Papers by Keyword: Magnesium Alloy

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Authors: Hanuš Seiner, Petr Sedlák, Lucie Bodnárová, Michal Landa, Jitka Stráská, Miloš Janeček
Abstract: Resonant ultrasound spectroscopy (RUS) was applied to monitor the micro-cracking process occurring during cooling at polished surfaces of an ultrafine-grained AZ31 magnesium alloy. It was observed that although the net of micro-cracks covered only narrow regions along the edges of the sample, its appearance resulted in a strong increase of the attenuation of the free elastic vibrations, and was, thus, sensitively detectable from the evolution of the RUS resonant spectra with temperature. This approach enabled a reliable determination of the threshold temperature for micro-cracking.
Authors: Ondrej Muránsky, David G. Carr, Petr Šittner, E.C. Oliver, P. Dobroň
Abstract: In-situ neutron diffraction has been used to study the pseudoelastic-like behaviour of hydrostatically extruded AZ31 magnesium alloy during stress-strain cycles in compression and tension along the extrusion direction. It has been confirmed that the activation of reversal twinning processes during unloading is responsible for the macroscopically observed hysteresis effect. Moreover, neutron diffraction data reveals the existence of high tensile stresses in grains which have just experienced significant twinning activity prior to the start of the unload cycle. It is thus proposed that this tensile stresses provides the necessary driving force for the activation of untwinning in already twinned grains.
Authors: Wei Min Gan, Yuan Ding Huang, Yu Ling Xu, Michael Hofmann, Karl Ulrich Kainer, Nobert Hort
Abstract: A new Mg-RE (rare earth) alloy was previously developed by micro-alloying method (RE< 0.4 wt.%), which achieves a high ductility and good corrosion resistance. In-situ tensile test via neutron and synchrotron diffraction were performed to investigate first the deformation behaviour; and second the texture evolution which can be related to the deformation mechanism, and finally to understand why the as-cast Mg-RE alloys show such a high tensile ductility.Preliminary results showed that a dominated basal fibre texture was gradually developed with the increase of tensile strain. However, before the sample was broken a (10.0) fibre texture showed a similar intensity to that in (00.2), which means more activations of the non-basal slip planes during tensile deformation. This could also contribute to a relatively high elongation of this new Mg-RE alloy at room temperature. Further discussion will be showed together with the microstructures.
Authors: Sha Luo, Qing Qing Zhang, Yan Chang Zhang, Chao Li, Xiao Qing Xu, Tie Tao Zhou
Abstract: Magnesium alloys have a good application prospect in the fields of bone implants and cardiovascular stents due to their excellent properties, such as close density and elastic modulus to those of nature bone, high specific strength and rigidity, biodegradation and biocompatibility. In this paper, the feasibility of the use of the forged Mg-Li-X alloys (Mg-Li-Al-Zn-Ca-Sr) as biodegradable metals was investigated by immersion tests in the Hanks solution and skin-tissue implantation tests. The methods of SEM-EDS and XRD were used to research the corrosion morphology and corrosion products of the forged Mg-Li-X alloys after the in-vitro and in-vivo tests. At last, the in-vitro cytotoxicity was investigated by the MTT tests on L929 cells. Results showed that corrosion mechanism of the forged Mg-Li alloys was pitting and the surfaces were covered by Mg (OH)2,CaCO3 and Ca (H2PO4)2 . During the 5 weeks implantation period, the rats survived from the operation, which indicates that the elements and the compounds formed are non-toxic to the rats. The forged Mg-Li alloy showed Grade 0~1 cytotoxicity, which manifests the forged Mg-Li alloy has good biocompatibility and eligible toxicity for implant applications.
Authors: Cheng Long Liu, Jiang Jiang, Meng Wang, Yue Ji Wang, Paul K Chu, Wei Jiu Huang
Abstract: Successful application of magnesium alloys as degradable load-bearing implants is determined by their biological performance especially degradation and corrosion behavior in the human body. Three magnesium alloys, namely WE43, ZK60, and AZ91 are investigated in this work. The in vitro degradation behavior, cytotoxicity, and genotoxicity are evaluated by corrosion tests, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and micronuclei tests, respectively. Immersion tests indicate that the ZK60 alloy has the best corrosion resistance and lowest corrosion rate in Hank’s solution, followed by AZ91 alloy and WE43 alloy in that order. The MTT results obtained from the three magnesium alloys after 7 days of immersion indicate good cellular viability. However, excessively high aluminum and magnesium concentrations have a negative influence on the genetic stability.
Authors: Gaur Swati, Anand Sawroop Khanna, Raghuvir Kumar Singh Raman
Abstract: In the present study, combinations of a phosphonato silane with a precursor, Methyltriethoxy silane (MTEOS) in various ratios were applied onto the alloy Mg-6Zn-Ca. The corrosion resistance of the coated and uncoated specimens in a modified simulated body fluid (m-SBF) was characterized by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Results suggest that the silane coating significantly decreases the degradation rate of the magnesium alloy, indicating its potential to be used as a corrosion barrier for magnesium alloy temporary implants.
Authors: Chun Lan Lu, He Yan Dong, Wei Wang, Gang Yang
Abstract: Magnesium alloys are very biocompatible and show promise for use in implant device. The focus of this article lies in the evaluation of the degradation performance and biological response of a paclitaxel-eluting biodegradable stent based on WE43 magnesium alloy by in vivo and in vitro studies. The corrosion characteristics analyzed by immersion testing in phosphate buffered solution (PBS) for 24h. Severe corrosion took place reveal fast degradation, lead to the stent strut easily fracture during expanding. The chemical nature of this conversion in vivo was investigated by scanning electron microscope (SEM) equipped with energy dispersive spectrum (EDS). For the endothelial surface coverage and the microstructure of the stent were also investigated by SEM. The results show that the deployment of the stent in arteries was safe, endothelial coverage occurred above stent struts and between struts after implanted 6 weeks, and more slowly than stainless steel stent and paclitaxel-eluting stainless steel stent. The grains boundaries of the stents are easily corroded in vivo environment, which should strongly affect the radial strength and mechanical integrity of the stent, leading early recoil contribute to restenosis.
Authors: Pierre Lhuissier, Mario Scheel, Luc Salvo, Elodie Boller, Marco Di Michiel, Jean Jacques Blandin
Abstract: As for aluminium alloys, magnesium alloys are generally sensitive to strain induced cavitation when they are deformed in superplastic conditions. It has been widely shown that X-ray micro tomography is a particularly efficient tool for studying in 3D damage mechanisms during superplastic deformation. However, such characterisations are generally performed in post mortem conditions, namely on samples first deformed up to given strains and then characterised. In the present investigation, thanks to particularly short acquisition times offered by ESRF, damage induced by superplastic deformation of a magnesium alloy is studied thanks to tomography analyses performed in 4D conditions, namely directly during high temperature deformation tests. Such conditions provide unique opportunities for investigating nucleation, growth and coalescence of cavities since it is thus possible to follow each cavity up to the fracture process.
Authors: Wei Jiu Huang, Rong Chang Zeng, An Hua Chen
Abstract: The paper studied the fretting properties and the fretting mechanism of AZ91D and AM60B magnesium alloy. The results showed that the AZ91D alloy displayed lower friction coefficient and smaller wear volume than those of AM60B alloy, and also showed superior ability than those of AM60B in resisting crack nucleation and propagation. The fretting wear mechanisms of AZ91D and AM60B alloy were similar, including adhesion wear, surface fatigue wears and abrasive wear.
Authors: Mok Young Lee, Woong Seong Chang, Sook Hwan Kim
Abstract: Magnesium alloys are becoming important material for light weight car body, due to their low specific density but high specific strength. However they have a poor weldability, caused by high oxidization tendency and low vapour temperature. In this study, the welding performance of magnesium alloy was investigated for automobile application. The material was rolled magnesium alloy sheet contains 3wt%Al, 1wt%Zn and Mg balance. The effects of filler wire addition was investigated on 2kW Nd:YAG laser welding. For the results, the mechanical properties of welded specimen were similar with base metal in laser welding with and without filler wire. The bridging ability was improved with filler wire without weld properties deterioration on laser welding of magnesium alloy.
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