AZ31 Magnesium Alloy Research Articles

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.

Fatigue and tensile behaviour of Ti+TiN+Ti+TiVN multilayer nitride films coated on AZ91 magnesium alloy by closed field unbalanced magnetron sputtering

Despite their extensive use in the automotive and aerospace industries, Mg and Mg alloys, which are light metals, exhibit low fatigue and tensile strength. In this study, transition metal-nitride (TMN) multilayer coatings (Ti+TiN+Ti+TiVN) were coated twice on AZ91 Mg alloy using a Confined Field Unbalanced Magnetron Sputtering (CFUBMS) system to increase fatigue and tensile strength. The structural properties of the films were analyzed by using X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometry (EDS) methods, and the mechanical properties were analyzed by rotating bending fatigue and tensile testing machines. Ti+TiN+Ti+TiVN multilayer nitride surface coatings on AZ91 Mg alloys showed a dense and columnar microstructure and according to XRD results (111) was the preferred orientation with the dominant peak. The fatigue limit value of the AZ91 base material was fixed at 60.46 MPa, while it increased to 68.48 MPa after being coated with multilayer nitride. Along with the multilayer nitride coating, the tensile strength increased from 169.98 MPa to 175.43 MPa. As a result, the multilayer hard nitride coating with low surface roughness, which fills the defects, notches, and voids on the surface of the AZ91 base material, increased the fatigue and tensile strength in parallel. Based on the outcomes of the research, the literature has been enriched with an innovative approach through the enhancement of fatigue and tensile strengths by applying a CFUBMS coating to lightweight metals and alloys, such as AZ91, especially in the transportation industry where lightness and dynamic load resistance are essential.

Effects of T6 treatment on the microstructure and mechanical properties of az80 magnesium alloy

The mechanical and microstructure properties of the AZ80 magnesium alloy in deformed and T6 states were evaluated and analyzed by tensile testing and metallographic analysis. The results showed that the grain size of the magnesium alloy increased after T6 treatment, whereas the number of deformed grains decreased considerably. These changes were accompanied by a transformation of the β-Mg17Al12 phase from a discontinuous point-like morphology to a continuous lath-like morphology. After T6 treatment, the tensile strength and yield strength of the material were significantly improved. These findings indicated that the microstructure of the AZ80 magnesium alloy was altered through T6 treatment, and its mechanical properties were markedly enhanced.

Investigating the weld joint characteristics of AZ31 and AZ91 magnesium alloys produced by friction stir welding

ABSTRACT In this work, FSW was used to join AZ31 and AZ91 magnesium (Mg) alloys to investigate the mechanism behind joint formation and its mechanical performance. The cross-sectional microstructure of the weld zone clearly indicated a strong metallurgical bonding between AZ31 and AZ91 sheets in addition to the mechanical interlocking due to the mixing of both base materials. Uniform hardness (62.9 ± 4.5 HV) was recorded in the weld joint and the values were between AZ31 (59.8 ± 2.4 HV) and AZ91 (78.7 ± 19.5 HV). Tensile test results demonstrated decreased strength (145 ± 4.2 MPa) compared with the base alloys (265 ± 7.3 MPa and 190 ± 4.8 MPa for AZ31 and AZ91, respectively. Ductility was noticed as decreased as reflected by the lower % of elongation for the weld joint compared with both AZ31 and AZ91 base materials. The fractography studies of the samples suggest a brittle mode of fracture in the weld joint similar to that of AZ91 base material.

Partially phosphorylated poly(vinyl alcohol) – A promising candidate in corrosion protection of magnesium for the biomedical industry?

Partially phosphorylated poly(vinyl alcohol) (PPVA) as anticorrosive coating for AZ31 magnesium alloy was investigated in Hank’s Balanced Salt Solution (HBSS). Four phosphoric acid levels were used to modify PVA, resulting in four PPVA products. They were characterized using thermogravimetric analysis (TGA), water contact angle (WCA), and swelling test. PPVA-coated Mg alloys were evaluated using hydrogen evolution, cathodic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). TGA indirectly revealed crosslinked regions in the PPVA structure that increased with acid content. WCA and hydrogen evolution tests suggested that PPVA is a promising polymer for biomedical applications. Corrosion tests showed that the PPVA with 10% acid addition significantly improved the impedance modulus and lowered the cathodic kinetics compared to uncoated samples. The findings of the study suggested that the acid addition in PVA must be at least 10 % to guarantee improved corrosion resistance in HBSS, which indicates this material has potential for biological applications.

Effect of particle size and concentration of Al2O3 on the corrosion behavior of silane-Al2O3/MWCNT double-layer coating: towards protecting the AZ91 magnesium alloy

Effect of particle size and concentration of Al2O3 on the corrosion behavior of silane-Al2O3/MWCNT double-layer coating: towards protecting the AZ91 magnesium alloy

Effect of Polytetrafluoroethylene Coating on Corrosion Wear Properties of AZ31 Magnesium Alloy by Electrophoretic Deposition

In this study, we aim to enhance the corrosion and wear resistance of AZ31 magnesium alloy using electrophoretic deposition (EPD) technology to apply a hydrophobic polytetrafluoroethylene (PTFE) coating. Polyethyleneimine (PEI) serves as a charged dispersant, facilitating uniform deposition of PTFE particles on the alloy surface. Results demonstrate a significant reduction in corrosion current density (from 67.5 μA/cm2 to 5.2 μA/cm2) and improved wear resistance (wear volume decreased from 0.24167 mm3 to 0.00167 mm3) in a 3.5 wt% NaCl solution compared to uncoated alloy. Moreover, the friction coefficient of the coated sample decreases. These findings underscore the potential of nano-PTFE coatings prepared via EPD in enhancing AZ31 magnesium alloy’s corrosion and wear resistance, providing a foundation for future protective coating design and optimization.

The Effect of Self-Healing Microcapsules in Corrosion Testing on Magnesium AZ31 Alloy and Fibre Metal Laminates

Fibre metal laminates (FMLs) are the most interesting composite materials of the past decade. They possess the properties of both polymer composites and metallic alloys. However, there is a problem with corrosion when the outer layers are made of aluminium or magnesium. The electrochemical changes that occur during the corrosion process and the mechanisms associated with the corrosion phenomenon are still being investigated. Recently, self-healing phenomena have emerged as a useful approach to prevent corrosion. However, there is limited research on the combination of FMLs and self-healing layers. Therefore, the main purpose of this article is to evaluate the self-healing ability of a magnesium/PEO layer based on microcapsules in a corrosion environment. It was observed that the corrosion mechanism in magnesium alloys is very complex. However, the use of a barrier layer with PEO treatment and microcapsules yielded positive anti-corrosion results. The FML samples were subjected to a 6-week corrosion test, and the addition of microcapsules to the layers showed positive results. In contrast, the samples without microcapsules exhibited intergranular corrosion. In the future, comprehensive tests using self-healing microcapsules in FMLs could greatly enhance their anti-corrosion properties and improve the integrity of the structure.

Corrosion resistance of a superhydrophobic polypropylene coating on magnesium alloy AZ31

PurposeTo improve the corrosion resistance of magnesium alloys, the construction of protective coatings is necessary to extend the service life of Mg-based materials.Design/methodology/approachSiO2 nanoparticles modified by dodecyltrimethoxysilane (DTMS) were added to the PP and a superhydrophobic Mg(OH)2/PP-60mSiO2 composite coating was fabricated on the surface of AZ31 magnesium alloy via the hydrothermal method and subsequently the immersion treatment.FindingsHydrophilic SiO2 nanoparticles become hydrophobic after modified by DTMS, showing a higher dispersibility in xylene. By incorporating modified SiO2 nanoparticles into the composite PP coating, the hydrophobicity of the layer was enhanced, resulting in a contact angle of 166.3° and a sliding angle of 3.4°. It also improved the water repellency and durability of the coating. Furthermore, the intermediate layer of Mg(OH)2 significantly strengthened the bond between the PP layer and the substrate. The Mg(OH)2/PP-60mSiO2 composite coating significantly enhances the corrosion resistance of the magnesium alloy by effectively blocking the infiltration of the corrosion anions during corrosion. The corrosion current density of the Mg(OH)2/PP-60mSiO2 composite coating is approximately 8.23 × 10–9 A·cm-2, which can achieve a magnitude three times lower than its substrate, making it a promising surface modification for the Mg alloy.Originality/valueThe composite coating effectively and durably enhances the corrosion resistance of magnesium alloys.

Mechanical anisotropy induced by the competition between twinning and basal slip of AZ31 magnesium alloy under biaxial tension

The mechanical behavior of a hot-rolled Mg AZ31 plate was studied under biaxial tensions along two perpendicular loading axes of x and y in the ND-TD plane, with the x-axis aligned at a 45° counterclockwise angle from the TD (ND and TD refer to the normal direction and transverse direction). A complex strain partitioning in two loading axes is observed with the variation of stress ratio σxx:σyy. For σxx:σyy= 1:1 and 1:1.5, the strains along the x- and y-axes, εxx and εyy, are both positive. However, With the stress ratio of σxx:σyy= 1:3, εyy remains positive, while εxx becomes negative. Interestingly, for σxx:σyy = 1:2, εxx changes from negative during the early stage of loading to positive upon failure. Crystal plasticity simulations and theoretical calculations reveal that the observed strain transition. The reasons for the strain transition with stress ratio is related to the competition between {101¯2} twinning and basal slip. For {101¯2} twinning, the accommodated strains by most of the twins are εxx>0 and εyy>0 for all the stress ratios considered. For basal slip, most of the basal variants accommodate a positive y-axis strain, while for loading cases with low stress ratios, most of the basal variants result in a negative x-axis strain. As the stress ratio decreases, basal slip becomes more active, while the activity of {101¯2} twinning gradually decreases, leading to the observed strain transition. For σxx:σyy = 1:2, the transition from negative to positive is related to the increasing activity of {101¯2} twinning with strain. Theoretical calculations reveal that the competition of basal slip and {101¯2} twinning under biaxial tension is determined by the variation of their Schmid factors with σxx:σyy.

AZ91 Magnesium Alloy CMT Cladding Layer Processed Using Friction Stir Processing: Effect of Traverse Speed on Microstructure and Mechanical Properties.

Friction stir processing (FSP) is a solid-state treating method to enhance the mechanical properties of materials by altering their microstructure. In this study, FSP was applied to the AZ91 magnesium alloy cladding layer prepared using cold metal transition (CMT) technology, and the purpose was to investigate the effect of the traverse speed of the H13 steel stirring head under a constant rotation speed on the microstructure and mechanical properties of the cladding layer. The results demonstrated that FSP could effectively decrease the grain size of the cladding layer and lead to the dispersion and dissolution of the coarse β-Mg17Al12 second phase into the α-Mg matrix. The mechanical characteristics of the processed cladding layer were significantly enhanced compared to the unprocessed cladding layer due to the grain refinement and second-phase strengthening induced by FSP. When the stirring head rotation speed was set at 300 r/min, the average microhardness and tensile properties of the specimens showed a tendency of initially increasing and then dropping as the traverse speed increased. The cladding layer, obtained at a traverse speed of 60 mm/min, displayed optimal mechanical properties with an average microhardness, tensile strength, and elongation of 85.6 HV0.1, 278.5 MPa, and 13.4%, respectively.

Effect of Stretch Bending on the Microstructure and Mechanical Properties of AZ31 Magnesium Alloy

Effect of Stretch Bending on the Microstructure and Mechanical Properties of AZ31 Magnesium Alloy