Behavior Of Mg Alloy Research Articles

Effect of rare earth element Y on the crack propagation behavior of Mg alloys: A molecular dynamics simulation

The effect of the distribution and concentration of rare earth (RE) element Y, crack orientation, temperature, and strain rate on the crack propagation behavior of the Mg alloys is investigated by molecular dynamics/Monte Carlo simulations. The results show that the RE element Y tends to form locally short-range order structures in the Mg alloys, and the introduction of the RE element Y can enhance the fracture toughness of the Mg alloys. The results indicate that with the increase of Y concentration, the crack propagation mode of the Mg alloys shifts from a mode, dominated by the dislocation emissions at the crack tip and the crack cleavage propagation to a mode dominated by the solid-state amorphization and the slip of amorphous bands. In addition, the results show that the faster the strain rate, the slower the crack propagation speed, and the crack propagation resistance increases with increasing temperature.

Physical field of dual-frequency ultrasonic vibration and its effect on solidification behavior of MgZnY alloy

A three-dimensional model was established for coupled simulation of the physical field in a liquid subjected to dual-frequency ultrasonic vibration. The effect of sonotrode position, tip shape, and vessel on the distributions of acoustic pressure and acoustic streaming were clarified. The influence of physical fields on the solidification behavior of Mg alloy was investigated. The simulation results show that the interaction between the two ultrasounds was weakened as the sonotrode spacing increased, and the radiating angle had little effect on the acoustic pressure distribution. The volume mean pressure in the liquid radiated by the plane tip was the smallest, but with the greatest acoustic streaming intensity. In contrast, the spherical tip radiated the highest volume mean pressure in the liquid medium, but the acoustic streaming was severely suppressed. Attributed to the smooth spherical surface that facilitated fluid flow, high flow velocity could be achieved using a round-bottomed crucible without severe acoustic pressure attenuation. The experimental results show that cavitation and acoustic flow caused the coarse dendrites to turn into fine isometric crystals. The acoustic flow accelerated the melt flow and alleviated the segregation and precipitation of Zn elements, leading to a decrease in the content and size of the second phase in the billet.

Comparing the Corrosion Behavior and Microstructure of a WE43 Mg Alloy in Simulated Body Fluids Under Different CO2 Conditions

With the low density and high specific strength, magnesium (Mg) alloys are lightweight alloys with various applications. In addition, combined with biocompatibility, similar mechanical properties to human bones, and unique biodegradability, Mg alloys are promising biodegradable implant materials for orthopedic surgeries. However, the degradation rates of Mg alloys are too fast in physiological environments, which limits the clinical applications of Mg implants. Therefore, understanding the corrosion behavior in physiological environments is crucial for developing biodegradable Mg alloys.During Mg alloy degradation, hydroxide (OH-) ions are generated, and the pH near the alloy surface increases. Since carbonate-bicarbonate (CO3 2--HCO3 -) is a vital pH buffer system in the human body, the corrosion behavior of Mg alloys would be affected by the CO2 concentrations of the test environments. In this study, we performed electrochemical and corrosion tests of a solution heat-treated WE43 (Mg-4 wt%Y-3 wt%Nd) alloy in Hanks’ balanced salt solutions (HBSS) at 37°C. By performing the tests in air and in an incubator maintained at 5% CO2, the effect of carbonate-bicarbonate pH buffering on the corrosion behavior and corrosion microstructure of the WE43 Mg alloy was investigated.When testing the WE43 Mg alloy in air, a general corrosion morphology was observed during the 24-hour immersion. In contrast, WE43 Mg alloy tested in the incubator shows a more active surface potential and localized corrosion initiates on the alloy surface in the early stages of immersion. Electrochemical impedance spectroscopy (EIS) analysis shows that WE43 Mg alloy tested in air has better corrosion resistance than in the incubator. Furthermore, the corrosion resistance of the alloy tested in air increases with immersion time but decreases when tested in the incubator. Potentiodynamic polarization curves after 24-hour immersion confirm that the corrosion current density (i corr) of the WE43 Mg alloy tested in the incubator is higher than that when tested in air. The difference in corrosion behavior is owing to the carbonate-bicarbonate pH buffering effect and will be discussed based on corrosion microstructure characterizations. Figure 1

Effect of grain boundary segregation of rare earth element on deformation behavior of Mg alloys

Effect of grain boundary segregation of rare earth element on deformation behavior of Mg alloys

The uniform corrosion of biodegradable Mg alloy induced by protein addition in Hanks’ balanced salt solution

The localized corrosion caused by the interphase potential differences and incompleteness of the corrosion product layer results in the premature failure of Mg alloys. In biomedical applications, understanding about the corrosion behavior of Mg alloys in complex environment is still insufficient. In this work, mechanical tests after corrosion were employed to indirectly but generally reflect the localized corrosion of Mg alloy in the protein-containing electrolytes. The results reveal that protein alters the Mg corrosion mode to uniform corrosion and an appropriate amount of protein is beneficial for maintaining its mechanical bearing capacity. This work is helpful for understanding the corrosion behavior of Mg alloys and consummating degradation evaluation systems for Mg alloys.

Data analysis of the influence of microstructure, composition, and loading conditions on stress corrosion cracking behavior of Mg alloys

Stress corrosion cracking (SCC) can be a crucial problem in applying rare earth (RE) Magnesium alloys in environments where mechanical loads and electrochemical driven degradation processes interact. It has been proven already that the SCC behavior is associated with microstructural features, compositions, loading conditions, and corrosive media, especially in-vivo. However, it is still unclear when and how mechanisms acting on multiple scales and respective system descriptors predictable contribute to SCC for the wide set of existing Mg alloys. In the present work, suitable literature data along SCC of Mg alloys has been analyzed to enable the development of a reliable SCC model for MgGd binary alloys. Pearson correlation coefficient and linear fitting are utilized to describe the contribution of selected parameters to corrosion and mechanical properties. Based on our data analysis, a parameter ranking is obtained, providing information on the SCC impact with regard to ultimate tensile strength (UTS) and fracture elongation of respective materials. According to the analyzed data, SCC susceptibility can be grouped and mapped onto Ashby type diagrams for UTS and elongation of respective base materials tested in air and in corrosive media. The analysis reveals the effect of secondary phase content as a crucial materials descriptor for our analyzed materials and enables better understanding towards SCC model development for Mg-5Gd alloy based implant.

Effect of microstructural and texture evolution of ECAP-processed Mg-Zn-Zr alloy on the corrosion and wear behaviours for bone repair applications

Mg-Zn-Zr alloys show great potential for replacing the currently used materials in biodegradable applications. They exhibit similar mechanical properties to that of human bones, while possessing favorable biodegradable properties that can be engineered to allow the complete, safe degradation of the alloy in the human body around the time the bones fully heal, without the need for a removal surgery. Literature confirms that grain refinement through processing via severe plastic deformation (SPD) techniques enhances both corrosion and wear behavior of Mg alloys; thus, in this study Mg-3Zn-0.6 Zr (ZK30) billets were ECAP-processed for up to 4-passes of route Bc to investigate their wear and corrosion behaviors improvement in relation to their microstructural and texture evolutions. Electron back-scatter diffraction (EBSD) was used to study microstructural and texture evolution of the billets, their electrochemical behavior was investigated using a body simulated fluid as a corrosive agent, and wear tests with load, velocity and distance parameters were carried out to investigate the improvements resulting from the produced ultrafine-grained structure and crystallographic texture. EBSD revealed that 4-pass ECAP processing yielded a grain size reduction of 92.7%. Accordingly, this ultrafine-grained structure reduced the corrosion rate by 94%, improved the corrosion resistance by 726%, and notably improved the billets’ wear behavior, compared to the as-annealed condition. Therefore, this in-depth analysis confirms the promising potential of ZK30 alloy for industrial use in bone applications.

Impact of scandium and terbium on the mechanical properties, corrosion behavior, and biocompatibility of biodegradable Mg-Zn-Zr-Mn alloys

Magnesium (Mg)-based bone implants degrade rapidly in the physiological environment of the human body which affects their structural integrity and biocompatibility before adequate bone repair. Rare earth elements (REEs) have demonstrated their effectiveness in tailoring the corrosion and mechanical behavior of Mg alloys. This study methodically investigated the impacts of scandium (Sc) and terbium (Tb) in tailoring the corrosion resistance, mechanical properties, and biocompatibility of Mg–0.5Zn–0.35Zr–0.15Mn (MZZM) alloys fabricated via casting and hot extrusion. Results indicate that addition of Sc and Tb improved the strength of MZZM alloys via grain size reduction and solid solution strengthening mechanisms. The extruded MZZM–(1–2)Sc–(1–2)Tb (wt.%) alloys exhibit compressive strengths within the range of 336–405 MPa, surpassing the minimum required strength of 200 MPa for bone implants by a significant margin. Potentiodynamic polarization tests revealed low corrosion rates of as–cast MZZM (0.25 mm/y), MZZM–2Tb (0.45 mm/y), MZZM–1Sc–1Tb (0.18 mm/y), and MZZM–1Sc–2Tb (0.64 mm/y), and extruded MZZM (0.17 mm/y), MZZM–1Sc (0.15 mm/y), MZZM-2Sc (0.45 mm/y), MZZM-1Tb (0.17 mm/y), MZZM-2Tb (0.10 mm/y), MZZM–1Sc-1Tb (0.14 mm/y), MZZM-1Sc-2Tb (0.40 mm/y), and MZZM–2Sc–2Tb (0.51 mm/y) alloys, which were found lower compared to corrosion rate of high-purity Mg (∼1.0 mm/y) reported in the literature. Furthermore, addition of Sc, or Tb, or Sc and Tb to MZZM alloys did not adversely affect the viability of SaOS2 cells, but enhanced their initial cell attachment, proliferation, and spreading shown via polygonal shapes and filipodia. This study emphasizes the benefits of incorporating Sc and Tb elements in MZZM alloys, as they effectively enhance corrosion resistance, mechanical properties, and biocompatibility simultaneously.

Effect of medium renewal mode on the degradation behavior of Mg alloys for biomedical applications during the long-term in vitro test

To build a suitable corrosion environment for testing the degradation behavior of magnesium alloy in vitro, the medium and test environment are constantly optimized. However, the applicability of medium renewal mode is still vague. In this study, based on three representative test protocols, the influence of the specific ratio of media volume to surface area and the disposable medium real-time renewal mode (flow-through) on Mg corrosion were investigated. It is found that in flow-through medium renewal mode, the composition of the medium is maintained quasi-constant which is essential for corrosion tests. The selection suggestion on medium renewal mode was also proposed. This work is beneficial for ultimately establishing the representative in vitro testing protocols for Mg bioabsorbable materials.

Promoted aging precipitation behavior of TC4/GZ151K magnesium matrix composites

The precipitation behavior of TC4/GZ151K composite (Ti–6Al–4V reinforced Mg-15Gd-1Zn-0.4Zr) after solution and aging heat treatment (T6-treated) has been investigated. Quantitative measurements of precipitates revealed that nano-β′ phase in T6-treated TC4/GZ151K composite was denser and thinner than that in T6-treated GZ151K matrix, generating higher ultimate tensile strength of composite than that of matrix (410 MPa vs. 373 MPa). it was disclosed by geometric phase analysis that there were more geometrically necessary dislocations in solution-treated composite than that in the matrix, which was caused by different coefficient of thermal expansion between TC4 and Mg. High-density dislocations are beneficial to precipitate fine and dense β′ phase in the composite while low-density dislocations result in coarse and loose β′ phase in the matrix after aging process. This work confirmed the accelerating effect of TC4 particles on Mg-matrix's aging precipitation, which was of great significance to regulate the precipitation behavior of Mg alloy and produce high strength-ductile Mg materials.

CORROSION PREDICTION OFMAGNESIUM IMPLANT USING MULTISCALE MODELING BASED ON MACHINE LEARNING ALGORITHMS

Significant thoughtful research is really necessary to improve the patient outcomes and reduce the social and financial burdens associated with implant failure. The primary focus of the researchers is to minimize the major implant failure due to corrosion attributed to making orthopedic surgery safer and more effective. Hence, a critical review has been done in this present article on the various multiscale modelings based on machine learning algorithms (MLAs) to predict the corrosion behavior of magnesium (Mg) alloy implants. According to the best of the authors' knowledge, all the available multiscale modelings tools, such as artificial neural network (ANN), least absolute shrinkage and selection operator (LASSO) regression model, multiple linear regression and random forest regression (RFR) models, etc., are methodically presented and discussed in detailed here for the prediction of corrosion mechanism. Subsequently, various multiscale model tools and assessment metrics for models have been thoroughly compared and criticized for better understanding and optimizing of the corrosion behavior of implants. The comparison indicates that the RFR model may be the best option, whereas the LASSO regression model and ANNs show inefficient performance for the prediction of corrosion behavior. Apart from the multiscale modeling approach, the authors have also explored the physiology and properties of alloys, bone implant, immune and tissue system, and the corrosion control mechanisms of Mg alloy. Finally, the present review on multiscale modeling approach and assessment metrics models will enhance the knowledge and understanding of the corrosion behavior of Mg alloy for implant application.

Surface modification of AZ31 Mg alloy by diopside/fluorohydroxyapatite/graphene oxide nanocomposite coating: Corrosion and bioactivity evaluations

There is a high research demand to enhance magnesium-based orthopedic implants' biocompatibility and corrosion resistance. This work reports the development of a nanocomposite ceramic coating based on diopside (Dio) / fluorohydroxyapatite (FHA) / graphene oxide (GO) via the electrophoretic deposition (EPD) method on the AZ31 Mg alloy substrate. FESEM, EDS, XRD, and FTIR were employed to characterize the physicochemical properties of the synthesized diopside and fluorohydroxyapatite ceramic nanoparticles and the EPD ceramic films. The introduction of GO in the Dio/FHA composite film eliminated pores and cracks, improved coating quality, and reduced the film thickness. AFM confirmed a decrease in surface roughness from 184.6 nm to 171.8 nm and wettability enhanced by contact angle reduction from 52.1° to 38.3°. Electrochemical polarization and EIS analyses indicated an 83% boost in corrosion resistance and a 52% reduction in corrosion current density in Dio/FHA/GO vs. Dio/FHA sample. Bioactivity evaluation after five days of immersion in simulated body fluid (SBF) was suggestive that the synergistic effect of Dio, FHA, and GO caused the most abundant apatite formation in Dio/FHA/GO film. The antibacterial activity findings showed that the Dio/FHA/GO coating could function as an antibacterial nanocomposite coating against S. Aureus and E. Coli. Overall, the Dio/FHA/GO EPD film is a highly potential ceramic biomedical coating to improve the corrosion resistance, surface properties, bioactivity, and antibacterial behavior of Mg alloys.

Effect of transverse gradient extrusion process on texture and mechanical properties of Mg–3Al–1Zn alloy sheets

Transverse gradient extrusion (TGE) processes with different die inclined angles of 15°, 30°, 45°and 60° were used to produce Mg–3Al–1Zn sheets, thereby tailoring texture and mechanical properties of Mg alloy sheets. Microstructure, deformation texture and final mechanical properties of the obtained sheets were detected and discussed. Furthermore, the rheological behavior of Mg alloys during extrusion was analyzed by finite element method. As the TGE die inclined angle changed, the flow velocity along the transverse direction (TD) and effective strain difference along extrusion direction (ED) were changed during extrusion, and therefore the microstructure and texture of extruded sheets are altered. With increase of TGE die inclined angles, fine grain size and uniform microstructure were obtained. The base poles of most grains for the extruded sheets gradually deviate from normal direction (ND) to ED at center region and inclined from ED to TD at 1/4 edge region. A large elongation of 33.9 % and a low yield stress of 125 MPa can be obtained in the TGE-45 sheet.

Prediction of electrochemical corrosion behavior of magnesium alloy using machine learning methods

The corrosion of magnesium (Mg) alloys is a major challenge in many industrial applications because of their extreme reactivity, this greatly limits their applicability. The traditional methods in the prediction of corrosion rate depend on experimental or empirical models that can be time-consuming and expensive. Besides how to integrate experiments with faster machine-learning approaches is still a challenge of research. In recent years machine learning (ML) algorithms have proved and promised better magnesium corrosion predictability. In this study, different training algorithms such as linear regression (LR), decision tree (DT), extra tree (ET), random forest (RF), K-nearest neighbor (KNN), extreme gradient boosting (XGBoost), and Artificial Neural Network (ANN) were used to develop and predict corrosion rate of magnesium alloys based on magnesium chemical alloy composition as independent input variables. The data used for model preparation and validation were obtained from literature and experimental studies respectively. The feature selection methods were used to identify the most important and influential input parameters for magnesium alloy thus Shapley Additive Explanations (SHAP) interpretation was employed in this manuscript to facilitate feature visualization of the model. The results of the study show that the random forest (RF) algorithm has the greatest prediction impact than other machine learning algorithms. The magnesium alloy corrosion prediction model provides a better ability for the prediction of magnesium corrosion alloys. The study demonstrates the potential of ML models in the prediction of the corrosion behavior of Mg alloys and these models can be used to optimize an alloy composition for designing improved corrosion resistance of new Mg alloys.

Understanding the Effect of Electrochemical Properties and Microstructure on the Microgalvanic Corrosion of Mg Alloys via Phase-Field Simulations

In this work, we apply a phase-field model to gain insights into the corrosion behavior of Mg alloys. Specifically, we study the effect of electrochemical properties of the materials and their environment and the spatial distribution of second phases in a magnesium alloy. To this end, we perform sensitivity analyses in which we separately vary the exchange current density and corrosion potential of the second phase, as well as the electrolyte conductivity. We describe the effects of these parameters on the corrosion current and the resulting corrosion-front morphology. We also confirm that the ratio between the Wagner length, calculated for the anodic phase, and the initial width of the anodic domain is a good predictor of the morphological characteristic of the corroding surface. In addition, we examine the effect of the microstructure on the corrosion behavior in both 2D and 3D systems by varying the shape, size, and distribution of the second-phase regions. Our findings provide insights into the influence of the two-phase microstructure on the corrosion behavior in a magnesium alloy.

Investigation on tribological characteristics of ball burnished Mg Ze41A alloy by ANOVA and ANFIS techniques

Magnesium (Mg) alloys exhibit superior strength, high castability and machinability. But, the application range of Mg alloys was limited because of low wear and corrosion resistance. Also, Mg alloys are being explored for biomedical applications due to their biocompatibility and biodegradability nature. The wear behavior of Mg alloys can be enhanced by mechanical, physical and chemical methods. This study deals with deployment of one of the mechanical methods such as ball burnishing on Mg Ze41A alloy. The contribution of each process parameter on tribological characteristics has been evaluated by ANOVA. The results reveal that burnishing force has contributed the highest with 39.16% on wear rate, 52.60% on CoF and 50.87% on interfacial temperature. The SEM images revealed wear phenomenons such as oxidation, plastic deformation. Further, the tribological characteristics at unknown test cases have been estimated by ANFIS technique. The model generated the results with an accuracy of 98.69%, 93.35% and 96.26% for wear rate, CoF and temperature respectively.

Localized magnetic moments variation for strengthening and tuning thermal expansion behavior of Mg alloys

We proposed the localized magnetic moments (LMMs) variation-induced strengthening for Mg alloys. Due to the strong interplay of magnetic and elastic, the introduction of merely 7 wt.% Mn3Ga0.7Ge0.3N in WE43 Mg alloy could not only reduce the coefficient of thermal expansion (CTE) but also enable an enhancement of ∼70% on compressive yield strength and less decrease of ∼2.1% on the elongation. We observed localized uniform lattice deformations and magnetic phase transitions for stress response and verified that the strain involves LMMs variation in the frustrated antiperovskite system, realizing simultaneously reinforcing and toughening in the compressive deformation process. Meanwhile, these magnetic transitions are accompanied by volume shrinkage and thus reduce the CTE of the WE43 Mg alloy. These results demonstrate that the introduction of the secondary phase with the variation of LMMs for stress response is an effective design strategy for alloys to achieve tunable thermal expansion behavior combined with high strength and moderate compressive deformability.

Effect of the microstructure parameters on the mechanical properties and corrosion behavior of Mg alloys with high Zn or Ca content

Effect of the microstructure parameters on the mechanical properties and corrosion behavior of Mg alloys with high Zn or Ca content

Effect of Y content on the microstructure and mechanical anisotropy of Mg–6Zn-xY-0.5Ce-0.4Zr alloy subjected to asymmetric rolling

An in-depth study of the anisotropic mechanical behavior of Mg alloys is essential for optimizing mechanical properties, designing high-performance Mg alloys, and developing processing processes. This work investigates the microstructure and mechanical anisotropy of Mg–6Zn-xY-0.5Ce-0.4Zr (MZCZ-xY) alloys with varying Y contents subjected to asynchronous rolling (ASR). The Y content significantly affects the microstructure and mechanical anisotropy of the MZCZ-xY alloy. In lower Y content alloys (MZCZ-0.2Y, MZCZ-0.5Y), the second phase mainly consists of Mg3Zn6Y (I phase) and Mg1.5Zn9.5Ce3, while the addition of 1.0 wt% Y leads to the appearance of Mg3Zn3Y2 (W phase) in the alloy. Furthermore, increasing Y content results in grain growth in the as-cast state, which will affect the average grain size after asymmetric rolling (ASR) deformation. However, alloys with higher Y content exhibit a more pronounced effect of grain refinement at the same ASR strain. Moreover, increasing Y content promotes the activation of tensile twins, with higher Y content leading to greater tensile twin activation after ASR treatment. The MZCZ-0.2Y alloy shows lower mechanical anisotropy, which is closely related to the homogeneous texture component and uniform Schmid factor (SF) in each loading direction. Therefore, the regulation of mechanical anisotropy in Mg alloys can be achieved by obtaining uniform texture components and uniform SF in each loading direction.

The inhibition effect of etidronate on degradation behavior of Mg–Zn–Y-Nd-Zr alloy

The control of corrosion behavior of Mg alloys for biomedical applications is a research hotspot in the field of biodegradable metallic implant materials. In recent years, the employment of corrosion inhibitors for regulating the corrosion behavior of Mg alloys has attracted attention. In this work, a promising corrosion inhibitor for Mg alloys, Etidronate (ETN), was selected from the drugs for the treatment of osteoporosis, and its effect on the corrosion behavior of Mg–Zn–Y-Nd-Zr (ZE21C Mg alloy) in simulated body fluids was systematically studied. The results show that ETN not only reduces the corrosion rate of the alloy, but also significantly weakens its tendency of localized corrosion, which is beneficial for improving the service reliability of Mg alloy for orthopedic application. This study provides an idea for corrosion control of biodegradable Mg alloys and is of great significance for promoting their development and applications.