Behavior Of Magnesium Alloy Research Articles

Orientation behavior in TRC-ZA21 magnesium alloy with fine grain size during nano-indentation process

The deformation behavior in magnesium alloy was greatly affected by grain orientation. It is crucial to analyze the relationship between deformation mechanism and grain orientation. In this study, the deformation behaviors in grains possessing different orientations for TRC-ZA21 alloy with fine grain size were investigated using the nano-indentation deformation coupling EBSD method. The effects of grain orientation and grain boundary on deformation behavior and propagation of deformation mechanism were discussed. The results illustrated that the irregular performance of the nano-mechanical properties could be attributed the inconsistency of grain orientation as well as the grain boundary misorientation angle. Grain orientation, followed by the criterion of Schmid factor, regulated the deformation mechanism of grains that were in direct contact with the nano-indenter. This signified the orientation dependence in plastic deformation. The deformation behavior in grains, induced by plastic deformation and indirectly in contact with the nano-indenter, was found to be influenced by the grain boundary. The orientation difference in adjacent grains determines the influence of grain boundary in plastic deformation, revealing the competitive and coordinative behavior associated with these deformation mechanisms. The c-axes angle between adjacent grains was the key factor to determine the influence of grain boundary on deformation propagation.

Microstructure and Hot Deformation Behaviour of Twin-Roll Cast AZ31 Magnesium Wire

Due to their low density and high specific strength, magnesium alloys offer great potential as a design material for lightweight construction. An economical and energy-efficient method for the production of magnesium wire is the technology of twin-roll casting. In this work, the deformation behaviour of twin-roll cast and heat-treated AZ31 wire pre-profile is investigated for the first time during the compression test at different temperatures (250–400 °C) and forming speeds (0.01–10 s−1). To obtain optimal parameters, a processing map is created, and the microstructural changes during the hot forming processes are determined by accompanying microstructure characterization through an optical microscope and scanning electron microscope. The heat treatment causes a reduction in segregation and a homogeneous microstructure. The average activating energy for plastic deformation of twin-roll cast and heat-treated magnesium alloy AZ31 is 159.008 kJ·mol−1. The instability region of the process map starts at a forming temperature of 250 °C and extends into the range of high forming speeds (1–10 s−1). In this area, cracks in the microstructure can be detected during hot forming. At high temperatures (300–350 °C), dynamic recrystallization at the grain boundaries is observed as the main forming mechanism. Based on these results and observations, existing models for describing the hot forming behaviour of magnesium alloys can be extended and validated.

Comparative Assessment of In Vitro and In Vivo Biodegradation of Mg-1Ca Magnesium Alloys for Orthopedic Applications.

Use of magnesium implants is a new trend in orthopedic research because it has several important properties that recommend it as an excellent resorbable biomaterial for implants. In this study, the corrosion rate and behavior of magnesium alloys during the biodegradation process were determined by in vitro assays, evolution of hydrogen release, and weight loss, and further by in vivo assays (implantation in rabbits’ bone and muscle tissue). In these tests, we also used imaging assessments and histological examination of different tissue types near explants. In our study, we analyzed the Mg-1Ca alloy and all the hypotheses regarding the toxic effects found in in vitro studies from the literature and those from this in vitro study were rejected by the data obtained by the in vivo study. Thus, the Mg-1Ca alloy represents a promising solution for orthopedic surgery at the present time, being able to find applicability in the small bones: hand or foot.

Material characterization for numerical simulation of manufacturing of automotive part made of magnesium alloy

Evaluation of the possibility of substitution of steel part in the car body by the one made of AZ31 alloy was the main objective of the whole project. The objective of this paper was to determine the flow stress model, which accounts for the difference in the behavior of magnesium alloys during tension and compression. Tension tests on Zwick machine and compression tests on Gleeble 3800 were performed. Inverse analysis was applied to interpretation of the results of the tests. Separate numerical models for tension and compression were implemented into Abaqus software and simulations of the stamping were performed. Sensitivity of the results to the flow stress model was evaluated.

Corrosion Behavior of AZ31 Magnesium Alloy Produced by Continuous Variable Cross Section Direct Extrusion

In order to study the corrosion behavior of magnesium alloys of high performance in the simulated seawater by continuous variable cross section direct extrusion (CVCDE), an electrochemical method and weight loss method were used to study the difference between AZ31 magnesium alloys produced by CVCDE with different numbers of interim dies to examine the electrochemical corrosion behavior and corrosion rate at 3.5 wt.% NaCl solution in this paper. Scanning electron microscopy and x-ray diffraction were used to analyze the morphology of corrosion surfaces and the composition of the corrosion products of samples soaked for different times. The results show that after CVCDE with different numbers of interim dies, the size of the microstructure is refined gradually, and the grain orientation is also different; with the increase in the number of interim dies, the thermodynamic corrosion tendencies are different, and the corrosion resistance of samples extruded by conventional extrusion is relatively good; the charge transfer and material transfer process are the two main factors affecting the corrosion rate, which determines the direction of the electrochemical reaction; the corrosion form of the sample extruded by CVCDE is the local corrosion which is the filiform corrosion and pitting corrosion, and the corrosion product is mainly water-insoluble Mg(OH)2.

Effect of polymer coating characteristics on the biodegradation and biocompatibility behavior of magnesium alloy

ABSTRACTThe permanence of cardiovascular stents and orthopedic fixation devices often cause problems; thus, it would be advantageous to make them biodegradable to prevent or minimize the issues caused by their long-term use. Magnesium is a biodegradable and biocompatible metal that is an excellent candidate for these implants, but it’s rapid degradation in vivo poses issues about its use. In order to slow down the rate at which magnesium corrodes, polymer coatings are being investigated however understanding of polymer attributes and capabilities and its subsequent impact on materials design in controlling the degradation of magnesium is lacking. In this manuscript we report the effect of polymer coating characteristics (polymer structure, molecular weight and thickness) on the biodegradation and biocompatibility behavior of magnesium alloy. Polyester based coating with varying thickness and molecular weights were dip coated on magnesium alloy. The samples were characterized and evaluated using thickness gauge, microscopic techniques, electrochemical corrosion analysis and biocompatibility studies respectively. Within the parameters chosen (molecular weight, thickness and polymer structure) results indicated coating thickness and polymer structure to have the greatest impact on controlling biodegradation of magnesium.

A comprehensive evaluation between the efficiency of different treatments in modifying the properties and behavior of magnesium alloys as degradable biomaterials

The addition of alloying elements to magnesium leads to microstructural refinement and improves its properties. However, this strategy is accompanied by another concurrent phenomenon − that is − intergranular segregation and the formation of secondary phases in grain boundaries, deteriorating the properties. In this work, the efficacy of two main factors on modifying the mechanical properties and corrosion behavior of Mg‐4Zn‐1Al‐0.2Ca alloy was investigated separately: 1) dissolution of secondary phases; and 2) grain refinement. Based on the results, heat treatment of the as‐cast alloy can increase the UTS from 174.4 to 213.2 MPa, decrease the corrosion current density from 81 to 49 μA/cm2, and enhance the polarization resistance from 1410 to 1780 Ω cm2. While, the UTS of the as‐rolled sample increased to 355 MPa, its corrosion current density decreased to 11 μA/cm2, and its polarization resistance improved to 2078 Ω cm2, indicating that compared to dissolution heat treatment, microstructural refinement plays a considerably more effective role in modifying the alloy's behavior. Cytotoxicity and cell adhesion studies also implied on the biosafety of this material in vitro.

A Study on Corrosion Behaviour of Magnesium Alloys

A biodegradable Mg-4Zn-0.6Zr alloy with different content of strontium (Sr) was prepared and studied for orthopedic applications biomaterials. The effects of Sr on the microstructure and corrosion degradation of the as-cast Mg-4Zn-0.6Zr-xSr (ZK40xSr) alloys were investigated. The optical micrograph (OM) observation, energy-dispersive spectrometer (EDS), X-ray diffractometer (XRD) and immersion test were used. The grain size of Mg-4Zn-0.6Zr alloys was reduced obviously with the addition of Sr. The excess of Sr would lead to grain size increasing and grain boundaries widening. The possible presence of the following constituent phases in the grain boundaries: α-Mg, Mg17Sr2, MgZn, ZnxSry binary and MgxZnySrz ternary phase. The formation of ZnxSry and MgxZnySrz phase owed to the larger difference of electronegativity values of Zn and Sr. The immersion tests indicated that the average corrosion rate of the as-cast ZK40xSr alloys increased with the increase of Sr content. It contributed to the micro-galvanic corrosion between the α-Mg with the continuous distribution of grain boundaries precipitates.

Deformation Behavior of Magnesium Alloys under Multi-axial Stress States

Deformation Behavior of Magnesium Alloys under Multi-axial Stress States

Preparation and in vitro degradation characterization of Si-containing coating on AZ31B alloy

Surface modification can be an effective way to control the biodegradation behaviour of magnesium alloys. In the present study, Si-containing coating was prepared on the surface of AZ31B alloy to decrease the degradation of the alloy by a chemical deposition method. The degradation behaviour of Si-containing coating in simulated body fluid was discussed. The results showed that the coating was mainly composed of Mg2SiO4, MgO and SiO2. The formation mechanism of the Si-containing coating on AZ31B alloy was proposed. The bonding strength of the coating with the substrate was higher than 24 MPa. The degradation of the coated alloy in simulated body fluid decreased compared to that of the uncoated alloy. Apatite was formed on the surface of Si-containing coated AZ31B alloy after immersion in Hank’s solution. The degradation mechanism of the Si-containing coated AZ31B alloy in Hank’s solution is proposed. It is concluded that Si-containing coating results in decreased degradation of AZ31B alloy, making it more suitable for clinical application.

Gigacycle Fatigue of Welded Joints of Structural Materials (A Review)

This review looks into the state of gigacycle fatigue behavior of some structural materials used in engineering works. Particular attention is given to the use of ultrasonic fatigue testing machine (USF-2000) due to its important role in conducting gigacycle fatigue tests. Gigacycle fatigue behavior of most materials used for very long life engineering applications is reviewed.Gigacycle fatigue behavior of magnesium alloys, aluminum alloys, titanium alloys, spheroid graphite cast iron, steels and nickel alloys are reviewed together with the examination of the most common material defects that initiate gigacycle fatigue failures in these materials. In addition, the stage-by-stage fatigue crack developments in the gigacycle regime are reviewed. This review is concluded by suggesting the directions for future works in gigacycle fatigue.

Degradation behaviors of magnesium alloy- Finite element model and experimental validation

Degradation behaviors of magnesium alloy- Finite element model and experimental validation

Corrosion behaviour of magnesium alloys in ringer's solution

Corrosion behaviour of magnesium alloys in ringer's solution

A Short Review on <i>In Vitro</i> Bioactivity Behavior of Magnesium Composites

Research and development on the biomaterials are increasing due to the demand for materials that can bond to the living bones and by any chance can avoid second surgery procedure. Good bonding between bones and biomaterials or artificial implant can avoid loosening that due to the friction and wear. Currently, magnesium alloys are being actively researched because of their ability to serve as structural support in short term and can be absorbed in the body after healing process is completed. The addition of bioactive components such as hydroxyapatite and bioglass into magnesium is made to improve the bioactivity behavior of magnesium alloys. This paper summarizes the past and current studies of magnesium alloys in regards of in vitro bioactivity behavior, biomineralization and apatite formation mechanism.

Biocompatibility of MgF2-coated MgNd2 specimens in contact with mucosa of the nasal sinus – A long term study

Up to now, different surgical techniques and stent systems have already been developed and tested for the continuous and adequate ventilation of the frontal sinuses. However, the results achieved still remain poor. Magnesium-based implants have been successfully used in numerous clinical applications. Offering excellent biocompatibility and biodegradability it may be the ideal material for the development of novel implants of the nasal sinus. Here, we present for the first time results on the behaviour of magnesium alloy in a unique environment, i.e. in contact to the nasal mucosa, air and nasal secretion. In a prospective longitudinal study, magnesium fluoride-coated MgNd2 specimens were implanted in the frontal sinuses of 12 minipigs for the investigation of biocompatibility and of the interface between the implant and the mucosa. Endoscopic examinations, histopathological evaluation and EDX measurements were performed regularly up to 180days. Endoscopic evaluation showed focal mucosal reaction, however, without affecting the patency of the sinus. In addition, no signs of bacterial infections were observed. The EDX analyses showed a marginal but steady increase in the Mg concentration in the mucosa over 180days. Histological analysis revealed a locally confined moderate mucosal hyperplasia and unspecific inflammatory reaction. Furthermore, we did not find any osteoinductive effects of the magnesium alloy. The results indicate the excellent biocompatibility of the MgNd2 alloy in contact with nasal mucosa and provide a novel material compound and solid proof-of-principle for the development of magnesium-based nasal stents.

Material design for magnesium alloys with high deformability

Magnesium alloys are very promising structural material, especially because of their low density, but their poor deformability at room temperature is making their commercial application impractical. Some alloying elements have been shown to improve the ductility dramatically, and a search for the yet better alloying elements is now a pressing task. In this study, we investigated the effects of several alloying elements on the mechanical and deformation behaviour of magnesium alloys using both first-principles calculations as well as experiments. The first-principles calculations indicate that the influential key factor for the activation of non-basal slips is the electronegativity and atomic radius. The experimental result proves that the alloys with a similar electronegativity as magnesium and a little larger atomic radius than that of magnesium, such as Ca, Sr and some rare earth elements, show superior ductility due to activation of non-basal dislocation slips. These results propose a promising design principle for the alloys with the improved deformability at room temperature ranges.

Prediction of flow stress and textures of AZ31 magnesium alloy at elevated temperature

The viscoplastic behaviour of magnesium alloys at high temperatures leads to highly temperature-dependent mechanical properties. While at high strain rates a notable strain hardening response is observed, at low strain rates the material shows a smooth plastic response with negligible amount of hardening. This complicated behaviour is due to different deformation mechanisms that are active at different strain rate regimes, resulting in different strain rate sensitivity parameters. In this study we show, by utilizing both numerical simulations and experiments, that this behaviour can be predicted by a model that combines two deformation mechanisms, grain boundary sliding mechanism and dislocation glide mechanism. We discuss the importance of each deformation mechanism at different strain rate regimes based on the findings of modelling and experimental results for AZ3 magnesium alloy. By developing a model that includes the above-mentioned two deformation mechanism, the prediction of flow properties is expanded to a wide range of strain rate regimes compared to previous study. The obtained numerical findings for the stress–strain behaviour as well as texture evolution show good agreement with the experimental results.

Experimental and Constitutive Study of Tensile Behavior of AZ31B Wrought Magnesium Alloy

AbstractAutomotive and aerospace manufacturers are looking for ways to reduce the gross weight of vehicles to economize on fuel consumption as well as improve performance. Magnesium alloys, being the lightest among the metals, are highly attractive as potential structural materials. However, their use is quite limited, especially in structural applications. As of this writing, knowledge of the dynamic behavior of magnesium alloys is not sufficient to depict their true response under dynamic loadings, and has been a hindrance to their widespread use. In this research, an experimental study, followed by constitutive and microstructural analyses, was carried out to investigate the behavior of AZ31B magnesium alloy. The alloy has been tested at strain rates in the range between 10−4 s−1 and 1.5×103 s−1 under tension.

Corrosion Fatigue Behaviour of a Common AZ91D Magnesium Alloy in Modified Simulated Body Fluid

Use of Magnesium alloys as body implants are breaking into a new paradigm of biomedical engineering as they are biocompatible, biodegradable and have mechanical properties close to that of bone. Even though corrosion fatigue (CF) and stress corrosion cracking (SCC) failures are among the most common concerns for metallic implants, CF behaviour of magnesium alloys in physiological environments has received little attention. This article reports the CF results of a common cast magnesium alloy (AZ91D) in modified simulated body fluid (m-SBF). Results showed that there was a remarkable difference in fatigue strength of Mg alloys when tests were performed in m-SBF.

306 大振幅振動におけるマグネシウム合金の非線形挙動に関する不安定性評価(OS-4 マグネシウム合金の変形とメカニクス(2))

306 大振幅振動におけるマグネシウム合金の非線形挙動に関する不安定性評価(OS-4 マグネシウム合金の変形とメカニクス(2))