Behavior Of Mg Alloy Research Articles

Microstructure and Mechanical Properties of Mg-6Zn-2Sn-1Al Alloy Designed by Numerical Analysis with Extrusion Process

In the extrusion process, the temperature of the workpiece results in non-uniformity of dimensions, microstructure, and mechanical properties of the product. Although many researchers are expected to participate in the extrusion behavior of Mg alloys, no specific information is available yet to clarify their roles in extrusion process of Mg alloys because of a wide variety of compositions. In this study, a good understanding the role of die in the extrusion process is expected to contribute to the improvement of processing efficiency for Mg-6Zn-2Sn-1Al alloy. To design Mg-6Zn-2Sn-1Al alloy, the parameters, such as temperature and angle of the designed materials, were determined using the commercial software DEFORM 3D. With this simulation model, the real-time extrusion temperature and angle of the die were adjusted according to the simulation results. Using the optimal extrusion process predicted by finite element method analysis, the Mg-6Zn-2Sn-1Al alloy was manufactured. Also, the extruded Mg-6Zn-2Sn-1Al alloys were evaluated on the microstructure and mechanical properties.

In-vitro degradation behavior of Mg alloy coated by fluorine doped hydroxyapatite and calcium deficient hydroxyapatite

Fluorine-doped hydroxyapatite (FHA) and calcium deficient hydroxyapatite (CDHA) were coated on the surface of biodegradable magnesium alloy using electrochemical deposition (ED) technique. Coating characterization was investigated by X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The result shows that nano-FHA coated sample presents nano needle-like structure, which is oriented perpendicular to the surface of the substrate with denser and more uniform layers compared to the nano-CDHA coated sample. The nano-FHA coating shows smaller crystallite size (65 nm) compared to the nano-CDHA coating (95 nm); however, CDHA presents thicker layer (19 μm in thickness) compared to the nano-FHA (15 μm in thickness). The corrosion behaviour determined by polarization, immersion and hydrogen evolution tests indicates that the nano-FHA and nano-CDHA coatings significantly decrease corrosion rate and induce passivation. The nano-FHA and nano-CDHA coatings can accelerate the formation of bone-like apatite layer and significantly decrease the dissolution rate as compared to the uncoated Mg alloy. The nano-FHA coating provides effective protection to Mg alloy and presents the highest corrosion resistance. Therefore, the nano-FHA coating on Mg alloy is suggested as a great candidate for orthopaedic applications.

Aqueous Corrosion Behavior of Micro Arc Oxidation (MAO)-Coated Magnesium Alloys: A Critical Review

Magnesium (Mg) and its alloys, in the current era of persistently growing engineering demands, have become the most promising materials finding widespread industrial applications. Numerous processes are available for surface protection of Mg and its alloys to potentially minimize corrosion damage. The micro arc oxidation (MAO), a fairly recent and eco-friendly coating process, emerged as a novel means to provide an adherent, hard, scratch-resistant, wear-resistant, and corrosion-resistant coatings on Mg alloys. However, the successful utilization of such coatings demands a thorough understanding of the influence of a relatively large number of process parameters such as electrolytic composition, presence of insoluble additives in the electrolyte, electrical parameters employed, and the composition of the Mg alloy substrate on the corrosion resistance. The detailed influence of all the above parameters on the corrosion behavior of Mg alloys is critically reviewed and presented in this article. In addition, this article also reviews the recent trends in terms of duplexing the MAO process using different techniques/processes such that the composite coatings are produced with enhanced corrosion resistance.

The Extrusion Behavior of Mg Alloys Interpenetrating with Stainless Steel Wire

The interpenetrating magnesium composites reinforced by three-dimensional braided stainless steel wire reinforcement were fabricated. And, the deformation behavior of materials was analyzed in four extrusion velocities by DEFORM-3D software. The results show that with the increases of extrusion velocities, the equivalent stress values exhibit a gradually increasing and then decreasing trend. Owing to the effect of three dimensional reinforcement, the basal plane orientation occur tilt. And, the microstructure turns refined.

The Effect of Nd on the Tension and Compression Deformation Behavior of Extruded Mg-1Mn (wt pct) at Temperatures Between 298 K and 523 K (25 °C and 250 °C)

The tension and compression deformation behavior of extruded magnesium-1 wt pct manganese alloys with nominally 0.3 wt pct (MN10) and 1 wt pct neodymium (MN11) was studied over the temperature range of 298 K to 523 K (25 °C to 250 °C). Nd additions to Mg alloys tend to reduce the strong basal texture exhibited by conventional wrought Mg alloys and this work was intended to study the effect of Nd on the deformation behavior of Mg alloys. Insitu tensile and compressive experiments were performed using a scanning electron microscopy, and electron backscatter diffraction was performed both before and after the deformation. A slip trace analysis technique was used to identify the distribution of the deformation systems as a function of strain, and based on this analysis and the texture of the undeformed samples, the critical resolved shear stress ratios between the deformation systems were estimated. In the case of MN11, the deformation behavior under tension at all temperatures was dominated by slip, while in compression, extension twinning was the major deformation mode. In tension at 323 K (50 °C), extension twinning, basal, prismatic 〈a〉, and pyramidal 〈c + a〉 slip were active in MN11. Much less extension twinning was observed at 423 K (150 °C), while basal slip and prismatic 〈a〉 slip were dominant and presented similar relative activities. At 523 K (250 °C), twinning was not observed, and basal slip controlled the deformation. With the reduction of Nd content, less slip deformation and more twinning were observed during the tensile deformation. However, like for MN11, the extent of twinning in MN10 decreased with increasing temperature and basal slip was the primary deformation mode at elevated temperatures. Extension twinning was the major deformation mode under compression for all test temperatures in MN10 and MN11. The tensile strength decreased with increasing temperature for both alloys, where MN10 was slightly stronger than MN11 at 323 K (50 °C), which was expected to be a result of the stronger basal texture exhibited by MN10 due to its lower Nd content. However, MN11 maintained its strength more at elevated temperatures compared with MN10, and this was explained to be a result of the greater Nd content.

Dynamic Behavior of a Rare-Earth-Containing Mg Alloy, WE43B-T5, Plate with Comparison to Conventional Alloy, AM30-F

The dynamic behavior of Mg alloys is an area of interest for applications such as crash-sensitive automotive components and armor. The rare-earth element-containing alloy WE43B-T5 has performed well in ballistic testing, so the quasi-static (~10−3 1/s) and dynamic (~600–5000 1/s) mechanical behaviors of two Mg alloys, rolled WE43B-T5 and extruded AM30-F, were investigated using servohydraulic and Kolsky bar testing in uniaxial tension and compression. The yield stress was surprisingly isotropic for WE43B-T5 relative to conventional Mg alloys (including extruded AM30-F). The WE43B plate was textured; however, it was not the typical basal texture of hot-rolled Mg-Al alloys. The effect of strain rate on the yield strength of WE43B-T5 is small and the strain-hardening behavior is only mildly rate sensitive (m = 0.008). The combination of high strength (~300 MPa), moderate ductility (0.07–0.20), and low density yield a material with good specific energy absorption capacity.

Wear Behavior of Mg Alloy Procduced by Equal Channel Angular Extrusion

A commercial Mg alloy was prepared through equal channel angular extrusion (ECAE) process. The effect of ECAE on mechanical and tribological properties of the alloy was investigated. Experimental results showed that the hardness and strength of the alloy with ECAE were higher than that of the alloy without ECAE and increased with the increase pass number. The friction coefficient and wear resistance of the alloy after ECAE were significantly improved.

Ignition-proof properties of a high-strength Mg-Gd-Ag-Zr alloy

A high-strength Mg-15.3Gd-1.8Ag-0.3Zr (GQ152K, mass fraction) alloy was prepared by conventional ingot metallurgy process. The solution and aging (denoted as T6) treated alloy exhibits remarkable mechanical properties with ultimate tensile strength of 421MPa and tensile yield strength of 309MPa. It has higher igniting temperature of 1 208 K. Moreover, it can stand against flame at 1 203K for over 6min in vertical burning tests, and its flammability behavior is very similar to that of 6101Al alloy. Vertical burning tests appear to be able to directly study the flammability behavior of Mg alloys and it appears to be a good approach to study the flammability behavior of Mg alloys in an aircraft fire accident.

Influence of Scandium on Corrosion Properties and Electrochemical Behaviour of Mg Alloys in Different Media

Influence of Scandium on Corrosion Properties and Electrochemical Behaviour of Mg Alloys in Different Media

Constitutive Equations for Finite Element Simulation

The necessity to simulate extrusion processes requires the knowledge of the material in terms of the constitutive equations. The present investigation deals with the development of a methodology based on the multivariable regression analysis in order to predict the flow behaviour of a ZEK200 Mg alloy in the interval of temperature varying between 150 and 450°C. The proposed models relate the flow curve levels with temperature, strain rate and deformation with the variables selected using the statistical method. It has been found that the proposed methodology allows the modeling of the flow behaviour of the Mg alloy under investigation from the beginning of the plastic deformation down to the softening phase taking into account the peak value. In addition, it is comparable, in terms of the temperature intervals considered in the modeling, with the Sellars and Tegart-based models.

Atomistic modeling of pure Li and Mg–Li system

Interatomic potentials for pure Li and the Mg–Li binary system have been developed based on the second nearest-neighbor modified embedded-atom method formalism. The potentials can describe various fundamental physical properties of pure Li (bulk, point defect, planar defect and thermal properties) and alloy behaviors (thermodynamic, structural and elastic properties) in reasonable agreement with experimental data or higher-level calculations. The applicability of the potential to atomistic investigations on the deformation behavior of Mg alloys and the effect of Li is demonstrated.

Correlation between current frequency and electrochemical properties of Mg alloy coated by micro arc oxidation

The present work investigated the electrochemical behavior of Mg alloy subjected to micro arc oxidation coating for 120s with respect to current frequencies from 60Hz to 2000Hz. The microstructure and chemical compound of thin coating layers with a thickness of ~3μm were analyzed using scanning electron microscopy and X-ray photoelectron spectroscopy. The microstructural observations on the surface and cross sections revealed that both the size of pores and the number of discharge channels decreased significantly as the current frequency increased, resulting in a compact coating layer. This was primarily attributed to the transition time of the alternating electrical wave, which was determined by the current frequencies tested. Based on potentiodynamic polarization tests, the sample coated at a frequency of 2000Hz demonstrated the highest polarization resistance of 6.37×105Ωcm2, implying that the corrosion resistance was superior to that obtained under other conditions due to its condensed structure. This electrochemical response was also interpreted in relation to the equivalent circuit model.

Influence of thermomechanical processing on the grain size, texture and mechanical properties of Mg-Al alloys

The work carried out by the authors over the last decade on the processing, microstructural characterization and the mechanical behaviour of Mg alloys is reviewed. In particular, the potential for grain refinement and for the development of specific textures of large strain hot rolling (LSHR), equal channel angular pressing (ECAP) and accumulative roll bonding (ARB) is discussed. The recrystallization and the deformation mechanisms predominant in Mg alloys are analyzed as a function of the grain size and the texture in a wide range of stresses, strain rates and temperatures. Finally, the the feasibility of superplatic forming of Mg alloys was examined, taking into account the influence of factors such as grain size stability and microstructural heterogeneities.

Biodegradable Mg and Mg alloys: Corrosion and biocompatibility

Abstract This review discusses the current state and challenges in understanding Mg alloy corrosion behavior, in view of use of these materials for biodegradable implants. After the description of some basic and specific aspects of Mg alloy corrosion, the influence of specific biological environments on the corrosion behavior of Mg alloys is summarized. Interactions between corroding Mg surfaces and cells are shortly discussed. Moreover, approaches to control the corrosion and biological performance of Mg alloys by surface modification are presented. The article tries to provide general, instead of alloy specific, information on the topics covered.

In vivo biocompatibility and degradation behavior of Mg alloy coated by calcium phosphate in a rabbit model

This study is conducted to investigate the biocompatibility and biodegradation behavior of calcium phosphate-coated Mg alloy invivo. Calcium phosphate (Ca-P) was coated on the Mg alloy (AZ31) by a chemical process. Samples of Ca-P coated rods, the naked alloy rods, and degradable polymer as controls were implanted into the thighbone of rabbits to investigate the bone response at the early stage. The reduction in implant volume was determined by micro-computed tomography and three-dimensional reconstruction of the remaining Mg alloy segmented from the bone matrix. It was observed that the biodegradation rate of naked Mg implant is faster than that of the coated ones. The bone-implant interface was characterized in sections by scanning electron microscopy with energy-dispersive spectroscopy. Biodegradation or reaction layer was formed on the surface of Mg alloy implants and direct contact with the surrounding bone. The layer was mainly composed of Ca, P, O, and Mg. After 8 weeks of post-operation, paraffin sections were generated for histomorphologic analysis; 100% implants were fixed and no inflammation was observed. Histological analysis showed that new bone tissue is formed around the Mg implants, and no fibrous capsule was found. Blood examination showed that the biodegradation of the Mg implant caused little change to blood composition. Ca-P coating on Mg alloy substrate might be an effective method to reduce the biodegradation rate of Mg alloy invivo and improve the surface bioactivity of Mg alloy implants.

Interrupted creep behaviour of Mg alloys developed for powertrain applications

A conventional magnesium alloy, AZ91D, and two creep resistant magnesium alloys, developed for powertrain applications, MRI 153M and MRI 230D, are prepared by high pressure die casting. These alloys are tested for their creep behaviour in the continuous manner, as is the current practice, and in the interrupted manner, which represents the real life situation more closely. It is observed that the interrupted creep tests give rise to a primary creep appearing at the beginning of each cycle resulting in a higher average strain rate than that encountered in the continuous creep tests. Further, the shorter the cycle time, higher is the average strain rate in the interrupted creep tests. A higher average strain rate will give rise to a higher strain over the same period. This is attributed to the recovery taking place during the cooling and heating between two cycles. The effect of additional precipitation during interrupted creep tests depends on the nature of the precipitates. The additional precipitation of β phase during the cooling and heating between two cycles increases the steady state strain rate in the AZ91D and MRI 153M alloys, whereas the additional precipitation of C36 phase during the cooling and heating between two cycles decreases the steady state strain rate in the MRI 230D alloy.

Effect of intermetallic phases on the creep behavior of AZ91 magnesium alloy

Intermetallic phases play a major role in the creep behavior of Mg alloys. The effects of intermetallic phases on the creep behavior of AZ91 alloy have been studied in the present investigation. Thermally stable and finer intermetallic phases such as Mg 2Si and Mg 3Sb 2 are introduced deliberately in AZ91 alloy by the addition of Si and Sb (0.5% Si, 0.5% Sb and 0.5% Si + 0.2% Sb, all are in wt%). Creep tests were carried out at 150 °C and 200 °C with an initial stress of 50 MPa on the as cast samples. The detailed microstructural analyses carried out on the crept samples indicate that the β-Mg 17Al 12 intermetallic phase in the AZ91 alloy suffers sever cracking and facilities cavity formation due to its low melting point and incoherency with Mg matrix, which results in poor creep resistance. On the other hand, the creep behavior of AZ91 alloy at 150 °C is greatly improved with the presence of Mg 2Si or Mg 3Sb 2 intermetallic phases because of their better thermal stability than Mg 17Al 12. These intermetallic phases strengthen the grain boundary against sliding and hence, reduce the possibility of void formation during creep. Furthermore, it also promotes more number of continuous Mg 17Al 12 dynamic precipitates near the grain boundary during creep, which in turn restricts the creep deformation.

Corrosion behavior of Mg and Mg-Zn alloys in simulated body fluid

The corrosion behavior of Mg and Mg-Zn in simulated body fluid was studied. The mass loss of pure Mg, Mg-Zn-Zr and Mg-Zn-Zr-Y in simulated body fluid was measured using photovoltaic scale meter. Corrosion rate was determined through electrochemical tests. Finally, the corrosion mechanism was thermodynamically studied. The results show that the corrosion rate decreases with the lapse of time for both pure Mg and Mg alloys. The purer the alloy, the better the corrosion resistance exhibits. The corrosion behavior of Mg alloy is improved by the addition of trace Y.

Corrosion Behavior of Anodized AZ91D Magnesium Alloy in NaCl Aqueous Solution

The corrosion behavior of anodized AZ91D magnesium alloy in neutral 1% (w) NaCl aqueous solution was investigated by salt spray test, polarization Curve, electrochemical impedance spectroscopy (E-IS), electrochemical noise (EN) and scanning electron microscope (SEM). The results showed that the corrosion behavior of Mg alloy presented characteristic changes due to anodization. For example, the unsealed anodic film Could be sustained in 5% NaCl salt spray beyond 200 h, E-corr of anodized magnesium alloy shifted up and the inductive period for pitting corrosion was obviously prolonged, and the impedance modules in high frequency of anodized alloy were several thousand times those of unanodized alloy. All these proved that anodization process made the alloy gain excellent property of anti-corrosion. The evolution of fractal dimension (D-r) was first utilized to depict the corrosion process of anodized AZ91D magnesium alloy and shown as rapid increasing in the initial, fluctuating in the medium and decreasing in the last. This evolution was related with the three different corrosion stages of anodized AZ91D magnesium alloy in 1% NaCl solution.

Effect of Texture on Deformation Behavior of AZ31 Mg Alloy

Hot rolled Mg alloy has a preferred orientation, which affects the deformation behavior of Mg alloy. In this work, load relaxation and tensile tests after hot rolling process were performed to clarify the effect of the texture on deformation behavior of AZ31 Mg alloy and the results were analyzed based on an internal variable theory proposed by one of the authors. The analysis of the deformation behavior is then correlated to XRD pole figure results of the texture. The analysis result of Mg alloy was found to be comparable to the results obtained from the test of Ti alloys, which has the same HCP structure.