Behavior Of AZ31 Magnesium Alloy Research Articles

Numerical study on the plastic deformation behavior of AZ31 magnesium alloy under different loading conditions

Based on the stress characteristics of the instantaneous cross-section deformation of the wall reducing section during the cold rolling of two-roll Pilger pipes, the rectangular samples with 0° and 90° to the extrusion direction (ED) were cut from the extruded AZ31 magnesium alloy bar for 3% pre-deformation test to simulate its stress state equivalently. The sample was then cut from the pre-deformed sample by wire cutting for secondary compression, and the sample that is not pre-deformed is selected. The mechanical behavior and texture evolution of AZ31 magnesium alloy under different loading conditions were respectively studied by EBSD experiment and VPSC simulation. Results show that the true stress–strain curve and texture evolution characteristics of AZ31 magnesium alloy during the secondary compression process are in good agreement with the prediction of the VPSC model. The secondary compression behavior can be effectively explained by the relative activity of the deformation modes. The pre-deformation in the ∥ED (⊥ED) direction is conducive to the shift of the pole density of the {0001} basal surface texture to the positive and negative directions of the ED (TD). The pre-deformed sample exhibits a higher yield strength than the non-pre-deformed sample in the same loading direction. The high ductility of magnesium alloys can be achieved by activating pyramidal 〈c + a〉 slippage.

Corrosion behavior of AZ31 magnesium alloys coated with PMMA/HA as biodegradable implants

Magnesium alloys' rapid corrosion rates have limited their use as biodegradable implants. As a result, designing a composite coating to slow the corrosion of the AZ31 magnesium alloy is critical. A spin coating process was used to cover an AZ31 alloy with a polymethylmethacrylate (PMMA)/hydroxyapatite (HA) composite coating. The coating characteristics was estimated using AFM, FESEM contact angle, and antibiofilm formation. In addition, potentiodaynamic polarisation and hydrogen evolution measurements were used to assess the coating's corrosion resistance and degradation behavior. In general, corrosion experiments revealed that specimens coated with one or two layers of PMMA polymer were successful in slowing down the rate of corrosion in Ringer's solution. Adding hydroxyapatite particles to the PMMA polymer also considerably reduces the rate of corrosion. Furthermore, the corrosion resistance of the coating with two layers of coatings is greatly improved.

Influence of Media pH on Corrosion Behaviour of AZ31 Magnesium Alloy in Chloride and Sulphate Media

Influence of Media pH on Corrosion Behaviour of AZ31 Magnesium Alloy in Chloride and Sulphate Media

Evaluation of the corrosion behavior of AZ31 magnesium alloy with different protein concentrations

PurposeThe purpose of this paper is to study systematically the corrosion behavior of AZ31 magnesium (Mg) alloy with different concentrations of bovine serum albumin (BSA) (0, 0.5, 1.0, 1.5, 2.0 and 5.0 g/L).Design/methodology/approachElectrochemical impedance spectroscopy and potential dynamic polarization tests were performed to obtain corrosion parameters. Scanning electrochemical microscopy (SECM) was used to analyze the local electrochemical activity of the surface film. Atomic force microscope (AFM), Scanning electron microscope-Energy dispersive spectrometer and Fourier transform infrared spectroscopy were used to determine the surface morphology and chemical composition of the surface film.FindingsExperimental results showed the presence of BSA in a certain concentration range (0 to 2.0 g/L) has a greater inhibitory effect on the corrosion of AZ31, however, the presence of high-concentration BSA (5.0 g/L) would sharply reduce the corrosion resistance.Originality/valueWhen the concentration of BSA is less than 2.0 g/L, the corrosion resistance of AZ31 enhances with the concentration. The adsorption BSA layer will come into being a physical barrier to inhibit the corrosion process. However, high-concentration BSA (5.0 g/L) will chelate with dissolved metal ions (such as Mg and Ni) to form soluble complexes, which increases the roughness of the surface and accelerates the corrosion process.

Enhance corrosion behavior of AZ31 magnesium alloy by tailoring the anodic oxidation time followed by heat treatment in simulated body fluid

Purpose This paper aims to investigate the impact of anodizing time and heat treatment on morphology, phase and corrosion resistance of formed coating. To characterize the anodic oxide layer, X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) that was equipped with energy dispersive spectroscopy (EDS) was hired. The corrosion behavior of oxide-coated samples was estimated by electrochemical polarization test in simulated body fluid (SBF). Design/methodology/approach Anodic oxidation method is applied to reinforce the corrosion and biological properties of biomaterials in the biomedical industry. In this paper, the alkaline NaOH (1 M) electrolyte was used for AZ31 magnesium alloy anodizing accompanied by heat treatment in the air. Findings It can be concluded that the best corrosion resistance belongs to the 10 min anodic oxidized sample and among the heat-treated samples the 30 min anodized sample represented the lowest corrosion rate. Originality/value In this study, to the best of the authors’ knowledge for the first time, this paper describes the effect of anodizing process time on NaOH (1 M) electrolyte at 3 V on corrosion behavior of magnesium AZ31 alloy with an alternate method to change the phase composition of the formed oxide layer. The morphology and composition of the obtained anodic oxide layer were investigated under the results of SEM, EDS and XRD. The corrosion behavior of the oxide coatings layer fabricated on the magnesium-based substrate was studied by the potentiodynamic polarization test in the SBF solution.

Review on the effect of different processing techniques on the microstructure and mechanical behaviour of AZ31 Magnesium alloy

Magnesium (Mg) alloys despite being the ideal candidate for structural applications, owing to their high specific strength and low density, are not widely used due to lack of active slip systems at room temperature in their hexagonal close-packed crystal structure, eliciting poor ductility and formability. Amongst the various series of Mg alloys, the AZ and ZK series alloys have been standouts, as they inherit better room temperature strength and flow characteristics through their solute elements. Grain refinement, as well as eliminating casting defects through metal processing techniques are vital for the commercial viability of these alloys since they play a key role in controlling the mechanical behaviour. As such, this review highlights the effect of different Bulk-deformation and Severe Plastic Deformation techniques on the crystal orientation and the corresponding mechanical behaviours of the AZ31 alloy. However, every process parameter surrounding these techniques must be well thought of, as they require specially designed tools. With the advent of finite element analysis, these processes could be computationally realized for different parameters and optimized in an economically viable manner. Hence, this article also covers the developments made in finite element methods towards these techniques.

Effect of calcium on the superplastic behavior of AZ31 magnesium alloy

In this short communication, the superplasticity of AZ31-0.5Ca Mg alloy was investigated and was compared to that of the Ca-free counterpart (AZ31 Mg alloy). For this purpose, AZ31 and AZ31-0.5Ca Mg alloy samples were subjected to elevated temperature tensile tests at various strain rates. The results reported in this work showed that the Ca addition lead to a higher superplasticity (~320%) at strain rate and temperature of 0.001 s−1 and 300 °C, respectively, as compared to that observed in the Ca-free AZ31 alloy.

Roles of pH in the NH4+-induced corrosion of AZ31 magnesium alloy in chloride environment

Corrosion behavior of AZ31 magnesium alloy in NH 4 + -bearing chloride solution with controlled pH was investigated by weight loss experiment, hydrogen collection, and electrochemical test combined with surface morphology and topography observation. The results show that NH 4 + and pH of the solution can affect the corrosion of AZ31 magnesium alloy. The existence of NH 4 + affects the formation and dissolution of corrosion products, which makes the protective effect of the corrosion product layer weaker. The change of pH value not only affects the corrosion mechanism of AZ31, but also alters the concentration of NH 4 + ions in the solution, which further influences the corrosion product layer of AZ31, and finally makes the corrosion of AZ31 change significantly.

Investigation of Electro-chemical performance of AZ31 Magnesium alloy – CaSiO3 Metal Matrix Composites in different environments

The electrochemical behaviour of AZ31 magnesium alloy as matrix made as metal matrix composites (MMC) by adding the reinforcement with various weight percentages of Calcium Silicate (CaSiO3) powder was investigated under the influence of 3.5 percent Sodium Chloride (NaCl) and Simulated Body Fluid (SBF) environments using electrochemical workstation. After experimentation, the results exhibit that the pure magnesium alloy sample with 0% calcium silicate exhibits the corrosion rate higher value (40.562mmpy) compared to the other samples when 4 % of calcium silicate is added as additive which exhibits the lower corrosion rate (25.510mmpy). Similarly, the polarisation resistance is also calculated for the samples and the average value of polarisation resistance for the pure magnesium sample is 153.813mA and the other for other samples it lies in between 140.5 mA to 185.72mA respectively. By experimentation it concludes that addition of reinforcement with various weight percentages plays a significant role in the reduction of corrosion rate of AZ31 magnesium alloy rather than using it in a pure form.

Erosion-Corrosion Resistance and Electrochemical Behavior of AZ31 Magnesium Alloy Processed by Equal Channel Angular Pressing (ECAP)

Erosion-Corrosion Resistance and Electrochemical Behavior of AZ31 Magnesium Alloy Processed by Equal Channel Angular Pressing (ECAP)

Mechanical Characterization of The Plastic Deformation Behavior of AZ31 Magnesium Alloy Processed Through Spinning Using Nanoindentation

The nanomechanical properties of an AZ31 magnesium alloy processed through spinning was systematically characterized with nanoindentation experiments using a Berkvoich indenter. The plastic deformation behavior of magnesium alloy was revealed by quantitatively studying microstructure evolution through spinning. Indentation depth, elastic recovery rate, yield strength, and hardening exponent were evaluated at the maximum loads. It was found that the grains observed by optical microscope were gradually refined. The nanoindentation plots revealed that the nanomechanical properties improved with the increase of spinning passes. Additionally, the calculated yield strength and hardening exponent of the cylinders were in the range of 42.0±0.5–125.5±0.6 MPa and 0.182–0.017 respectively with the increase of spinning passes. In summary, it was possible to evaluate the elastoplastic behavior of AZ31 magnesium alloy after spinning using the results of the nanoindentation tests.

Effect of surface condition on the corrosion behaviour of AZ31 magnesium alloy

Corrosion of magnesium (Mg) is generally manifested by cathodic hydrogen gas evolution and concomitant anodic Mg dissolution. The surface condition significantly modified the corrosion of Mg, especially related to the deformation. The corrosion behaviour of AZ31 Mg alloy with emphasis on surface condition effect has been investigated. Filiform-like corrosion was observed significantly along the grinding path due to surface modification by mechanical grinding. From the cross-section characterization, the corrosion attack into the crystallographic structure. The analysis of corrosion behaviour is based on the polarization behaviour during the electrochemical measurement and scanning vibration electrode technique (SVET) measurement for local electrochemical quantification. Cathodic filiform body with Mg(OH)2 formation promoted the anodic corrosion propagation. Thick non-protective corrosion product formed after a longer immersion period was associated with uniform pitting propagation tunneled underneath the alloy, confirming the autocatalytic cathodic activation.

Effect of glycine addition on the in-vitro corrosion behavior of AZ31 magnesium alloy in Hank’s solution

This study reports on the effect of the addition of Glycine to Hank’s solution on the in-vitro corrosion behavior of AZ31 magnesium (Mg) alloy at 37 ℃ and a pH of 7.4 studied by using potentiodynamic polarization (PDP), hydrogen collecting techniques and electrochemical impedance spectroscopy (EIS) in combination with surface characterization techniques such as optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy analysis (XPS). The results reveal that adsorption of glycine initially subdues the dissolution of AZ31 Mg alloy while in long run it enhances the dissolution of the alloy due to the commencement of the chelation effect of glycine with Ca2+ released from hydroxyapatite. The chelation of glycine with Ca2+ induces the formation of cracks in the surface film which further promotes the dissolution of AZ31 Mg alloy thereby forming a porous corrosion products layer on the surface of the alloy. As a result, both the continuous dissolution of AZ31 magnesium alloy and the hydrogen evolution rate (HER) are enhanced with increasing the immersion time in Hank’s solution.

Deformation mechanisms and differential work hardening behavior of AZ31 magnesium alloy during biaxial deformation

Magnesium alloys are frequently subjected to biaxial stress during manufacturing process, however, the work hardening behavior under such circumstance are not well understood. In this study, the deformation mechanisms and differential work hardening behavior of rolled AZ31 magnesium alloy sheets under biaxial loading are investigated. The change of plastic work contours with increasing plastic strain indicates the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state, resulting in higher macroscopic work hardening rates of biaxial loading than uniaxial loading, with the elastic-plastic transition part of work hardening extended and stage III hardly emerged. Electron backscatter diffraction and Schmid factor analysis confirm the low activation of non-basal 〈a〉 slip during biaxial loading tests. While the thickness strain is primarily accommodated by pyramidal 〈 c + a 〉 slip at the initial stage of biaxial deformation, {10–11} contraction twinning is activated at larger plastic strain. The low activation of non-basal 〈a〉 slip also retards the dynamic recovery and cross-slip of basal and prismatic 〈a〉 slips, leading to the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state.

Anisotropic Yield Criterion of Rolled AZ31 Magnesium Alloy via Nanoindentation

In this paper, the anisotropic mechanical properties of rolled AZ31 magnesium alloys are investigated using nanoindentation tests at room temperature. Nanoindentation was carried out at four angles, including the rolling direction (0°), diagonal direction (45°), transverse direction (90°), and vertical direction (ND). Experimental results show that hardness increases as the rolling angle increases from 0° to 90° and is lowest in the ND direction. The hardness independent of the effect of indentation depth is obtained by analyzing the indentation size effect and then converting hardness values into yield strengths. A new criterion is proposed on the basis of the Hill48 yield criterion. The data obtained through the above experiments are used to determine the parameters in the new criterion. Finally, a solution to the challenge of modeling a function that accurately describes the anisotropic yielding behavior of AZ31 magnesium alloys is proposed using the nanoindentation technique to solve the requirements of specimen size and experimental methods of the macro test.

WITHDRAWN: Influence of Coconut Shell ash particle (CSAp) as reinforcement on mechanical and wear behavior of AZ31 magnesium alloy

Desires of materials with lesser weight made wide spread use of alloys based on Magnesium in automobiles and aerospace applications in the view of overcoming lower strength of these materials when compared to Aluminium, these materials are added with some hard materials like ceramics, metal oxides or natural remaining as a reinforcing phase with a proof for improvement in properties In the present work AZ31 alloy is strengthened by adding Coconut Shell Ash particles (CSAp) by means of powder metallurgy, and the examinations like Microstructure, Micro hardness, Compressive strength and wear are conducted. The ash particles content as reinforcement has not imparted larger variation in the strength and hardness, the wear resistance is increased with the addition of ash particles and the addition of CSAp exceeding 3% lead to crack.

Effect of Cross Rolling on the Corrosion Resistance of AZ31 Magnesium Alloy

The effect of different rolling methods on the microstructure and corrosion behavior of AZ31 magnesium alloy in a 3.5% NaCl solution was studied via potentiodynamic polarization scanning, constant current discharge and electrochemical impedance spectroscopy. Results show that the corrosion current densities of cross rolling and unidirectional rolling are 8.60�10-3 and 4.68�10-2 A/cm2, respectively. Their difference is 5.4fold, the charge transfer resistance of cross rolling is large, the corrosion of one-way rolling is more serious than that of cross rolling, the discharge performance of cross rolling is more stable, and the anode polarization is small. After cross rolling, the grain size of the plate is relatively uniform and the corrosion products are non-adherent and less, so it is easy to fall off from its surface, which increases the effective contact between the electrolyte and the alloy surface and has more stable discharge performance.

Effect of warm shot peening treatments on surface properties and corrosion behavior of AZ31 magnesium alloy

Magnesium alloys are considered as a suitable choice for temporary biodegradable implants due to their biocompatible and biodegradable properties, able to avoid a second surgery when implant removal is needed. Nevertheless, nowadays one of the shortcomings of magnesium-based materials is their poor corrosion resistance and the associated high corrosion rate. This fact considerably hinders their application in biomedical field. The aim of this work is to induce a severe plastic deformation on the upper layer of the AZ31 Mg alloy in order to modulate its surface properties to slow down the kinetics of the corrosion damage. Specimens were submitted to conventional and severe shot peening treatments at room temperature, 240 °C (near recrystallization temperature) and 360 °C (above recrystallization temperature); the specimens were then analyzed in terms of grain refinement, surface roughness, work hardening, and residual stresses. Potentiodynamic polarization tests were also performed to evaluate the influence of the shot peening treatments on the specimens' corrosion resistance. The results evidenced surface roughness as the most influential factor in corrosion behavior, although for the specimens with similar roughness, also the effect of grain size is notable.

Effect of D-fructose on the in-vitro corrosion behavior of AZ31 magnesium alloy in simulated body fluid

The effect of adding d-fructose to simulated body fluid (SBF) on the corrosion behavior of AZ31 magnesium (Mg) alloy at 37 °C and at a pH of 7.4 was studied by potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), potentiostatic polarization and hydrogen (H2) collecting techniques, Raman spectroscopy technique, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy analysis (XPS) and Fourier transformed infrared (FTIR). The results demonstrated that the addition of fructose enhanced the deposition of phosphates forming thick and compact corrosion products, which inhibited the transmission of aggressive ions into the Mg substrate. As a result, both the anodic dissolution of Mg and negative difference effect (NDE) were suppressed. Thus, the corrosion resistance of AZ31 Mg alloy in SBF was significantly improved.

Role of counterfaces with DLC and N-based coatings on frictional behaviour of AZ31 magnesium alloy subjected to plasma electrolytic oxidation (PEO) process

This work examines the role of counterface materials on the tribological behaviour of Mg alloys subjected to plasma electrolytic oxidation (PEO) process and focuses on reducing the sliding coefficient of friction (COF) values of PEO treated surfaces. Surfaces of AZ31 grade Mg alloy were subjected to a PEO treatment in a sodium metasilicate and potassium hydroxide containing electrolyte. Unlubricated sliding wear tests were conducted using counterfaces made of nitride based (N-based), TiN, TiCN, CrN and hydrogenated diamond-like carbon (H-DLC) coated as well as uncoated SAE 52100 grade bearing steel balls. MgO based coatings formed on the surfaces of samples during PEO process increased the wear resistance of AZ31, regardless of the type of counterface material used. Sliding the PEO treated surfaces against counterfaces made of uncoated steel and N-based coatings yielded high COF values of 0.6–0.8 that exceeded those of the uncoated AZ31 against the same counterfaces. During dry sliding of H-DLC counterface on the MgO coating, smooth and stable friction curves with a low steady state COF value of 0.13, were recorded. Therefore, a major drawback of PEO treatment that gives rise to surfaces with high COF could be addressed by running them against H-DLC coated counterfaces, a method that could be applied to development lightweight tribological components that are both sliding wear resistant and have low COF.