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H Windhagen - One of the best experts on this subject based on the ideXlab platform.
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in vitro and in vivo corrosion measurements of Magnesium Alloys
Biomaterials, 2006Co-Authors: Frank Witte, J Fischer, Jens Nellesen, Horstartur Crostack, Volker Kaese, A Pisch, Felix Beckmann, H WindhagenAbstract: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 vitro environmental conditions were compared to corrosion rates in an in vivo animal model. Two gravity-cast Magnesium Alloys (AZ91D, LAE442) were used in these investigations. Standardized immersion and electrochemical tests according to ASTM norms were performed. The in vivo corrosion tests were carried out by intramedullar implantation of sample rods of the Magnesium Alloys in guinea pig femura. The reduction in implant volume was determined by synchrotron-radiation-based microtomography. We found that in vivo corrosion was about four orders of magnitude lower than in vitro corrosion of the tested Alloys. Furthermore, the tendency of the corrosion rates obtained from in vitro corrosion tests were in the opposite direction as those obtained from the in vivo study. The results of this study suggest, that the conclusions drawn from current ASTM standard in vitro corrosion tests cannot be used to predict in vivo corrosion rates of Magnesium Alloys.
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in vivo corrosion of four Magnesium Alloys and the associated bone response
Biomaterials, 2005Co-Authors: Frank Witte, Volker Kaese, Heinz Haferkamp, E Switzer, Andrea Meyerlindenberg, Carl Joachim Wirth, H WindhagenAbstract:Degrading metal Alloys are a new class of implant materials suitable for bone surgery. The aim of this study was to investigate the degradation mechanism at the bone-implant interface of different degrading Magnesium Alloys in bone and to determine their effect on the surrounding bone. Sample rods of four different Magnesium Alloys and a degradable polymer as a control were implanted intramedullary into the femora of guinea pigs. After 6 and 18 weeks, uncalcified sections were generated for histomorphologic analysis. The bone-implant interface was characterized in uncalcified sections by scanning electron microscopy (SEM), element mapping and X-ray diffraction. Results showed that metallic implants made of Magnesium Alloys degrade in vivo depending on the composition of the alloying elements. While the corrosion layer of all Magnesium Alloys accumulated with biological calcium phosphates, the corrosion layer was in direct contact with the surrounding bone. The results further showed high mineral apposition rates and an increased bone mass around the Magnesium rods, while no bone was induced in the surrounding soft tissue. From the results of this study, there is a strong rationale that in this research model, high Magnesium ion concentration could lead to bone cell activation.
Karl Ulrich Kainer - One of the best experts on this subject based on the ideXlab platform.
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Recent research and developments on wrought Magnesium Alloys
Journal of Magnesium and Alloys, 2017Co-Authors: Sihang You, Yuan Ding Huang, Karl Ulrich Kainer, Norbert HortAbstract:Wrought Magnesium Alloys attract special interests as lightweight structural material due to their homogeneous microstructure and enhanced mechanical properties compared to as-cast Alloys. In this contribution, recent research and developments on wrought Magnesium Alloys are reviewed from the viewpoint of the alloy design, focusing on Mg-Al, Mg-Zn and Mg-rare earth (RE) systems. The effects of different alloying elements on the microstructure and mechanical properties are described considering their strengthening mechanisms, e.g. grain refinement, precipitation and texture hardening effect. Finally, the new alloy design and also the future research of wrought Magnesium Alloys to improve their mechanical properties are discussed.
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New Perspectives for Wrought Magnesium Alloys
Materials Science Forum, 2009Co-Authors: Jan Bohlen, Dietmar Letzig, Karl Ulrich KainerAbstract:In view of the increasing needs for efficient usage of natural resources and environmental protection in our modern society, weight reduction in transportation such as cars, trains or aircrafts is of fundamental interest. In order to solve this major issue, improved concepts are necessary which also emphasize the usage of light weight materials in construction. Especially Magnesium and its Alloys as the lightest available constructional metals have a major potential in this regard. Since Magnesium cast components have found their application, interest is now spreading towards wrought Alloys for use as structural components. However, the use of wrought Magnesium Alloys in the transportation industry is still limited at present. In this paper we give an overview on the present state of the art as well as on specific requirements for the processing of wrought Magnesium Alloys. We will show the technical potential in terms of improved economic aspects for wrought Magnesium and discuss research topics such as process-specific alloy design.
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Wrought Magnesium Alloys for structural applications
Materials Science and Technology, 2008Co-Authors: Dietmar Letzig, Jan Bohlen, J. Swiostek, P. A. Beaven, Karl Ulrich KainerAbstract:Wrought Magnesium Alloys are of special interest as lightweight structural components as a result of their more homogeneous microstructures and improved mechanical properties compared to cast components. Extrusion as a shaping technology offers the possibility to produce a wide variety of Magnesium alloy profiles. In this contribution, the authors describe the role of extrusion parameters such as extrusion rate, ratio and temperature as well as the type of extrusion process on the microstructure of AZ series Magnesium Alloys and the resulting mechanical properties. The effect of microstructure on the tensile/compression deformation behaviour of the Alloys has also been investigated. In a further step, extruded material has been used in die forging experiments. Aspects of alloy development and process optimisation designed to overcome technical and economic limitations and thus establish Magnesium alloy profiles for industrial applications will also be discussed.
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Intermetallics in Magnesium Alloys
Advanced Engineering Materials, 2006Co-Authors: Norbert Hort, Yuanding Huong, Karl Ulrich KainerAbstract:Intermetallic phases can be found in almost every Magnesium alloy. These intermetallic compounds play a very important role in optimizing the microstructure and mechanical properties. The present paper reviews the effects of intermetallics in Magnesium Alloys mainly based on their stabilities: dissolvable intermetallics at low temperatures and thermal stable intermetallics at elevated temperatures. The effects of intermetallics are discussed in the age hardenable and creep resistant Magnesium Alloys, separately. Finally, the further investigations are remarked on the intermetallics, including their precipitation processes, crystal structures and crystallographic orientation relations with Magnesium matrix. The aim is to supply useful information in developing new wrought and creep-resistant Magnesium Alloys which will be used in the powertrain at elevated temperatures.
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Fatigue of Magnesium Alloys
Advanced Engineering Materials, 2004Co-Authors: Carsten Potzies, Karl Ulrich KainerAbstract:Magnesium Alloys show a high specific strength and are therefore increasingly used for light-weight constructions in transportation industry.[1,2] To predict the behaviour of the material under the influence of cyclic loading it is vital to understand the fatigue behaviour of Magnesium Alloys. Only when understood properly, it is possible to fully apply the potential weight reduction by using Magnesium Alloys. A very important aspect in fatigue of Magnesium Alloys is the influence of a corrosive media and elevated temperatures, of which both are relevant in automotive applications. These two factors tend to have deleterious effects on Magnesium Alloys and therefore also have to be considered in investigations on the fatigue behaviour of Magnesium Alloys.
Frank Witte - One of the best experts on this subject based on the ideXlab platform.
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progress and challenge for Magnesium Alloys as biomaterials
Advanced Engineering Materials, 2008Co-Authors: Rongchang Zeng, Norbert Hort, Frank Witte, W Dietzel, Carsten BlawertAbstract:Magnesium Alloys are very biocompatiable and show promise for use in orthopaedic implant. Significant progress of research on bioabsorbable Magnesium stents and orthopaedic bones has been achieved in recent years. The issues on degradation, hydrogen evolution, and corrosion fatigue and erosion corrosion of Magnesium Alloys and various influencing factors in simulated body fluid (SBF) are discussed. The research progress on Magnesium and its Alloys as biomaterials and miscellaneous approaches to enhancement in corrosion resistance is reviewed. Finally the challenges and strategy for their application as orthopaedic biomaterials are also proposed.
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in vitro and in vivo corrosion measurements of Magnesium Alloys
Biomaterials, 2006Co-Authors: Frank Witte, J Fischer, Jens Nellesen, Horstartur Crostack, Volker Kaese, A Pisch, Felix Beckmann, H WindhagenAbstract: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 vitro environmental conditions were compared to corrosion rates in an in vivo animal model. Two gravity-cast Magnesium Alloys (AZ91D, LAE442) were used in these investigations. Standardized immersion and electrochemical tests according to ASTM norms were performed. The in vivo corrosion tests were carried out by intramedullar implantation of sample rods of the Magnesium Alloys in guinea pig femura. The reduction in implant volume was determined by synchrotron-radiation-based microtomography. We found that in vivo corrosion was about four orders of magnitude lower than in vitro corrosion of the tested Alloys. Furthermore, the tendency of the corrosion rates obtained from in vitro corrosion tests were in the opposite direction as those obtained from the in vivo study. The results of this study suggest, that the conclusions drawn from current ASTM standard in vitro corrosion tests cannot be used to predict in vivo corrosion rates of Magnesium Alloys.
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in vivo corrosion of four Magnesium Alloys and the associated bone response
Biomaterials, 2005Co-Authors: Frank Witte, Volker Kaese, Heinz Haferkamp, E Switzer, Andrea Meyerlindenberg, Carl Joachim Wirth, H WindhagenAbstract:Degrading metal Alloys are a new class of implant materials suitable for bone surgery. The aim of this study was to investigate the degradation mechanism at the bone-implant interface of different degrading Magnesium Alloys in bone and to determine their effect on the surrounding bone. Sample rods of four different Magnesium Alloys and a degradable polymer as a control were implanted intramedullary into the femora of guinea pigs. After 6 and 18 weeks, uncalcified sections were generated for histomorphologic analysis. The bone-implant interface was characterized in uncalcified sections by scanning electron microscopy (SEM), element mapping and X-ray diffraction. Results showed that metallic implants made of Magnesium Alloys degrade in vivo depending on the composition of the alloying elements. While the corrosion layer of all Magnesium Alloys accumulated with biological calcium phosphates, the corrosion layer was in direct contact with the surrounding bone. The results further showed high mineral apposition rates and an increased bone mass around the Magnesium rods, while no bone was induced in the surrounding soft tissue. From the results of this study, there is a strong rationale that in this research model, high Magnesium ion concentration could lead to bone cell activation.
David H. Stjohn - One of the best experts on this subject based on the ideXlab platform.
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potency of high intensity ultrasonic treatment for grain refinement of Magnesium Alloys
Scripta Materialia, 2008Co-Authors: A Ramirez, Ma Qian, B Davis, T Wilks, David H. StjohnAbstract:High-intensity ultrasonic treatment (UT) for grain refinement of Magnesium Alloys has been investigated using a novel theoretical approach in order to better understand its grain-refining potential and the mechanism of nucleation. The process demonstrated significantly superior grain-refining potency to carbon inoculation for Al-containing Magnesium Alloys but inferior potency to zirconium for Al-free Alloys. Details revealed by applying the theoretical approach to ultrasonic grain refinement provide new clues to understanding the mechanism of grain nucleation by UT.
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grain refinement of Magnesium Alloys
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2005Co-Authors: David H. Stjohn, Peng Cao, Ma Qian, Mark Alan Easton, Zoe HildebrandAbstract:The literature on grain refinement of Magnesium Alloys is reviewed with regard to two broad groups of Alloys: Alloys that contain aluminum and Alloys that do not contain aluminum. The Alloys that are free of aluminum are generally very well refined by Zr master Alloys. On the other hand, the understanding of grain refinement in aluminum bearing Alloys is poor and in many cases confusing probably due to the interaction between impurity elements and aluminum in affecting the potency of nucleant particles. A grain refinement model that was developed for aluminum Alloys is presented, which takes into account both alloy chemistry and nucleant particle potency. This model is applied to experimental data for a range of Magnesium Alloys. It is shown that by using this analytical approach, new information on the refinement of Magnesium Alloys is obtained as well as providing a method of characterizing the effectiveness of new refiners. The new information revealed by the model has identified new directions for further research. Future research needs to focus on gaining a better understanding of the detailed mechanisms by which refinement occurs and gathering data to improve our ability to predict grain refinement for particular combinations of alloy and impurity chemistry and nucleant particles.
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Grain coarsening of Magnesium Alloys by beryllium
Scripta Materialia, 2004Co-Authors: Peng Cao, Ma Qian, David H. StjohnAbstract:A trace of beryllium can lead to dramatic grain coarsening in Mg-Al Alloys at normal cooling rates. It is, however, unclear whether this effect applies to aluminium-free Magnesium Alloys or not. This work shows that a trace of beryllium also causes considerable grain coarsening in Mg-Zn, Mg-Ca, Mg-Ce and Mg-Nd Alloys and hinders grain refinement of Magnesium Alloys by zirconium as well. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Norbert Hort - One of the best experts on this subject based on the ideXlab platform.
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Recent research and developments on wrought Magnesium Alloys
Journal of Magnesium and Alloys, 2017Co-Authors: Sihang You, Yuan Ding Huang, Karl Ulrich Kainer, Norbert HortAbstract:Wrought Magnesium Alloys attract special interests as lightweight structural material due to their homogeneous microstructure and enhanced mechanical properties compared to as-cast Alloys. In this contribution, recent research and developments on wrought Magnesium Alloys are reviewed from the viewpoint of the alloy design, focusing on Mg-Al, Mg-Zn and Mg-rare earth (RE) systems. The effects of different alloying elements on the microstructure and mechanical properties are described considering their strengthening mechanisms, e.g. grain refinement, precipitation and texture hardening effect. Finally, the new alloy design and also the future research of wrought Magnesium Alloys to improve their mechanical properties are discussed.
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progress and challenge for Magnesium Alloys as biomaterials
Advanced Engineering Materials, 2008Co-Authors: Rongchang Zeng, Norbert Hort, Frank Witte, W Dietzel, Carsten BlawertAbstract:Magnesium Alloys are very biocompatiable and show promise for use in orthopaedic implant. Significant progress of research on bioabsorbable Magnesium stents and orthopaedic bones has been achieved in recent years. The issues on degradation, hydrogen evolution, and corrosion fatigue and erosion corrosion of Magnesium Alloys and various influencing factors in simulated body fluid (SBF) are discussed. The research progress on Magnesium and its Alloys as biomaterials and miscellaneous approaches to enhancement in corrosion resistance is reviewed. Finally the challenges and strategy for their application as orthopaedic biomaterials are also proposed.
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Intermetallics in Magnesium Alloys
Advanced Engineering Materials, 2006Co-Authors: Norbert Hort, Yuanding Huong, Karl Ulrich KainerAbstract:Intermetallic phases can be found in almost every Magnesium alloy. These intermetallic compounds play a very important role in optimizing the microstructure and mechanical properties. The present paper reviews the effects of intermetallics in Magnesium Alloys mainly based on their stabilities: dissolvable intermetallics at low temperatures and thermal stable intermetallics at elevated temperatures. The effects of intermetallics are discussed in the age hardenable and creep resistant Magnesium Alloys, separately. Finally, the further investigations are remarked on the intermetallics, including their precipitation processes, crystal structures and crystallographic orientation relations with Magnesium matrix. The aim is to supply useful information in developing new wrought and creep-resistant Magnesium Alloys which will be used in the powertrain at elevated temperatures.
