AZ31 Magnesium Alloy Research Articles

Synergistic approach to wear rate forecasting in AZ31/5% Yttria stabilized zirconia reinforced composite through response surface methodology-genetic algorithm integration

In this work, the wear behavior of a novel AZ31 magnesium alloy reinforced with 5% yttria-stabilized zirconia (YSZ) composite was evaluated using a hybrid Response Surface Methodology (RSM) and Genetic Algorithm (GA) approach. The composite was fabricated using ultrasonic-assisted stir squeeze casting technique, ensuring homogeneous distribution of spherical YSZ particles, as validated by the scanning electron microscope integrated with energy dispersive spectroscope. Wear tests were carried out according to the ASTM standards using a pin-on-disc (POD) tribometer, with applied load (AL), sliding speed (SS), and sliding distance (SD) as the main parameters. An empirical wear rate regression model was developed using RSM/Box-behnken design, and Genetic Algorithm was deployed for parametric optimization, achieving a minimal wear rate of 0.0144 g/m under a load of 30 N, sliding speed of 260 rpm, and sliding distance of 400 m. Confirmation tests were performed to validate the GA predictions. The wear mechanisms were observed, showing reduced wear in GA-optimized samples due to optimized load distribution resulting minimized ploughing, grooving and delamination. This work highlights the efficacy of the hybridized RSM / GA for the wear performance in advanced magnesium alloy matrix composites.

Deformation and microstructure radial gradient evolution of AZ31 magnesium alloy bar during three-roll skew rolling

AZ31 magnesium alloy bar with radial gradient microstructure was prepared by three-roll skew rolling process (TRS), and achieving an excellent combination of ductility and strength. To elucidate the formation mechanism of this gradient microstructure, the deformation behavior during rolling was analyzed through experiments and simulations. The simulation results indicated that the metal flow of the bar in a spatial helical trajectory during rolling, with the trajectory inclination angle gradually decreasing from the center to the surface, promoting dynamic recrystallization in the surface and near-surface regions. The radial equivalent strain decreased from 1.5 at the surface to 0.01 at the center, and the shear strain decreased from 0.051 at the surface to 0.00012 at the center. Experimental results showed that the grain size of the bars decreased from 49.77 µm at the center to 19.72 µm at the surface, and the tensile twin volume fraction decreased from 34.1 % to 19.4 %. Dynamic recrystallization predominantly occurred in the outer ring region of the bars, while significant {10−12} tensile twin activation was observed in the central region, with twin-induced dynamic recrystallization observed at the twin boundaries. Mechanical property tests demonstrated that the gradient structure endowed the bars with a favorable combination of strength and elongation, with hardness significantly increasing from 50 HV at the center to 90 HV at the surface. This indicates that the three-roll skew rolling technology effectively promotes dynamic recrystallization at the surface, and the resulting gradient microstructure achieves an excellent combination of strength and plasticity in magnesium alloy bars.

GTN poroplastic damage model construction and forming limit prediction of magnesium alloy based on BP-GA neural network

During plastic deformation processes, the ductile solids damage and fracture at the microscopic level originate from the evolution of micro -voids, including nucleation, growth and coalescence of voids. In this study, the fracture caused by damage of the AZ31 magnesium alloy sheet is analyzed using the Gurson-Tvergaard-Needleman (GTN) model. The damage parameters of the GTN model are determined by statistical void volume fractions (VVF) in three damage stages during uniaxial tensile experiments with scanning electron microscopy (SEM). The damage parameters are then optimized by the Back Propagation-Genetic Algorithms (BP-GA) neural network. According to the result, the main GTN damage parameters: the initial void volume, the critical volume fraction, the void volume fraction of the nucleation part, and the void volume fraction when the material finally fails are obtained, respectively. Comparing the simulation with the test, the results of the optimized parameters fit better. The void growth reflects the damage during the deformation process, and the GTN model can accurately predict the ductile damage. Furthermore, the experimental forming limit diagrams (FLDs) of the AZ31 sheet at 200℃ are accurately predicted using the parameters obtained by the GTN model. Good agreement has been observed between the experimental and predicted FLDs.

Flow softening and recrystallization accompanied flow in AZ61 magnesium alloy during thermomechanical processing

The present work deals with characterizing the recrystallization accompanied flow and high temperature softening behavior of an extruded AZ61 magnesium alloy. This was supported by conducting a set of hot compression tests at temperatures in the range of 250–450 °C under the strain rate ranging from 0.001 to 0.1s−1. The flow curves at all thermomechanical conditions indicated high fractional softening representing the domination of dynamic recrystallization mechanism. Through a new quantitative approach, “Arrhenius type model”, “modified Avrami equations” and Poliak and Jonas method were simultaneously employed to investigate the kinetic of dynamic recrystallization. It was revealed that the strain required for the same amount of recrystallization fraction increased with decreasing deformation temperature, and at a specified temperature, the required strain increases with increasing strain rate. Interestingly, an anomaly was found at 400 °C under the strain rate of 0.001s−1, where the recrystallization kinetic was faster than that of what was recorded at 450 °C. This anomaly was discussed relying on the nanoprecipitation of γ-phase at the prior boundaries and sub-boundaries which prohibited the grain boundary migration and also the rotation and coalescence of adjacent sub-grains.

Effect of Ceramic Coating on Mechanical Properties of AZ31 Magnesium Alloy

Effect of Ceramic Coating on Mechanical Properties of AZ31 Magnesium Alloy

A study on properties of electroless Ni-B/MgB2 coatings on AZ91 magnesium alloy

This study explores MgB2 as a reinforcing agent in electroless deposition on AZ91 magnesium alloy substrates, evaluating its impact on coating properties. X-ray diffraction (XRD) analysis shows that the amorphous Ni-B coating masks initial magnesium peaks, while MgB2 enhances MgB2O(OH)6, MgB2O5, MgO, and MgB2xOy oxide phases. SEM images illustrate morphological shifts from cauliflower-like Ni-B structures to dendritic and fibrous MgB2 forms, with higher MgB2 concentrations leading to granular structures with randomly oriented crystallites resembling platelets, indicating increased magnesium content. MgB2-reinforced Ni-B coatings exhibited higher hardness than the substrate but lower than as-deposited Ni-B. Friction coefficients initially decreased with Ni-B, increased significantly with 0.1 g MgB2, and decreased with higher reinforcements, remaining higher than substrate and as-deposited Ni-B. MgB2 reinforcement increased surface roughness, causing local agglomerations in 0.5 g MgB2 coatings. Contact angle measurements demonstrated enhanced hydrophilicity due to MgB2's superhydrophilic properties influenced by surface roughness. Antibacterial tests revealed superior properties with 0.1 g MgB2, suggesting a transition to MgB2-enriched structures and influencing material properties. While Ni-B/MgB2 coatings improved over substrate, further research is needed to optimize parameters and understand stabilizer effects. These coatings also exhibited superhydrophilicity and promising antibacterial properties, suggesting potential in advanced surface engineering applications.

Silicon carbide-embedded AZ91E alloy nanocomposite hybridised with chopped basalt fibre: performance measures

ABSTRACT This study uses vacuum stir casting to manufacture magnesium alloy hybrid nanocomposites of silicon carbide nanoparticles (50 nm) and chopped basalt fibre. The different weight percentages (0 wt%, 3 wt%, 6 wt% and 9 wt%) of chopped basalt fibres with a constant weight percentage of 7.5 wt.% silicon carbide nanoparticles were added into molten AZ91E magnesium alloy at 600 rpm constant stirring speed. During the final casting process, 0.1 MPa vacuum pressure was applied to all the composites to reduce the casting defects. The prepared hybrid composite was characterised by physical, mechanical, microstructural and wear properties. The Quanta FEG model SEM apparatus was used to examine the distribution of silicon carbide nanoparticles and basalt fibre. The mechanical characteristics, such as ultimate tensile strength (UTS), yield strength and impact strength, were obtained for 7.5 wt% SiCnp/9 wt% basalt fibre reinforced AZ91E magnesium alloy matrix hybrid nanocomposite. Adding chopped basalt fibre enhanced the wear properties of conventional AZ91E magnesium alloy.

Enhancing Mechanical Performance of Friction Stir Welded AZ31 Magnesium Alloy with Nano-TiC Reinforcements Using Grey Relational Analysis

Enhancing Mechanical Performance of Friction Stir Welded AZ31 Magnesium Alloy with Nano-TiC Reinforcements Using Grey Relational Analysis

Investigation on the machining characteristics of AZ91 magnesium alloy using uncoated and CVD-diamond coated WC-Co inserts

An investigation has been performed to study the compatibility of machining AZ91 magnesium alloy in dry conditions using uncoated and CVD diamond-coated WC-Co inserts. The machining characteristics such as built-up edge (BUE) formation, surface roughness, cutting forces and chip morphology were studied at the cutting speeds, 350, 650 and 950 m/min. The results revealed severe adhesion of the AZ91 Mg alloy on the uncoated WC-Co inserts with increasing cutting speed and contributed to an increase in surface roughness and cutting forces. The CVD diamond-coated inserts have shown negligible built-up edges at various cutting speeds due to their unique properties like low coefficient of friction, low chemical affinity and high thermal conductivity. Snarled types of long continuous chips were observed while machining with CVD diamond-coated WC-Co inserts, whereas short continuous chips were observed with uncoated WC-Co inserts.

Effect of SiO2-reinforcement and alkali treatment on the corrosion resistance of plasma electrolytic oxide coating on AZ31 magnesium alloy

Plasma electrolytic oxidation (PEO) produces an oxide coating containing pores and cracks lowering corrosion protection. The defects can be sealed by in-situ or post-treatment methods. This work compares the sealing effect of SiO2 particles and post-alkali treatment on the corrosion resistance of PEO coatings formed on AZ31 magnesium (Mg) alloy. PEO was conducted in a phosphate-based electrolyte containing 2 g/l nanoparticle SiO2 at a constant current density of 300 A/m2 for 10 min. The post-alkali treatment was performed in 0.5 M NaOH solution at 80 °C for 30 min. The corrosion resistance was evaluated using polarization, electrochemical impedance spectroscopy, and weight loss tests. The SiO2 particles were successfully embedded uniformly in the Mg3(PO4)2 coating, enhancing the coating compactness and stability. The reinforced coating exhibited ten times higher impedance modulus and lower corrosion current density. The post-alkali treatment improved corrosion resistance but not as high as the SiO2 reinforcement. The impedance modulus of the alkali-treated specimen increased five times, and the corrosion current density decreased three times of the base coating. The weight loss test consistently showed that the SiO2-reinforced coating generated lower mass loss during 14 days of immersion in simulated body fluid.

Improving the mechanical and wear properties of AZ91 magnesium alloy via laser cladded (AlCu)3.5CoCrNiSnx (x = 0 and 1) high entropy alloy coatings

(AlCu)3.5CoCrNiSnx (x = 0 and 1) high entropy alloy (HEA) coatings were prepared on AZ91 magnesium alloy substrate by laser cladding technology. Both the HEA coatings consisted of FCC phase and BCC phase. The addition of Sn could lead to an increase in the relative proportion of the BCC phase and the formation of coarse dendritic structure in the HEA coating. The average microhardness and average wear weight loss of the (AlCu)3.5CoCrNi coating (612.2 HV and 2.9 mg) and (AlCu)3.5CoCrNiSn coating (562.1 HV and 3.9 mg) were both higher and lower than those of the AZ91 substrate (70.5 HV and 5.5 mg), indicating that the prepared HEA coatings could significantly improve the properties of the substrate. The (AlCu)3.5CoCrNi coating showed better performance than the (AlCu)3.5CoCrNiSn coating due to the grain refinement effect.

Low cycle fatigue behavior of AZ31 magnesium alloy joined by friction stir welding

AbstractThis study, aims to weld the 5.2 mm thick AZ31 magnesium alloy with conventional friction stir welding at the highest joining efficiency. As a result of the experiments, 88% joining efficiency in tensile strength has been obtained at 1250 rpm, 400 mm.min−1 welding parameter. As a result of micro–macrostructure photographic examinations of the samples joined with these parameters, it is seen that the joining is fully realized. Samples joined with these parameters have been used in fatigue tests. According to the strain‐controlled low cycle fatigue test results performed on welded and base metal samples, the base metal samples have exceeded the 50,000‐cycle limit without failure, with an elongation rate of 0.3%, and the welded samples with an elongation rate of 0.2%. Low cycle fatigue parameters of welded and base metal samples have been obtained according to the Coffin‐Manson‐Basquin equation.

Micro-structure design of black ceramic composite surface towards photothermal superhydrophobic anti-icing

Conventional superhydrophobic surfaces have limitations in the melting and icing process in response to ambient temperature. In this study, we fabricated a composite coating using plasma-etched black ceramic as a low layer on the surface of AZ31 magnesium alloy, and loaded-polydimethylsiloxane nanoparticles (PDMS NPs) as a top layer to achieve a photothermal and superhydrophobic anti-icing. The absorbance and forbidden bandwidth of the ceramic layer exhibit the excellent photothermal properties of solid solution (Mg1-XCuXO). The ceramic phase exhibits a bandgap of 3.62 eV and achieves a temperature of up to 69.4 °C, demonstrating desirable light absorption and photothermal properties. The microstructure and polar bonds of Si-O-Si provide excellent superhydrophobic properties, allowing the surface contact angle to reach 156°. The wetting of water droplets on the composite coating’s surface is simulated using molecular dynamics, which is consistent with experimental findings and emphasizes the coating’s exceptional superhydrophobic. Additionally, the transition process between Cassie-Baxter and Wenzel was analyzed by researching the dynamic icing and ice-melting processes. This composite surface converts light energy into heat, melts snow/ice, and uses hydrophobicity to promptly desorb it from the surface, enabling a photothermal active and superhydrophobic passive anti-icing strategy.

Understanding the mechanism of bimodal texture evolution and DRX behavior of AZ31 magnesium alloy during shear deformation

Shear deformation in commercial magnesium alloys frequently resulted in an additional atypical texture where the basal plane aligned nearly parallel to the extrusion direction, affecting the alloy's mechanical anisotropy. This study prepared AZ31 magnesium alloys with both typical shear texture and atypical texture using a two-stage shear method at 250 °C, 290 °C, and 340 °C. The formation mechanism of the bimodal texture and their relationship with dynamic grain refinement and deformation parameters were comprehensively investigated. While temperature-dependent activation of <c+a> slip usually contributed to the atypical texture, this study identified a {101¯2} twin associated microstructure that reinforced the abnormal texture at lower processing temperature. It was found that the abundant nucleation of the multi-orientation {101¯2} twin bands in the initial stage and their differential slip activations facilitated the evolution of an alternating banded structures characterized by bimodal texture. These microstructures inherited the grain boundary rotation axis of {101¯2} twin and was potentially assimilated into specialized θ[112¯0] symmetric tilt grain boundaries with lower interface energy during continuous shear, stabilizing the bimodal texture. During shear deformation, grain nucleation strengthened the [101¯0]−[112¯0] fibers with bimodal texture by generating ∼30°[0001] grain boundaries through the preferential accumulation of prismatic dislocations. However, more continuous dynamic recrystallization, discontinuous dynamic recrystallization, and micro-shear bands facilitated the nucleation of grains with dispersed basal orientations via dominant non-prismatic dislocations, weakening the overall texture. Besides, the mechanical anisotropy of the alloys was comprehensively influenced by atypical texture and microstructure. At higher deformation temperatures, the reduction in twinning bands and the increase in dynamic recrystallization level relieved the alloy’s tension-compression asymmetry, but deprived its yield strength. This study supplemented the formation mechanisms of bimodal texture during shear deformation, providing valuable insights for optimizing wrought magnesium alloys with superior mechanical properties.

A study on microstructural, mechanical properties, and optimization of wear behaviour of friction stir processed AZ31/TiC composites using response surface methodology

The primary objective of this study is to investigate the microstructural, mechanical, and wear behaviour of AZ31/TiC surface composites fabricated through friction stir processing (FSP). TiC particles are reinforced onto the surface of AZ31 magnesium alloy to enhance its mechanical properties for demanding industrial applications. The FSP technique is employed to achieve a uniform dispersion of TiC particles and grain refinement in the surface composite. Microstructural characterization, mechanical testing (hardness and tensile strength), and wear behaviour evaluation under different operating conditions are performed. Response surface methodology (RSM) is utilized to optimize the wear rate by considering the effects of process parameters. The results reveal a significant improvement in hardness (41.3%) and tensile strength (39.1%) of the FSP-TiC composite compared to the base alloy, attributed to the refined grain structure (6–10 μm) and uniform distribution of TiC particles. The proposed regression model accurately predicts the wear rate, with a confirmation test validating an error percentage within ± 4%. Worn surface analysis elucidates the wear mechanisms, such as shallow grooves, delamination, and oxide layer formation, influenced by the applied load, sliding distance, and sliding velocity. The enhanced mechanical properties and wear resistance are attributed to the synergistic effects of grain refinement, particle-accelerated nucleation, the barrier effect of TiC particles, and improved interfacial bonding achieved through FSP. The optimized FSP-TiC composites exhibit potential for applications in industries demanding high strength, hardness, and wear resistance.

Improved wear and corrosion resistance of MoS2/MgO/MgAl2O4 composite layer in-situ prepared by one-step micro-arc oxidation

In this study, a MoS2/MgO/MgAl2O4 composite layer was prepared on AZ31 magnesium alloy via a one-step in-situ plasma electrolytic oxidation (PEO) method to enhance its wear and corrosion resistance. Results indicated that the addition of Na2MoO4 and Na2S significantly increased the critical and final voltages during the PEO process, and gradually reduced the layer porosity. When 2.5 g/L Na2MoO4 and 5 g/L Na2S were added, the layer exhibited optimal wear resistance, with an average coefficient of friction (COF) of 0.1521±0.007 and a wear volume of 0.0193±0.001 mm³. Additionally, when 1.5 g/L Na2MoO4 and 3 g/L Na2S were added, the layer exhibited optimal corrosion resistance, with a corrosion current density of 1.466×10−9 A/cm² and a corrosion potential of −0.351 V. Compared to the AZ31 substrate and the single PEO layer, the corrosion current density improved by 4 and 2 orders of magnitude, respectively, and the corrosion potential shifted positively by 0.968 V and 0.182 V, respectively. Elemental analysis showed that S and Mo were primarily distributed at the interface between the layer and the substrate, with their concentration decreasing from the inner to the outer layers of the layer, indicating their involvement in the layer formation process. MoS2 was mainly distributed within the interior of the layer.

Double effects of recrystallization behavior on grain morphology evolution and mechanical properties of Al/Mg/Al composite plate by hard plate rolling

Enhancing the bonding strength, optimizing the microstructure and refining the properties represent effective strategies for the fabrication of heterogeneous composite plates. In this study, composite plates of Al/Mg/Al were fabricated through hard plate rolling (HPR) with a reduction in rolling ranging from 40 ​% to 80 ​%. The research primarily concentrates on the substrate in the influence of rolling dynamic recrystallization (DRX) behavior on the grain morphology evolution and mechanical properties of AZ31 magnesium alloy sheets during the process. The findings indicate that at a compression amount of 60 ​%, the composite plate exhibits an ultimate tensile strength (UTS), a maximum elongation (EL) of 12.5 ​%, and improved interface bonding. Comparative analysis reveals the occurrence of DRX on the Mg side, resulting in the formation of small DRXed grains being generated. With an increase in reduction, DRX is facilitated, leading to an initial rise and subsequent decline in the proportion of DRXed grains. The proliferation of fine grains hinder dislocation movement, thereby reinforcing composite plate. Moreover, an elevation in the degree of recrystallization enhances the initiation of non-basal slip and enhances the plasticity of sheet metal. This study offers valuable scientific guidance and technical assistance for the production of forming high-quality Mg–Al composite plates.

Achieving high strength-ductility of AZ91 magnesium alloy via wire-arc directed energy deposition assisted by interlayer friction stir processing

The coarse grain size and poor mechanical properties of wire-arc directed energy deposition (DED) magnesium (Mg) alloys have hindered their wider application. In this study, the AZ91 Mg alloy component was fabricated by wire-arc DED assisted by interlayer friction stir processing (IFSP), and the highest strength and elongation were obtained in wire-arc DED AZ91 Mg alloy, which was mainly attributed to grain refinement, fragmentation/dispersion/dissolution of β-Mg17Al12 phase and heterogeneous microstructure in the IFSP stir zone (SZ). The formation of heterogeneous structure is caused by the fact that the refined grains in the SZ of the previous layer are affected by the thermal cycling of the subsequent additive manufacturing process, which led to different degrees of grain growth in different micro-zones within a SZ, and ultimately formed the microstructure characteristics with alternating distribution of coarse and fine grains. Compared with the wire-arc DED samples, the ultimate tensile strength of the wire-arc DED + IFSP samples in the perpendicular and parallel to the building directions increased from 284 and 264 MPa to 315 and 324 MPa, respectively. These values are comparable to those of their wrought counterparts, and the elongation increased by over 50 %. This study thus provides new insights into microstructure modification and performance enhancement of wire-arc DED fabricated Mg-alloys via a novel IFSP technique.

Influence of heat treatment and forming cycle on the precise forming of AZ31 magnesium alloy sheet

Precision forming of 3 mm thick rolled AZ31 magnesium alloy sheet at 90° results in severe cracking and a considerable rebound angle. The effects of different sheet heat treatments and changes in the forming cycle on the value of the forming angle were investigated using 90° precision forming tests. The reasons of sheet cracking were examined using tensile tests and numerical simulations. Microscopic analysis and characterization techniques such as metallographic experiments, SEM observations, and EBSD tests are used to clarify the mechanism of improvement and control of the forming angle value. The results indicate that annealing treatment exhibits high sensitivity to controlling sheet cracking, but low sensitivity to controlling rebound. Among them, after heat treatment at 250 °C+1 h, the sheet no longer cracks during forming. In incomplete annealing, the more small grains produced by recrystallization and the greater the number of dimples in the fracture, the closer the forming angle is to 90°. Full annealing can result in a small reduction in the forming angle value compared to incomplete annealing treatments. After extending the forming cycle for 1 h, the increase in the ratio of dual tensile twin boundaries and low angle grain boundaries resulted in a significant decrease in the value of the forming angle and no cracking of the sheet. The increase of recrystallized tissue on the tensile side and the increase of the KAM value led to the decrease of the forming angle value to the minimum value at 300 °C+1 h heat treatment condition.

Microstructure and mechanical properties of hammer-forging assisted wire-arc directed energy deposition AZ91 alloy

ABSTRACT With the development of lightweight aerospace equipment, magnesium alloys are receiving increasing attention. Wire-arc directed energy deposition (Wire-arc DED) is a highly promising manufacturing method for magnesium alloy parts, but its development has been severely restricted by the problems of coarse grain size and low mechanical properties. To address these issues, a hammer-forging assisted Wire-arc DED technology for magnesium alloy AZ91 is proposed. The effects of interlayer hammer-forging and synchronous hammer-forging on macrostructure, microstructure and mechanical properties of the Wire-arc DED samples are compared, and the microstructure evolution and performance enhancement mechanism are discussed. The results show that the maximum plastic deformation caused by hammer forging reaches 11.7%. Hammer forging can significantly refine grains, and the average grain size decreases from 27.7 μm to 13.5 μm. Synchronous hammer-forging is better than interlayer hammer-forging in terms of performance enhancement, the UTS reaches 301.8 MPa, an increase of 10.9%, which is comparable to that of traditional forged parts, mainly attributed to the grain refinement and increased dislocation density.