AZ31 Magnesium Alloy Research Articles

Microstructure and mechanical properties of friction stir welded AZ31 magnesium alloy reinforced with ZrB2

Abstract Metal matrix composites (MMC) have advantages over polymer matrix composites such as high stiffness and strength, high-temperature resistance, better abrasion resistance, creep resistance, resistance to degradation by fluids, dimensional stability, and non-flammability. Metal matrix composites are used for various applications in the automotive, aerospace and sporting goods industries. The primary objectives of the current research work encompass the fabrication of Metal Matrix Composites (MMCs) AZ31 with 0.5%, 1.0% and 1.5% zirconium boride (ZrB2) nano-powder by the stir casting process, followed by welding through Friction Stir Welding (FSW). The metallographic analysis was carried out on the weldments of all cases. The macroscopic and microscopic analysis confirmed the defect-free weld joint. Tensile and hardness tests were conducted to study the mechanical properties of the materials. The tensile strength and the percentage of elongation increased with the percentage of ZrB2. But, after 1.0% addition of nano particles the strength decreased. The same pattern had been observed in both base and welded samples. The defect-free welding joints were fabricated with an efficiency of 79.1%, 79.7% and 77.7% for the materials with 0.5%, 1.0% and 1.5% nano powder, respectively. EIS and PDP tests were conducted in 3.5% NaCl to study the corrosion behaviour of base and welded materials. The corrosion tests on the base MMC samples showed that the corrosion resistance increased after the addition of ZrB2 nanoparticles. In addition, the corrosion resistance of all the welded samples improved compared with their respective base materials.

Towards Understanding {10-11}-{10-12} Secondary Twinning Behaviors in AZ31 Magnesium Alloy during Fatigue Deformation.

Tensile-compression fatigue deformation tests were conducted on AZ31 magnesium alloy at room temperature. Electron backscatter diffraction (EBSD) scanning electron microscopy was used to scan the microstructure near the fatigue fracture surface. It was found that lamellar {10-11}-{10-12} secondary twins (STs) appeared inside primary {10-11} contraction twins (CTs), with a morphology similar to the previously discovered {10-12}-{10-12} STs. However, through detailed misorientation calibration, it was determined that this type of secondary twin is {10-11}-{10-12} ST. Through calculation and analysis, it was found that the matrix was under compressive stress in the normal direction (ND) during fatigue deformation, which was beneficial for the activation of primary {10-11} CTs. The local strain accommodation was evaluated based on the geometric compatibility parameter (m') combined with the Schmid factor (SF) of the slip system, leading us to propose and discuss the possible formation mechanism of this secondary twin. The analysis results indicate that when the local strain caused by basal slip at the twin boundaries cannot be well transmitted, {10-11}-{10-12} STs are activated to coordinate the strain, and different loading directions lead to different formation mechanisms. Moreover, from the microstructure characterization near the entire fracture surface, we surmise that the presence of such secondary twins is not common.

Microstructure and Corrosion of Mg-Based Composites Produced from Custom-Made Powders of AZ31 and Ti6Al4V via Pulse Plasma Sintering.

Magnesium (Mg) and its alloys offer promise for aerospace, railway, and 3D technology applications, yet their inherent limitations, including inadequate strength, pose challenges. Magnesium matrix composites, particularly with metallic reinforcements like titanium (Ti) and its alloys, present a viable solution. Therefore, this study investigates the impact of Ti6Al4V reinforcement on AZ31 magnesium alloy composites produced using pulse plasma sintering (PPS). Results show enhanced microhardness of the materials due to improved densification and microstructural refinement. However, Ti6Al4V addition decreased corrosion resistance, leading to strong microgalvanic corrosion and substrate dissolution. Understanding these effects is crucial for designing Mg-based materials for industries like petrochemicals, where degradation-resistant materials are vital for high-pressure environments. This research provides valuable insights into developing Mg-Ti6Al4V composites with tailored properties for diverse industrial applications, highlighting the importance of considering corrosion behavior in material design. Further investigation is warranted to establish predictive correlations between Ti6Al4V content and corrosion rate for optimizing composite performance.

First-principles modeling of corrosion potential/current and its application in AZ and AZ-RE magnesium alloys

First-principles modeling for magnesium corrosion potential/current has been established in this work. The corrosion potential formulation should be UaSHE=ln10RTlgnFkTh+Gv+NAN×S×Esurf+(10ln10)RT+0.65λ2nF−(λ1+λ2)nF(the intersection point of anodic and cathodic branch). And the one for the corrosion current density should belgJtot=lgJm+km×∑(fm×∆Em)+ki×∑(fi×∆Ei)(including matrix corrosion lgJm, matrix interplane galvanic corrosion km×∑(fm×∆Em), second phase galvanic corrosionki×∑(fi×∆Ei) and ∆E is the intergranular potential difference between phase/matrix planes and Mg(0001)). Applied the modeling to simulate AZ and AZ-RE electrochemical corrosion, the predicted potential/current values are quite coherent with the experimental polarization ones. The role of alloying element on corrosion have also been discussed at atomic level. The main alloying element (such as Al or Zn in AZ, or AZ-RE) would affect work function Φ, surface energy density Esurf/ρ, and hydrogen atom adsorption free energy ∆GH*, so it influences anode/cathode reaction greatly and works a lot on Ua and lgJm. Furthermore, main alloy and minor alloy (such as RE in AZ-RE) would make their own contribution on galvanic corrosion by holding the potential difference ∆Em or ∆Ei and keeping mole fraction fm or fi. The work provide the modeling which could predict the corrosion potential/current values for magnesium alloy, which are directly correspond to the polarization curves. It also could give a theoretical understanding for alloying effect on corrosion. It suggests a more flexible way for seeking corrosion-resistant alloys.

Effect of preheating temperature on the microscopic structure and mechanical performance of pulsed laser welding in sheet AZ31 alloy

To achieve high quality welding of an AZ31 magnesium alloy sheet, butt experiments are conducted using an Nd:YAG pulsed laser welder to weld the AZ31 magnesium alloy (1 mm). The influence of preheating temperature on the microscopic structure and mechanical performance of AZ31 magnesium alloy pulsed laser welding is studied. Experimental results show that with the rising of preheating temperature, the grain size of an equiaxed crystal in the weld center and columnar crystal at the fusion boundary (FB) first decreases and then increases and reaches the minimum values of 18.89 ± 0.45 and 32.09 ± 1.52 μm, respectively, when preheated at 200 °C. The maximum force and tensile strength increase first and decrease and reach the maximum of 2.32 kN and 193.3 MPa, respectively, when the preheating temperature is 300 °C. Above all, the welds with excellent mechanical performance can be obtained at the preheating temperature of 300 °C.

BIOSOLUBLE MAGNESIUM-BASED ALLOYS FOR OSTEOSYNTHESIS

The impact of micro-alloying of AZ91 and NZ30K magnesium alloys with silver and scandium to produce biosoluble implants for osteosynthesis is studied in the paper. The application of these alloys is limited due to the significant reduction of the mechanical properties of magnesium during the regeneration of fractures. It was found that the higher the concentration of the above-mentioned elements, the bigger the amount of intermetalloids that appear and the smaller they become. There were different mechanical properties observed at the sample cross-section, but the difference was successfully eliminated by thermal treatment. It reduced the chemical heterogeneity of the workpiece at the cross-section and, respectively, the value of micro-hardness. It is shown that microalloying these alloys with 0.05…0.1 % of silver and scandium ensures the grinding of the structural elements of the metal and a significant increase of the set of their properties. The research of the developed alloys showed that NZ30K alloy, which additionally contains 0,05 ... 0,1% of silver, after a three-month treatment with gelofusine saves its mechanical properties like those of the bone tissue. Pre-clinical research revealed that they are non-toxic, have an antibacterial effect and preserve the whole set of properties till the complete fracture consolidation.

Effect of pulse shaping on coupling efficiency of laser spot welding in AZ31 magnesium alloy

Effect of pulse shaping on coupling efficiency of laser spot welding in AZ31 magnesium alloy

Electrochemical behaviour of sputter-coated titanium films on AZ31 magnesium alloy

Lightweight magnesium-based structural alloy AZ31 is normally prone to high corrosion in an aqueous environment. A detailed study is reported in this work on AZ31 Mg alloy coated with Ti thin films of different thicknesses by DC sputtering to investigate the capability of Ti coating to prevent corrosion of AZ31 under an aqueous environment similar to seawater. Ti films have been fabricated to 50, 100 and 150 nm thicknesses. Utilising grazing incidence-XRD and SEM, the films’ structure and microstructure were studied. The films were amorphous. Due to corrosion, interesting micro-structures evolved. Corrosion inhibition characteristics of the Ti films were characterised by electrochemical techniques such as potentiodynamic polarisation and impedance spectroscopy. Ti films with 100 nm and 150 nm thickness show a good inhibition capability. The corrosion mechanism was investigated using XPS and X-ray energy dispersive spectra.

MgAl Oxide Coatings Modified with CeO2 Particles Formed by Plasma Electrolytic Oxidation of AZ31 Magnesium Alloy: Photoluminescent and Photocatalytic Properties

MgAl oxide coatings composed of MgO and MgAl2O4 phases were doped with CeO2 particles via plasma electrolytic oxidation (PEO) of AZ31 magnesium alloy in a 5 g/L NaAlO2 water solution. Subsequently, particles of CeO2 up to 8 g/L were added. Extensive investigations were conducted to examine the morphology, the chemical and phase compositions, and, most importantly, the photoluminescent (PL) properties and photocatalytic activity (PA) during the photodegradation of methyl orange. The number of CeO2 particles incorporated into MgAl oxide coatings depends on the concentration of CeO2 particles in the aluminate electrolyte. However, the CeO2 particles do not significantly affect the thickness, phase structure, or surface morphology of the coatings. The PL emission spectrum of MgAl oxide coatings is divided into two bands: one in the 350–600 nm range related to structural defects in MgO, and another much more intense band in the 600–775 nm range attributed to the F+ centres in MgAl2O4. The incorporated CeO2 particles do not have a significant effect on the PL intensity of the band in the red spectral region, but the PL intensity of the first band increases with the concentration of CeO2 particles. The PA of MgAl/CeO2 oxide coatings is higher than that of pure MgAl oxide coatings. The MgAl/CeO2 oxide coating developed in aluminate electrolyte with a concentration of 2 g/L CeO2 particles exhibited the highest PA. The MgAl/CeO2 oxide coatings remained chemically and physically stable across multiple cycles, indicating their potential for applications.

THE CORROSION INHIBITION EFFECT ON THE ALUMINUM ALLOY AZ91C'S FATIGUE BEHAVIOR IN THE SALINE ENVIRONMENT

Investigations were made into the fatigue in the magnesium alloy AZ 91C cast in corrosive fluids and air at varied NaCl solution concentrations. Fatigue specimens will be subjected to surface stress testing in corrosive conditions with a stress amplitude of 75 MPa both after and before coating. To comprehend the behavior of the magnesium material, its fatigue life, corrosion product (X-ray spectra), and fracture properties will be examined. The corroding medium (NaCl) has been found to significantly shorten the fatigue life of the magnesium alloy AZ91C. Chemical conversion treatment was applied to the AZ91C alloy to improve corrosion resistance and corrosion fatigue resistance. MgSnO3 was found in the XRD patterns of the stannite-treated AZ91C alloy, and this treatment slightly improved the alloy's corrosion resistance in an alkaline stannite solution with a pH of 7. H2O and SEM images demonstrate that chloride ions can penetrate the substrate through porous structures.

Effect of Heat Treatment on Formability of AZ61 Magnesium Alloys

The current paper focuses on enhancing the manufacturability of AZ61 magnesium alloys by heat treatment. Specimens are subjected to solution heat treatment. First, all samples underwent a 15-hour treatment at 415°C before aging at 50°C, 100oC, and 150°C. The specimens were furnace cooled and quenched after achieving the precise aging temperature. The results have been extracted from tensile and cupping tests. The outcomes of each test have been compared with the data taken without heat treatment, so the ductility increase can be observed. Tests revealed better results for furnace-cooled specimens. The increase in formability of about 9% along with a decrease in strength of only 11% is observed for 150°C aging temperature.

Enhancing mechanical and wear performances of magnesium matrix composites using low-cost squid quill ash

The increasing demand for lightweight, cost-effective aerospace and automotive components with higher performance promotes interest in the use of naturally occurring materials, such as magnesium composites with natural and low-cost reinforcements. This research focuses on stir casting to reinforce magnesium matrix composites with squid quill ash (SQA) particles, aiming to improve their mechanical and wear performances. The results show that the mechanical and wear properties of magnesium matrix composites can be improved significantly by increasing the SQA content. Incorporating 10% SQA reinforcements in AZ91 magnesium alloy leads to a maximum increase in hardness, yield strength, and ultimate tensile strength by 32.34%, 18.86%, and 12.34%, respectively. When compared to the matrix alloy, the wear resistance of the composites reinforced with 5 wt% and 10 wt% of SQA particles is improved by 14.05% and 30.81%, respectively. These findings demonstrated the feasibility of using SQA particles in the production of magnesium matrix composites. This not only reduces environmental impact by repurposing SQA, but also provides a practical method for the economical utilization of SQA particles in the fabrication of magnesium matrix composites for aerospace and automotive applications.

Enhanced Wear and Corrosion Resistance of AZ91 Magnesium Alloy via Adherent Si-DLC Coating with Si-Interlayer: Impact of Biasing Voltage

Magnesium alloys are the lowest-density structural metals with a wide range of applications, such as aircraft skins, engine casings and automobile hubs. However, its low surface hardness and non-corrosion resistance in natural environments limit its wide range of applications. In this work, Si-DLC coatings (Si: 15 at.%) are fabricated on AZ91 alloy using a hollow cathode discharge combined with a DC bias voltage from 0 to −300 V to increase the deposition rate and modulate the structure and properties of the coatings. The Si interlayer with a thickness of around 0.6 µm is deposited first to enhance the adhesion. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy are used to investigate the effect of DC bias on the microstructure evolution of Si-DLC coatings. Meanwhile, corrosion and wear resistance of the coatings at various bias voltages have been investigated using electrochemical workstations and pin-on-desk wear testers. It is shown that the bias-free coating has a loose structure and is less resistant to corrosion and wear. The bias coating has a compact structure, small carbon cluster size, high chloride ion corrosion resistance, and high wear resistance against Al2O3 spheres. The corrosion potential of the coating bias at −300 V is −0.98 V, the corrosion current density is 1.35 × 10−6 A·cm−2, the friction coefficient is 0.08, and the wear rate is 10−8 orders of magnitude. The formation of SiC nanocrystals and high sp3-C, as well as the formation of transfer films on the surface of their counterparts, are the main reasons for the ultra-high wear resistance of the bias coatings. The wear rate, coefficient of friction, and corrosion rate of the coating are 0.0069 times, 0.2 times, and 0.0088 times that of the AZ91 alloy, respectively. However, the bias coating has only short to medium-term protection against the magnesium alloy and no long-term protection due to cracks caused by its high internal stress.

Growth mechanism and corrosion resistance of layered double hydroxide film on magnesium alloy without external addition of magnesium and aluminum salts

This study first reports in-situ growth of layered double hydroxide (LDH) coatings on magnesium alloy surface without external adding magnesium (Mg2+) and aluminum (Al3+) salts with the aid of a chelating agent at ambient pressure and relatively low temperature (≤ 95 °C). The morphology, composition, and structure of the deposits on the magnesium alloy surface were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), etc. Combined with open-circuit potential (OCP)-time curves, the mechanism of growth and formation process of the LDH film was proposed. The process was divided into four stages, i.e., dissolution of the Mg substrate, formation of Mg(OH)2, nucleation of LDH by transformation of Mg(OH)2 phase, and growth of LDH phase. The corrosion resistance of the LDH coating before and after treatment with vanadate and tungstate was evaluated through electrochemical impedance spectroscopy (EIS), Tafel curves, and immersion measurements. Compared to bare magnesium alloy and pristine and vanadate-treated LDH, the LDH coating modified with tungstate exhibited the most effective corrosion protection for magnesium alloy AZ31, without obvious signs of corrosion after exposure to a 3.5 wt% NaCl solution for seven days.

Sustainable smart coatings of chitosan and LDH loaded with natural inhibitors for corrosion protection of Mg AZ31 alloy

In this study, sustainable smart coatings based on chitosan and layered double hydroxides (LDH), loaded with natural anions, were developed to enhance the corrosion resistance of AZ31 magnesium alloy. The LDH was synthesized using the co-precipitation method, loaded with natural inhibitors (vanillate, gallate and citrate anions) by an anion exchange process and characterized by various techniques, such as scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis. The kinetics of inhibitor release was investigated at different pH and the results show higher rates as the pH increases. The corrosion resistance offered by the sustainable smart coatings was determined by electrochemical impedance spectroscopy and hydrogen evolution tests, while the coating morphology, before and after the corrosion tests, was analyzed by SEM and optical microscopy, respectively. All of the results demonstrated that the smart coating containing gallate ions significantly improved the corrosion resistance of AZ31 magnesium alloy.

Influence of cryogenic treatment time on the mechanical properties of AZ31 magnesium alloy sheets after cross-rolling

To investigate the influence of cryogenic treatment time on the mechanical properties and the microstructure of the AZ31 Mg alloy sheets, the different times of cryogenic treatment after two-pass cross-rolling were carried out at air-cooling, 1 hour, 3 hours and 6 hours. The consequences of the tensile experiment illustrated that the cross-rolling Mg alloy with 1-hour cryogenic treatment showed the highest ultimate tensile strength (343 MPa), which was 9.6%, 9.6% and 11.7% higher than air-cooling, 3-hour cryogenic and 6-hour cryogenic samples. The primary reasons for this include fine-grained strengthening, twin strengthening, low-angle grain boundaries (LAGBs) strengthening, dislocation strengthening and precipitation strengthening. The internal grain of the magnesium alloy sheet after 1 hour of cryogenic treatment was refined to 5.2 μm. The {10−11} contraction twin, {10−12} extension twin and {10−12}-{10−11} double twin were surveyed according to the electron backscatter diffraction (EBSD) results. On the <11–20> axis, all the four samples exhibited the {0001} basal texture. And the sample of 1-hour cryogenic treatment exhibited the highest basal texture intensity. According to the micro-structure observation, high-density dislocation and several precipitates were illustrated in the sample of 1-hour cryogenic treatment.

Effect of indium and yttrium on the corrosion behavior of AZ63 magnesium alloy

Indium (In) and yttrium (Y) can activate and alleviate the corrosion of magnesium alloy, respectively. The effects of 1 wt% In and 1 wt% Y on the microstructure and electrochemical behaviors of Mg-6 wt%Al-3 wt%Zn (AZ63) magnesium alloy are investigated via materials characterizations associated with electrochemical techniques. The results showed that co-alloying of In and Y would increase the number of intermetallic phases in AZ63 by generating discrete Al2Y phase and continuous Mg17Al12 phase. During the process of corrosion, the corrosion of Mg-6 wt%Al-3 wt%Zn-1 wt%In-1 wt%Y(AZ63InY) initiates from the intermetallic phases and propagates locally. The corrosion products are apt to adhere on the corroded surface, underneath which a severe corrosion takes place due to the enhanced dissolution-reprecipitation effect of In on activating Mg.

Comparative analysis of microstructure and selected properties of WC-Co-Cr coatings sprayed by high-velocity oxy fuel on S235 and AZ31 substrates

Abstract The purpose of this work was to carry out comparative studies of WC-Co-Cr coatings deposited using the high velocity oxy fuel (HVOF) method onto two types of substrate material: structural steel S235 and magnesium alloy AZ31. The influence of the substrate material type on the microstructure, phase composition, crystallite size, porosity, Vickers microhardness, instrumental hardness (HIT), Young’s modulus (EIT), and fracture toughness was investigated. For both substrates, the deposited coatings deposited were characterized with fine-grained and compact microstructure. The X-ray diffraction (XRD) revealed presence of following phases: WC, W2C, Co0.9W0.1, and Co3W9C4. The WC phase was the most desirable and stable one with crystallites were below 100 nm. On the other hand, the size of the W2C crystallites was below 30 nm. The coatings obtained showed porosity values equal to 2.3 ± 0.4 vol% and 2.8 ± 0.7 vol% for AZ31 and S235, respectively. The average Vickers microhardness for both types of sample was appproximately 1200 HV0.3. The average HIT values for carbide particles and metallic matrix were around 29 GPa and 6.5 GPa, respectively. In the case of EIT, it was around 620 GPa and 190 GPa for WC and Co-Cr, respectively. The differences between coatings were negligible. The EIT value for both coatings was equal to 344 ± 11 GPa. The fracture toughness was around 4.5 MPa · m1/2 in both cases. The investigations revealed that it is possible to replace steel substrate material with a much lighter equivalent, in this case AZ31 alloy, without deterioration of the coating properties.

Hydroxyapatite/palmitic acid superhydrophobic composite coating on AZ31 magnesium alloy with both corrosion resistance and bacterial inhibition

Hydroxyapatite/palmitic acid superhydrophobic composite coating on AZ31 magnesium alloy with both corrosion resistance and bacterial inhibition

Influence of machining process of MoS2/B4C/Az31 Mg alloy composite and its tribological characteristics

The automotive, biomedical, and aerospace industries are among those with a rising need for lightweight materials with enhanced mechanical and tribological qualities. Composites based on magnesium alloys have attracted interest because of their excellent strength-to-weight ratio and promise to improve component performance. Magnesium (Mg) alloy-based composites find applications in sports and leisure equipment, aerospace, biomedical implants, and more. The research outlined here serves a critical need in the field of materials science and engineering, particularly regarding the development of advanced magnesium (Mg) alloy-based composites. In this study, we have created a new aluminum composite using the AZ31 alloy mixed with 5% boron carbide (B4C) and 5% molybdenum disulfide (MoS2) as reinforcement through a powder metallurgical technique. The magnesium alloy contains 3% aluminum and 1% zinc. Our research aims to understand the mechanical and tribological behaviors and the impact of Electrical Discharge Machining (EDM) process parameters on AZ31 magnesium alloy. We need to modify these properties for various applications. Many industrial researchers have studied the machinability of magnesium alloys using EDM. We conducted wear tests on AZ31 alloy reinforced with both B4C and MoS2 in altered quantities using a pin-on-disc setup. The outcome displays that the wear resistance of these composites is considerably better matched to other magnesium matrix composites (MMCs). We also measured various densities of the hybrid composite, including apparent density, green density, and sintered density, which were found to be 0.839, 1.495, and 1.504 g/cm3, respectively—better than other composites. In addition, the hybrid composite exhibited a substantial increase in micro hardness, reaching 22.012 HV, indicating improved wear resistance of the material. Comparatively, low density, minimum wear profile, and maximum hardness were recorded for the sample of AZ31 + 5%MoS2 + 5%B4C. The influence of EDM parameters was discussed.