The Experts below are selected from a list of 9189 Experts worldwide ranked by ideXlab platform
R Ebrahimi - One of the best experts on this subject based on the ideXlab platform.
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investigation on the feasibility of room temperature plastic deformation of Pure Magnesium by simple shear extrusion process
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: Bayat N Tork, N Pardis, R EbrahimiAbstract:Abstract This paper investigates the feasibility of room temperature plastic deformation of Pure Magnesium through a method of severe plastic deformation (SPD), namely simple shear extrusion (SSE). Different SPD techniques were performed at room temperature and SSE was considered as a promising technique for deformation of Magnesium at room temperature. An extrusion process was performed prior to SSE technique to change the initial grain size and texture in the samples. In addition, the effect of different extrusion temperatures and processing strain rates were also studied and a procedure was presented for successful SSE processing of Magnesium at room temperature. Finally, the effect of these processing conditions on hardness and microstructural evolutions were investigated.
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investigation on the feasibility of room temperature plastic deformation of Pure Magnesium by simple shear extrusion process
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: Bayat N Tork, N Pardis, R EbrahimiAbstract:Abstract This paper investigates the feasibility of room temperature plastic deformation of Pure Magnesium through a method of severe plastic deformation (SPD), namely simple shear extrusion (SSE). Different SPD techniques were performed at room temperature and SSE was considered as a promising technique for deformation of Magnesium at room temperature. An extrusion process was performed prior to SSE technique to change the initial grain size and texture in the samples. In addition, the effect of different extrusion temperatures and processing strain rates were also studied and a procedure was presented for successful SSE processing of Magnesium at room temperature. Finally, the effect of these processing conditions on hardness and microstructural evolutions were investigated.
Toshiji Mukai - One of the best experts on this subject based on the ideXlab platform.
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Effect of deformation twins on damping capacity in extruded Pure Magnesium
Journal of Alloys and Compounds, 2015Co-Authors: Hiroyuki Watanabe, Yasuyoshi Sasakura, Naoko Ikeo, Toshiji MukaiAbstract:Abstract The damping capacity, which was characterized by bending vibration decay, was examined in extruded Pure Magnesium to understand the role played by pre-existing twins introduced by pre-strain. For materials without pre-strain, the damping capacity consisted of the strain-independent and the strain-dependent parts, which emerged above a critical strain. The critical strain observed for the damping capacity corresponded to the proportional limit observed for the tensile or compressive curves. For materials pre-strained to −1% and −8% in the extrusion direction, the damping capacity began to increase at low strains below the proportional limit and was higher than that without pre-strain. The higher damping capacity is thought to occur because of the alternate shrinkage and growth of pre-existing twins.
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Nanoindentation creep behavior of grain boundary in Pure Magnesium
Philosophical Magazine Letters, 2010Co-Authors: Hidetoshi Somekawa, Toshiji MukaiAbstract:Nanoindentation creep tests were performed at the grain boundary and grain interior in Pure Magnesium. The grain boundary showed a high strain rate sensitivity exponent and was dominated by grain boundary sliding due to the high diffusion rate at the grain boundary. The grain boundary affected the deformation behavior of the area at a distance of 2 µm into the grain interior. On the other hand, the grain interior had a low strain rate sensitivity exponent, because its matrix was too large to be influenced by the grain boundary. The deformation mechanism in the grain interior was determined to be dislocation slip.
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precipitation control of calcium phosphate on Pure Magnesium by anodization
Corrosion Science, 2008Co-Authors: Sachiko Hiromoto, Akiko Yamamoto, Hidetoshi Somekawa, Tamao Shishido, Norio Maruyama, Toshiji MukaiAbstract:Calcium phosphate precipitated on Pure Magnesium from artificial plasma (modified Hanks’ solution) was varied by anodization and autoclaving, aiming the control of corrosion rate of bioabsorbable Magnesium. Rough and smooth anodized film was formed depending on anodizing voltage in 1 N NaOH. The amount of calcium phosphate precipitated on the porous film was 2–3 times larger than that on the smooth film. The Ca/P ratio on the porous film was slightly higher than that on the smooth film. The autoclaving did not significantly influence the morphology of anodized film; however, the precipitation of calcium phosphate was restricted. No significant local corrosion occurred after the immersion in modified Hanks’ solution. It is demonstrated that the precipitation of calcium phosphate on Magnesium can be controlled by anodization and autoclaving.
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effect of grain refinement on fracture toughness in extruded Pure Magnesium
Scripta Materialia, 2005Co-Authors: Hidetoshi Somekawa, Toshiji MukaiAbstract:Abstract The fracture toughness of extruded Pure Magnesium increased with grain refinement due to the effect of the plastic zone, which is a sensitive factor related to the mechanical properties of yield strength, elongation-to-failure and strain hardening exponent.
Paul K Chu - One of the best experts on this subject based on the ideXlab platform.
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controllable degradation of biomedical Magnesium by chromium and oxygen dual ion implantation
Materials Letters, 2011Co-Authors: Xiongbo Yang, Paul K ChuAbstract:Abstract The surface stability of biodegradable Magnesium is crucial to tissue growth on implants in the initial healing stage. Inspired by the design principle of biomedical stainless steels, we implant chromium as a passive element into Pure Magnesium to alter the surface biodegradation behavior. However, because Cr exists in the metallic state in the implanted layer to induce the galvanic effect, excessively fast degradation is observed. Ensuing implantation of oxygen produces a thicker surface oxidized layer composed of chromium oxide, which successfully retards the surface degradation of Pure Magnesium. The dual implantation process offers a promising means to improve the initial surface stability of Mg in the physiological environment.
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degradation behaviour of Pure Magnesium in simulated body fluids with different concentrations of hco3
Corrosion Science, 2011Co-Authors: Yunchang Xin, Paul K ChuAbstract:Abstract Corrosion behaviour of Pure Magnesium in simulated body fluids (SBF) with HCO 3 − concentrations of 4, 15 and 27 m mol/L is studied. Magnesium is not sensitive to pitting corrosion in all the SBFs. Higher HCO 3 − concentration effectively slow down the corrosion rates. Uniform and compact corrosion product layer preferentially forms in SBF with HCO 3 − of 27 m mol/L. Potentiodynamic polarization test indicates that HCO 3 − of 27 m mol/L dramatically enhance corrosion potential and induce passivation. EIS results further confirm that higher concentration of HCO 3 − induce more effective protection layer, especially in SBF with HCO 3 − of 27 m mol/L.
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influence of tris in simulated body fluid on degradation behavior of Pure Magnesium
Materials Chemistry and Physics, 2010Co-Authors: Yunchang Xin, Paul K ChuAbstract:Abstract In current paper, influence of tris-hydroxymethyl-aminomethane (tris) in simulated body fluid (SBF) on degradation behavior of Pure Magnesium is investigated using electrochemical tests as well as degradation measurement. Our results shows that tris mainly affects earlier degradation behavior of Pure Magnesium alloy. Tris and HCl used in preparation of SBF will form Tris–HCl which only lowers corrosion potential of Magnesium slightly but accelerates degradation rates of Pure Magnesium by teens times. Consumption of OH− generated during Magnesium dissolution by Tris–HCl progressively promotes transformation from Mg to Mg2+, which is the main reason for quite high degradation rate of Pure Magnesium in SBF. Pure Magnesium is also more sensitive to pitting corrosion due to inclusion of Tris–HCl in SBF. This study deepens the understanding on degradation mechanism of biomedical Magnesium alloys.
Ke Yang - One of the best experts on this subject based on the ideXlab platform.
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In Vivo Study on Degradation Behavior and Histologic Response of Pure Magnesium in Muscles
Journal of Materials Science & Technology, 2017Co-Authors: Shanshan Chen, Ke Xu, Bingchun Zhang, Ke YangAbstract:When an orthopedics device is implanted into bone injury site, it will contact the soft tissue (skeletal muscle, fascia, ligament etc.) except for bone. Magnesium based biodegradable metals are becoming an important research object in orthopedics due to their bioactivity to promote bone healing. In this study, Pure Mg rods with and without chemical conversion coating were implanted into the muscle tissue of rabbits. Implants and their surrounding tissues were taken out for weight loss measurement, cross-sectional scanning electron microscopy observation, elemental distribution analysis and histological examination. The results showed that the chemical conversion coating would increase the in vivo corrosion resistance of Pure Mg and decrease the accumulation of calcium (Ca) and phosphorus (P) elements around the implants. For the bare Magnesium implant, both Ca and P contents in the surrounding tissues increased at the initial stage of implantation and then decreased at 12 weeks implantation, while for the Magnesium with chemical conversion coating, Ca and P contents in the surrounding tissues decreased with the implantation time, but were not significant. The histological results demonstrated that there was no calcification in the muscle tissue with implantation of Magnesium for up to 12 weeks. The chemical conversion coating not only increased the in vivo corrosion resistance of Pure Mg, but also avoided the depositions of Ca and P in the surrounding tissues, meaning that Pure Magnesium should be bio-safe when contacting with muscle tissues.
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preliminary study on a bioactive sr containing ca p coating on Pure Magnesium by a two step procedure
Surface & Coatings Technology, 2014Co-Authors: Peng Wan, Ke Yang, Bingchun Zhang, Lili Tan, Jinxin LinAbstract:Abstract In this study, a bioactive Sr containing Ca–P (Sr–CaP MAO) coating was obtained through the combination of preceding chemical deposition and micro-arc oxidation treatments for the purpose of modifying the surface of the Magnesium to promote the bioactivity and to reduce the degradation rate. The microstructure, element and phase composition of the coating were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Electrochemical and immersion tests were conducted to evaluate the degradation behavior of the Sr–CaP MAO coating in a Hank’s solution. The results showed that Sr was successfully incorporated into the Pre-CaP coating by the two-step procedure. The in vitro degradation evaluation indicated that the Sr–CaP MAO coating could significantly reduce the corrosion rate of Pure Magnesium and show better biomineralization property.
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synthesis and characterization of ca sr p coating on Pure Magnesium for biomedical application
Ceramics International, 2014Co-Authors: Lili Tan, Bingchun Zhang, Jinxin Lin, Ke YangAbstract:Abstract There are growing evidences that Sr-containing calcium phosphate biomaterials can promote better osteo-precursor cell attachment and proliferation than Pure calcium phosphate biomaterials. In this study, attempts were made to fabricate two kinds of Sr-substituted calcium phosphate (Ca–Sr–P) coatings on Pure Magnesium in electrolyte solutions with differing amounts of Sr(NO3)2 for biomedical application. The surface microstructure, composition and chemistry of the coatings were characterized by Scanning Electron Microscope (SEM), Energy-dispersive X-ray Spectroscopy (EDS), and X-ray Diffractometer (XRD), respectively. In addition, electrochemical and immersion tests were performed to evaluate the corrosion resistance of the Ca–Sr–P coated Magnesium in phosphate buffered saline solution (PBS).
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bioactive ca p coating with self sealing structure on Pure Magnesium
Journal of Materials Science: Materials in Medicine, 2013Co-Authors: Junjie Gan, Ke Yang, Lili Tan, Qiang Zhang, Xinmin FanAbstract:Bioactive coatings containing Ca and P with self-sealing structures were fabricated on the surface of Pure Magnesium using micro-arc oxidation technique (MAO) in a specific calcium hydroxide based electrolyte system. Coatings were prepared at three applied voltages, i.e. 360, 410 and 450 V, and the morphology, chemical composition, corrosion resistance and the degradation properties in Hank’s solution of the MAO-coated samples with three different applied voltages were investigated. It was found that all the three coatings showed similar surface morphologies that the majority of micro-pores were filled with compound particles. Both the porous structures and the compound particles were found to contain consistent chemical compositions which were mainly composed of O, Mg, F, Ca and P. Electrochemical tests showed a significant increase in corrosion resistance for the three coatings, meanwhile the coating obtained at 450 V exhibited the superior corrosion resistance owing to the largest coating thickness. The long term immersion tests in Hank’s solution also revealed an effective reduction in corrosion rate for the MAO coated samples, and the pH values of the coated samples always maintained a lower level. Besides, all the three coatings were subjected to a mild and uniform degradation, while the coating obtained at 360 V showed a relatively obvious degradation characteristic and appreciable Ca and P contents on the surfaces of the three coatings were observed after immersion in Hank’s solution. The results of the present study confirmed that the MAO coatings containing bioactive Ca and P elements with self-sealing structures could significantly enhance the corrosion resistance of Magnesium substrate in Hanks’ solution with great potential for medical application.
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study of bio corrosion of Pure Magnesium
Acta Metallurgica Sinica, 2005Co-Authors: Yibin Ren, Ke Yang, Bingchun Zhang, Jingjing Huang, Zhiming Yao, Hao WangAbstract:Magnesium and its alloys as bio-materials have many obvious advantages. It is possible to develop new type of bio-degradable medical Magnesium alloys by use of the poor corrosion resistance of Magnesium. The effect of impurity content and processing state on the bio-corrosion properties of two Pure Magnesiums in the physiological saline solution were investigated. The results showed that both the reduction of impurity content and the grain refinement can enhance the open circuit potential of Pure Magnesium and decrease the corrosion rate in the physiological saline solution. The corrosion rate of Pure Magnesium can be controlled through ways of changing the impurity content, grain refinement and solution treatment, which makes Magnesium suitable as a new type of pre-developed bio-degradable metal material.
Bayat N Tork - One of the best experts on this subject based on the ideXlab platform.
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investigation on the feasibility of room temperature plastic deformation of Pure Magnesium by simple shear extrusion process
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: Bayat N Tork, N Pardis, R EbrahimiAbstract:Abstract This paper investigates the feasibility of room temperature plastic deformation of Pure Magnesium through a method of severe plastic deformation (SPD), namely simple shear extrusion (SSE). Different SPD techniques were performed at room temperature and SSE was considered as a promising technique for deformation of Magnesium at room temperature. An extrusion process was performed prior to SSE technique to change the initial grain size and texture in the samples. In addition, the effect of different extrusion temperatures and processing strain rates were also studied and a procedure was presented for successful SSE processing of Magnesium at room temperature. Finally, the effect of these processing conditions on hardness and microstructural evolutions were investigated.
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investigation on the feasibility of room temperature plastic deformation of Pure Magnesium by simple shear extrusion process
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: Bayat N Tork, N Pardis, R EbrahimiAbstract:Abstract This paper investigates the feasibility of room temperature plastic deformation of Pure Magnesium through a method of severe plastic deformation (SPD), namely simple shear extrusion (SSE). Different SPD techniques were performed at room temperature and SSE was considered as a promising technique for deformation of Magnesium at room temperature. An extrusion process was performed prior to SSE technique to change the initial grain size and texture in the samples. In addition, the effect of different extrusion temperatures and processing strain rates were also studied and a procedure was presented for successful SSE processing of Magnesium at room temperature. Finally, the effect of these processing conditions on hardness and microstructural evolutions were investigated.
