AZ31 Magnesium Alloy Research Articles

Deformation Behavior of AZ31 Magnesium Alloy with Pre-Twins under Biaxial Tension.

In the present study, the mechanical response and deformation behavior of a Mg AZ31 plate with different types of pre-twins was systematically investigated under biaxial tension along the normal direction (ND) and transverse direction (TD) with different stress ratios. The results show that significant hardening was observed under biaxial tension. The yield values in the direction of larger stress values were higher than those under uniaxial loading conditions, and the solute atom segregation at twin boundaries generates more obvious strengthening effect. Noting that, for TRH (with cross compression along the rolling direction (RD) and TD and annealing at 180 °C for about 0.5 h) sample, the strength effect of the RD yield stress σRD:σND = 2:1 was higher than that of the ND yield stress under stress ratio σRD:σND = 1:2. There is a complex competition between twinning and detwinning under biaxal tension along the ND and TD of the pre-twinned samples with the variation in the stress ratio along the TD and RD. The variation in the twin volume fractions for all samples under biaxial firstly decreases and then increases with a higher stress ratio along the ND. As for the TDH sample (precompression along the TD and annealing), the changes of the twin volume fraction were lower than that of the TR sample (cross compression along the TD and RD). However, the amplitude of variation in twin volume fraction of the TRH sample is higher than that of the TR sample. This is because the relative activity of detwinning decreases and that of twinning increases, as the ND stress mainly leads to the growth of pre-twins and the TD stress often promotes detwinning of primary twins. With a higher stress ratio along the ND, the activity of twinning deformation increases and that of detwinning decreases.

Research on stamping formability and process simulation of AZ31 magnesium alloy based on deep learning

To study the formability of AZ31 magnesium alloy under different temperature conditions and improve the forming quality of its parts, this paper aims to solve the minimization problem of pursuing the “maximum thinning rate”. This study obtained the mechanical properties of AZ31 magnesium alloy at 25 °C, 150 °C, 250 °C, and 350 °C through uniaxial tensile tests and explored the stamping formability of AZ31 magnesium alloy mobile phone cases using the finite element inverse calculation method (MSTEP). Based on the hot stamping of AZ31 magnesium alloy at 250 °C, the Monte Carlo Simulation (MCS) method was used to randomly sample the blank holder force, stamping speed, friction coefficient, and resistance coefficient, and then simulate to obtain the corresponding “maximum thinning rate”. In addition, a hybrid prediction model optimized by Genetic Algorithm (GA) and Dung Beetle Optimization (DBO) based on the Back Propagation Neural Network (BPNN) - Random Forest (RF) was used to explore the nonlinear relationship between blank holder force, stamping speed, friction coefficient, resistance coefficient, and the “maximum thinning rate”. The results show that the plasticity of AZ31 magnesium alloy enhances with the temperature increase, especially exhibiting the best stamping formability at 250 °C. Feature importance indicates that the resistance coefficient and stamping speed have a greater impact on the maximum thinning rate, while the influence of blank holder force and friction coefficient is relatively smaller. Mean Square Error (MSE) shows that the predictive capability of the hybrid model is significantly superior to that of the single BP neural network and Random Forest model, displaying optimal efficiency. The predicted maximum thinning rate by the model is 15.39 %, with an error rate of only 0.32 % compared to the DYNAFORM finite element software simulation results, confirming the correctness, accuracy, and effectiveness of the prediction model. Overall, this study provides practical optimization strategies for metal stamping forming processes, with significant practical application value.

Step-by-step in-situ preparation of magnesium-aluminum layered double hydroxide film to improve the corrosion resistance of AZ31 magnesium alloy

In this study, a hydrothermal method was employed to cultivate Mg(OH)2 precursor layers on the surface of AZ31 magnesium alloy samples. Subsequently, Mg-Al LDHs films were successfully synthesized through an in-situ growth approach. The phase composition of the films were analyzed using X-ray diffraction and infrared spectroscopy. The growth process and surface morphology of the films at the microstructure level were examined and interpreted using scanning electron microscopy and EDS. The corrosion resistance of the films was assessed through potentiodynamic polarization curves, electrochemical impedance spectroscopy, and hydrogen evolution tests. The findings indicate that the Mg(OH)2 precursor effectively mitigates defects in the Mg-Al LDHs films and improves the LDHs microstructure. Moreover, the precursor synthesized at a pH range of 10–12 better enhances the corrosion resistance of the Mg-Al LDHs film.

Influence of Aging Condition on the Characteristics of Continuous Precipitates of AZ80 Magnesium Alloy

The aim of this work is to evaluate the characteristics of continuous precipitates (CP) developed within the grain and grain boundary precipitates through statistical analysis of the number density and size (i.e., length and width) at varying aging conditions of AZ80 Mg alloy. Scanning electron microscopy illustrates the characteristics and features of precipitates, distinctively. The results reveal an increment of number density, whereas the reduction in the size of precipitates with decrease in the aging temperature for the varying aging times. The variation in hardness values at different aging conditions has been ascribed to this.

Numerical simulation and experimental investigation on friction stir welding of AZ31 magnesium alloy

Integrated numerical simulations and experimental investigations were employed to scrutinize the thermal, mechanical, and microstructural transformations of the AZ31 magnesium alloy during the friction stir welding (FSW) process. Especially, the primary focus was on the influence of process parameters such as rotational speed and welding speed on the temperature distribution, grain refinement, and mechanical properties of welded joints in alloys. By employing Deform-3D coupled with the integration of constitutive equations and dynamic recrystallization (DRX) models, the FSW process was investigated. The investigation revealed a significant increase in temperature when the tool’s shoulder made contact with the weld, resulting in the substantial accumulation of heat during FSW. Distinctions became apparent between the advancing side (AS) and the receding side (RS), with the AS exhibiting slightly elevated levels of temperature, equivalent stress, strain, and grain size. Specifically, adjustments in the rotational speed of the stirring tool and a reduction in welding speed resulted in larger grain sizes within the alloy. For example, when the rotational speed was set at 1200 rpm and the travel rate was 200 mm min−1, the initial grain size of the weld experienced a substantial decrease from 57.8 μm to 8.2 μm. Subsequent experimental verification, considering grain size and microhardness, was carried out to optimize FSW parameters for achieving the desired material properties. The accuracy of simulation results was validated through a meticulous comparison with experimental findings, underscoring the potential of numerical simulation in comprehending and predicting FSW processes.

Effect of deformation temperature on microstructure and texture of AZ31 magnesium alloy processed by new plastic deformation method

Effect of deformation temperature on microstructure and texture of AZ31 magnesium alloy processed by new plastic deformation method

Machine learning based prediction models for uniaxial ratchetting of extruded AZ31 magnesium alloy

The detrimental effect of ratchetting on the fatigue life of materials requires precise prediction models to guarantee the safety of engineering structures. This study focuses on predicting the uniaxial ratchetting of extruded AZ31 magnesium (Mg) alloy using machine learning (ML) based approaches. At first, the evolution and deformation mechanisms of ratchetting are summarized based on the existing experimental results of the Mg alloy. Subsequently, a semi-empirical prediction model, tailored for engineering applications, is developed to describe the evolution of ratchetting strain. Then, a pure data-driven ML based prediction model is proposed to overcome the shortcoming existed in the semi-empirical model and improve the prediction accuracy to the uniaxial ratchetting of the Mg alloy. Finally, a physics-informed ML based model, incorporating the physical information derived from the semi-empirical one, is proposed to further enhance its prediction accuracy and generalization ability. The comparison with correspondent experimental data demonstrates that the proposed physics-informed ML based model exhibits high prediction accuracy and generalization ability.

Scalable DC casting of large-size AZ80 magnesium alloy slab under out-of-phase pulsed magnetic field: Experiment and simulation

The large-size AZ80 magnesium alloy slab was manufactured using direct chill casting assisted by out-of-phase pulsed magnetic field. Subsequently, the effects of OPMF on the as-cast structure and the Al content were investigated. By using numerical simulation, the macro physical fields including the flow field, the temperature distribution, and the sump profile were simulated and compared between the slab with and without OPMF. After introducing the OPMF, significant grain refinement occurred, and the macrosegregation degree of the Al element was alleviated. Compared with the case without OPMF, the simulations revealed that the melt flow rate and its range were greatly increased, accelerating the convective heat transfer in the sump. As a result, the temperature field was more uniformed distributed, the cooling rate was increased and the sump depth became shallower. The relevant mechanisms between the experimental results and the simulation results were discussed in detail.

Development and Evaluation of an AZ31 Magnesium Alloy and Eggshell Powder Composite for Orthopedic Surgical Implants

This research investigates the development and evaluation of a novel composite material composed of AZ31 magnesium alloy and eggshell powder, designed for use in surgical bone implants. The primary objective is to enhance the mechanical properties and biocompatibility of AZ31 by incorporating eggshell powder, which is known for its hardness and strength. The composite is fabricated using the stir casting technique, where the molten magnesium is mixed with finely ground eggshell powder to achieve uniform dispersion. The resulting samples are subjected to rigorous mechanical testing, including tensile and compressive strength evaluations, as well as hardness measurements. Additionally, the internal structure and particle distribution of the composite are analyzed using scanning electron microscopy and X-ray diffraction, respectively. This study aims to provide a comprehensive understanding of the material properties and structural characteristics of the composite, with a focus on its potential applications in orthopedic load-bearing implants and fixation devices, such as bone plates, joint replacements, screws, rods, dental implants, and cardiac stents. The findings are expected to contribute to the development of improved biomaterials for medical applications, leveraging the unique benefits of both magnesium alloy and eggshell powder.

Preparation and Characterization of Duplex PEO/UV-Curable Powder Coating on AZ91 Magnesium Alloys

Preparation and Characterization of Duplex PEO/UV-Curable Powder Coating on AZ91 Magnesium Alloys

Assessing the properties of biodegradable magnesium alloy AZ31 protected by a polymer layer on a plasma electrolytic oxidized (PEO) surface

In the present work we consider the AZ31 Mg alloy for applications as medical implants with bone contact. The alloy has the advantages that it combines a high strength with light weight. Most importantly, it eventually dissolves in the body environment and there is therefore no need to remove implants by additional surgery. However, this dissolution should not happen too fast in order to guarantee mechanical integrity during the healing process. This requires the application of appropriate composite coatings. In a first step, an inorganic protective layer is formed by plasma electrolytic oxidation (PEO) using an electrolyte which contains calcium glycerophosphate (CaGP). Special emphasis is placed on the effect of varying CaGP concentrations in the electrolyte, considering molar concentrations between 0.01 and 0.03 mol/l. In a second step, polymer coatings were applied on composite layers to find out whether the system properties can be further improved. Two types of polymer layers were developed using a spin coating method, based on the biodegradable polymer systems polycaprolactone and polyethylene glycol. The results obtained in the present investigation suggest that introducing CaGP into the electrolyte of plasma electrolyte oxidation induces a composite layer consisting of MgO and CaP compounds. The coatings developed in 0.02 mol/l CaGP electrolyte exhibit superior adhesion strength. A significant tenfold increase in corrosion resistance and the highest cell viability are observed on coatings developed in 0.02 mol/l CaGP electrolyte and then superimposed with PCL. These results suggest that a coating on AZ31, after PEO in an electrolyte with 0.02 mol/l CaGP and then superimposed with PCL, represents a promising candidate for applications as bio-absorbable bone implant material. The coated material by far outperforms the material with no surface treatment.

Corrosion Behavior of CMT Cladding Layer of AZ91 Magnesium Alloy Subjected to Friction Stir Processing.

Friction stir processing (FSP) was performed on an AZ91 magnesium alloy cladding layer fabricated by a cold metal transfer (CMT) technique. Electrochemical properties and immersion corrosion behavior of the cladding layer before and after FSP in 3.5 wt.% NaCl solution were investigated. After applying the FSP, the corrosion potential and corrosion current density of the cladding layer increased from -1.455 V to -1.397 V and decreased from 4.135 μA/cm2 to 1.275 μA/cm2, respectively. The results of OM and SEM displayed the refinement of grains and the dispersion of β-Mg17Al12 second phase in the friction stir processed (FSPed) cladding layer and more severe corrosion of the unprocessed sample. The corrosion rate of the FSPed cladding layer was lower, and a more compact corrosion product film was formed on the surface of the FSPed cladding layer. EDS results and XRD patterns showed that the corrosion products was mainly composed of Mg(OH)2. The increase in Al content in the α-Mg matrix, grain refinement, and fragmentation and dispersion of the β-Mg17Al12 second phase induced by FSP were the main factors that led to the improvement in corrosion resistance of the cladding layer of the AZ91 magnesium alloy fabricated by CMT.

Construction of hot processing map, dynamic recrystallization critical conditions and kinetic model of AZ61 alloy

Under temperature of 300–450 °C and strain rates from 0.003 s−1 to 1 s−1 and deformation of 70 %, hot compression experiments of AZ61 magnesium alloy were carried out on Gleeble-1500 test machine, to study its thermal deformation behavior. Based on the dynamic material theory model, a three-dimensional hot working map was obtained. Based on the work hardening rate curves inflection point, the critical strain model was built. Subsequently, the dynamic recrystallization kinetics model was constructed according to critical conditions. The findings showed that at low strain rates and high temperatures, materials with larger power dissipation factors exhibit better processability, and at high strain rates and low temperatures, materials are more prone to instability with the increase of strain. Considering the connection between peak strain εp and critical strain εc, it is observed that εc precedes εp, indicating that dynamic recrystallization occurs before reaching the peak strain. Based on the kinetics model, observed the dynamic recrystallization volume fraction curves follow a “slow-fast-slow” changing trend, exhibiting an “S” shaped growth, which was agreed with the kinetics curve in classical dynamics.

Effect of strain on the adiabatic shear behaviour of AZ31 magnesium alloy

The effect of strain on the adiabatic shear behaviour of AZ31 magnesium alloy under high strain rate compression was studied using split Hopkinson pressure bar (SHPB). The microstructure of the specimen was characterised using optical microscopy and electron backscatter diffraction. The results indicate that the adiabatic shear sensitivity increased with the strain. The microstructure evolution of adiabatic shear deformation has been investigated. Firstly, a large number of twins and dislocations are formed and accumulate in the early stage of deformation. Subsequently, they transform into dynamic recrystallised grains, forming an adiabatic shear band (ASB) and ultimately leading to crack formation. The dynamic recrystallisation mechanism in the ASB involves twinning-induced dynamic recrystallisation (TDRX) and rotational dynamic recrystallisation (RDRX). This study has analysed the ASB mechanism, which provides a foundation for material selection and the design of magnesium alloys.

Performance of anionic dimeric surfactant on AZ31 Magnesium alloy in neutral medium unveiled through experimental and theoretical investigation

The synthesis of a novel eco-friendly anionic Gemini surfactant, pursuing three parameters of green chemistry: economic, environmental factor, and mass reaction efficiency is developed as a corrosion inhibitor for AZ31 Mg alloy. Herein, the corrosion inhibition ability of novel EDTA-based dimeric surfactant on AZ31 Mg alloy in corrosive media with varying concentrations of NaCl and Na2SO4 at temperatures between 30–50 °C were studied. The surfactant’s molecular structure is affirmed by FT-IR, NMR, and LC–MS techniques. Electrochemical techniques and surface morphology were employed to evaluate the corrosion inhibition efficiency. The inhibitor studied exhibited appreciable corrosion inhibition at 30 °C. The surfactant shows physical adsorption as per the data obtained in the Gibbs free energy and enthalpy of adsorption studies. The adsorption of the inhibitor was found to be a film-like layer on the surface of AZ31 Mg alloy and, is confirmed by SEM–EDX and XPS techniques. In addition, theoretical simulations were performed to compare with experimental results. Conclusively, the work provides a deeper understanding of the intricacies involved in the development of a new anionic dimeric surfactant as an effective corrosion inhibitor.

Quantitative study on the influence of strain amplitude on deformation mechanisms and cracking modes during cyclic torsion of AZ31 magnesium alloy

AbstractThe influence of strain amplitude on deformation mechanisms and cracking modes during cyclic torsion of the AZ31 magnesium (Mg) alloy was quantitatively investigated via EBSD‐SEM characterization. At 0.42% strain amplitude, basal slip was the dominated deformation mechanism throughout the entire fatigue life. At 1.732% strain amplitude, the activation of deformation mechanisms was featured by the periodic transition: tension twinning + basal slip (during counterclockwise torsion) then detwinning + tension twinning + basal slip (during reverse torsion). Moreover, cracking along slip traces (ST) and tension twins (TTW) were the primary cracking modes at 0.42% and 1.732% strain amplitude, respectively. ST cracking and TTW cracking preferentially appeared in soft‐oriented grains for basal slip and tension twinning, respectively. The underlying mechanisms governing the activation of various deformation mechanisms, cracking modes, and cyclic stress–strain responses were systematically discussed.

Effect of Co-addition of Sn, Traces of RE and Ca on the Mechanical and Micro Structural Properties of As-cast AZ80 Alloy

In this study, the effect of co-addition of tin (0, 6 and 9 wt.%), cerium (0, 0.3 and 0.6 wt.%), gadolinium (0, 0.6 and 0.9 wt.%) and calcium (0, 0.6 and 0.9 wt.%) on the mechanical and microstructural properties of AZ80 magnesium alloy is investigated. The results indicate that the mechanical properties are improved for all the as-cast alloys when compared to base alloy except for one alloy which is due to the presence of Mg-Sn-Ca phase in high volume fraction. Also, it is found that the existence of Al2Ca, Mg2Ca, Al2RE, MgSnRE and Mg2Sn phases have a significant impact on the mechanical and microstructural characteristics of the as-cast AZ80 alloys. It is observed that without the addition of Sn content, the best room temperature tensile properties are obtained for the alloy containing 1.5 wt.% of RE and 0.9 wt.% of Ca. With the addition of Sn, it is found that the best room temperature tensile properties are obtained for the alloy containing 6 wt.% of Sn, 0.9 wt.% of RE and 0.5 wt.% of Ca.

Eu-substituted hydroxyapatite/silica sol-gel treatment for corrosion protection of AZ31 magnesium alloy

Europium-hydroxyapatite (Eu-HA) nanocomposite was developed via continuous hydrothermal synthesis. Eu+3 ions partially replaced the Ca+2 ions within hydroxyapatite molecular structure. High quality Eu-HA nanorods of 20 nm width and 6 μm lengths were verified via TEM micrographs. Eu-HA maintained the crystalline structure of HA with minimum change; material studio software confirmed the partial replacement of Ca+2 by Eu+3. XPS analysis demonstrated Eu+3 content of 6.91 atom %. Ca/P ratio was found to be 1.405 and 0.118 for virgin HA and Eu-HA respectively; this was ascribed to the partial replacement of Ca+2 with Eu +3. The EDAX mapping verified the uniform dispersion of Eu ions within Eu-HA structure. Eu-HA nanocomposite was uniformly distributed in silica sol-gel matrix; subsequently it was applied on AZ31 magnesium alloy. The corrosion performance of Eu-HA sol-gel coating nanocomposite (Eu–S) was evaluated using different electrochemical techniques including Potentiodynamic Polarization (PDP), Electrochemical Impedance Spectroscope (EIS), and Electrochemical Noise (EN) in aerated 0.1 M NaCl solution. Corrosion protection was assessed to that of neat silica sol-gel coating (NSG). Pitting was detected over the whole NSG coated sample, after few hours of immersion in the corrosive solution. EuS coated AZ31 withstand up to 144 h without any sign of corrosion or delamination. EIS analysis with PDP parameters suggested the formation of protective layer; that is responsible for the corrosion resistance. Europium has unique ability to form a protective oxide layer acting as a barrier layer that could prevent the penetration of corrosive electrolyte to the underlying metal substrate.

Formation of Surface Deformed Layer of AZ31 Magnesium Alloy Subjected to Conventional Mechanical Grinding

Formation of Surface Deformed Layer of AZ31 Magnesium Alloy Subjected to Conventional Mechanical Grinding

Cryogenic and conventional milling of AZ91 magnesium alloy

Use of magnesium is the need of the hour due to its low density as well as its high strength-to-weight and stiffness-to-weight ratio etc. This study focuses on the effectiveness of liquid nitrogen (LN2) assisted cryogenic machining on the surface integrity (SI) characteristics of AZ91 magnesium alloy. Face milling using uncoated carbide inserts have been performed under liquid nitrogen (LN2) assisted cryogenic condition and compared with conventional (dry) milling. Experiments are performed using machining parameters in terms of cutting speeds of 325, 475, 625 m/min, feed rates of 0.05, 0.1, 0.15 mm/teeth and depth of cuts of 0.5, 1, 1.5 mm respectively. Most significant surface integrity characteristics such as surface roughness, microhardness, microstructure, and residual stresses have been investigated. Behaviour of SI characteristics with respect to milling parameters have been identified using statistical technique such as ANOVA and signal-to-noise (S/N) ratio plots. Additionally, the multi criteria decision making (MCDM) techniques such as additive ratio assessment method (ARAS) and complex proportional assessment (COPRAS) have been utilized to identify the optimal conditions for milling AZ91 magnesium alloy under both dry and cryogenic conditions. Use of LN2 during machining, resulted in reduction in machining temperature by upto 29% with a temperature drop from 251.2 °C under dry condition to 178.5 °C in cryogenic condition. Results showed the advantage of performing cryogenic milling in improving the surface integrity to a significant extent. Cryogenic machining considerably minimized the roughness by upto 28% and maximised the microhardness by upto 23%, when compared to dry machining. Cutting speed has caused significant impact on surface roughness (95.33% – dry, 92.92% – cryogenic) and surface microhardness (80.33% – dry, 82.15% – cryogenic). Due to the reduction in machining temperature, cryogenic condition resulted in compressive residual stresses (maximum σ║ = -113 MPa) on the alloy surface. Results indicate no harm to alloy microstructure in both conditions, with no alterations to grain integrity and minimal reduction in the average grain sizes in the near machined area, when compared to before machined (base material) surface. The MCDM approach namely ARAS and COPRAS resulted in identical results, with the optimal condition being cutting speed of 625 m/min, a feed rate of 0.05 mm/teeth, and a depth of cut of 0.5 mm for both dry and cryogenic environments.