structural applications of magnesium components require low-cycle fatigue (LCF) behavior, since cyclic loading or thermal stresses are often encountered. The aim of this article was to study the cyclic deformation characteristics and evaluate LCF behavior of a recently developed AM30 extruded magnesium alloy. This alloy exhibited a strong cyclic hardening characteristic, with a cyclic strain-hardening exponent of 0.33 compared to the monotonic strain-hardening exponent of 0.15. With increasing total strain amplitude, both plastic strain amplitude and mean stress increased and fatigue life decreased. A significant difference between the tensile and compressive yield stresses occurred, leading to asymmetric hysteresis loops at high strain amplitudes due to twinning in compression and subsequent detwinning in tension. A noticeable change in the modulus was observed due to the pseudoelastic behavior of this alloy. The Coffin-Manson law and Basquin equation could be used to describe the fatigue life. At low strain ratios the alloy showed strong cyclic hardening, which became less significant as the strain ratio increased. The lower the strain ratio, the lower the stress amplitude and mean stress but the higher the plastic strain amplitude, corresponding to a longer fatigue life. Fatigue life also increased with increasing strain rate. Fatigue crack initiation occurred from the specimen surface and crack propagation was mainly characterized by striation-like features. Multiple initiation sites at the specimen surface were observed at higher strain amplitudes.

Begum, S.; Chen, D. L.; Xu, S.; Luo, Alan A.

2008-12-01

222

Effect of plasma electrolytic oxidation treatment on the corrosion and stress corrosion cracking behaviour of AM50 magnesium alloy  

Microsoft Academic Search

The effect of a silicate-based plasma anodization treatment on the corrosion and stress corrosion cracking behaviour of a cast AM50 magnesium alloy was studied. Electrochemical tests revealed the beneficial effect of the plasma electrolytic oxidation (PEO) in improving the corrosion resistance of the alloy. Although the coating had provided an improved resistance to stress corrosion cracking in this test environment

P. Bala Srinivasan; C. Blawert; W. Dietzel

2008-01-01

223

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

224

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

225

Microstructure and corrosion characteristics of laser-alloyed magnesium alloy AZ91D with Al Si powder  

NASA Astrophysics Data System (ADS)

Blown-powder laser surface alloying was performed on the magnesium alloy AZ91D with Al-Si alloy powder to improve corrosion resistance. Characterization by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD) analysis revealed that intermetallic compounds (IMCs) of Mg2Si, Al12Mg17 and Al3Mg2 were formed in the matrix of ?-Mg and Al solid solutions in Al-Si alloyed layers. The anodic polarization test in 3.5% NaCl aqueous solution showed that preferential corrosion occurred in the ?-Mg matrix of the AZ91D base metal. The Al-Si alloyed layers exhibited a lower corrosion rate and a higher polarization resistance than AZ91D. The compactly dispersed dendritic Mg2Si phase, and the dendritic and angular phases of Al12Mg17 and Al3Mg2 in the alloyed microstructure were observed to be corrosion-resistant, constituting a barrier that retards corrosion. Corrosion initiated at the interface between IMCs and the solid solution matrix, and at substructures of the matrix, subsequently pervaded into the surrounding microstructure.

Qian, Ming; Li, Da; Jin, Chang

2008-04-01

226

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

SciTech Connect

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

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

2010-12-01

227

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-6xZn-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.

2013-10-01

228

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

229

Modeling dynamic strain aging of aluminum-magnesium alloys  

NASA Astrophysics Data System (ADS)

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 this structure is rather low and it dissolves at room temperature when only dynamic associations of doublets or triples of solute atoms are observed. In presence of dislocations and at room temperature, Mg clusters at cores forming the coherent phase observed in the undistorted lattice at lower temperatures. The size, shape and structure of the cluster cannot be predicted by elementary calculations based on the pressure field generated by the unclustered dislocation. Then diffusion for Mg in Al-Mg alloys is investigated by Molecular Statics and the Nudged Elastic Band method. The activation energy for diffusion of Mg in the bulk is evaluated in the dilute solution limit for the nearest neighbor and the ring mechanisms. It is concluded that bulk diffusion at low and moderate temperatures must be assisted by vacancies. Further, diffusion of Mg along the core of edge, 60° and screw dislocations is studied. The vacancy formation energy in the core and the migration energy for vacancy-assisted Mg is evaluated for a large number of diffusion paths in the core region. The analysis shows that pipe diffusion; which is currently considered as the leading mechanism responsible for dynamic strain aging in these alloys, is too slow in absence of excess vacancies. Finally, the time-dependent Mg solute clustering process is studied using a continuum model calibrated based on atomistic information. The solute atmosphere around an edge dislocation is evaluated in terms of a chemical potential gradient, which is obtained from Monte-Carlo simulations. The solute clustering process is modeled by coupled diffusion-deformation partial differential equations (PDEs). The PDEs are implemented with a plane strain formulation and numerically solved with ABAQUS general purpose finite element program. The evolutions of cluster size and concentration at various selected sites are investigated.

Zhang, Dawei

230

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

231

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

232

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 4.2-295 K is studied as a function of its microstructure following squeeze casting (SC) and after severe plastic deformation (SPD) by hot rolling and equal-channel angular pressing. SPD reduces the average grain size and creates a texture that favors basal-plane dislocation glide. It is found that plastic deformation becomes unstable (serrated) at temperatures of 4.2-25 K 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<=100 K is independent of microstructure and is determined by intersections with forest dislocations. As the temperature is raised over 150-295 K 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

233

Fatigue of AZ91E-T6 cast magnesium alloy  

SciTech Connect

The purpose of this research was to obtain room temperature fatigue behavior of AZ91E-T6 cast magnesium alloy and to determine if commonly used models that depict fatigues behavior are applicable to this cast alloy. Axial strain-controlled fatigue behavior using cylindrical specimens were employed to determine low cycle fatigue behavior. The conventional log-log total strain low cycle fatigue model properly represented the R = [minus]1 axial fatigue data. Significant means stress relaxation occurred for all R = 0 and [minus]2 axial fatigue tests. However, for the smaller strain amplitude tests with R = 0, sufficient mean stresses were retained such that fatigue life was reduced. The mean strains/stresses had little influence on the cyclic stress-strain curve which exhibited cyclic strain hardening. Mean stress effects were analyzed using the Morrow, SWT and Lorenzo-Laird models and similar, but oftentimes nonconservative, calculations resulting. Region 1 and 2 fatigue crack growth behavior was determined using C(T) specimens with load ratios R = P[sub min]/P[sub max] = 0.05 and 0.5. The commonly used low cycle fatigue and fatigue crack growth models appear to reasonably represent most of the results with this AZ91E-T6 cast magnesium alloy.

Goodenberger, D.L.; Stephens, R.I. (Univ. of Iowa, Iowa City, IA (United States). Mechanical Engineering Dept.)

1993-10-01

234

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

235

Interface structure and fractography of a magnesium-alloy, metal-matrix composite reinforced with SiC particles  

Microsoft Academic Search

The interfacial structure in SiC-particle-reinforced, as-cast and heat-treated magnesium-alloy-matrix composites was investigated using analytical electron microscopy. No extensive chemical reactions were observed between the magnesium and the SiC particles or the SiC and the eutectic phase. However, most of the eutectic phase appeared to nucleate at the surface of the SiC particles. In addition to the lamellar eutectic, a fine

B. Inem; G. Pollard

1993-01-01

236

Evaluation of the anti-corrosive effect of acid pickling and sol–gel coating on magnesium AZ31 alloy  

Microsoft Academic Search

The effect of different acid pre-treatment procedures on the corrosion of magnesium AZ31 alloy was compared by measuring the amount of hydrogen gas formed when the surface was in contact with aqueous 5% sodium chloride solution. A 4–7?m thick sol–gel coating prepared by phosphoric acid catalyzed sol–gel processing of a methyltriethoxysilane\\/tetraethoxysilane mixture was applied to the differently pre-treated magnesium surfaces.

Ralf Supplit; Thomas Koch; Ulrich Schubert

2007-01-01

237

Pore formation during hybrid laser-tungsten inert gas arc welding of magnesium alloy AZ31B—mechanism and remedy  

Microsoft Academic Search

One of the major concerns during high speed welding of magnesium alloys is the presence of porosity in the weld metal that can deteriorate mechanical properties. This study seeks to analyze the presence method and quantity of pore during hybrid laser-tungsten inert gas arc (TIG) welding of magnesium alloy AZ31B by radiography, optical microscopy and electron probe microanalysis (EMPA). At

Liming Liu; Gang Song; Guoli Liang; Jifeng Wang

2005-01-01

238

The effect of current mode and discharge type on the corrosion resistance of plasma electrolytic oxidation (PEO) coated magnesium alloy AJ62  

Microsoft Academic Search

Magnesium alloys are increasingly being used as lightweight materials in the automotive, defense, electronics, biomaterial and aerospace industries. However, their inherently poor corrosion and wear resistance have, so far, limited their application. Plasma electrolytic oxidation (PEO) in an environmentally friendly aluminates electrolyte has been used to produce oxide coatings with thicknesses of ~80?m on an AJ62 magnesium alloy. Optical emission

R. O. Hussein; P. Zhang; X. Nie; Y. Xia; D. O. Northwood

239

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

240

Mechanism and Microstructure of Oxide Fluxes for Gas Tungsten Arc Welding of Magnesium Alloy  

Microsoft Academic Search

Five single oxide fluxes—MgO, CaO, TiO2, MnO2, and Cr2O3—were used to investigate the effect of active flux on the depth\\/width ratio in AZ31B magnesium alloy. The microstructure\\u000a and mechanical property of the tungsten inert gas (TIG) welding seam were studied. The oxygen content in the weld seam and\\u000a the arc images during the TIG welding process were analyzed. A series

L. M. Liu; Z. D. Zhang; G. Song; L. Wang

2007-01-01

241

Tribological Characteristics of Magnesium Alloy Using BN-Containing Additives under Boundary Lubricating Condition  

Microsoft Academic Search

\\u000a Three kinds of BN-containing compound have been synthesized and a stable ring of B with N coordination has been formed in\\u000a the molecule of borate esters. The BN-containing compounds and MoDTC were added into poly-alpha-olefin (PAO) as additives,\\u000a and then the friction and wear characters were evaluated with these four lubrications by sliding AZ91D magnesium alloy discs\\u000a against SAE52100 steel

Zhengfeng Jia; Yanqiu Xia; Weimin Liu; Bin Li

242

Thermal control coatings on magnesium alloys prepared by plasma electrolytic oxidation  

NASA Astrophysics Data System (ADS)

Four kinds of oxide coatings with different solar absorptance properties were prepared on AZ91D magnesium alloys by plasma electrolytic oxidation. They were of different colors due to the different additives in the electrolytes. The microstructure and composition were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The optical properties were investigated by the UV-VIS-NIR spectrophotometer, and the thermal control properties were measured by solar spectrum reflectometer as well as emissivity tester. Results showed that the solar absorptance of the coatings ranged from 0.439 to 0.918 while the emittance remained unchanged.

Wang, Lingqian; Zhou, Jiansong; Liang, Jun; Chen, Jianmin

2013-09-01

243

Influences of Welding Processes on Microstructure, Hardness, and Tensile Properties of AZ31B Magnesium Alloy  

NASA Astrophysics Data System (ADS)

This article reports the influences of welding processes such as gas tungsten arc welding (GTAW), friction stir welding (FSW), and laser beam welding (LBW) on tensile properties of AZ31B magnesium alloy. The lowest hardness distribution profile (LHDP) is constructed across the weld section to identify the fracture path. From this investigation, it is found that LBW joints exhibited superior tensile properties compared to GTAW and FSW joints and this is mainly due to the formation of very fine grains in the fusion zone and absence of heat-affected zone (HAZ).

Padmanaban, G.; Balasubramanian, V.; Sarin Sundar, J. K.

2010-03-01

244

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

245

A study and application of zinc phosphate coating on AZ91D magnesium alloy  

Microsoft Academic Search

A technology for obtaining the zinc phosphate coating on an AZ91D magnesium alloy was investigated. The main ingredients in the phosphating bath were H3PO4, ZnO and NaF. This coating has typical phosphate microstructure, and the compositions in this coating analyzed by XRD are Zn3(PO4)2·4H2O, Zn, AlPO4 and MgZn2(PO4)2. Scanning electron microscopy (SEM) has shown that very fine zinc particles surrounded

L. Y. Niu; Z. H. Jiang; G. Y. Li; C. D. Gu; J. S. Lian

2006-01-01

246

Temperature dependence of magnesium alloy spall strength in the temperature range of 90...750K  

NASA Astrophysics Data System (ADS)

The paper presents the results of studies of the temperature dependence behavior of magnesium alloy MA14T1 spall strength. The studies were performed using a light-gas gun by the impact method with the measurement of stress-waves profiles by a two-channel laser interferometer VISAR within one velocity loading range (~345 m/s). The temperature dependence of spall strength within the temperature range of 90°K...750°K was obtained. Changes in the shape and the amplitude of the elastic precursor in the specified temperature range were measured.

Pavlenko, Alexander; Malugina, Svetlana; Kazakov, D. N.; Bychkov, V. V.

2012-03-01

247

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.

2013-07-01

248

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

249

Biomimetic coating of magnesium alloy for enhanced corrosion resistance and calcium phosphate deposition.  

PubMed

Degradable metals have been suggested as biomaterials with revolutionary potential for bone-related therapies. Of these candidate metals, magnesium alloys appear to be particularly attractive candidates because of their non-toxicity and outstanding mechanical properties. Despite their having been widely studied as orthopedic implants for bone replacement/regeneration, their undesirably rapid corrosion rate under physiological conditions has limited their actual clinical application. This study reports the use of a novel biomimetic peptide coating for Mg alloys to improve the alloy corrosion resistance. A 3DSS biomimetic peptide is designed based on the highly acidic, bioactive bone and dentin extracellular matrix protein, phosphophoryn. Surface characterization techniques (scanning electron microscopy, energy dispersive X-ray spectroscopy and diffuse-reflectance infrared spectroscopy) confirmed the feasibility of coating the biomimetic 3DSS peptide onto Mg alloy AZ31B. The 3DSS peptide was also used as a template for calcium phosphate deposition on the surface of the alloy. The 3DSS biomimetic peptide coating presented a protective role of AZ31B in both hydrogen evolution and electrochemical corrosion tests. PMID:23816653

Cui, W; Beniash, E; Gawalt, E; Xu, Z; Sfeir, C

2013-06-29

250

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

251

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

252

A new approach coupled with the cellular automata to simulate the microstructural evolution of AM80 magnesium alloy  

NASA Astrophysics Data System (ADS)

Hot compression tests of AM80 magnesium alloy were performed on the Gleeble-1500 machine to obtain the flow curves under temperatures of 300, 350, and 400°C and strain rates of 0.01, 0.1 and 1s-1. The work hardening curves were predicted by the Avrami kinetic. A new approach, which considered the yield stress during compression, was used to simulate the microstructural evolution and the volume fraction recrystallized for AM80 magnesium alloy. The simulated results were in good agreement with experimental findings.

Liu, Xiao; Li, Luoxing; Zhu, Biwu

2013-05-01

253

CO 2 and diode laser welding of AZ31 magnesium alloy  

NASA Astrophysics Data System (ADS)

Magnesium alloys are being increasingly used in automotive and aerospace structures. Laser welding is an important joining method in such applications. There are several kinds of industrial lasers available at present, including the conventional CO 2 and Nd:YAG lasers as well as recently available high power diode lasers. A 1.5 kW diode laser and a 2 kW CO 2 laser are used in the present study for the welding of AZ31 alloys. It is found that different welding modes exist, i.e., keyhole welding with the CO 2 laser and conduction welding with both the CO 2 and the diode lasers. This paper characterizes welds in both welding modes. The effect of beam spot size on the weld quality is analyzed. The laser processing parameters are optimized to obtain welds with minimum defects.

Zhu, Jinhong; Li, Lin; Liu, Zhu

2005-07-01

254

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

255

Surface alloying of magnesium base alloys with high power CO2-laser  

Microsoft Academic Search

In addition to the well established processes of laser hardening of steel and laser remelting of cast iron, the laser surface modification of light metals finds more and more interest in the research community. While a lot of work concentrates on aluminum and titanium, only a few investigations on the laser treatment of magnesium are published. In this work the

R. Galun; Andreas Weisheit; Barry L. Mordike

1997-01-01

256

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

SciTech Connect

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

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

2005-08-05

257

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

258

Identification of an advanced constitutive model of Magnesium alloy AZ31B  

SciTech Connect

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 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 registered. 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. [CEMEF, Centre de Mise en Forme des Materiaux, Ecole Nationale Superieure des Mines de Paris 1, rue Claude Daunesse, BP 207, 06904, Sophia-Antipolis Cedex (France)

2011-05-04

259

Adsorption orientation of sodium of polyaspartic acid effect on anodic films formed on magnesium alloy  

NASA Astrophysics Data System (ADS)

We previously reported organic addition agent in improving the performance of anodic film formed on magnesium alloy. Here we report that the environment-friendly electrolyte with sodium of polyaspartic acid (PASP) affects the anodizing process including the microstructure, phase constituents and corrosion performance. We have used SEM, XRD, XPS and polarization curve to study in detail the electrolyte impact. Our results show that the anodic film in electrolyte with 19.2-28.8 g/L PASP is compact, smooth and high corrosion resistant. And also, increasing the PASP concentration ranging from 9.6 to 28.8 g/L results in enhancing the cell voltage, thickness and the content of compound including MgO and Mg 2SiO 4 in anodic film. Interestingly, the anodic film is non-stoichiometric oxide. Comparing with Tafel curves of the anodic film to the addition of PASP or not to, the corrosion current density is 1-2 magnitudes less than the later. Furthermore, a plausible model we propose that the anodizing process is regulated by two main plausible adsorption orientations of PASP at the surface anode. With the increasing of PASP content, the adsorption orientation may transit from "end-on" to "flat-on". This research using organic addition agent PASP may further broaden applications of organic additive in the anti-corrosion engineering and electrochemical surface treatment of magnesium alloy.

Liu, YuPing; Zhang, Dingfei; Chen, Changguo; Zhang, Jiangang; Cui, libo

2011-06-01

260

Microstructure control during twin roll casting of an AZ31 magnesium alloy  

NASA Astrophysics Data System (ADS)

The existing twin roll casting technique for magnesium alloys suffers heterogeneity in both microstructure and chemistry and downstream processing is required to improve the strip quality, resulting in cost rise. In the present work, twin roll casting was carried out using an AZ31 magnesium alloy, with the application of intensive shearing melt conditioning prior to casting. The effect of process parameters such as pouring temperature and casting speed on microstructure control during casting and subsequent downstream processing was studied. Experimental results showed that the melt conditioning treatment allowed the production of AZ31 strips with uniform and refined microstructure free of centreline segregations. It was also shown that an optimized combination of pouring temperature and casting speed, in conjunction with a strip thickness control operation, resulted in uniformly distributed stored energies due to enhanced plastic deformation, which promoted recrystallization during casting and subsequent heat treatment. Strips prepared by twin roll casting and homogenization developed similar microstructural features to those prepared by twin roll casting followed by lengthy downstream processing by homogenization, hot rolling and annealing and displayed a weaker basal texture, exhibiting a potentially better formability.

Huang, Y.; Bayandorian, I.; Fan, Z.

2012-01-01

261

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

SciTech Connect

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

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

2011-05-04

262

Surface modification of steels and magnesium alloy by high current pulsed electron beam  

NASA Astrophysics Data System (ADS)

High current pulsed electron beam (HCPEB) is now developing as a useful tool for surface modification of materials. When concentrated electron flux transferring its energy into a very thin surface layer within a short pulse time, superfast processes such as heating, melting, evaporation and consequent solidification, as well as dynamic stress induced may impart the surface layer with improved physico-chemical and mechanical properties. This paper presents our research work on surface modification of steels and magnesium alloy with HCPEB of working parameters as electron energy 27 keV, pulse duration ˜1 ?s and energy density ˜2.2 J/cm2 per pulse. Investigations performed on carbon steel T8, mold steel D2 and magnesium alloy AZ91HP have shown that the most pronounced changes of phase structure state and properties occurring in the near-surface layers, while the thickness of the modified layer with improved microhardness (several hundreds of micrometers) is significantly greater than that of the heat-affected zone. The formation mechanisms of surface cratering and non-stationary hardening effect in depth are discussed based on the elucidation of non-equilibrium temperature filed and different kinds of stresses formed during pulsed electron beam melting treatment. After the pulsed electron beam treatments, samples show significant improvements in measurements of wear and corrosion resistance.

Hao, Shengzhi; Gao, Bo; Wu, Aimin; Zou, Jianxin; Qin, Ying; Dong, Chuang; An, Jian; Guan, Qingfeng

2005-11-01

263

Semisolid die forging process, microstructures and properties of AZ31 magnesium alloy mobile telephone shells  

NASA Astrophysics Data System (ADS)

A semisolid slurry of AZ31 magnesium alloy was prepared by vibrating wavelike sloping plate process, and the semisolid die forging process, microstructures, and properties of the magnesium alloy mobile telephone shell were investigated. The semisolid forging process was performed on a YA32-315 four-column universal hydraulic press. The microstructures were observed by optical microscopy, the hardness was analyzed with a model 450SVD Vickers hardometer, the mechanical properties was measured with a CMT5105 tensile test machine, and the fractograph of elongated specimens was observed by scanning electron microscopy (SEM). The results reveal that with the increase of die forging force, the microstructures of the product become fine and dense. A lower preheating temperature and a longer dwell time are favorable to the formation of fine and dense microstructures. The optimum process conditions of preparing mobile telephone shells with excellent surface quality and microstructures are a die forging force of 2000 kN, a die preheating temperature of 250°C, and a dwell time of 240 s. After solution treatment at 430°C and aging at 220°C for 8 h, the Vickers hardness is 61.7 and the ultimate tensile strength of the product is 193 MPa. Tensile fractographs show the mixing mechanisms of quasi-cleavage fracture and ductile fracture.

Guan, Ren-Guo; Chen, Li-Qing; Cao, Fu-Rong; Zhao, Zhan-Yong; Ren, Yong

2011-12-01

264

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

265

Biocorrosion behavior and cell viability of adhesive polymer coated magnesium based alloys for medical implants  

NASA Astrophysics Data System (ADS)

The present study was ultimately aimed to design novel adhesive biodegradable polymer, poly(vinyl acetate) (PVAc), coatings onto Mg based alloys by the dip-coating technique in order to control the degradation rate and enhance the biocompatibility of magnesium alloys. The influence of various solvents on PVAc surface topography and their protection of Mg alloys were dramatically studied in vitro. Electrochemical polarization, degradation, and PVAc film cytocompatibility were also tested. Our results showed that the solvent had a significant effect on coating quality. PVAc/dichloromethane solution showed a porous structure and solution concentration could control the porous size. The coatings prepared using tetrahydrofuran and dimethylformamide solvents are exceptional in their ability to generate porous morphology even at low polymer concentration. In general, the corrosion performance appears to be different on different PVAc-solvent system. Immersion tests illustrated that the porous morphology on PVAc stabilized corrosion rates. A uniform corrosion attack in artificial simulation body fluid was also exhibited. The cytocompatibility of osteoblast cells (MC3T3) revealed high adherence, proliferation, and survival on the porous structure of PVAc coated Mg alloy, which was not observed for the uncoated samples. This novel PVAc coating is a promising candidate for biodegradable implant materials, which might widen the use of Mg based implants.

Abdal-hay, Abdalla; Dewidar, Montasser; Lim, Jae Kyoo

2012-11-01

266

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

267

Microstructure and creep behavior of magnesium-aluminum alloys containing alkaline and rare earth additions  

NASA Astrophysics Data System (ADS)

In the past few decades governmental regulation and consumer demands have lead the automotive companies towards vehicle lightweighting. Powertrain components offer significant potential for vehicle weight reductions. Recently, magnesium alloys have shown promise for use in powertrain applications where creep has been a limiting factor. These systems are Mg-Al based, with alkaline earth or rare earth additions. The solidification, microstructure, and creep behavior of a series of Mg-4 Al- 4 X:(Ca, Ce, La, and Sr) alloys and a commercially developed AXJ530 (Mg--5 Al--3 Ca--0.15 Sr) alloy (by wt%) have been investigated. The order of decreasing freezing range of the five alloys was: AX44, AXJ530, AJ44, ALa44 and ACe44. All alloys exhibited a solid solution primary alpha-Mg phase surrounded by an interdendritic region of Mg and intermetallic(s). The primary phase was composed of grains approximately an order of magnitude larger than the cellular structure. All alloys were permanent mold cast directly to creep specimens and AXJ530 specimens were provided in die-cast form. The tensile creep behavior was investigated at 175 °C for stresses ranging from 40 to 100 MPa. The order of decreasing creep resistance was: die-cast AXJ530 and permanent mold cast AXJ530, AX44, AJ44, ALa44 and ACe44. Grain size, solute concentration, and matrix precipitates were the most significant microstructural features that influenced the creep resistance. Decreases in grain size or increases in solute concentration, both Al and the ternary addition, lowered the minimum creep rate. In the Mg-Al-Ca alloys, finely distributed Al2Ca precipitates in the matrix also improved the creep resistance by a factor of ten over the same alloy with coarse precipitates. The morphology of the eutectic region was distinct between alloys but did not contribute to difference in creep behavior. Creep strain distribution for the Mg-Al-Ca alloys developed heterogeneously on the scale of the alpha-Mg grains. As additional bulk strain accumulated, strain localized along grain boundaries between grains with significantly different Schmid factors. At these locations cavities and cracks formed that led to the eventual creep failure. Grain size influenced the plastic strain distribution during creep.

Saddock, Nicholas David

268

Effect of Zr on the microstructure, mechanical properties and corrosion resistance of Mg–10Gd–3Y magnesium alloy  

Microsoft Academic Search

The influence of Zr on the microstructure, mechanical properties and corrosion resistance of Mg–10Gd–3Y (wt.%) magnesium alloy was investigated. The grain size of alloys decreased with Zr content from 0% to 0.93% (wt.%). The addition of Zr greatly improved the ultimate tensile strength (UTS) and the elongation (EL), while slightly improved the tensile yield strength (TYS). The UTS and the

Ming Sun; Guohua Wu; Wei Wang; Wenjiang Ding

2009-01-01

269

High Cycle Fatigue Properties of Die-Cast Magnesium Alloy AZ91D with Addition of Different Concentrations of Cerium  

Microsoft Academic Search

The effect of addition of different concentrations of Ce on high-cycle fatigue behavior of die-cast magnesium alloy AZ91D was investigated. Mechanical fatigue tests were conducted at the stress ratio of R = 0.1, and fatigue strength was evaluated using up-and-down loading method. The results show that the grain size of AZ91D alloy is remarkably refined, and the amount of porosity

You Yang; Yongbing Liu; Shuying Qin; Yi Fang

2006-01-01

270

Effect of the cooling rate in crystallization on the structural and phase state of deformable magnesium alloys  

Microsoft Academic Search

The traditional method of improving the mechanical properties of deformable magnesium alloys by using alloying components\\u000a has been studied quite well and its possibilities have been virtually exhausted. A new solution of the problem can be found\\u000a by using a nontraditional technology, in particular, one involving a super-high-speed crystallization. The present work concerns\\u000a the results of a study of the

E. F. Volkova; V. M. Lebedev; F. L. Gurevich

1998-01-01

271

Abnormal distribution of microhardness in tungsten inert gas arc butt-welded AZ61 magnesium alloy plates  

Microsoft Academic Search

In this study, the effects of heat input on the distribution of microhardness of tungsten inert gas (TIG) arc welded hot-extruded AZ61 magnesium alloy joints were investigated. The results show that with an increase of heat input, the distributions of microhardness at the top and bottom of the welded joints are different because they are determined by both the effect

Nan Xu; Jun Shen; Weidong Xie; Linzhi Wang; Dan Wang; Dong Min

2010-01-01

272

Plasma electrolytic oxidation of AM60 magnesium alloy: Monitoring by acoustic emission technique. Electrochemical properties of coatings  

Microsoft Academic Search

Magnesium alloy AM60 (6% Al) behaviour during Plasma Electrolytic Oxidation (PEO) was monitored by the Acoustic Emission (AE) technique. The process is divided into four stages, each one emitting characteristic acoustic signals. The following physical phenomena could be distinguished: bubbles during the conventional anodising step (stage 1), two discharge regimes, named microarc (stage 2) and arcing (stage 3) and film

M. Boinet; S. Verdier; S. Maximovitch; F. Dalard

2005-01-01

273

Electrochemical corrosion behaviour of plasma electrolytic oxidation coatings on AM50 magnesium alloy formed in silicate and phosphate based electrolytes  

Microsoft Academic Search

PEO coatings were produced on AM50 magnesium alloy by plasma electrolytic oxidation process in silicate and phosphate based electrolytes using a pulsed DC power source. The microstructure and composition of the PEO coatings were analyzed by scanning electron microscopy (SEM) and X-ray Diffraction (XRD). The corrosion resistance of the PEO coatings was evaluated using open circuit potential (OCP) measurements, potentiodynamic

J. Liang; P. Bala Srinivasan; C. Blawert; M. Störmer; W. Dietzel

2009-01-01

274

Growth process of plasma electrolytic oxidation films formed on magnesium alloy AZ91D in silicate solution  

Microsoft Academic Search

In order to get a clear picture for describing the growth process of the oxide film formed on magnesium alloy AZ91D under plasma electrolytic oxidation (PEO) in alkaline silicate solution, the characteristics of PEO films formed at different reaction stages were systemically investigated. The results of morphologies, compositions and electronic properties indicated that the PEO films had a different growth

Hongping Duan; Chuanwei Yan; Fuhui Wang

2007-01-01

275

Determination of an empirical law of aluminium and magnesium alloys absorption coefficient during Nd : YAG laser interaction  

Microsoft Academic Search

Welding laser modelling requires knowledge about relative changes of many thermo-physical parameters involved in the interaction. The absorptivity of the material is one of the most important. In this study, experimental measurements of absorptivity with an integrating sphere on two alloys (aluminium and magnesium) were made. These results were compared with an analytical calculation that takes into account the trapping

Nicolas Pierron; Pierre Sallamand; Jean-Marie Jouvard; Eugen Cicala; Simone Matteï

2007-01-01

276

The surface modified composite layer formation with boron carbide particles on magnesium alloy surfaces through pulse gas tungsten arc treatment  

Microsoft Academic Search

A novel fabrication process of surface modified composite layer by pulse current gas tungsten arc (GTA) surface modification process was used to deposit B4C particles on the surface of magnesium alloy AZ31. This method is an effective technique in producing a high performance surface modified composite layer. During the pulse current GTA surface modification process, considerable convection can exist in

W. B. Ding; H. Y. Jiang; X. Q. Zeng; D. H. Li; S. S. Yao

2007-01-01

277

ESEM observation of the process of hydrogen generation around the micro-droplets forming on AZ91 magnesium alloy  

Microsoft Academic Search

The process of hydrogen generation around micro-droplets on as-cast AZ91 magnesium alloy in an atmosphere of water vapor was in situ observed using an environmental scanning electron microscope (ESEM). The procedure for hydrogen generation was described. It indicated that the cathodic or anodic location gradually changed with the generation of hydrogen bubbles and the formation of corrosion products.

Jian Chen; Jianqiu Wang; Enhou Han; Wei Ke

2008-01-01

278

Effect of temperature of differential speed rolling on room temperature mechanical properties and texture in an AZ31 magnesium alloy  

Microsoft Academic Search

Differential speed rolling (DSR) was applied to the AZ31 magnesium alloy, intended to modify the texture and thus to enhance the room temperature ductility. Especially, effect of DSR temperature on resulting room temperature tensile properties and texture was investigated at a fixed rolling speed ratio of 1.1. The strength was not affected by the rolling temperature: the yield strength and

Hiroyuki Watanabe; Toshiji Mukai; Koichi Ishikawa

2007-01-01

279

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

280

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

SciTech Connect

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

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

2007-05-17

281

In situ spectroscopic ellipsometry study of the hydrogenation process of switchable mirrors based on magnesium-nickel alloy thin films  

Microsoft Academic Search

The hydrogenation process of switchable mirrors using magnesium-nickel alloy thin films including a thin palladium cap layer was analyzed by measuring the variation in ellipsometric angles Psi and Delta using in situ spectroscopic ellipsometry. The process was divided into three phases and each phase was identified as follows. The first phase was the process in which the solid solution was

Y. Yamada; S. Bao; K. Tajima; M. Okada; M. Tazawa; A. Roos; K. Yoshimura

2010-01-01

282

Stability of body-centered cubic iron-magnesium alloys in the Earth's inner core  

PubMed Central

The composition and the structure of the Earth's solid inner core are still unknown. Iron is accepted to be the main component of the core. Lately, the body-centered cubic (bcc) phase of iron was suggested to be present in the inner core, although its stability at core conditions is still in discussion. The higher density of pure iron compared with that of the Earth's core indicates the presence of light element(s) in this region, which could be responsible for the stability of the bcc phase. However, so far, none of the proposed composition models were in full agreement with seismic observations. The solubility of magnesium in hexagonal Fe has been found to increase significantly with increasing pressure, suggesting that Mg can also be an important element in the core. Here, we report a first-principles density functional study of bcc Fe–Mg alloys at core pressures and temperatures. We show that at core conditions, 5–10 atomic percent Mg stabilizes the bcc Fe both dynamically and thermodynamically. Our calculated density, elastic moduli, and sound velocities of bcc Fe–Mg alloys are consistent with those obtained from seismology, indicating that the bcc-structured Fe–Mg alloy is a possible model for the Earth's inner core.

Kadas, Krisztina; Vitos, Levente; Johansson, Borje; Ahuja, Rajeev

2009-01-01

283

Parametric Study of Friction Stir Processing of Magnesium-Based AE42 Alloy  

NASA Astrophysics Data System (ADS)

Friction stir processing (FSP) is one of the severe plastic deformation processes which can significantly affect the material properties. The friction stir processed (FSPed) zone is extremely sensitive to the FSP parameters. The main aim of the current investigation is to analyze the simultaneous influence of the major FSP parameters on the mechanical behavior of a magnesium-based AE42 alloy. In this investigation, Taguchi's experimental design approach was utilized to determine the optimized set of investigated FSP parameters for processing the AE42 alloy. Hardness of the FSPed specimens was considered as the output response of the experimental design. Cooling temperature during FSP, FSP tool rotational speed, and number of FSP passes were found to be the most influential FSP parameters in the current investigation. A nonlinear regression equation for the output response and the FSP process parameters was also developed using MINITAB 16 software. The developed equation was found to accurately predict the output response of the FSPed AE42 alloy

Arora, H. S.; Singh, H.; Dhindaw, B. K.

2012-11-01

284

Grain refinement of DC cast magnesium alloys with intensive melt shearing  

NASA Astrophysics Data System (ADS)

A new direct chill (DC) casting process, melt conditioned DC (MC-DC) process, has been developed for the production of high quality billets/slabs of light alloys by application of intensive melt shearing through a rotor-stator high shear device during the DC casting process. The rotor-stator high shear device provides intensive melt shearing to disperse the naturally occurring oxide films, and other inclusions, while creating a microscopic flow pattern to homogenize the temperature and composition fields in the sump. In this paper, we report the grain refining effect of intensive melt shearing in the MC-DC casting processing. Experimental results on DC casting of Mg-alloys with and without intensive melt shearing have demonstrated that the MC-DC casting process can produce magnesium alloy billets with significantly refined microstructure. Such grain refinement in the MC-DC casting process can be attributed to enhanced heterogeneous nucleation by dispersed naturally occurring oxide particles, increased nuclei survival rate in uniform temperature and compositional fields in the sump, and potential contribution from dendrite arm fragmentation.

Zuo, Y. B.; Jiang, B.; Zhang, Y.; Fan, Z.

2012-01-01

285

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

SciTech Connect

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

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

2011-05-04

286

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

287

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

SciTech Connect

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 [Center for Advanced Die Engineering and Technology, Gifu University, Yanagido Gifu, 501-1193 (Japan); Hattori, Toshio [Department of Mechanical and Systems Engineering, Gifu University, ditto. (Japan); Sato, Joji [Research Institute for Machinery and Materials, Gifu Prefectural Government, 1288 Oze Seki, 501-3265 (Japan)

2011-01-17

288

Optical properties of switchable mirrors based on magnesium-calcium alloy thin films  

NASA Astrophysics Data System (ADS)

Switchable mirrors based on magnesium-calcium alloy thin films were prepared using a direct-current magnetron sputtering method and their gasochromic properties have been investigated. Pd-capped Mg1-zCaz (0.04

Yamada, Y.; Bao, S.; Tajima, K.; Okada, M.; Yoshimura, K.

2009-05-01

289

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

SciTech Connect

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

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

2008-01-01

290

Macro- and Microstructural Studies of Laser-Processed WE43 (Mg-Y-Nd) Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The macro- and microstructural changes in the fusion zone (FZ) of WE43 magnesium alloy processed by a diode-pumped ytterbium (IPG YLS-3000) continuous wave fiber laser for specified processing conditions (from 4.17 to 12.5 × 107 J/m2) were studied. With the aid of computational heat-transfer model, the temperature history and cooling rate were determined for different laser-processing conditions. The computational heat-transfer results of laser-processed samples were used to correlate with microstructures characterized using optical, scanning, and transmission electron microscopies, and electron backscatter and X-ray diffraction analyses. The microhardness measurement was carried out to establish the structure-property relationship, and the results indicated that the minimal hardness variation (1 pct) within laser FZ was due to a constant heat extraction time (0.1 second), narrow variation in grain size (4 to 7 ?m), and the type of precipitate (?-phase) formation.

Santhanakrishnan, S.; Kumar, N.; Dendge, N.; Choudhuri, D.; Katakam, S.; Palanivel, S.; Vora, H. D.; Banerjee, R.; Mishra, R. S.; Dahotre, Narendra B.

2013-10-01

291

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

PubMed

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

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

2012-11-05

292

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

293

Fatigue Lives and Crack Propagation Behavior of the Extruded Magnesium Alloy Processed under Various Extrusion Conditions  

NASA Astrophysics Data System (ADS)

The fatigue properties of extruded magnesium alloy AZ31 were evaluated using material processed under two different extrusion ratios and two different extrusion temperatures. The effect of the extrusion ratios and extrusion temperatures on the fatigue lives and crack propagation behavior is discussed. The fatigue crack initiation and propagation processes were observed by the replica method. It was found that cracks initiated early in the fatigue process, and therefore the total fatigue life can be approximated as the crack propagation life. The crack propagation behavior observed in those materials was analyzed using a modified linear elastic fracture mechanics parameter, M. The relation crack propagation rate vs. M parameter was found to be useful in predicting fatigue lives and crack propagation curves.

Ishihara, Sotomi; McEvily, Arthur J.; Sato, Masanori; Shibata, Hiroshi; Goshima, Takahito; Shimizu, Masayoshi

294

Transition of dominant diffusion process during superplastic deformation in AZ61 magnesium alloys  

NASA Astrophysics Data System (ADS)

The superplastic behavior of the AZ61 magnesium alloy sheet, processed by one-step hot extrusion and possessing medium grain sizes of ˜12 µm, has been investigated over the temperature range of 523 to 673 K. The highest superplastic elongation of 920 pct was obtained at 623 K and a deformation rate of 1×10-4 s-1. In the lower and higher strain rate regimes, with apparent m values of ˜0.45 and ˜0.25, respectively, grain-boundary sliding (GBS) and dislocation creep appeared to dominate the deformation, consistent with the scanning electron microscopy (SEM) examination. The SEM examination also revealed that individual GBS started to operate from the very initial deformation stage in the strain rate range with m˜0.45, which was attributed to the relatively high fraction (88 pct) of high-angle boundaries. The analyses of the superplastic data over 523 to 673 K and 5×10-5 to 1×10-3 s-1 revealed a true stress exponent of ˜2, and the activation energy was close to that for grain-boundary and lattice diffusion of magnesium at 523 to 573 K and 573 to 673 K, respectively. The transition temperature of activation energy is ˜573 K, which is attributed to the change in the dominant diffusion process from grain-boundary diffusion to lattice diffusion. It is demonstrated that the effective diffusion coefficient is a valid parameter to characterize the superplastic behavior and the dominant diffusion process.

Wang, Y. N.; Huang, J. C.

2004-02-01

295

Laser Keyhole Welding of Dissimilar Ti-6Al-4V Titanium Alloy to AZ31B Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Laser keyhole welding of Ti-6Al-4V titanium alloy to AZ31B magnesium alloy was developed, and the correlations of process parameters, joint properties, and bonding mechanism were studied. The results show that the offset from the laser beam center on AZ31B side to the edge of the weld seam plays a big role in the joint properties by changing the power density irradiated at the Ti-Mg initial interface. The optimal range of the offset is 0.3 to 0.4mm in the present study. Some lamellar and granular Ti-rich mixtures are observed in the fusion zone, which is formed by intermixing melted Ti-6Al-4V with liquid AZ31B. The maximum ultimate tensile strength of the joints reaches 266 MPa. Furthermore, the fracture surface consists of scraggly remaining weld metal and smooth Ti surface. The higher the failure strength, the smaller the proportion of smooth Ti surface to whole interface is. Finally, the bonding mechanism of the interfacial layer is summarized by the morphologies and test results of fracture surfaces.

Gao, M.; Wang, Z. M.; Li, X. Y.; Zeng, X. Y.

2012-01-01

296

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

297

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

298

Electrolytic magnesium production and its hydrodynamics by using an Mg–Pb alloy cathode  

Microsoft Academic Search

Physical interaction of magnesium and chlorine was minimized by collecting magnesium in a molten Pb cathode at the bottom of the electrolyte and placing anode at the top where the chlorine gas was evolved. Thus the magnesium losses associated with the formation of suspending droplets and fine magnesium particles were eliminated and current losses were mainly due to the recombination

Gökhan Demirci; ?shak Karakaya

2008-01-01

299

Porosity, underfill and magnesium loss during continuous wave Nd:YAG laser welding of thin plates of aluminum alloys 5182 and 5754  

Microsoft Academic Search

The influence of various welding parameters on porosity and underfill formation and magnesium loss during continuous wave Nd:YAG laser beam welding of thin plates of aluminum-magnesium Alloys 5182 and 5754 was investigated. The porosity within the welds was characterized by radiography, optical microscopy and SEM. The compositional change in the welds was measured by electron microprobe analysis. The experimental results

M. Pastor; H. Zhao; R. P. Martukanitz; T. Debroy

1999-01-01

300

Corrosion protection and improved cytocompatibility of biodegradable polymeric layer-by-layer coatings on AZ31 magnesium alloys.  

PubMed

Composite coatings of electrostatically assembled layer-by-layer anionic and cationic polymers combined with an Mg(OH)2 surface treatment serve to provide a protective coating on AZ31 magnesium alloy substrates. These ceramic conversion coating and layer-by-layer polymeric coating combinations reduced the initial and long-term corrosion progression of the AZ31 alloy. X-ray diffraction and Fourier transform infrared spectroscopy confirmed the successful application of coatings. Potentiostatic polarization tests indicate improved initial corrosion resistance. Hydrogen evolution measurements over a 2week period and magnesium ion levels over a 1week period indicate longer range corrosion protection and retention of the Mg(OH)2 passivation layer in comparison to the uncoated substrates. Live/dead staining and DNA quantification were used as measures of biocompatibility and proliferation while actin staining and scanning electron microscopy were used to observe the cellular morphology and integration with the coated substrates. The coatings simultaneously provided improved biocompatibility, cellular adhesion and proliferation in comparison to the uncoated alloy surface utilizing both murine pre-osteoblast MC3T3 cells and human mesenchymal stem cells. The implementation of such coatings on magnesium alloy implants could serve to improve the corrosion resistance and cellular integration of these implants with the native tissue while delivering vital drugs or biological elements to the site of implantation. PMID:23684762

Ostrowski, Nicole; Lee, Boeun; Enick, Nathan; Carlson, Benjamin; Kunjukunju, Sangeetha; Roy, Abhijit; Kumta, Prashant N

2013-05-16

301

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

2009-12-04

302

The electroless nickel-plating on magnesium alloy using NiSO 4·6H 2O as the main salt  

Microsoft Academic Search

In this paper, the electroless nickel-plating on magnesium alloy was studied, using NiSO4·6H2O as the main salt in the electroless plating alkaline solutions. The effects of the buffer agent and plating parameters on the properties and structures of the plating coatings on magnesium alloy were investigated by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray

Jianzhong Li; Zhongcai Shao; Xin Zhang; Yanwen Tian

2006-01-01

303

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

304

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

305

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

SciTech Connect

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; Peng Yinghong [School of Mechanical and Power Engineering, Shanghai Jiaotong University, 800 Dongchuan Road, Shanghai (China); State Key Laboratory of Mechanical System and Vibration, Shanghai Jiaotong University, 800 Dongchuan Road, Shanghai (China); Zhang Shaorui; Tang Weiqin; Huang Shiyao [School of Mechanical and Power Engineering, Shanghai Jiaotong University, 800 Dongchuan Road, Shanghai (China)

2010-06-15

306

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

SciTech Connect

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

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

2008-08-15

307

Corrosion behavior of the composite ceramic coating containing zirconium oxides on AM30 magnesium alloy by plasma electrolytic oxidation  

Microsoft Academic Search

The deterioration process of a plasma electrolytic oxidation (PEO) coating containing zirconium oxides on AM30 magnesium alloy in 3.5wt.% NaCl solution have been investigated. The coating consists of an outer porous layer and an inner dense layer. The content of MgF2 is high in the pores and an MgO-rich layer is evident in the inner layer. The corrosion resistance of

Feng Liu; Dayong Shan; Yingwei Song; En-Hou Han; Wei Ke

2011-01-01

308

Effect of current density on the microstructure and corrosion behaviour of plasma electrolytic oxidation treated AM50 magnesium alloy  

Microsoft Academic Search

Plasma electrolytic oxidation (PEO) of an AM50 magnesium alloy was accomplished in a silicate-based electrolyte using a DC power source. Coatings were produced at three current densities, i.e. 15mAcm?2, 75mAcm?2, and 150mAcm?2 and were characterised for thickness, roughness, microstructural morphology, phase composition, and corrosion resistance. Even though the 15min treated coatings produced at higher current density levels were thicker, they

P. Bala Srinivasan; J. Liang; C. Blawert; M. Störmer; W. Dietzel

2009-01-01

309

Effect of potassium fluoride on structure and corrosion resistance of plasma electrolytic oxidation films formed on AZ31 magnesium alloy  

Microsoft Academic Search

Plasma electrolytic oxidation films on AZ31 magnesium alloy were prepared in silicate–KOH–glycol (base electrolyte) electrolyte with the addition of different KF concentration. The effect of KF on the characteristic of discharge in electrolytes was studied. The compositions, structures and morphologies of the oxide films formed in different KF concentration were determined by energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD)

Li Wang; Li Chen; Zongcheng Yan; Honglin Wang; Jiazhi Peng

2009-01-01

310

Effect of plasma electrolytic oxidation coating on the stress corrosion cracking behaviour of wrought AZ61 magnesium alloy  

Microsoft Academic Search

An attempt was made to understand the effect of silicate based plasma electrolytic oxidation (PEO) coating on the stress corrosion cracking (SCC) behaviour of an AZ61 wrought magnesium alloy. The SCC behaviour of untreated and PEO coated specimens was assessed using slow strain rate tensile tests at two different nominal strain rates, viz. 1×10?6s?1 and 1×10?7s?1, in ASTM D1384 test

P. Bala Srinivasan; C. Blawert; W. Dietzel

2008-01-01

311

Effect of electrolyte additives on performance of plasma electrolytic oxidation films formed on magnesium alloy AZ91D  

Microsoft Academic Search

Various plasma electrolytic oxidation (PEO) films were prepared on magnesium alloy AZ91D in a silicate bath with different additives such as phosphate, fluoride and borate. Effects of the additives on chemical composition and corrosion resistance of the PEO films were examined by means of scanning electron microscopy (SEM), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. The

Hongping Duan; Chuanwei Yan; Fuhui Wang

2007-01-01

312

Investigation of plasma electrolytic oxidation processes of magnesium alloy MA2-1 under pulse polarisation modes  

Microsoft Academic Search

Process of plasma electrolytic oxidation (PEO) of magnesium alloy MA2-1 in an electrolyte containing sodium hydroxide and sodium tri-polyphosphate was investigated. The use of pulse shape of polarising current in both positive and negative semi-periods significantly improved efficiency of coating deposition, which is connected with increase in number of microdischarges on the article surface and intensification of plasma chemical synthesis

A. V. Timoshenko; Yu. V. Magurova

2005-01-01

313

Preparation and characterization of oxide films containing crystalline TiO 2 on magnesium alloy by plasma electrolytic oxidation  

Microsoft Academic Search

Oxide films have been produced on AM60B magnesium alloy using plasma electrolytic oxidation process in an alkaline phosphate electrolyte with and without addition of titania sol. The microstructure and composition of the oxide films were analyzed by Scanning Electron Microscope (SEM), X-ray Photoelectron Spectroscope (XPS) and X-ray Diffraction (XRD). The corrosion resistances of the oxide films were evaluated using potentiodynamic

Jun Liang; Litian Hu; Jingcheng Hao

2007-01-01

314

Investigation of minimum creep rates and stress exponents calculated from tensile and compressive creep data of magnesium alloy AE42  

Microsoft Academic Search

Creep specimens prepared of magnesium alloy AE42 were investigated under constant load in compressive and in tensile creep. Material was cast via the squeeze casting process in order to obtain a dense microstructure without pores. Creep tests were performed at constant temperatures between 150°C and 240°C and constant applied stresses between 40MPa and 120MPa until a minimum creep rate was

Hajo Dieringa; Norbert Hort; Karl Ulrich Kainer

2009-01-01

315

Influence of shot peening on notched fatigue strength of the high-strength wrought magnesium alloy AZ80  

Microsoft Academic Search

Influence of shot peening (SP) on notched fatigue strength of the high-strength wrought magnesium alloy AZ80 has been investigated by using different SP media (including glass, Zirblast B30 and Ce–ZrO2 (ZrO2 stabilized by Ce) shots) and various Almen intensities. The results showed that shot peening improved the notched fatigue strength of AZ80 more effectively than the un-notched fatigue strength. The

P. Zhang; J. Lindemann; C. Leyens

2010-01-01

316

Electroless nickel-plating on AZ91D magnesium alloy: effect of substrate microstructure and plating parameters  

Microsoft Academic Search

Electroless nickel-plating on AZ91D magnesium alloy has been investigated to understand the effect of substrate microstructure and plating parameters. The initial stage of the deposition was investigated using scanning electron microscopy (SEM) and energy dispersive X-ray analysis on substrates plated for a very short interval of time. The early stage of growth was strongly influenced by the substrate microstructure. Plating

Rajan Ambat; W Zhou

2004-01-01

317

Fatigue and Tensile Behavior of Cast, Hot-Rolled, and Severely Plastically Deformed AZ31 Magnesium Alloy  

Microsoft Academic Search

The work focuses on experimental examination of the fatigue behavior of magnesium alloy AZ31 produced by three different procedures:\\u000a squeeze casting (SC), hot rolling (HR), and equal-channel angular pressing (ECAP). The microstructures produced were studied\\u000a by light and transmission electron microscopy (TEM). Squeeze-cast AZ31 had low porosity and coarse grains, while hot-rolled\\u000a material showed microstructure with grain size of 3

Z. Zúberová; L. Kunz; T. T. Lamark; Y. Estrin; M. Janecek

2007-01-01

318

Application of X-ray microtomography to analysis of cavitation in AZ61 magnesium alloy during hot deformation  

Microsoft Academic Search

The efficiency of particles in acting as cavity formation sites during hot deformation was investigated for a fine-grained wrought magnesium–aluminium–zinc (AZ series) alloy using X-ray micro tomography. Two methodologies were developed to determine the particle\\/cavity association from 3-dimensional data, each clearly demonstrating that particles act as a major formation site for cavitation. The particles forming cavities were identified and characterised.

H. M. M. A. Rashed; J. D. Robson; P. S. Bate; B. Davis

2011-01-01

319

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

Microsoft Academic Search

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

Z. Chen; J. Huang; R. F. Decker; S. E. Lebeau; L. R. Walker; O. B. Cavin; T. R. Watkins; C. J. Boehlert

2011-01-01

320

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

Microsoft Academic Search

Tensile, fatigue, fracture toughness, and creep experiments were performed on a commercially available magnesium-aluminum\\u000a alloy (AM60) after three processing treatments: (1) as-THIXOMOLDED (as-molded), (2) THIXOMOLDED then thermomechanically processed\\u000a (TTMP), and (3) THIXOMOLDED then TTMP then annealed (annealed). The TTMP procedure resulted in a significantly reduced grain\\u000a size and a tensile yield strength greater than twice that of the as-molded material

Zhe Chen; J. Huang; R. F. Decker; S. E. Lebeau; Larry R Walker; Odis Burl Cavin; Thomas R Watkins; C. J. Boehlert

2011-01-01

321

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

322

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

323

Characterization of High-Frequency Induction Brazed Magnesium Alloy Joint with an Al-Mg-Zn Filler Metal  

Microsoft Academic Search

In this paper, a novel Al-Mg-Zn filler metal was designed to join magnesium alloy AZ31B plates by means of high-frequency\\u000a induction brazing in argon gas shield condition. The microstructure and the mechanical properties of the brazed joint were\\u000a investigated. The experimental results showed that the brazed joint contained large amount of ?-Mg and ?-Mg17(Al, Zn)12 phases. The homogeneous Mg32(Al, Zn)49

Li Ma; Dingyong He; Xiaoyan Li; Jianmin Jiang

2011-01-01

324

Characterization of High Strain Rate Mechanical behavior of AZ31 magnesium alloy using 3D Digital Image Correlation  

Microsoft Academic Search

Characterization of the material mechanical behavior at sub-Hopkinson regime (0.1 to 1000 s¹) is very challenging due to instrumentation limitations and the complexity of data analysis involved in dynamic loading. In this study, AZ31 magnesium alloy sheet specimens are tested using a custom designed servo-hydraulic machine in tension at nominal strain rates up to 1000 s¹. In order to resolve

Yanli Wang; Hanbing Xu; DONALD L ERDMAN; J Michael Starbuck; Srdjan Simunovic

2011-01-01

325

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

326

Microstructure and mechanical properties of ZA104 (0.3–0.6Ca) die-casting magnesium alloys  

Microsoft Academic Search

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

Z. Zhang; R. Tremblay; D. Dubé

2004-01-01

327

A layer-by-layer approach to natural polymer-derived bioactive coatings on magnesium alloys.  

PubMed

The development of polyelectrolyte multilayered coatings on magnesium alloy substrates that can be used for controlled delivery of growth factors and required biomolecules from the surface of these degradable implants could have a significant impact in the field of bone tissue regeneration. The current work reports on the fabrication of multilayered coatings of alginate and poly-l-lysine on alkaline- and fluoride-pretreated AZ31 substrates using a layer-by-layer (LbL) technique under physiological conditions. Furthermore, these coatings were surface functionalized by chemical cross-linking and fibronectin immobilization, and the resultant changes in surface properties have been shown to influence the cellular activity of these multilayered films. The physicochemical characteristics of these coated substrates have been investigated using attenuated total reflectance Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Cytocompatibility studies using MC3T3-E1 osteoblasts show that the fluoride-pretreated, cross-linked and fibronectin-immobilized LbL-coated substrates are more bioactive and less cytotoxic than the hydroxide-pretreated, cross-linked and fibronectin-immobilized LbL-coated samples. The in vitro degradation results show that the multilayered coatings of these natural polysaccharide- and synthetic polyamino acid-based polyelectrolytes do not alter the degradation kinetics of the substrates; however, the pretreatment conditions have a significant impact on the overall coating degradation behavior. These preliminary results collectively show the potential use of LbL coatings on magnesium-based degradable scaffolds to improve their surface bioactivity. PMID:23707500

Kunjukunju, Sangeetha; Roy, Abhijit; Ramanathan, Madhumati; Lee, Boeun; Candiello, Joe E; Kumta, Prashant N

2013-05-22

328

Effect of cerium additive on aluminum-based chemical conversion coating on AZ91D magnesium alloy  

NASA Astrophysics Data System (ADS)

Based on environmentally friendly and recycling of magnesium alloys, chemical conversion coatings were prepared in aluminum nitrate solutions with cerium nitrate additive on AZ91D magnesium alloys surfaces. Effect of additive's concentration on the surface morphology, composition and corrosion resistance of aluminum-based conversion coating on magnesium alloys was studied. The surface morphology, composition, microstructure and corrosion resistance of conversion coatings were investigated using scanning electron microscopy (SEM), X-ray energy dispersion spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical tests respectively. The results show that the cerium content of the conversion coatings surface increased with increasing additive concentration. The conversion coatings' morphologies first gradually became dense and the micro-cracks on the coating surface became narrow with the increase of the additive concentration. Then the coatings' morphologies became bad and the micro-cracks widened after the additive concentration reached 0.005 mol/L. When the additive concentration was 0.005 mol/L, the conversion coating consists of Al(OH)3, Al2O3, Mg(OH)2, MgO, CeO2 and Ce2O3; the conversion coating surface morphology was the densest and the micro-cracks were the narrowest, and the corrosion resistance was also the best.

Wang, Ximei; Zhu, Liqun; He, Xiang; Sun, Fenglou

2013-09-01

329

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

SciTech Connect

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

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

2011-06-15

330

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.

331

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

Microsoft Academic Search

Magnesium components are increasingly being considered for use in vehicle structures due to the potential for weight reduction,\\u000a fuel economy improvement, and emission reduction. Apart from castings, magnesium sheet components can open an entirely new\\u000a opportunity for mass reduction. Magnesium’s poor ductility at room temperature, however, requires sheet forming to be carried\\u000a out at elevated temperatures. The forming limits of

Emilie Hsu; John E. Carsley; Ravi Verma

2008-01-01

332

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

333

Modelling the Thermo-Mechanical Behavior of Magnesium Alloys during Indirect Extrusion  

SciTech Connect

One of the basic metal forming process for semi-finished products is extrusion. Since extrusion involves complex thermo-mechanical and multiaxial loading conditions resulting in large strains, high strain rates and an increase in temperature due to deformation, a proper yield criterion and hardening law should be used in the numerical modelling of the process. A phenomenological model based on a plastic potential has been proposed that takes strain, strain rate and temperature dependency on flow behaviour into consideration. A hybrid methodology of experiment and finite element simulation has been adopted in order to obtain necessary model parameters. The anisotropy/asymmetry in yielding was quantified by tensile and compression tests of specimens prepared from different directions. The identification of the corresponding model parameters was performed by a genetic algorithm. A fully coupled thermo-mechanical analysis has been used in extrusion simulations for calculation of the temperature field by considering heat fluxes and heat generated due to plastic deformation. The results of the approach adopted in this study appeared to be successful showing promising predictions of the experiments and thus may be extended to be applicable to other magnesium alloys or even other hcp metals.

Steglich, D. [GKSS Research Centre, Geesthacht (Germany); G.I.F.T., POSTECH, Pohang, Gyeongbuk (Korea, Republic of); Ertuerk, S.; Bohlen, J.; Letzig, D. [GKSS Research Centre, Geesthacht (Germany); Brocks, W. [Faculty of Engineering, Christian-Albrechts-University of Kiel (Germany)

2010-06-15

334

Influence of chemical liquids on the fatigue crack growth of the AZ31 magnesium alloy  

NASA Astrophysics Data System (ADS)

The fatigue crack growth behavior of an AZ31 magnesium alloy was investigated by comparing the effect of zirconate and phosphate chemical liquids. The morphology, components, and phase compositions of the chemical depositions at the fatigue crack tip were analyzed by employing scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD), respectively. For samples with and without the chemical liquids, their stress-intensity factor values at the fatigue crack tip were compared by using a stress-strain gauge. The results demonstrated that a zirconate film (Zr x O y ·Zn x O y ) and a phosphate film (Zn3(PO4)2·4H2O and MgZnP2O7) could be formed on the fatigue crack-surface at the fatigue crack tip. The stress distribution was changed because of the chemical depositions and the causticity of the chemical liquids. This could decrease the stress-intensity factor value and thus effectively cause fatigue crack closure, which reduces the fatigue crack growth rate. Moreover, it was found that the fatigue crack closure effect of zirconates was more positive than that of phosphates.

Wang, Zhang-Zhong; He, Xian-Cong; Bai, Yun-Qiang; Ba, Zhi-Xin; Dai, Yu-Ming; Zhou, Heng-Zhi

2012-03-01

335

Fatigue Life Prediction of Rolled AZ31 Magnesium Alloy Using AN Energy-Based Model  

NASA Astrophysics Data System (ADS)

Fatigue behavior of rolled AZ31 magnesium alloy, which shows an anisotropic deformation behavior due to the direction dependent formation of deformation twins, was investigated by carrying out stress and strain controlled fatigue tests. The anisotropy in deformation behavior introduced asymmetric stress-strain hysteresis hoops, which make it difficult to use common fatigue life prediction models, such as stress and strain-based models, and induced mean stress and/or strain even under fully-reversed conditions; the tensile mean stress and strain were found to have a harmful effect on the fatigue resistance. An energy-based model was used to describe the fatigue life behavior as strain energy density was stabilized at the early stage of fatigue life and nearly invariant through entire life. To account for the mean stress and strain effects, an elastic energy related to the mean stress and a plastic strain energy consumed by the mean strain were appropriately considered in the model. The results showed that there is good agreement between the prediction and the experimental data.

Park, Sung Hyuk; Hong, Seong-Gu; Lee, Byoung Ho; Lee, Chong Soo

336

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

337

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

338

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 14days. 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

2012-11-02

339

Friction properties of protective DLC films on magnesium alloy in aqueous NaCl solution  

NASA Astrophysics Data System (ADS)

Friction properties of DLC films deposited on magnesium alloy, AZ31 (Mg 3%Al 1%Zn) were investigated using a ball-on-flat type reciprocal friction tester in aqueous 0.05 M NaCl solution. The DLC, DLC/interlayer and Si-DLC films were prepared on the sputter-deposited AZ31 films on glass substrates using a bi-polar type plasma based ion implantation and deposition (PBII&D). The DLC/interlayer/AZ31 sample shows good friction and wear properties in NaCl solution, but the large corrosion pits were developed on the surface during the friction test in NaCl solution. The low adhesion strength and high internal stress of the DLC coatings on the AZ31 are the reason for the poor corrosion properties in corrosive NaCl solution. The Si-DLC coating on the AZ31 has high adhesion strength and a low internal stress, and no large corrosion pits are observed on the surface after the friction test in NaCl solution. The Si-DLC coating also shows stable friction properties.

Choi, Junho; Kim, Jongduk; Nakao, Setsuo; Ikeyama, Masami; Kato, Takahisa

2007-04-01

340

Influence of circumferential notch and fatigue crack on the mechanical integrity of biodegradable magnesium-based alloy in simulated body fluid.  

PubMed

Applications of magnesium alloys as biodegradable orthopaedic implants are critically dependent on the mechanical integrity of the implant during service. In this study, the mechanical integrity of an AZ91 magnesium alloy was studied using a constant extension rate tensile (CERT) method. The samples in two different geometries that is, circumferentially notched (CN), and circumferentially notched and fatigue cracked (CNFC), were tested in air and in simulated body fluid (SBF). The test results show that the mechanical integrity of the AZ91 magnesium alloy decreased substantially (?50%) in both the CN and CNFC samples exposed to SBF. Fracture surface analysis revealed secondary cracks suggesting stress corrosion cracking susceptibility of the alloy in SBF. PMID:21210510

Bobby Kannan, M; Singh Raman, R K; Witte, F; Blawert, C; Dietzel, W

2010-12-17

341

Effect of gd on the Microstructures and Corrosion Behaviors of Magnesium Alloy Mg-8.0Al-1.0Zn  

NASA Astrophysics Data System (ADS)

Magnesium alloy is a promising candidate for use as biodegradable implant material. However, its corrosion rate is too fast in human body fluid. Thereby, improving corrosion resistance is an urgent problem for application of the magnesium alloy in the medical field. Presently, Mg-8.0Al-1.0Zn-xGd alloys were prepared. Effect of rare earth Gd on the microstructures and corrosion resistance of magnesium alloy were investigated. Results showed that the most of Al3Gd particles, a high melting point rare earth compound, are distributed in ? phases (Mg17Al12). With the increase of the content of Gd, the amount of precipitation of ? phases increased and interconnected each other. Fine network-like ? phases acted as corrosion barrier and effectively impeded the corrosion extending. The corrosion resistance improved with the increase of rare earth Gd.

Li, Lei; Xie, Shuisheng; Huang, Guojie

2011-06-01

342

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

SciTech Connect

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

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

1987-01-01

343

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

NASA Astrophysics Data System (ADS)

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

Busch, Eric Michael

344

Electrolytic Deposition and Diffusion of Lithium onto Magnesium-9 Wt Pct Yttrium Bulk Alloy in Low-Temperature Molten Salt of Lithium Chloride and Potassium Chloride  

NASA Astrophysics Data System (ADS)

The electrolytic deposition and diffusion of lithium onto bulk magnesium-9 wt pct yttrium alloy cathode in molten salt of 47 wt pct lithium chloride and 53 wt pct potassium chloride at 693 K were investigated. Results show that magnesium-yttrium-lithium ternary alloys are formed on the surface of the cathodes, and a penetration depth of 642 ?m is acquired after 2 hours of electrolysis at the cathodic current density of 0.06 A·cm-2. The diffusion of lithium results in a great amount of precipitates in the lithium containing layer. These precipitates are the compound of Mg41Y5, which arrange along the grain boundaries and hinder the diffusion of lithium, and solid solution of yttrium in magnesium. The grain boundaries and the twins of the magnesium-9 wt pct yttrium substrate also have negative effects on the diffusion of lithium.

Dong, Hanwu; Wu, Yaoming; Wang, Lidong; Wang, Limin

2009-10-01

345

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

SciTech Connect

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

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

2010-06-15

346

The use of wrought magnesium in bicycles  

NASA Astrophysics Data System (ADS)

The basic properties of magnesium alloys suggest that they would readily find use in bicycles. Magnesium alloys have low density and a high strength-to-weight ratio, are readily extrudable, and some alloys are highly weldable. A lack of information about wrought magnesium alloys, a lack of suppliers to complete the production process, and a lack of information in how to set up a manufacturing plant to process wrought magnesium alloys have contributed to only limited market penetration by magnesium into bicycle applications. This article examines what has worked and what has not in the use of magnesium alloys in the bicycle business.

Deetz, Josh

2005-05-01

347

Electroless Ni-P/Ni-B duplex coatings for improving the hardness and the corrosion resistance of AZ91D magnesium alloy  

NASA Astrophysics Data System (ADS)

The Ni-P/Ni-B duplex coatings were deposited on AZ91D magnesium alloy by electroless plating process and their structure, morphology, microhardness and corrosion resistance were evaluated. The duplex coatings were prepared using dual baths (acidic hypophosphite- and alkaline borohydride-reduced electroless nickel baths) with Ni-P as the inner layer. The coatings were amorphous in as-plated condition and crystallized and produced nickel borides upon heat-treatment. SEM observations showed that the duplex interface on the magnesium alloy was uniform and the compatibility between the layers was good. The Ni-P/Ni-B coatings microhardness and corrosion resistance of having Ni-B coating as the outer layer was higher than Ni-P coatings. The Ni-P/Ni-B duplex coatings on AZ91D magnesium alloy with high hardness and good corrosion resistance properties would expand their scope of applications.

Zhang, W. X.; Jiang, Z. H.; Li, G. Y.; Jiang, Q.; Lian, J. S.

2008-06-01

348

Magnesium industry overview  

SciTech Connect

Magnesium products provide an excellent strength-to-weight ratio, good fatigue strength, high impact strength, good corrosion resistance, high-speed machinability, and good thermal and electrical conductivities. As a result, applications are expanding in almost every industry. Dozens of automotive components are now made of magnesium, including steering wheels, valve covers, and seat frames. Magnesium alloys are also used in computer housings, in-line roller skates, golf clubs, tennis racquets, and baseball bats. Good strength and stiffness at both room and elevated temperatures make magnesium alloys especially valuable for aerospace applications. This article presents an overview of magnesium technology, world production, increasing demand, and recycling.

Clow, B.B. [International Magnesium Association, McLean, VA (United States)

1996-10-01

349

Microstructure and second-phase particles in low- and high-pressure die-cast magnesium alloy AM50  

Microsoft Academic Search

The microstructure and phase composition of low-pressure die-cast (LPDC) and high-pressure diecast (HPDC) magnesium alloy\\u000a AM50 were examined by transmission electron microscopy (TEM) techniques in combination with optical microscopy, scanning electron\\u000a microscopy (SEM), and electron-probe microanalysis (EPMA). It has been established that the dimensions and morphology of the\\u000a constituent phases (?-Mg solid solution, Mg17Al12, and Al8Mn5) depend on the processing

Val Y. Gertsman; Jian Li; Su Xu; James P. Thomson; Mahi Sahoo

2005-01-01

350

In situ spectroscopic ellipsometry study of the hydrogenation process of switchable mirrors based on magnesium-nickel alloy thin films  

NASA Astrophysics Data System (ADS)

The hydrogenation process of switchable mirrors using magnesium-nickel alloy thin films including a thin palladium cap layer was analyzed by measuring the variation in ellipsometric angles ? and ? using in situ spectroscopic ellipsometry. The process was divided into three phases and each phase was identified as follows. The first phase was the process in which the solid solution was formed because a Mg-Ni alloy in its metal state absorbs hydrogen. The second phase was the hydrogenation processes of the solid solution and the metal Pd layers. The third phase was the hydrogenation process of residual metal Pd in the Pd layer. In the initial state of the second phase, a hydride of the alloy was nucleated at the film/substrate interface as a result of hydrogenation of the solid solution, and a mixture layer of the hydride and solution was formed. With proceeding hydrogenation, the thickness of the mixture layer increased and the homogenous hydride layer was afterwards formed at the film/substrate interface. As a result of further hydrogenation, the Mg-Ni alloy layer was completely hydrogenated. After the alloy layer was completely hydrogenated, the hydrogenation of Pd was terminated.

Yamada, Y.; Bao, S.; Tajima, K.; Okada, M.; Tazawa, M.; Roos, A.; Yoshimura, K.

2010-02-01

351

Microstructure Formation and Mechanical Properties of AZ31 Magnesium Alloy Solidified with a Novel Mechanical Vibration Technique  

NASA Astrophysics Data System (ADS)

A novel mechanical vibration for refining microstructure is reported where vibration energy was directly exerted into a molten alloy by a vibrating horn, and the vibrating horn was melted during vibration. Effects of vibration intensity and melt superheat on the microstructure and mechanical properties of AZ31 magnesium alloy were investigated. It is confirmed that the melting of the vibrating horn could effectively extract the superheat and latent heat from the interior of the molten alloy, leading to rapid cooling during the initial stage of solidification, and the cooling rate is strongly dependent on the vibration acceleration and melt superheat. This study showed that it was difficult to refine the solidified microstructure when the treated alloy was kept in the full liquid state within the entire vibrating duration. A significantly refined microstructure was obtained by applying mechanical vibration during the nucleation stage, and a globular microstructure could form in a few seconds after solidification. When the molten alloy was treated from 920 K to 903 K (647 °C to 630 °C), with increasing vibration acceleration from 2.5 to 19 m s-2, the coarse dendritic microstructure of the produced AZ31 billets transformed into a well-refined, reasonably uniform, and non-dendritic one, and mechanical properties were improved significantly. Moreover, the mechanisms of microstructure formation are discussed.

Guo, H. M.; Zhang, A. S.; Yang, X. J.; Yan, M. M.; Ding, Y.

2013-09-01

352

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

NASA Astrophysics Data System (ADS)

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 sheets and plates can be reached by cold working but in this case, plasticity reduces. An effective way to improve strength of aluminium-magnesium alloys is their alloying with scandium. The alloying with scandium leads to modification of the structure of ingots (size reduction of cast grain) and formation of supersaturated solid solutions of scandium and aluminium during crystallization. During subsequent heatings (annealing of the ingots, heating for deformation) the solid solution disintegrates with the formation of disperse particles of Al3Sc type, that cause great strengthening of the alloy. High degree of dispersion and density of distribution in the matrix of secondary Al3Sc particles contribute to the considerable increase of the temperature of recrystallization of deformed intermediate products and to the formation of stable non-recrystallized structure. The alloying of alluminium-magnesium alloys with scandium increases their strength and operational characteristics, preserves their technological and corrosion properties, improves weldability. The alloys can be used within the temperature limits ­196-/+150 0C. The experimental structures of propellant tanks made of alluminium-magnesium alloys with scandium have been manufactured and tested. It was ascertained that the propellant tanks have higher margin of safety during loading with internal pressure and higher stability factor of the shrouds during loading with axial compression force which is caused by higher value of yield strength. The analysis of the performed work showed good prospects of using the alluminium-magnesium alloys with increased mechanical characteristics for making body elements of propellant tanks of the Zenit -2S launch vehicles. The use of these alloys can give the increase of structural strength by 20-30% and considerable increase of payload weight.

Sitalo, V.; Lytvyshko, T.

2002-01-01

353

Characterization of High-Frequency Induction Brazed Magnesium Alloy Joint with an Al-Mg-Zn Filler Metal  

NASA Astrophysics Data System (ADS)

In this paper, a novel Al-Mg-Zn filler metal was designed to join magnesium alloy AZ31B plates by means of high-frequency induction brazing in argon gas shield condition. The microstructure and the mechanical properties of the brazed joint were investigated. The experimental results showed that the brazed joint contained large amount of ?-Mg and ?-Mg17(Al, Zn)12 phases. The homogeneous Mg32(Al, Zn)49 phase in the original filler metal was consumed due to the intensive alloying during the brazing process. The results indicate that the shear strength of the brazed joint is 35 MPa. The fracture morphology of the brazed joint exhibits intergranular fracture mode, and the fracture originates from the hard ?-Mg17(Al, Zn)12 phase.

Ma, Li; He, Dingyong; Li, Xiaoyan; Jiang, Jianmin

2011-03-01

354

Preparation and properties of Mg–Cu–Mn–Zn–Y damping magnesium alloy  

Microsoft Academic Search

This paper presents the successful preparation of a high-damping, high-strength Mg–Cu–Mn–Zn–Y alloy by alloying and extrusion. The damping capacity of the as-cast Mg–3Cu–1Mn alloy (alloy 1) displayed evident variations with changes in Y and Zn content. The as-cast Mg–3Cu–1Mn–2Zn–1Y alloy (alloy 2) exhibited excellent damping capacity and unusual damping growth in the high-strain amplitude stage; the damping capacity of alloy

Jingfeng Wang; Wenwen Wei; Xuefei Huang; Long Li; Fusheng Pan

2011-01-01

355

Influence of the grain size on the in vivo degradation behaviour of the magnesium alloy LAE442.  

PubMed

The aim of this study was to investigate the differences in the in vivo degradation behaviour of magnesium implants with various grain sizes and damaged surfaces. For this purpose, three different LAE442 magnesium implants were produced: cast, single and double extruded implants, in order to obtain different grain sizes. Furthermore, defects were positioned on the surfaces of some of the single extruded implants. The initial stability was determined. Four pins of each implant material were implanted into rabbits' tibiae and regularly clinically, radiologically and micro-computed tomographically investigated over a period of 27 weeks. Following explantation, investigations were carried out using stereo and scanning electron microscopy including energy-dispersive X-ray analyses. Weight and strength changes were measured. The double extruded implants possessing the finest grains exhibited the highest initial stability (179.18 N). These implants demonstrated the lowest in vivo corrosion rates (0.0134 mm/year) and the least radiologically visible changes. The highest corrosion rate was computed for the implants possessing damaged surfaces. Radiologically discernible bone changes occurred at almost the same time as implant changes for all groups. Based on these results, the aim should be to produce fine-grained magnesium-based alloys for resorbable implants and to avoid any surface damage. PMID:23662348

Ullmann, Berit; Reifenrath, Janin; Seitz, Jan-Marten; Bormann, Dirk; Meyer-Lindenberg, Andrea

2013-03-01

356

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

357

Mesoscale Modeling and Validation of Texture Evolution during Asymmetric Rolling and Static Recrystallization of Magnesium Alloy AZ31B  

NASA Astrophysics Data System (ADS)

The focus of the present research is to develop an integrated deformation and recrystallization model for magnesium alloys at the microstructural length scale. It is known that in magnesium alloys nucleation of recrystallized grains occurs at various microstructural inhomogeneities such as twins and localized deformation bands. However, models need to be developed that can predict the evolution of the grain structure and texture developed during recrystallization and grain growth, especially when the deformation process follows a complicated deformation path such as in asymmetric rolling. The deformation model is based on a crystal plasticity approach implemented at the length scale of the microstructure that includes deformation mechanisms based on dislocation slip and twinning. The recrystallization simulation is based on a Monte Carlo technique that operates on the output of the deformation simulations. The nucleation criterion during recrystallization is based on the local stored energy, and the Monte Carlo technique is used to simulate the growth of the nuclei resulting from local stored energy differences and curvature. The model predictions are compared with experimental data obtained through electron backscatter analysis and neutron diffraction.

Radhakrishnan, B.; Gorti, S. B.; Stoica, G. M.; Muralidharan, G.; Stoica, A. D.; Wang, X.-L.; Specht, E. D.; Kenik, E.; Muth, T.

2012-05-01

358

Mesoscale Modeling and Validation of Texture Evolution during Asymmetric Rooling and Static Recrystallization of Magnesium Alloy AZ31B  

SciTech Connect

The focus of the present research is to develop an integrated deformation and recrystallization model for magnesium alloys at the microstructural length scale. It is known that in magnesium alloys nucleation of recrystallized grains occurs at various microstructural inhomogeneities such as twins and localized deformation bands. However, there is a need to develop models that can predict the evolution of the grain structure and texture developed during recrystallization and grain growth, especially when the deformation process follows a complicated deformation path such as in asymmetric rolling. The deformation model is based on a crystal plasticity approach implemented at the length scale of the microstructure that includes deformation mechanisms based on dislocation slip and twinning. The recrystallization simulation is based on a Monte Carlo technique that operates on the output of the deformation simulations. The nucleation criterion during recrystallization is based on the local stored energy and the Monte Carlo technique is used to simulate the growth of the nuclei due to local stored energy differences and curvature. The model predictions are compared with experimental data obtained through electron backscatter analysis and neutron diffraction.

Radhakrishnan, Balasubramaniam [ORNL; Gorti, Sarma B [ORNL; Stoica, Grigoreta M [ORNL; Muralidharan, Govindarajan [ORNL; Stoica, Alexandru Dan [ORNL; Wang, Xun-Li [ORNL; Specht, Eliot D [ORNL; Kenik, Edward A [ORNL; Muth, Thomas R [ORNL

2012-01-01

359

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

NASA Astrophysics Data System (ADS)

Aluminum and magnesium alloys are widely used in the automobile and aerospace industries as structural materials due to their light weight, high specific strength and good formability. However, they suffer from the poor hot rolling characteristics due to undesired impurities like calcium, potassium, lithium and sodium. They increase the hydrogen solubility in the melt and promote the formation of porosity in aluminum castings. During fabrication of aluminum alloys, they cause the hot-shortness and embrittlement due to cracking. They also led to "blue haze" corrosion which promotes the discoloration of aluminum under humid condition. The removal of these elements increases overall melt loss of aluminum alloys when aluminum products are remelted and recast. Na is one of the common impurities in the Al and Mg alloys. In industry, primary Al is produced by the Hall-Heroult process, through the electrolysis of the mixture of molten alumina and cryolite (Al2O3+Na 3AlF6), the latter being added to lower the melting point. Therefore, Al inevitably contains some Na (>0.002%) without further treatment. The Na content in Al is influenced by the thermodynamics and kinetics of the electrolysis. Similarly, in the electrolytic production and subsequent processing of Mg, Mg is commonly in contact with molten salt mixtures of NaCl and MgCl 2. Consequently, 2--20 wt. ppm Na is often found in Mg alloys. Besides originating from the industrial production process, Na can be introduced in laboratory experiments from alumina crucibles by the reaction between the molten Al-Mg alloys and the Na2O impurity in the alumina crucible. The trace element K plays a similar role in Al alloys although it is seldom discussed. No systematic theoretic research has been carried out to investigate the behavior of these impurities during the processing of aluminum alloys. The thermodynamic description of the Al-Ca-K-Li-Mg-Na system is needed to understand the effects of Ca, K, Li and Na on phase stability of aluminum and magnesium alloys. As the first step of the thermodynamic description of the high-order system, the constitutive-binary systems were modeled in the present work using the CALPHAD technique combined with first-principles calculations. Then, ternaries and higher order systems can be modeled. For ternary systems without experimental data, the thermodynamic description is extrapolated by combining three constitutive-binary systems. Alkali-metal induced high temperature embrittlement (HTE) and loss of ductility were investigated in Al-Li, Al-Mg and Mg-Li alloys. It was discovered that the alkali-metal-rich liquid-2 phase is the cause of HTE and the loss of ductility is proportional to the mole fraction of the liquid phase and the grain size. The calculated results are consistent with experimental observations in the literature and were used to determine HTE safe and sensitive zones, maximum and critical hot-rolling temperatures and the maximum allowable Na content in alloys, which can be used to industrial processing of Al and Mg alloys. The degree of HTE is proportional to the mole fraction of the liquid-2 phase and the grain size.

Zhang, Shengjun

360

Slow strain rate stress corrosion cracking behaviour of as-welded and plasma electrolytic oxidation treated AZ31HP magnesium alloy autogenous laser beam weldment  

Microsoft Academic Search

The joining of a thin section AZ31HP magnesium alloy was accomplished by laser beam welding in the autogenous mode using a Nd-YAG laser system. Micro hardness evaluation and slow strain rate tensile (SSRT) tests in air revealed that the weld metal had near-matching mechanical properties corresponding to that of the parent alloy. However, in terms of stress corrosion cracking (SCC)

P. Bala Srinivasan; S. Riekehr; C. Blawert; W. Dietzel; M. Koçak

2009-01-01

361

The use of resistivity data in calculating the kinetics of precipitate evolution in aluminium-copper-magnesium alloys based on Johnson-Mehl-Avrami theory  

Microsoft Academic Search

This paper describes the procedure and results of using resistivity data in calculating the amount of precipitation in aluminium-copper-magnesium alloys based on the Johnson-Mehl-Avrami (JMA) theory. Two alloys have been studied, Al-4.38%Cu-1.67%Mg and Al-4.5%Cu-0.56%Mg. The results have demonstrated that resistivity data can be treated to reveal the degree of transformation, for periods when there is a constant increase in its

W. Sha

2005-01-01

362

Review of Recent Developments. Aluminum and Magnesium.  

National Technical Information Service (NTIS)

Contents: Propellant tank fabricated from 2021 alloy; Improved properties by controlled solidification; Finishing techniques for magnesium; Improving stress-corrosion resistance of high-strength aluminum-zinc-magnesium alloys; Reducing quench sensitivity ...

D. N. Williams

1970-01-01

363

Corrosion behaviour of magnesium in ethylene glycol  

Microsoft Academic Search

Corrosion of magnesium engine components by coolant is an important issue in the automotive industry where magnesium alloys may be used. It is of significance to understand the corrosion behaviour of pure magnesium in ethylene glycol solutions, as this can provide a basis for developing new coolants for magnesium alloy engine blocks. In this paper, through corrosion and electrochemical tests,

Guangling Song; David StJohn

2004-01-01

364

A study on the effect of plasma electrolytic oxidation on the stress corrosion cracking behaviour of a wrought AZ61 magnesium alloy and its friction stir weldment  

Microsoft Academic Search

Friction stir weldments of a wrought AZ61 magnesium alloy produced in a robotic friction stir welder under optimised welding conditions were characterised for microstructure, mechanical properties, corrosion and stress corrosion cracking (SCC) behaviour. The effect of surface modification in the form of a plasma electrolytic oxidation (PEO) coating on the corrosion behaviour of the weldment was assessed. The weldment exhibited

P. Bala Srinivasan; R. Zettler; C. Blawert; W. Dietzel

2009-01-01

365

Comparison of electrochemical corrosion behaviour of MgO and ZrO 2 coatings on AM50 magnesium alloy formed by plasma electrolytic oxidation  

Microsoft Academic Search

Two types of PEO coatings were produced on AM50 magnesium alloy using pulsed DC plasma electrolytic oxidation process in an alkaline phosphate and acidic fluozirconate electrolytes, respectively. The phase composition and microstructure of these PEO coatings were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The corrosion behaviour of the coated samples was evaluated by open circuit potential

J. Liang; P. Bala Srinivasan; C. Blawert; W. Dietzel

2009-01-01

366

Improvement of bioactivity with magnesium and fluorine ions incorporated hydroxyapatite coatings via sol–gel deposition on Ti6Al4V alloys  

Microsoft Academic Search

Magnesium (Mg) is a trace element in natural bone, its existence plays an important role in cell adhesion and bone formation. To improve the biological properties, Mg and fluorine (F) are simultaneously incorporated in hydroxyapatite (HA) to form MgxFHA coating on titanium alloy via sol–gel process. In vitro bioactivity of the coating is evaluated by examination of apatite precipitation on

Yanli Cai; Sam Zhang; Xianting Zeng; Yongsheng Wang; Min Qian; Wenjian Weng

2009-01-01

367

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

368

Heat-Transfer Coefficient and In-Cavity Pressure at the Casting-Die Interface during High-Pressure Die Casting of the Magnesium Alloy AZ91D  

NASA Astrophysics Data System (ADS)

The present article deals with the application of a new measurement method to determine the heat-transfer coefficient (HTC) and the heat flux density at the casting-die interface during high-pressure die casting (HPDC) and solidification of the magnesium AZ91D alloy. The main measurements during the trial included velocity and the position of the piston that delivers the metal into the die, the pressure in the die cavity and at the tip of the piston, the alloy surface temperature, and the die temperature at different depths from the surface of the die. The temperature data were analyzed using an inverse method to determine the HTC at the casting-die interface during solidification. This article examines in detail the influence of the piston velocity and in-cavity pressure on heat transfer at the casting-die interface during casting and solidification of the magnesium AZ91D alloy.

Hamasaiid, A.; Dour, G.; Dargusch, M. S.; Loulou, T.; Davidson, C.; Savage, G.

2008-04-01

369

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

370

Development Program for Improving Foundry and Repair Welding Techniques for ZE41-type Magnesium Alloy Castings.  

National Technical Information Service (NTIS)

This report describes a development program for improved foundry and repair welding techniques for large complex ZE41-type magnesium castings, such as currently specified by the designers of next generation of army aircraft (e.g. the AAH, UTTAS, etc.). Th...

J. Desai

1976-01-01

371

Orientation effects on acoustic emission during tensile deformation of hot rolled magnesium alloy AZ31  

Microsoft Academic Search

Acoustic emission (AE) is observed during tensile testing of commercial AZ31 magnesium sheets in different temper conditions. Tests were conducted in rolling direction (RD) and transverse direction (TD), respectively. The results are discussed with respect to the crystallographic texture and the microstructure in terms of the orientation-dependent activation of different deformation mechanisms like dislocation glide and twinning.

J. Bohlen; F. Chmel??k; P. Dobro?; F. Kaiser; D. Letzig; P. Luká?; K. U. Kainer

2004-01-01

372

Effect of the Pulse Duty Cycle on Characteristics of Plasma Electrolytic Oxidation Coatings Formed on AZ31 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Ceramic coatings are synthesized on AZ31 magnesium alloy in alkaline silicate solution by the method of plasma electrolytic oxidation. The effect of two different duty cycles (10% and 50%) on the structure and corrosive properties of the coatings is investigated. It is found that the coatings are mainly composed of MgO, Mg2SiO4 and MgF2 through XRD analysis. SEM images indicate that coatings formed at 50% duty cycle have a relatively coarse surface with larger pore size and fewer pores, and have a slower growth rate than those formed at 10% duty cycle with the same treatment time. However, the results of potentiodynamic polarization tests demonstrate that coatings formed at 50% duty cycle exhibit better corrosion resistance as a result of more compact microstructure.

Chen, Huan; Lv, Guo-Hua; Zhang, Gu-Ling; Pang, Hua; Wang, Xing-Quan; Zhang, You-Wei; Lee, Heon-Ju; Yang, Si-Ze

2009-09-01

373

The Impact of Melt-Conditioned Twin-Roll Casting on the Downstream Processing of an AZ31 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Melt conditioning by intensive shear was used prior to twin-roll casting of AZ31 magnesium alloy strip to promote heterogeneous nucleation and to provide a refined and uniform microstructure without severe macrosegregation. The cast strip was then processed by homogenization, hot rolling, and annealing, and its downstream processing was compared with a similar cast strip produced without melt conditioning. Melt conditioning produced strip with accelerated kinetics of recrystallization during homogenization and improved performance in hot rolling and improved tensile properties. An average tensile elongation of ~28 pct was achieved, which is substantially higher than the ~9 pct obtained for the strip produced without melt conditioning which is consistent with reported values (~6 pct to 16 pct). The as-cast, homogenized, and hot-rolled microstructures of the strip were characterized. The kinetics of homogenization and hot-rolling process have been discussed in detail.

Bayandorian, I.; Huang, Y.; Fan, Z.; Pawar, S.; Zhou, X.; Thompson, G. E.

2012-03-01

374

Determination of an empirical law of aluminium and magnesium alloys absorption coefficient during Nd : YAG laser interaction  

NASA Astrophysics Data System (ADS)

Welding laser modelling requires knowledge about relative changes of many thermo-physical parameters involved in the interaction. The absorptivity of the material is one of the most important. In this study, experimental measurements of absorptivity with an integrating sphere on two alloys (aluminium and magnesium) were made. These results were compared with an analytical calculation that takes into account the trapping of the beam by multiple reflections inside the keyhole. Based on a statistical method, an empirical law is proposed connecting absorptivity with the peak power of the laser and the duration of interaction. During the interaction, two distinct phenomenologies are brought to light. A threshold is then defined after which the physical process becomes stable. Below this threshold, the measurement of absorptivity is problematic, and the values are widely dispersed.

Pierron, Nicolas; Sallamand, Pierre; Jouvard, Jean-Marie; Cicala, Eugen; Matteï, Simone

2007-04-01

375

Study on the corrosion residual strength of the 1.0 wt.% Ce modified AZ91 magnesium alloy  

SciTech Connect

The effect of corrosion on the tensile behaviour of the 1.0 wt.% Ce modified AZ91 magnesium alloy was investigated by the immersion of the test bar in 3.5 wt.% NaCl aqueous solution for 0, 12, 40, 108, 204, 372 and 468 h with the subsequent tensile tests in this paper. The fractography was analyzed by scanning electron microscopy. The results show that pitting corrosion should be responsible for the drop of the corrosion residual strength within the testing time. The depth of the corrosion pits was statistically and quantitatively obtained by an optical microscopy and the maximal value was recorded as the extreme depth of the corrosion pit. Furthermore, the corrosion residual strength is linearly dependent on the extreme depth of the corrosion pit, which can be attributed to the loss of cross-sectional area and the emergence of stress concentration caused by the initiation and development of corrosion pits.

Li Chunfang [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun 130025 (China); Liu Yaohui, E-mail: liuyaohui2005@yahoo.com [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun 130025 (China); Wang Qiang; Zhang Lina; Zhang Dawei [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun 130025 (China)

2010-01-15

376

Characterization of the Surface Film Formed on Molten AZ91D Magnesium Alloy in Atmospheres Containing SO2  

NASA Astrophysics Data System (ADS)

The surface film formed on molten AZ91D magnesium alloy in an atmosphere containing SO2 was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The surface film primarily contained MgO and MgS and had a network structure. MgS increased the Pilling-Bedworth ratio of the film and enhanced its protective capability. The films with a few pores at the surface consisted of two layers with an outer MgO layer and an inner layer of MgO and MgS. The film without pores at the surface also contained MgS and small amounts of MgSO4 in the outer layer. Increasing the SO2 content in the atmosphere promoted film growth and the formation of the protective film was prevented with the increased temperature.

Wang, Xian-Fei; Xiong, Shou-Mei

2012-11-01

377

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.

2013-08-01

378

Controlling the degradation rate of AZ91 magnesium alloy via sol-gel derived nanostructured hydroxyapatite coating.  

PubMed

Magnesium (Mg) alloys have been introduced as new generation of biodegradable orthopedic materials in recent years since it has been proved that Mg is one of the main minerals required for osseous tissue revival. The main goal of the present study was to establish a desired harmony between the necessities of orthopedic patient body to Mg(2+) ions and degradation rate of the Mg based implants as a new class of biodegradable/bioresorbable materials. This prospect was followed by providing a sol-gel derived nanostructured hydroxyapatite (n-HAp) coating on AZ91 alloy using dip coating technique. Phase structural analysis, morphology study, microstructure characterization, and functional group identification were performed using X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The prepared samples were immersed in simulated body fluid in order to study the formation of apatite-like precipitations, barricade properties of the n-HAp coating, and to estimate the dosage of released Mg(2+) ions within a specified and limited time of implantation. Electrochemical polarization tests were carried out to evaluate and compare the corrosion behavior of the n-HAp coated and uncoated samples. The changes of the in vitro pH values were also evaluated. Results posed the noticeable capability of n-HAp coating on stabilizing alkalization behavior and improving the corrosion resistance of AZ91 alloy. It was concluded that n-HAp coated AZ91 alloy could be a good candidate as a type of biodegradable implant material for biomedical applications. PMID:23910282

Rojaee, Ramin; Fathi, Mohammadhossein; Raeissi, Keyvan

2013-05-15

379

Polishing-assisted galvanic corrosion in the dissimilar friction stir welded joint of AZ31 magnesium alloy to 2024 aluminum alloy  

SciTech Connect

Galvanic corrosion of a dissimilar friction stir welded 2024-T3 Al/AZ31B-H24 Mg joint prepared using a water-based and a non-water-based polishing solution was characterized. Microstructure and the distribution of chemical elements were analyzed using optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The stir zone polished using water-based solution was observed to be much more susceptible to galvanic corrosion attack than that obtained using non-water-based polishing solution. The location of corrosion attack was observed in the narrow regions of AZ31 Mg alloy adjacent to Al2024 regions in the stir zone. The occurrence of galvanic corrosion was due to the formation of Mg/Al galvanic couples with a small ratio of anode-to-cathode surface area. The corrosion product was primarily the porous magnesium hydroxide with characteristic microcracks and exhibited a low microhardness value.

Liu, C. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada); Chen, D.L. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada)], E-mail: dchen@ryerson.ca; Bhole, S. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada); Cao, X.; Jahazi, M. [Aerospace Manufacturing Technology Centre, Institute For Aerospace Research, National Research Council Canada, 5145 Decelles Avenue, Montreal, Quebec H3T 2B2 (Canada)

2009-05-15

380

Photoemissive properties of binary magnesium-barium and aluminium-lithium metallic alloys  

NASA Astrophysics Data System (ADS)

The photoemissive properties of binary Mg-Ba and Al-Li metallic alloys, suitable as high-current photocathodes, were studied. The photoelectron energy-distribution curves and the quantum yield's spectral characteristics are presented for these materials. The concept of forming the advanced photoemissive properties for metallic solid solutions and heterophase alloys is suggested.

Tkachenko, V. G.; Maksimchuk, I. N.; Shklover, V. V.; Katrich, G. A.; Klimov, V. V.

1996-03-01

381

Effect of Pb and Sb additions on the precipitation kinetics of AZ91 magnesium alloy  

Microsoft Academic Search

Effect of Pb and Sb additions on the precipitation sequence and ageing kinetics of AZ91 alloy has been studied using the differential thermal analyzer, optical microscopy and scanning electron microscopy. The precipitation sequence in the AZ91 alloy is not altered whereas the enthalpy required for dissolution of ? phases changes with respect to the individual additions of Pb and Sb.

N. Balasubramani; A. Srinivasan; U. T. S. Pillai; B. C. Pai

2007-01-01

382

Processing maps for hot deformation of rolled AZ31 magnesium alloy plate: Anisotropy of hot workability  

Microsoft Academic Search

Processing maps on rolled AZ31 magnesium plate have been developed in the range 300–550°C and 0.0003–10s?1 by hot compression of specimens parallel to the rolling direction (RD), the transverse direction (TD), or the normal direction (ND) with a view to examine whether the hot workability is anisotropic. The processing map for RD specimens exhibited a single wide domain of workability

Y. V. R. K. Prasad; K. P. Rao

2008-01-01

383

Effect of magnesium on the distribution of tin and lead in Al?Si alloys  

Microsoft Academic Search

1.In Al\\\\t-Si\\\\t-Mg alloys with additions of tin or lead the phase of the Mg2Si type has a substantial amount of tin or lead, which changes the composition of the phase to Mg2Si0.3B0.7, where B is tin or lead.These ratios were not observed in alloys with tin and lead together.2.In Al\\\\t-Si\\\\t-Cu\\\\t-Mg alloys the tin and lead prevent the formation of the

V. S. Grebenkin; T. V. Sil'chenko; A. A. Gorshkov; I. Ya. Dzykovich

1972-01-01

384

Effect of magnesium content on the semi solid cast microstructure of hypereutectic aluminum-silicon alloys  

NASA Astrophysics Data System (ADS)

A comprehensive study of microstructural evolution of A390 hypereutectic aluminum-silicon alloy (Al-17%Si-4.5%Cu-0.5%Mg) with addition of Mg contents up to 10% was carried out during semi solid metal processing as well as conventional casting. As a first step, the FACTSAGE thermodynamic databank and software was applied in order to investigate the phase diagram, the solidification behavior as well as the identification of the components that are formed during the solidification of A390 alloy with different Mg contents for equilibrium and non-equilibrium (Schiel) conditions. With higher Mg content between 4.2 - 7.2 %, the Mg2Si intermetallic phase is solidified in the eutectic network according to the ternary reaction together the primary silicon due to the binary reaction of Liq ? Si + Mg2Si. However the primary silicon is still the first solidified phase in this critical Mg zone. For Mg contents greater than 7.2%, the Mg2Si solidifies first as a primary phase. In fact, the Mg2Si is solidified during the primary, the binary and the ternary reactions and can be observed in the microstructure as a eutectic phase and a pro-eutectic phase with different morphology. In the next stage, the experimental tests were carried out in order to verify the accuracy of the results obtained by the FACTSAGE software. The microstructures of the A390 and the 6 and 10 wt% Mg alloys were investigated using conventional casting and rheocasting (stir casting) processes with continuous cooling solidification. The results showed that, for both processes, the microstructure of the eutectic network for high Mg alloys, specifically the eutectic Si phase is modified compared to the eutectic Si in the microstructure of A390 alloy. However the alloys with 6% and 10% Mg have a similar eutectic morphology. The eutectic formation temperature was measured by placing the thermocouple into the melt for determination of the cooling curves. DSC (Differential Scanning Calorimeter) test were also carried out. The results are in good agreement with the FACTSAGE results confirming the reduction of eutectic formation temperature with addition of Mg up to 4.2% and nearly the same temperature for 6 and 10% Mg alloys. Finally, the hardness of the A390 and the 6 and 10% Mg alloys was evaluated for conventionally cast samples and after T6 heat treatment. As expected, the high Mg content alloys showed higher hardness values compared to the A390 alloy. This is a significant finding because A390 is used in high wear resistance applications at medium or elevated temperature. Therefore, the A390 alloy with higher Mg addition can improve the wear resistance of this alloy. The reason for the increased in hardness of Mg can be attributed to the modification of eutectic silicon in the matrix, the presence of eutectic Mg2 Si in the matrix as well as the increase of solid fraction of primary phases from 6.1% for A390 to 12.2% for the 10% Mg alloy. The T6 heat treatment increased the value of hardness for all samples. However, contrary to the as-cast samples, the hardness of A390 alloy in T6 condition shows higher increase than the high Mg alloys. This phenomenon can be attributed to the precipitation hardening of alpha-Al phase during the heat treatment. Since the matrix of A390 consists of more alpha-Al phase when compared to the high Mg content alloys, the increases in hardness of A390 alloy is more significant.

Hekmat-Ardakan, Alireza

385

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

386

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

387

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

388

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

389

Effect of heat treatments on oxidation kinetics in AZ91 and AM60 magnesium alloys  

SciTech Connect

The effect of heat treatments on a non protective atmosphere (air) on the morphology and composition of the oxide in AM60 and AZ91 alloys has been evaluated. With the aim of evaluating the loss of alloying elements during heat treatment, a study of these alloys has been carried out using thermogravimetric analysis (TGA). In order to determine the nature of the oxides the reaction products generated were evaluated by scanning electron microscopy and X-ray diffraction. Results show that the nature and morphology of the oxides generated are related to the temperature and the time of the heating conditions applied. - Highlights: {yields} The effect of heat treatments on the oxide growth in Mg-Al alloys has been evaluated. {yields} The nature and morphology of the oxides have been characterized. {yields} These oxides are associated to the time and the temperature conditions.

Barrena, M.I., E-mail: ibarrena@quim.ucm.es; Gomez de Salazar, J.M.; Matesanz, L.; Soria, A.

2011-10-15

390

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

391

Titanium and magnesium Co-alloyed hematite thin films for photoelectrochemical water splitting  

NASA Astrophysics Data System (ADS)

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, Houwen; Yin, Wan-Jian; Matin, M. A.; Wang, Heli; Deutsch, Todd; Al-Jassim, Mowafak M.; Turner, John A.; Yan, Yanfa

2012-04-01

392

A Trace Element Effect in Alloys based on the Aluminium-Zinc-Magnesium System  

Microsoft Academic Search

THE remarkable changes in properties which may be achieved by the addition of small quantities, or traces, of certain elements to age-hardening alloy systems has aroused much interest recently. A notable example is the pronounced effect of traces of cadmium, indium, or tin on the elevated temperature ageing characteristics of aluminium-copper alloys1. Similar observations have been made in a number

I. J. Polmear

1960-01-01

393

Corrosion of AZ91D magnesium alloy with a chemical conversion coating and electroless nickel layer  

Microsoft Academic Search

A chemical conversion treatment and an electroless nickel plating were applied to AZ91D alloy to improve its corrosion resistance. By conversion treatment in alkaline stannate solution, the corrosion resistance of the alloy was improved to some extent as verified by immersion test and potentiodynamic polarization test in 3.5 wt.% NaCl solution at pH 7.0. X-ray diffraction patterns of the stannate

Hongwei Huo; Ying Li; Fuhui Wang

2004-01-01

394

Creep deformation mechanisms in high-pressure die-cast magnesium-aluminum-base alloys  

Microsoft Academic Search

Creep of die-cast Mg alloys is described as an integral part of their plastic deformation behavior in terms of stress-strain-rate-strain\\u000a relations. Creep tests yield information on yield stress, work hardening, maximum deformation resistance (minimum creep rate),\\u000a and work softening. Testing in compression avoids influences by fracture. Data on the alloy AJ52 (5Al, 2Sr) in the temperature\\u000a range between 135 °C

W. Blum; Y. J. Li; X. H. Zeng; P. Zhang; B. von Großmann; C. Haberling

2005-01-01

395

Effect of Microstructure on Cavitation during Hot Deformation of a Fine-Grained Aluminum-Magnesium Alloy as Revealed through Three-Dimensional Characterization  

NASA Astrophysics Data System (ADS)

The effect of microstructure on cavitation developed during hot deformation of a fine-grained AA5083 aluminum-magnesium alloy is investigated. Two-point correlation functions and three-dimensional (3-D) microstructure characterization reveal that cavitation depends strongly on the mechanism that controls plastic deformation. Grain-boundary-sliding (GBS) creep produces large, interconnected cavities rapidly during plastic straining. Solute-drag (SD) creep produces isolated cavities with less total volume fraction at a given strain. The 3-D microstructure data reveal adjacency between various microstructural features. Cavities are observed to be preferentially adjacent to large Al6(Mn,Fe) particles and to Mg-Si particles of all observed sizes. These data suggest that cavities preferentially nucleate at Mg-Si particles and at large Al6(Mn,Fe) particles. This result may be applied to reduce cavitation in commercial hot-forming operations utilizing aluminum-magnesium alloys.

Chang, Jung-Kuei “Brian”; Taleff, Eric M.; Krajewski, Paul E.

2009-12-01

396

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

397

Effects of TiO 2 coating on the microstructures and mechanical properties of tungsten inert gas welded AZ31 magnesium alloy joints  

Microsoft Academic Search

The effects of TiO2 coating on the macro-morphologies, microstructures and mechanical properties of tungsten inert gas (TIG) welded AZ31 magnesium alloy joints were investigated by microstructural observations, microhardness tests and tensile tests. The results showed that an increase in the amount of the TiO2 coating resulted in an increase in the weld penetration and the depth\\/width (D\\/W) ratio of the

Linzhi Wang; Jun Shen; Nan Xu

2011-01-01

398

Effect of heat input on the microstructure and mechanical properties of tungsten inert gas arc butt-welded AZ61 magnesium alloy plates  

Microsoft Academic Search

In this paper, the effects of heat input on the microstructures and mechanical properties of tungsten inert gas arc butt-welded AZ61 magnesium alloy plates were investigated by microstructural observations, microhardness tests and tensile tests. The results show that with an increase of the heat input, the grains both in the fusion zone and the heat-affected zone coarsen and the width

Dong Min; Jun Shen; Shiqiang Lai; Jie Chen

2009-01-01

399

Influence of pH on the deterioration of plasma electrolytic oxidation coated AM50 magnesium alloy in NaCl solutions  

Microsoft Academic Search

The corrosion deterioration process of plasma electrolytic oxidation (PEO) coatings on AM50 magnesium alloy prepared from two different based electrolytes, i.e., an alkaline phosphate electrolyte and an acidic fluozirconate electrolyte, were investigated using electrochemical impedance spectroscopy (EIS) in a 0.1M NaCl solution with pH of 3, 7 and 11, respectively. It was found that the PEO coating formed in alkaline

J. Liang; P. Bala Srinivasan; C. Blawert; W. Dietzel

2010-01-01

400

Study on the microstructure and corrosion resistance of ZrO 2-containing ceramic coatings formed on magnesium alloy by plasma electrolytic oxidation  

Microsoft Academic Search

ZrO2-containing ceramic coatings were prepared on AZ91D magnesium alloy by plasma electrolytic oxidation (PEO) technique in three different zirconate electrolytes. The morphology and phase composition of the ceramic coatings were characterized by environmental scanning electron microscopy (ESEM) and X-ray diffractometer (XRD). The corrosion properties of the coatings were examined by immersion test and electrochemical corrosion test in 3.5wt.% NaCl solution

Haihe Luo; Qizhou Cai; Bokang Wei; Bo Yu; Jian He; Dingjun Li

2009-01-01

401

Effect of (NaPO 3) 6 concentrations on corrosion resistance of plasma electrolytic oxidation coatings formed on AZ91D magnesium alloy  

Microsoft Academic Search

Different plasma electrolytic oxidation (PEO) coatings were prepared on AZ91D magnesium alloy in electrolytes containing various concentrations of (NaPO3)6. The morphologies, chemical compositions and corrosion resistance of the PEO coatings were characterized by environmental scanning electron microscopy (ESEM), X-ray diffractometer (XRD), energy dispersive analysis of X-rays (EDAX), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) test. The results showed that the

Haihe Luo; Qizhou Cai; Bokang Wei; Bo Yu; Dingjun Li; Jian He; Ze Liu

2008-01-01

402

Effects of current frequency on the structural characteristics and corrosion property of ceramic coatings formed on magnesium alloy by PEO technology  

Microsoft Academic Search

Plasma electrolytic oxidation (PEO) process was carried out on magnesium alloy with a pulsed direct current (dc) power source at high and low frequencies. The morphology and phase composition of the coatings were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion performances of the different coatings were evaluated via a three-electrode system in a 3.5-wt.% NaCl

Guo-Hua Lv; Huan Chen; Wei-Chao Gu; Li Li; Er-Wu Niu; Xian-Hui Zhang; Si-Ze Yang

2008-01-01

403

On the role of the constitutive model and basal texture on the mechanical behaviour of magnesium alloy AZ31B sheet  

Microsoft Academic Search

The recently developed elastic-viscoplastic self-consistent model with various self-consistent schemes was applied to study\\u000a the effect of basal texture on the mechanical behavior of magnesium alloy AZ31B sheet. The influence of the basal texture\\u000a was investigated using various initial textures generated by artificially tilting the measured texture of the reference AZ31B\\u000a sheet around in a transverse direction. The material parameters

H. Wang; P. D. Wu; K. W. Neale

2010-01-01

404

Corrosion resistance of magnesium-beryllium alloys in aqueous solutions of potassium bichromate and carbon dioxide at various temperatures and pressures  

Microsoft Academic Search

behavior of PMB-2 magnesium--beryl lium, alloys and to ascertain the role of carbon dioxide. The corrosion behavior of PMB-2 was studied in solutions with various concentrations of K2Cr207 at temperatures of 20-100~ and pressures ranging from 10 kPa to 2 MPa. The specimens for corrosion testing were made from PMB-2 tubes with the following chemical composition, in wt.%: 2.0 Be,

A. P. Petlitsa; M. I. Ermolaev; V. F. Kapitanov; N. A. Dugin

1978-01-01

405

AC impedance spectroscopy study of the corrosion behavior of an AZ91 magnesium alloy in 0.1 M sodium sulfate solution  

Microsoft Academic Search

The corrosion behavior of an AZ91 magnesium alloy in 0.1M sodium sulfate solution at the corrosion potential (Ecorr) was investigated using electrochemical impedance spectroscopy (EIS), environmental scanning electron microscopy (ESEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The results showed that when the immersion time was less than 18th, general corrosion occurred on the surface and the

Jian Chen; Jianqiu Wang; Enhou Han; Junhua Dong; Wei Ke

2007-01-01

406

Corrosion fatigue of AZ91ET6 cast magnesium alloy in a 3.5 percent NaCl aqueous environment  

Microsoft Academic Search

The objective of this research was to obtain and compare constant and variable amplitude fatigue behavior of AZ91E-T6 cast magnesium alloy in both an air and 3.5% NaCl aqueous corrosive environment. An additional objective was to determine if commonly used models that describe fatigue behavior and fatigue life are applicable to this material and test environment. Fatigue tests included constant

R. I. Stephens; C. D. Schrader; K. B. Lease

1995-01-01

407

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

408

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

409

Corrosion resistance of AZ91D magnesium alloy with electroless plating pretreatment and Ni-TiO{sub 2} composite coating  

SciTech Connect

In this paper, a protective multilayer coating, with electroless Ni coating as bottom layer and electrodeposited Ni-TiO{sub 2} composite coating as top layer, was successfully prepared on AZ91D magnesium alloy by a combination of electroless and electrodeposition techniques. Scanning electron microscopy and X-ray diffraction were employed to investigate the surface, cross-section morphologies and phase structure of coatings, respectively. The electrochemical corrosion behaviors of coatings in 3.5 wt.% NaCl solutions were evaluated by electrochemical impedance spectroscopy, open circuit potential and potentiodynamic polarization techniques. The results showed that the corrosion process of Ni-TiO{sub 2} composite coating was mainly composed of three stages in the long-term immersion test in the aggressive media, and could afford better corrosion and mechanical protection for the AZ91D magnesium alloy compared with single electroless Ni coating. The micro-hardness of the Ni-TiO{sub 2} composite coating improved more than 5 times than that of the AZ91D magnesium alloy.

Zhang Shiyan [School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Li Qing, E-mail: liqingswu@yeah.net [School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Yang Xiaokui [School of Materials Science and Engineering, Southwest University, Chongqing, 400715 (China); Zhong Xiankang; Dai Yan; Luo Fei [School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

2010-03-15

410

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

411

Evaluation of the delayed hydride cracking mechanism for transgranular stress corrosion cracking of magnesium alloys  

Microsoft Academic Search

This paper evaluates the important elements of delayed hydride cracking (DHC) for transgranular stress corrosion cracking (TGSCC) of Mg alloys. A DHC model was formulated with the following components: (i) transient H diffusion towards the crack tip driven by stress and H concentration gradients; (ii) hydride precipitation when the H solvus is exceeded; and (iii) crack propagation through the extent

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

2007-01-01

412

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

Microsoft Academic Search

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

Christopher Daniel Boland

2010-01-01

413

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

NASA Astrophysics Data System (ADS)

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) and a low copper variant (Al-6.87Zn-2.65Mg-0.06Cu). Crack growth rate tests were performed in 90% relative humidity (RH) air between 25 and 90°C to assure hydrogen embrittlement control. The underaged, peak aged, and overaged tempers were investigated. Hydrogen uptake in humid air, hydrogen diffusion, and hydrogen trapping were investigated for each temper. Lastly, near crack tip hydrogen concentration depth profiles were analyzed via nuclear reaction analysis (NRA) and secondary ion mass spectroscopy (SIMS) using a liquid gallium, focused ion beam sputtering source (FIB/SIMS). The results of this study help explain and quantify empirically known trends concerning HEAC resistance and also establish new findings. In the copper bearing alloy, overaged tempers are more resistant but not immune to HEAC. Humid air is an aggressive environment for Al-Zn-Mg alloys because water vapor reacts with bare aluminum to produce high surface concentrations of hydrogen. This occurs in all tempers. Hydrogen diffuses from the near surface region to the high triaxial stress region ahead of the crack tip and collects at the high angle grain boundaries. The combination of tensile stress and high hydrogen concentration at the grain boundaries then causes intergranular fracture. Crack extension bares fresh metal and the process of hydrogen production, uptake, diffusion to the stressed grain boundary, and crack extension repeats. One reason increased degree of aging improves HEAC resistance in copper bearing 7XXX series alloys is that volume lattice and effective hydrogen diffusion are slower. Overaging has little benefit on the stage II crack growth rate of low copper alloys because no such decrease in the diffusivity of hydrogen occurs.

Young, George Aloysius, Jr.

414

The magnesium silicide germanide stannide alloy: A new concept in ocean thermal energy conversion  

SciTech Connect

In devices hitherto used for the direct conversion of heat into electricity, commonly known as ''thermoelectric energy converters'', the efficiency of conversion is appreciably lower than that of conventional reciprocating or rotary heat engines. This low efficiency is brought about by the physical properties of the materials selected for the manufacture of these devices. The materials that are currently being used for this purpose are either simple elements and alloys thereof, such as silicon and germanium, or intermetallic compounds, either simple or alloys and solid solutions thereof. Of the latter, mention may be made of bismuth telluride, antimony telluride, lead telluride, antimony silver telluride, lead selenide, bismuth selenide, antimony selenide, etc., as well as mixtures and solid solutions of these and other compounds. A search in respect of these materials carried out in the U.S. Patent literature indicates indeed a quite substantial and impressive record.

Nicolaou, M.C.

1983-12-01

415

Environmental friendly plasma electrolytic oxidation of AM60 magnesium alloy and its corrosion resistance  

Microsoft Academic Search

Plasma electrolytic oxidation of Mg-based AM60 alloys was investigated using 50 Hz AC anodizing technique in an alkaline borate solution, which contained a new kind of organic. The anodic film is relatively smooth with some micro pores and cracks, while the anodic film consists of MgO, MgAl2O4 and MgSiO3. The electrochemical behavior of anodic film was studied by electrochemical impedance

Fa-he CAO; Long-yong LIN; Zhao ZHANG; Jian-qing ZHANG; Chu-nan CAO

2008-01-01

416

Quantitative characterization of processing-microstructure-properties relationships in pressure die-cast magnesium alloys  

Microsoft Academic Search

The central goal of this research is to quantitatively characterize the relationships between processing, microstructure, and mechanical properties of important high-pressure die-cast (HPDC) Mg-alloys. For this purpose, a new digital image processing technique for automatic detection and segmentation of gas and shrinkage pores in the cast microstructure is developed and it is applied to quantitatively characterize the effects of HPDC

Soon Gi Lee

2006-01-01

417

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 910 to 1070 K, atX\\u000a Mg = 0.1 to 0.7 and for the dilute range whenX\\u000a Mg = 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

418

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

419

Fatigue crack growth in IMV6 magnesium alloy at temperaturesof 293 and 140/sup 0/K  

SciTech Connect

The authors investigate the influence of low temperature on the fatigue crack growth rate and fracture microrelief in a broad range of cycle stress intensity factors K /SUB max/ of IMV6 alloy. Microfractographic analysis of the fracture surface was made on an electron microscope by the platinum-carbon replica method. Microfractograms of specimens are presented. It was shown that striations with a constant facing are fromed if the size of the plastic zone is comparable with the grain size.

Grinberg, N.M.; Kodryavtseva, E.E.; Serdyuk, V.A.

1986-03-01

420

Infiltration and wetting of alumina participate preforms by aluminum and aluminum-magnesium alloys  

Microsoft Academic Search

The infiltration and wetting of alumina participates by Al and by Al-Mg alloys was studied through pressure infiltration experiments.\\u000a In these experiments, a noninvasive capacitance technique was used to determine the infiltration front position as a function\\u000a of time. An unsaturated slug flow model was used to interpret the infiltration results and determine capillary pressures characteristic\\u000a of the infiltration process.

Tamala R. Jonas; James A. Cornie; Kenneth C. Russell

1995-01-01

421

Creep behavior of pure magnesium and Mg–Al alloys in active environments  

Microsoft Academic Search

Environment-enhanced creep, which we have called “corrosion creep” (CC), was investigated in pure Mg and die-cast AZ91D, AM50 and AS21 alloys in a borate buffer solution and 3.5% NaCl at room temperature. In contrast to the data in the air demonstrating only the first stage of creep process, in corrosive solutions, secondary and tertiary creep due to the plasticization effect

Ya. Unigovski; Z. Keren; A. Eliezer; E. M. Gutman

2005-01-01

422

Microstructural evolution and strengthening mechanisms in aluminum-scandium and aluminum-magnesium-scandium alloys  

NASA Astrophysics Data System (ADS)

Al-Sc alloys are potential candidates for structural industrial applications because of their excellent mechanical properties due to the presence of small, coherent Al3Sc (L12 structure) precipitates that are formed during aging. Additional Mg alloying not only enhances the mechanical properties by solid-solution hardening but also provides corrosion resistance and better weldability. Understanding and controlling the microstructure, i.e. the temporal evolution of the Al3Sc precipitate morphologies and the effects of other alloying elements such as Mg, are critical for optimizing mechanical properties. First, this research aims at describing the microstructural evolution of the Al3Sc precipitates during aging using transmission electron microscopies. The effects of Mg additions on precipitation are described using high-resolution transmission electron microscopy observations and three-dimensional atom-probe microscopy analyses. Results on Mg segregation, on the nanoscale level, at the coherent Al/Al3Sc interface are presented. A second goal of this research is to understand the precipitation-strengthening parameters controlling optimal yield strength at room temperature and creep resistance at elevated temperature (0.6 Tm), the effects of precipitate size and volume fraction upon yield and creep strengths of dilute Al-Sc and Al-Mg-Sc alloys are studied. Room temperature strength is described in terms of precipitate shearing and Orowan dislocation looping. Creep threshold stresses are found to be about ten times lower than the yield stresses at 300°C, indicative of a climb-controlled bypass mechanism, which is modeled by extending existing dislocation-particle interaction models.

Marquis, Emmanuelle Anne

2002-08-01

423

Abnormal distribution of microhardness in tungsten inert gas arc butt-welded AZ61 magnesium alloy plates  

SciTech Connect

In this study, the effects of heat input on the distribution of microhardness of tungsten inert gas (TIG) arc welded hot-extruded AZ61 magnesium alloy joints were investigated. The results show that with an increase of heat input, the distributions of microhardness at the top and bottom of the welded joints are different because they are determined by both the effect of grain coarsening and the effect of dispersion strengthening. With an increase of the heat input, the microhardness of the heat-affected zone (HAZ) at the top and bottom of welded joints and the fusion zone (FZ) at the bottom of welded joints decreased gradually, while the microhardness of the FZ at the top of welded joints decreased initially and then increased sharply. The reason for the abnormal distribution of microhardness of the FZ at the top of the welded joints is that this area is close to the heat source during welding and then large numbers of hard {beta}-Mg{sub 17}(Al,Zn){sub 12} particles are precipitated. Hence, in this case, the effect of dispersion strengthening dominated the microhardness.

Xu Nan [College of Material Science and Engineering, Chongqing University, Chongqing 400044 (China); Shen Jun, E-mail: shenjun2626@163.com [College of Material Science and Engineering, Chongqing University, Chongqing 400044 (China); Xie Weidong; Wang Linzhi; Wang Dan; Min Dong [College of Material Science and Engineering, Chongqing University, Chongqing 400044 (China)

2010-07-15

424

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

425

Microstructural Evolution and Flow Behavior of Twin-Roll Cast AZ41 Magnesium Alloy during Hot Compression  

NASA Astrophysics Data System (ADS)

Microstructural evolution and flow behavior of twin-roll cast AZ41 magnesium alloy during hot compression were characterized by employing deformation temperature of 300°C, 350°C and 400°C, and strain rate ranging from 10-3 to 10-2s-1. When compressed at different temperature (300°C, 350°C and 400°C) and strain rate (10-3 and 10-2s-1) all stress strain curves showed a flow softening behavior before strained to 0.51 due to dynamic recrystallization, even though concurrent twinning was quite active. Twinning contributed to the flow hardening behavior appeared during the end of hot compression (? > 0.51) at a strain rate of 10-2s-1 and elevated temperature (300°C, 350°C and 400°C) in spite of the softening effect of concurrently occurred dynamic recrystallization. TEM image showed that discontinuous recrystallization occurred when deformed at elevated temperature as high as 400°C and the strain rate ranging from 10-2 to 10-3s-1. It is suggested that dislocation slip, twinning and recrystallization develop in a cyclic mode from initial stage to the end of hot compression.

Liu, Zhiyi; Chen, Xu; Hou, Yanhui; Kang, Sukbong

2012-12-01

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

Ductile Fracture Prediction in Rotational Incremental Forming for Magnesium Alloy Sheets Using Combined Kinematic/Isotropic Hardening Model  

NASA Astrophysics Data System (ADS)

To predict the ductile fracture of a magnesium alloy sheet when using rotational incremental forming, a combined kinematic and isotropic hardening law is implemented and evaluated from the histories of the ductile fracture value ( I) using a finite element analysis. Here, the criterion for a ductile fracture, as developed by Oyane ( J. Mech. Work. Technol., 1980, vol. 4, pp. 65-81), is applied via a user material based on a finite element analysis. To simulate the effect of the large amount of heat generation at elements in the contact area due to the friction energy of the rotational tool-specimen interface on the equivalent stress-strain evolution in incremental forming, the Johnson-Cook (JC) model was applied and the results compared with equivalent stress-strain curves obtained from tensile tests at elevated temperatures. The finite element (FE) simulation results for a ductile fracture were compared with the experimental results for a (80 mm × 80 mm × 25 mm) square shape with a 45 and 60 deg wall angle, respectively, and a (80 mm × 80 mm × 20 mm) square shape with a 70 deg wall angle. The trends of the FE simulation results agreed quite well with the experimental results. Finally, the effects of the process parameters, i.e., the tool down-step and tool radius, on the ductile fracture value and FLC at fracture (FLCF) were also investigated using the FE simulation results.

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

2010-08-01

428

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

429

Effects of Rare Earth Element Additions on the Impression Creep Behavior of AZ91 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The effects of 1, 2, and 3 wt pct rare earth (RE) element additions on the microstructure and creep behavior of cast AZ91 Mg alloy were investigated by impression tests. The tests were carried out under constant punching stress in the range 200 to 650 MPa at temperatures in the range 425 to 525 K. Analysis of the data showed that for all loads and temperatures, the AZ91-2RE alloy had the lowest creep rates and, thus, the highest creep resistance among all materials tested. This is attributed to the formation of Al11RE3 with a branched morphology, reduction in the volume fraction of the eutectic ?-Mg17Al12 phase, and solid solution hardening effects of Al in the Mg matrix. The stress exponents and activation energies were the same for all alloy systems studied, 5.3 to 6.5 and 90 to 120 kJ mol-1, respectively, with the exception that the activation energy for the AZ91-3RE system was 102 to 126 kJ mol-1. An observed decreasing trend of creep-activation energy with stress suggests that two parallel mechanisms of lattice and pipe diffusion-controlled dislocation climb are competing. Dislocation climb controlled by dislocation pipe diffusion is controlling at high stresses, whereas climb of edge dislocations is the controlling mechanism at low stresses.

Kabirian, F.; Mahmudi, R.

2009-09-01

430

Hydroxyapatite-Coated Magnesium-Based Biodegradable Alloy: Cold Spray Deposition and Simulated Body Fluid Studies  

NASA Astrophysics Data System (ADS)

A simple modified cold spray process in which the substrate of AZ51 alloys were preheated to 400 °C and sprayed with hydroxyapatite (HAP) using high pressure cold air nozzle spray was designed to get biocompatible coatings of the order of 20-30 ?m thickness. The coatings had an average modulus of 9 GPa. The biodegradation behavior of HAP-coated samples was tested by studying with simulated body fluid (SBF). The coating was characterized by FESEM microanalysis. ICPOES analysis was carried out for the SBF solution to know the change in ion concentrations. Control samples showed no aluminum corrosion but heavy Mg corrosion. On the HAP-coated alloy samples, HAP coatings started dissolving after 1 day but showed signs of regeneration after 10 days of holding. All through the testing period while the HAP coating got eroded, the surface of the sample got deposited with different apatite-like compounds and the phase changed with course from DCPD to ?-TCP and ?-TCMP. The HAP-coated samples clearly improved the biodegradability of Mg alloy, attributed to the dissolution and re-precipitation of apatite showed by the coatings as compared to the control samples.

Noorakma, Abdullah C. W.; Zuhailawati, Hussain; Aishvarya, V.; Dhindaw, B. K.

2013-05-01

431

Quantitative characterization of processing-microstructure-properties relationships in pressure die-cast magnesium alloys  

NASA Astrophysics Data System (ADS)

The central goal of this research is to quantitatively characterize the relationships between processing, microstructure, and mechanical properties of important high-pressure die-cast (HPDC) Mg-alloys. For this purpose, a new digital image processing technique for automatic detection and segmentation of gas and shrinkage pores in the cast microstructure is developed and it is applied to quantitatively characterize the effects of HPDC process parameters on the size distribution and spatial arrangement of porosity. To get better insights into detailed geometry and distribution of porosity and other microstructural features, an efficient and unbiased montage based serial sectioning technique is applied for reconstruction of three-dimensional microstructures. The quantitative microstructural data have been correlated to the HPDC process parameters and the mechanical properties. The analysis has led to hypothesis of formation of new type of shrinkage porosity called, "gas induced shrinkage porosity" that has been substantiated via simple heat transfer simulations. The presence of inverse surface macrosegregation has been also shown for the first time in the HPDC Mg-alloys. An image analysis based technique has been proposed for simulations of realistic virtual microstructures that have realistic complex pore morphologies. These virtual microstructures can be implemented in the object oriented finite elements framework to model the variability in the fracture sensitive mechanical properties of the HPDC alloys.

Lee, Soon Gi

432

Effect of microalloying on microstructure and hot working behavior for AZ31 based magnesium alloy  

NASA Astrophysics Data System (ADS)

The formability of Mg alloy sheet in the as-hot rolled condition depends on the microstructure developed during hot rolling. In general, the formability of Mg alloys is improved by finer grain sizes. 'Microalloying' levels of calcium (Ca), strontium (Sr), and cerium (Ce) have been found to refine the as-cast structure, but there is no information as to whether this effect will be reflected in the as-hot worked structure and formability. Thus, in this work, the effects of microalloying levels of calcium (Ca), strontium (Sr), and cerium (Ce) on the microstructures (from as-cast to as-hot rolled) and subsequent hot deformation behavior of AZ31, nominally 3% Al, 1% Zn, and 0.3%Mn, were systematically investigated. To include the effect of solidification rate these alloys were cast in different moulds (preheated steel mould, Cu-mould, and water cooled Cu-mould). One-hit compression testing at temperatures between 250°C ˜ 400 °C, strain rates of 0.001, 0.01, 0.1 s-1 and strains from 0.2 up to 1.0, was performed to investigate the basic hot compression behavior, while two-hit compression testing was conducted to determine the static softening behavior. Hot rolling of the microalloyed AZ31 alloys was then carried out to study the effects of microalloying on as-hot rolled structure under two sets of rolling schedules. To investigate the formability of these microalloyed sheets, tensile tests were completed over a temperature range between ambient and 450°C, at strain rates between 0.1 and 0.0003 s-1. Results show that Ca and Sr act to refine the as cast grain size and the second phases, consistently promoting fine and uniform as-hot rolled grain structure. With regard to grain refinement, calcium has the strongest effect, whereas Ce is most effective for second phase refinement. In addition, microalloying retards grain growth during hot tensile testing. Multiple alloying presents a combined and complementary effect. A refined and uniform grain structure combined with well dispersed and thermally stable second phases significantly improves the hot formability of AZ31 sheets by promoting dynamic recrystallization (DRX) in the matrix, resisting grain coarsening, and retarding the development of cavitation and necking. Under the superplastic condition of 450°C and 0.0003 s -1, the elongation was improved by 17% with Ca only, 26% with Ca and Ce, 51% with Ca and Sr, and 59% with Ca, Sr and Ce.

Shang, Lihong

433

Characterization of complex, solid-state flow and mixing in the friction-stir welding (FSW) of aluminum alloy 6061-T6 to magnesium alloy AZ91D using color metallography  

Microsoft Academic Search

Semi-solid-cast magnesium (Mg) alloy AZ91D (3% solid fraction) was friction-stir welded (FSW) to aluminum (Al) alloy 6061-T6\\u000a in continuous non-porous welds. The resulting welds were analyzed in order to understand the solid-state mixing mechanisms\\u000a that create the chaotic intercalated weld zone microstructure characterized by swirls and vortexes of dynamically recrystallized\\u000a material. Severe plastic deformation in the solid-state is accommodated by

A. C. Somasekharan; L. E. Murr

2006-01-01

434

Porosity, underfill and magnesium loss during continuous wave Nd:YAG laser welding of thin plates of aluminum alloys 5182 and 5754  

SciTech Connect

The influence of various welding parameters on porosity and underfill formation and magnesium loss during continuous wave Nd:YAG laser beam welding of thin plates of aluminum-magnesium Alloys 5182 and 5754 was investigated. The porosity within the welds was characterized by radiography, optical microscopy and SEM. The compositional change in the welds was measured by electron microprobe analysis. The experimental results showed that the instability of the keyhole was the dominant cause of macro-porosity formation during laser welding of thin plates of aluminum Alloys 5182 and 5754. Hydrogen did not play a significant role in porosity formation. Although underfill was commonly observed at the root of full-penetration welds, sharp or deep notches, which are harmful to the mechanical properties of the welds, were not present. Reduction in magnesium concentration was more pronounced during conduction mode welding. Welding in keyhole mode resulted in much larger weld pool and less pronounced composition change. The extent of defocusing of the laser beam greatly affected the stability of the keyhole, weld pool geometry, pore formation and composition change.

Pastor, M.; Zhao, H.; Martukanitz, R.P.; Debroy, T. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

1999-06-01

435

Magnesium Tube Hydroforming  

NASA Astrophysics Data System (ADS)

Magnesium alloys can be considered as alternative materials towards achieving light weight structures with high material stiffness. The formability of two magnesium alloys, viz. AZ31 and ZM21 has been experimentally tested using the IHP forming process. A new die set up for hot IHP forming has been designed and the process experimentally investigated for temperatures up to 400 °C. Both alloys exhibit an increase in formability with increasing forming temperature. The effect of annealing time on materials forming properties shows a fine grained structure for sufficient annealing times as well as deterioration with a large increase at the same time. The IHP process has also been used to demonstrate practicability and feasibility for real parts from manufacture a technology demonstrator part using the magnesium alloy ZM21.

Liewald, M.; Pop, R.; Wagner, S.

2007-04-01

436

Characterization of adiabatic shear bands in AM60B magnesium alloy under ballistic impact  

SciTech Connect

Adiabatic shear bands in Mg alloy under ballistic impact at a velocity of 0.5 km.s{sup -1} were characterized by means of optical microscope, scanning electron microscope, transmission electron microscope and indenter technique. The results show that adiabatic shear bands were formed around the impacted crater, and the deformed and transformed bands were distinguished by etching colors in metallographic observation. TEM observation shows that the deformed bands were composed of the elongated grains and high density dislocations, while the transformed bands composed of the ultrafine and equiaxed grains were confirmed. In initial stage, the severe localized plastic deformation led to the formation of elongated grains in the deformed bands. With localized strain increasing, the severe localized deformation assisted with the plastic temperature rising led to the severe deformation grains evolved into the ultrafine and equiaxed grains, while the deformed bands were developed into transformed bands. The formation of the ultrafine and equiaxed grains in the transformed bands should be attributed to the twinning-induced rotational dynamic recrystallization mechanism. High microhardness in the bands was obtained because of the strain hardening, grain refining and content concentration. - Research Highlights: {yields} Deformed and transformed bands are found in Mg alloy under ballistic impact. {yields} The microstructures in the deformed and transformed bands are characterized. {yields} The evolution process of the microstructure in the bands is discussed.

Zou, D.L.; Zhen, L., E-mail: lzhen@hit.edu.cn; Xu, C.Y.; Shao, W.Z.

2011-05-15

437

Effects of Zr Additions on the Microstructure and Impression Creep Behavior of AZ91 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The effects of 0.2, 0.6, and 1.0 wt pct Zr additions on the microstructure and creep behavior of AZ91 Mg alloy were investigated by impression tests carried out under constant punching stress ( ? imp) in the range 100 to 650 MPa, corresponding to the modulus-compensated stress levels of {{0.007 le ?_{{imp}} } {G le 0.044}} , at temperatures in the range 425 K to 570 K (152 °C to 297 °C). The alloy containing 0.6 wt pct Zr showed the best creep resistance mainly due to the favorable formation of Al3Zr2 and Al2Zr intermetallic compounds, reduction in the volume fraction of the eutectic ?-Mg17Al12 phase, and solid solution hardening effects of Al in the Mg matrix. Based on the obtained stress exponents of 4.2 to 6.5 and activation energies of 90.7 to 127.1 kJ/mol, it is proposed that two parallel mechanisms of lattice and pipe-diffusion-controlled dislocation climb compete. Dislocation climb controlled by dislocation pipe diffusion prevails at high stresses, whereas climb of edge dislocations is the controlling mechanism at low stresses.

Kabirian, F.; Mahmudi, R.

2010-12-01

438

Simulation of Stresses during Casting of Binary Magnesium-Aluminum Alloys  

NASA Astrophysics Data System (ADS)

A viscoplastic stress model is used to predict contraction forces measured during casting of two binary Mg-Al alloys. Force measurements from castings that did not hot tear, together with estimates from data found in the literature, are used to obtain the high-temperature mechanical properties needed in the stress model. In the absence of hot tearing, the simulation results show reasonably good agreement with the measurements. It is found that coherency of the semisolid mush starts at a solid fraction of about 0.5 and that the maximum tensile strength for the Mg-1 and 9 wt pct Al alloys at their final solidification temperatures is 1.5 and 4 MPa, respectively. In the presence of hot tearing, the measured stresses are generally overpredicted, which is attributed to the lack of a fracture model for the mush. Based on the comparison of measured and predicted stresses, it is also shown that coupling of the stress model to feeding flow and macrosegregation calculations is needed in order to accurately predict stresses in the presence of hot tearing.

Pokorny, M. G.; Monroe, C. A.; Beckermann, C.; Zhen, Z.; Hort, N.

2010-12-01

439

The corrosion performance of die-cast magnesium alloy MRI230D in 3.5% NaCl solution saturated with Mg(OH){sub 2}  

SciTech Connect

The environmental behavior of die-cast magnesium alloy MRI230D designated for high-temperature applications was evaluated in comparison with regular AZ91D alloy. The microstructure examination was carried out using SEM, TEM, and X-ray diffraction analysis; the corrosion performance in 3.5% NaCl solution was evaluated by immersion test, salt spray testing, potentiodynamic polarization analysis, and stress corrosion behavior by Slow Strain Rate Testing (SSRT). Although the general corrosion resistance of MRI230D was slightly improved compared to that of AZ91D alloy its stress corrosion resistance was relatively reduced. The variations in the environmental behavior of the two alloys were mainly due to the differences in their chemical composition and microstructure after die casting. In particular, the differences were related to the reduced Al content in MRI230D and the addition of Ca to this alloy, which consequently affected its relative microstructure and electrochemical characteristics. - Research Highlights: {yields}Corrosion and SCC resistance of a new Mg alloy MRI230D was evaluated vs. regular AZ91D. {yields}MRI230D has a minor advantage in corrosion performance compared with AZ91D. {yields}The SCC resistance of MRI230D by SSRT analysis was relatively reduced. {yields}The reduced SCC resistance of MRI230D was due to the detrimental effect of Ca on ductility.

Aghion, E., E-mail: egyon@bgu.ac.il; Lulu, N.

2010-11-15

440

Effects of temperature-dependent material properties and shielding gas on molten pool formation during continuous laser welding of AZ91 magnesium alloy  

NASA Astrophysics Data System (ADS)

Laser welding processes are widely used for fabrications in many engineering applications such as aerospace and automotives. In this paper, a moving distributed heat source model based on Goldak's method [1] has been implemented into finite volume thermal simulations in order to predict temperature distributions during the welding process of a magnesium alloy and to study the effects of variations in thermal properties, absorption coefficient and gas shielding on the computed temperature distributions and weld pool dimensions. The main conclusion is the significant effects of varying the thermal conductivity and absorption coefficient of magnesium. Also, it has been seen that the shielding gas, besides its main role of protection against oxidation, has a significant effect on the width of the weld pool. Finally, the obtained results have been compared to the experimental ones and a satisfactory correlation has been observed, indicating the reliability of the model developed in this study.

Bannour, Sana; Abderrazak, Kamel; Mhiri, Hatem; Le Palec, Georges

2012-11-01

441

The Small Fatigue Crack Growth Behavior of an AM60 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The effects of thermomechanical processing and subsequent heat treatment on the small fatigue crack growth (FCG) behavior of an AM60 (Mg-6.29Al-0.28Mn wt pct) alloy were evaluated. The effects of mechanical loading parameters, such as maximum stress and load-ratio, on the small FCG behavior were also determined. Maximum stress did not appear to affect the crack propagation rate of small cracks in the stress and crack size ranges considered. Materials with different microstructures and yield stresses, introduced by different processing conditions, showed similar crack growth rates at equivalent stress intensity factor ranges. The effect of load ratio on small crack growth rates was recorded. Fracture surface characterization suggested that the fatigue crack propagation mechanism was a mixture of transgranular and intergranular cracking. Porosity and other material defects played respective important roles in determining the fatigue crack initiation and propagation behavior.

Chen, Zhe; Shyam, Amit; Huang, Jack; Decker, Ray F.; LeBeau, Steve E.; Boehlert, Carl J.

2013-02-01

442

Localized corrosion behavior of aluminum-magnesium-silicon alloy in ground water  

SciTech Connect

The localized corrosion behavior of Al-Mg-Si alloy (Al 6063, UNS A96063) in five types of ground waters found in Japan was studied in terms of the relationship between chemical composition of the ground water and the electrochemical characteristics. Localized corrosion (nodular pitting corrosion surrounded with white corrosion products) occurred in all aerated, original ground water after immersion for 480 h, but weight loss of the specimens different according to the type of ground water. Weight loss was inversely proportional to the difference between pitting potential (E[sub pit]) and corrosion potential (E[sub corr]). E[sub pit] was dominated mainly by chloride ion concentration, and E[sub corr] increased with an increase in calcium hardness. From electrochemical studies in ground water and synthetic waters, the increase of E[sub corr] was caused by enhancement of dissolved oxygen reduction in the presence of calcium ions, bicarbonate, and dissolved oxygen.

Sato, F.; Asakawa, Y. (Kobe Steel, Ltd., Hyogo (Japan). Aluminum and Copper Div.)

1999-05-01

443

Long-term in vivo degradation behaviour and biocompatibility of the magnesium alloy ZEK100 for use as a biodegradable bone implant.  

PubMed

Magnesium alloys are the focus of research as resorbable materials for osteosynthesis, as they provide sufficient stability and would make surgery to remove implants unnecessary. The new degradable magnesium alloy ZEK100 was developed to improve the stability and corrosion resistance by alloying with zinc, rare earth metals and zirconium. As the implants were degraded to only a limited extent after 6months implantation in a previous in vivo study the present study was conducted to evaluate the long-term degradation behaviour and biocompatibility in the same animal model over 9 and 12months. Five rabbits each with intramedullary tibia implants were examined over 9 and 12months. Three legs were left without an implant to serve as negative controls. Numerous examinations were performed in the follow-up (clinical examinations, serum analysis, and radiographic and in vivo micro-CT investigations) and after death (ex vivo micro-CT, histology, and implant analysis) to assess the in vivo degradation and biocompatibility. It could be shown that favourable in vivo degradation behaviour is not necessarily associated with good biocompatibility. Although ZEK100 provided a very high initial stability and positive biodegradation, it must be excluded from further biomedical testing as it showed pathological effects on the host tissue following complete degradation. PMID:22922249

Dziuba, Dina; Meyer-Lindenberg, Andrea; Seitz, Jan Marten; Waizy, Hazibullah; Angrisani, Nina; Reifenrath, Janin

2012-08-23

444

Fatigue design of welded joints from the wrought magnesium alloy AZ31 by the local stress concept with the fictitious notch radii of r f = 1.0 and 0.05 mm  

Microsoft Academic Search

Investigations were carried out with three different types of MIG- and TIG-welded joints of the magnesium alloy AZ31(ISO-MgAl3Zn1): fully or partially penetrated butt welds, transversal stiffeners. The evaluation of the results showed that the local stress concept using the fictitious notch radius of rf=1.0 mm can be applied to magnesium welded joints from plates with thicknesses t?5 mm independently of

Ö. Karakas; C. Morgenstern; C. M. Sonsino

2008-01-01

445

A calorimetric investigation of recrystallization in aluminum magnesium silicon copper alloys  

NASA Astrophysics Data System (ADS)

The recrystallization behavior of three Al--Mg--Si--Cu alloys with varying iron and manganese additions was studied by differential power scanning calorimetry under non-isothermal annealing conditions. The influence of cold deformation on the precipitation sequence and its interaction with recrystallization was also investigated. The DSC experiments were complemented by hardness measurements and microstructural studies by optical and electron microscopy. The DSC signals, after optimization of the baseline, were used for the calculation of the kinetic parameters of the recrystallization process. Two different modeling approaches based on global JMAK kinetics were implemented. The first approach utilizes the classical isothermal JMAK expression directly, while the second approach introduces a path variable related to the thermal history of the material in the JMAK description. Model-independent estimates of the activation energy were also evaluated using the Flynn-Wall-Ozawa integral isoconversion method. The results show that the initial stages of recrystallization are not affected by the preceding precipitation processes and recrystallization always follows the precipitation of the Q' phase. However, during recrystallization enhanced coarsening of the Q' phase takes place leading to its transformation to the more stable Q phase. The Q phase exerts a Zener pinning pressures on the migrating boundaries preventing the formation of an equilibrium grain structure. Moreover, for high Fe and Mn additions, discontinuous precipitation of Mg2Si overlaps with the end of recrystallization and exerts an additional pinning pressure on the boundaries. Varying the Fe and Mn content significantly affects the recrystallization kinetics. PSN is promoted in alloys with the higher Fe and Mn content and the recrystallization temperature shifts to lower values. The modeling results show that the recrystallization process conforms to the classical JMAK type behavior. The course of the reaction was reproduced successfully by the path variable approach and the evaluated activation energies were in good agreement with the isoconversional model-independent estimates. However, when the classical JMAK expression was applied directly to non-isothermal measurements, a dependency of the recrystallization process on thermal history was observed.

Abou Khatwa, Mohamed

446

Propagation mode of Portevin-Le Chatelier plastic instabilities in an aluminium-magnesium alloy  

SciTech Connect

The Portevin-Le Chatelier (PLC) effect is characterized by the appearance of serrations in load (hard tensile machine for constant strain rate tests) or by steps (soft tensile machine for constant stress rate tests) or by steps (soft tensile machine for constant stress rate tests) on the stress-strain curves. It is now widely accepted that the PLC propagative instability stems from the dynamic interaction between diffusing solute atoms and mobile dislocations in the temperature and strain rate ranges where dynamic strain ageing (DSA) takes place. This competition results in a negative strain-rate sensitivity. However, in some alloys, like concentrated solid solutions, shearing of precipitates accompanied by their dissolution and subsequent reprecipitation during tensile test may also lead to a negative strain rate sensitivity. In view of the renewed theoretical interest in propagative instabilities, it is important that the experimental features of band propagation be well characterized. In this work the authors present experimental results that are obtained from the investigation of the PLC bands associated with discontinuous yielding. These results show that the band strain, the band velocity and the propagation mode of the bands depend on the stress rate when the test is carried out on a soft tensile machine.

Zeghloul, A.; Mliha-Touati, M.; Bakir, S. [Univ. de Metz (France). Lab. de Physique et Mecanique des Materiaux

1996-11-01

447

Grain Growth in Multiple Scales of Polycrystalline AZ31 Magnesium Alloy by Phase-Field Simulation  

NASA Astrophysics Data System (ADS)

A multiscale phase-field model was established on the assumption of an isotropic single-phase system to simulate the realistic spatiotemporal process of grain growth for polycrystalline Mg-Al-Zn alloy AZ31, especially to determine the mechanisms for unique nanostructure evolution. The expression of the local free energy density function was improved according to different driving forces. The grain boundary range and grain boundary energy were studied in each scale to determine the correct gradient and coupling parameters, respectively. It is shown that the grain boundary energy in nanoscales is lower down to about half that in the micron scale, the time exponent n in the kinetic equation is varied from 5 to 2 from the nanograins to the micrograins, and the grain growth rate in nanoscale is much slower in an order of magnitude than that in the micron scale. These findings can be proven by the limited experimental results in the literature. Simulations expose that the solute atoms like to segregate at the grain boundaries much more severely in nanostructure than that in conventional microstructure, an