ZM21 Magnesium Alloy Research Articles

A surface and corrosion characterisation of micro arc oxidation treated friction stir welded ZM21 and ZE41 magnesium alloy: a comparison study

Magnesium alloys have gained attention as promising materials in industrial applications, for their high specific strength and low density. Magnesium alloys have desirable mechanical properties, but their poor corrosion resistance prevents their safe implementation. Alloys such as ZM21 and ZE41, possess unique properties that provide improved machinability and increased red-hot strength, respectively, while remaining prone to corrosion. To improve corrosion resistance, surface treatments and coating processes are employed. Comparing the corrosion characteristics of ZM21 and ZE41 is vital for aerospace and automotive applications, directly affecting component durability, reliability, and performance against corrosion. Magnesium alloys are frequently joined through friction stir welding (FSW), hence, similar importance is provided to studying the corrosion performance of welds, since FSW introduces microstructural changes that alter corrosion performance of welded joints. The paper discusses electrochemical corrosion mechanisms and analyzes the effect of Micro Arc Oxidation (MAO) coating on electrode potential, passivity, and electrical resistance of ZM21 and ZE41 plates welded through FSW. MAO treatments were performed on both base material and FSW joints. The corrosion performance of MAO-coated FSWed ZM21 and ZE41 alloys was compared through the Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarisation (PDP) tests. The PDP test revealed that MAO treatment enhanced the corrosion resistance of both base and FSWed ZM21 and ZE41 magnesium alloys. There was an improvement in potential polarization (Rp) values from 565 Ω cm2 to 11245 Ω cm2 for ZM21 and from 1184.4 Ω cm2 to 11435.69 Ω cm2 for ZE41 alloys. While exhibiting improvements in corrosion resistance, MAO-treated ZE41 performed better than MAO-treated ZM21. PDP results were verified through confirmatory EIS results. Therefore, MAO treatments are effective methods to improve the corrosion performance of Mg alloys. Evaluation of MAO coating performance on various FSW Mg alloys and studying their corrosion performance is crucial for engineering material selection.

Study on the Optimization of the Preparation Process of ZM5 Magnesium Alloy Micro-Arc Oxidation Hard Ceramic Coatings and Coatings Properties

Hard ceramic coatings were successfully prepared on the surface of ZM5 magnesium alloy by micro-arc oxidation (MAO) technology in silicate and aluminate electrolytes, respectively. The optimization of hard ceramic coatings prepared in these electrolyte systems was investigated through an orthogonal experimental design. The microstructure, elemental composition, phase composition, and tribological properties of the coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and tribological testing equipment. The results show that the growth of the hard ceramic coatings is significantly influenced by the different electrolyte systems. Coatings prepared from both systems have shown good wear resistance, with the aluminate electrolyte system being superior to the silicate system in performance. The optimized formulation for the silicate electrolyte solution has been determined to be sodium silicate at 8 g/L, sodium dihydrogen phosphate at 0.2 g/L, sodium tetraborate at 2 g/L, and potassium hydroxide at 1 g/L. The optimized formulation for the aluminate electrolyte solution consists of sodium aluminate at 5 g/L, sodium fluoride at 3 g/L, sodium citrate at 3 g/L, and sodium hydroxide at 0.5 g/L.

Microstructure and properties of AlCrFeNiMoNb high-entropy alloys coating on ZM5 magnesium alloy prepared by high-velocity air fuel (HVAF) spray

AlCrFeNiMoNb high-entropy alloys were successfully coated onto a ZM5 alloy using high-velocity air fuel spray (HVAF). Microcomputed tomography(micro-CT) results revealed that the porosity of the coating was only 0.36%, which demonstrates the coating has a highly dense structure. The average microhardness of high-entropy alloys coating was ＞ 5 times greater than that of the ZM5 alloy substrate. The changes of ZM5 substrate microhardness can be attributed to dynamic recrystallisation. The corrosion potential (Ecorr) of the AlCrFeNiMoNb coating was improved to approximately∼ − 0.998 V and the corrosion current (Icorr) of the coating significantly decreased by two orders of magnitude. The wear volume loss of the coating was ∼15 times lower than that of the ZM5 substrate. This indicates that the coating of the AlCrFeNiMoNb high-entropy alloy on the ZM5 substrate significantly improved the wear resistance of the ZM5 alloy. The ZM5 alloy surface had better corrosion and wear resistance properties owing to the protection offered by the AlCrFeNiMoNb high-entropy alloy.

Effect of polycaprolactone coating on the corrosion and biological characteristics of plasma electrolytic oxidised ZM21 magnesium alloy

Plasma electrolytic oxidation (PEO) treated magnesium alloys have immense potential as biodegradable orthopaedic implants. Nevertheless, there is a need to further enhance its corrosion resistance and biocompatibility. The current work aims to develop a biocompatible polymeric layer over PEO-treated samples to control the corrosion rates during the bone's healing period. ZM21 is PEO treated in silicate-based electrolyte for 10 min and post-treated by immersing in a biodegradable polycaprolactone (PCL) dissolved in 50 % of chloroform, and 50 % of di-chloromethane for 1 s, 5 s, and 10 s. Various characterisation techniques were used to study morphology, corrosion, adherence, bioactivity, and cytotoxicity. The corrosion resistance, surface roughness, adherence, and bioactivity were high for the 5 s dipped sample, attributed to the web-like network structure of polymer film formed over the sample. The cytotoxicity test showed that the 5 s dipped sample was best with cell viability >90 % ascribed to its high corrosion resistance and the presence of favourable species like Mg, Zn, Si, and PCL. Considering all physiochemical and biochemical results, it can be concluded that the PEO + PCL-treated ZM21 can be a promising candidate for biodegradable orthopaedic implants.

Corrosion resistance and biodegradability of micro-arc oxidation coatings with the variable sodium fluoride concentration on ZM21 magnesium alloys

As a biodegradable metal implant material with mechanical properties closest to those of natural bone, the degradation rate of magnesium (Mg) alloy is so fast in body fluid environment. Therefore, the preparation of a coating on Mg alloy surface to improve its corrosion resistance has become a research focus. In the study, Mg-2Zn-Mn (ZM21) alloys and micro-arc oxidation (MAO) are used as the substrate and surface modification method, respectively. Then, the influence of sodium fluoride (NaF) concentration in silicate basic electrolyte on the corrosion resistance and biodegradability of MAO coatings are investigated. The results show that (1) When NaF concentration increases to 1.0 g/L, the thickening and hydrophilic effect of MAO coating are more obvious. (2) Adding 1.0 g/L NaF makes excellent corrosion resistance and great adhesion, because F- can enhance discharge and refine sparks to enhance the interface adhesion and form a more uniform surface. (3) Excessive NaF concentration (＞ 1.0 g/L) can decrease the breakdown voltage, produce the abundant discharge channels, and degrade the coating quality. (4) The remarkable reduced weight loss rate and pH value of MAO samples after immersion shows the certain biological safety. (5) Cytotoxicity and cell adhesion test proves the available biocompatibility.

Effect of potassium fluotitanate concentration on the corrosion resistance and degradation property of micro-arc oxidized ZM21 magnesium alloys

Magnesium (Mg) alloy is a focus biomaterial at present, while the rapid degradation rate in body fluid will hinder the practical clinical application. Therefore, surface modification of Mg alloy is essential. In the study, Mg–2Zn–Mn (ZM21) alloys and micro-arc oxidation (MAO) are used as the substrate and surface modification method. Then, the influence of potassium fluotitanate (K2TiF6) concentration in silicate basic electrolyte on the corrosion resistance and degradation of MAO coatings are studied. The results show that (1) TiF62− has obviously thickening effect, and adding 0.25 and 0.50 g/L K2TiF6 make the better corrosion resistance. (2) TiF62− concentration affects the coating quality, which is mainly attributed to F− generated by the reaction of TiF62− + 4OH− = TiO2 + 6F− + 2H2O. (3) Anatase TiO2 formed by ionization of TiF62− plays a role in sealing the micro-pores of MAO coating. (4) The hydrophilicity is improved, weight loss rate and pH value of MAO samples after immersion are obviously reduced, and available biological safety are improved, of which it is worth noting that the surface of K-0.75 sample has generated particles with a Ca/P ratio similar to hydroxyapatite (Ca10(PO4)6(OH)2, HA). (5) Cell adhesion test proves the available cytocompatibility.

Uniforming outer diameter by control of microstructural evolution for biodegradable ZM21 magnesium alloy tube during dieless drawing

Uniforming outer diameter by control of microstructural evolution for biodegradable ZM21 magnesium alloy tube during dieless drawing

Modeling of Galvanic Corrosion in three-metal Systems Consisting of ZM5 Magnesium Alloy, 6XXX Series Aluminium Alloy and 304 Stainless Steel under Thin Electrolyte Layer by Numerical Simulation, Electrochemical and Salt Spray Test

Modeling of Galvanic Corrosion in three-metal Systems Consisting of ZM5 Magnesium Alloy, 6XXX Series Aluminium Alloy and 304 Stainless Steel under Thin Electrolyte Layer by Numerical Simulation, Electrochemical and Salt Spray Test

Effect of Rolling Deformation on Microstructure and Mechanical Properties of As-Cast and Rolled ZM21 Magnesium Alloy

Effect of Rolling Deformation on Microstructure and Mechanical Properties of As-Cast and Rolled ZM21 Magnesium Alloy

Evolution of primary and secondary twins during tensile cyclic loading in magnesium alloy ZM21 by quasi in situ EBSD

Large-scale microscopy at consecutive strains using quasi in situ EBSD was used to monitor the texture evolution in specific areas of extruded magnesium alloy ZM21 samples under cyclic tensile loading-unloading. Twin formation throughout the various cycles is highly dependent on slip and twin activity in the neighboring grains, so slip-trace analysis was conducted to monitor the activity of various slip systems. Slip traces were observed on three different glide planes: prismatic plane, first-order pyramidal plane, and second-order pyramidal plane. Formation of primary (including extension and contraction) twins and secondary twins was investigated in detail by overlapping the EBSD maps after pre-compression and after subsequent tension. Parent grains and twins were classified based on their orientations with respect to the ED (loading direction). The inverse pole figure map for the twins was plotted for the ED to calculate the position of the c-axis for twins. All extension twins that formed under reverse loading were located within 45°–90° of the ED axis, whereas the twins that formed during pre-compression were located within 45° of the ED axis. Extension twins are formed during tension loading perpendicular to the pre-existing twins from pre-compression (which have undergone a detwinning process under load reversal). Twin residues from compression interact with grain boundaries or new twins that have formed within the grains during tensile loading. Such interactions between twins and dislocations can result in damage-accumulation mechanisms which lead to crack initiation.

Continuous observation of twinning and dynamic recrystallization in ZM21 magnesium alloy tubes during locally heated dieless drawing

Compared to cold drawing, dieless drawing has shown great potential for manufacturing biodegradable Mg alloy microtubes due to the large reduction in area acquired in a single pass. However, owing to the local heating and local deformation, the deformation mechanism during dieless drawing is not clear, and thus causing difficulties in controlling the microstructure of dieless drawn tubes. For the purpose of acquiring a desired microstructure, in this study the deformation mechanism of ZM21 Mg alloy tube was clarified by conducting continuous observation of the microstructural evolution during dieless drawing. The results show that both SRX and DRX occurred during dieless drawing. SRX occurred before the plastic deformation to soften dieless drawn tubes. With increase of feeding speed, the deformation mechanism changed accordingly: (1) At the low-speed of 0.02 mm/s, the deformation mechanism was dominated by twin-slip sliding, during which {10–12} tension twins were generated inside grains to accommodate the plastic deformation by changing the crystal orientation. (2) At the intermediate-speed of 2 mm/s, a twin-DRX process related to {10–12} tension twin was observed, which was characterized by the generation of abundant {10–12} tension twins and the evolution of misorientation angle of {10–12} tension twins. Moreover, the transformation from twin-DRX to CDRX can be observed at the late stage of plastic deformation, which was attributed to the inhomogeneous conditions of dieless drawing. (3) At the high-speed of 5 mm/s, a CDRX process was observed, during which grain boundary sliding and grain tilting were observed, in addition to the gradual rotation of subgrains. These results show that during dieless drawing, DRX is not only a temperature-dependent phenomenon, but also influenced by the variation of feeding speed.

Corrosion Resistance and Biocompatibility of Micro-Arc Oxidation Coatings with the Variable Sodium Fluoride Concentration on Zm21 Magnesium Alloys

Corrosion Resistance and Biocompatibility of Micro-Arc Oxidation Coatings with the Variable Sodium Fluoride Concentration on Zm21 Magnesium Alloys

Evaluation of rupture life and Larson Miller parameter using Monkman-Grant relationship from impression creep data of magnesium alloy ZM21

The creep behavior of various materials is being increasingly studied using impression tests. However, the impression tests can provide data for the primary and secondary stages of the creep curve but not the third stage for the specimen doesn’t fail during the test. Creep studies without rupture data leaves the analysis incomplete. Hence there is a need to correlate the minimum velocity obtained from impression tests with rupture time to make the creep analysis complete. The present paper attempts to evaluate rupture time and Larson Miller parameter (LMP) from the impression test data of ZM21 Magnesium alloy. The rupture time (trup) was calculated from the steady state impression velocity using Monkman-Grant relationship (MGR) and the trup was used to calculate LMP. Impression tests were carried out between equivalent stresses of 180 MPa and 66.67 MPa and the temperature was varied between 448 K and 523 K. Larson-Miller constant of 10 was found to describe the LMP by logarithm of applied stress.

Investigating machining characteristics and degradation rate of biodegradable ZM21 magnesium alloy in end milling process

Surface properties play a significant role in the biocompatibility and biodegradation of Mg-alloy implants which primarily depends on the manufacturing route followed. In the present work, the milling process has been optimized on ZM21 Mg-alloy to obtain the trade-off between the material removal rate (MRR), surface roughness (SR), and degradation rate (DR). Milling parameters vary the amount of force and pressure developed between the tool and work interface, thus, affecting the MRR and SR. The weight loss of machined samples was measured after seven days of immersion in simulated body fluid (SBF) to calculate the DR. L16 orthogonal array was used to study the effect of milling parameters such as tool rotation speed (TRS), feed rate (FR), and depth of cut (DoC). The result showed that the variation in the values of milling parameters significantly influences the surface integrity of Mg-alloy, thus affecting the DR. Chip morphology and surface cracks with scanning electron microscopy (SEM) were evaluated to correlate the influence of milling parameters on the machining performance of ZM21 Mg-alloy. The machined surface of Mg-alloy must be of very low SR and cracks-free to avoid fast corrosion. Therefore, grey relational analysis (GRA) has been employed for multi-optimization to get the best trade-off for higher MRR and lower SR and DR. The optimized setting suggested by GRA for milling of ZM21 Mg alloy is TRS: 2700 rpm, FR: 25 mm/min, and DoC: 1.25 mm.

High temperature impression creep behavior and microstructures of wrought ZM21 magnesium alloy

Mg-Zn alloys are promising candidates for their application in automotive, electronics and aerospace applications. For their successful application, one of the performance parameters that needs to be evaluated is their creep behavior at elevated temperatures. Hence this paper evaluates the high temperature creep behavior of wrought ZM21 magnesium alloy by impression test The tests were performed under constant temperature and stress. A flat ended cylindrical punch was used to create impressions. The temperature was varied between 398 K and 598 K while the stresses were varied from 200 MPa to 500 MPa (normalized stress: 0.014 ≤ σimp/ G ≥ 0.032). A power-law creep deformation was assumed to calculate creep exponent and activation energy using the steady state minimum impression velocity obtained from impression tests. The creep behavior was analyzed with the help of impression creep curves and plastic deformation was analyzed with the help of micrographs. It was found that creep exponent varied between 4.5 and 6 and activation energy between 73.28 and 113.35 kJ/mol were obtained. From the study it was concluded that the creep mechanism involved was pipe-diffusion-controlled dislocation climb.

Improving the Corrosion Resistance of Wrought ZM21 Magnesium Alloys by Plasma Electrolytic Oxidation and Powder Coating

Plasma Electrolytic Oxidation (PEO) was applied to extruded ZM21 Mg alloys to improve their corrosion resistance in a chloride-containing environment. PEO was carried out in DC mode and voltage control in a fluoride-free electrolyte. Potentiodynamic polarization tests in 3.5 wt.% NaCl aqueous solution and neutral salt spray (NSS) tests were carried out. Microstructural and profilometric characterization, as well as NSS tests were performed in different conditions: (i) bare ZM21, (ii) PEO-treated ZM21, (iii) powder-coated ZM21 (without PEO interlayer), and (iv) PEO-treated ZM21 with powder coating top layer (carboxyl-functionalized polyester resin). The PEO + powder coating double layer was identified as the best-performing corrosion protection.

Fabrication of ceramic coatings on the biodegradable ZM21 magnesium alloy by PEO coupled EPD followed by laser texturing process

Abstract Zirconia (ZrO2) incorporated ceramic coatings were fabricated on biodegradable ZM21 Mg alloy by the PEO coupled with EPD process. Subsequently, the sample surface was modified by laser texturing to improve the corrosion resistance, roughness and cell proliferation and growth properties. The corrosion performance of the fabricated samples along with the substrate was studied by electrochemical measurements under simulated body fluid (SBF) environment. The cell direct contact assay was conducted for the substrate and fabricated samples using L -929 mouse fibroblast cells for 24 h. The phase contrast images of cell direct contact assay revealed that fabricated samples exhibited better contact and response with the fibroblast cells, compared to the substrate. The addition of nanoparticles in the PEO process, called PEO coupled EPD process, resulted in attaining a higher thickness and improved corrosion performance of the samples than the PEO coated samples. Among all the samples, laser surface textured PEO, and PEO-EPD coated samples unveiled enhanced corrosion resistance, cell growth, thereby enabling it as a suitable prototype for biodegradable implant applications.

Influence of pulse frequency on the morphological and corrosion characteristics of the plasma electrolytic oxidized ZM21 magnesium alloy

• Effect of pulse frequency on PEO of ZM21 alloy was studied. • ZM21 alloy PEO treated at higher frequency showed superior corrosion resistance. • PDP test results well matched with the EIS test results. The process of plasma electrolytic oxidation was employed to fabricate ceramic oxide layer over the surface of ZM21 Mg alloy. PEO coatings were developed in an electrolyte composed of 10 g L −1 Na 2 SiO 3 ·9H 2 O, 4 g L −1 KOH and 2 g L −1 Na 2 B 4 O 7 ·10H 2 O in deionized water. The influence of pulse frequency on coating formation at 50 Hz and 1000 Hz was studied. The surface morphology and the phase analysis of the coatings were assessed by the SEM and XRD techniques, respectively. The corrosion performance of the coated specimens along with the bare substrate was studied by potentiodynamic polarization (PDP) and the electrochemical impedance spectroscopy (EIS) tests in the simulated body fluid (SBF) solution. The coating produced at 1000 Hz frequency showed the most favourable surface morphology and corrosion resistance, thereby enabling the suitable prototype for further development of corrosion resistant coatings for biodegradable magnesium implants in biomedical applications.

Evolution of Twinning During Cyclic Loading of Magnesium Alloy ZM21 Examined by Quasi-in-Situ EBSD

Most complex engineering components experience varied loading in use. We conducted successive experiments of cyclic tensile deformation followed by electron-backscattered diffraction imaging of the same area on each of several ZM21 magnesium alloy sample to investigate the microstructure and texture evolution during cyclic loading. In this way we correlated the evolving deformed microstructure of cyclically loaded magnesium to the initial grain orientations. To investigate the effects of the strain path, the behaviour of samples with and without pre-compression was compared. Twins can propagate from grain to grain and twin chains will form in the material without any pre-deformation. Twin chains are a result of twin transmission at grain boundaries and twin transmission frequency decreases with increasing grain boundary angles. In the absence of pre-compression, the fraction of extension twins increases from 0.003 to 0.019 after two cycles of tensile loading to a strain of 0.03, after which it changes only slightly as strain is increased. Twin chains in the pre-compressed specimen are activated without any obvious dependence on the matrix orientation. The fraction of extension twinning is 0.2 for the pre-compressed specimen. After a cycle of tensile loading to a total plastic strain of 0.015, 90% of the extension twins undergo detwinning. The detwinning starts just after reverse loading. Secondary twins forming within primary twin interfaces start to nucleate in the microstructure of the pre-compressed material at an early stage (at plastic strain values of 0.056). This is different from the nucleation of secondary twins in the material without pre-compression that occurs at a strain of 0.104. The early formation of secondary twinning is due to the presence of residual primary twins in the microstructure of the pre-compressed material as a result of detwinning of the initial twins.

Influence of Internal Pressure and Axial Compressive Displacement on the Formability of Small-Diameter ZM21 Magnesium Alloy Tubes in Warm Tube Hydroforming

In this study, the influence of internal pressure and axial compressive displacement on the formability of small-diameter ZM21 magnesium alloy tubes in warm tube hydroforming (THF) was examined experimentally and numerically. The deformation behavior of ZM21 tubes, with a 2.0 mm outer diameter and 0.2 mm wall thickness, was evaluated in taper-cavity and cylinder-cavity dies. The simulation code used was the dynamic explicit finite element (FE) method (FEM) code, LS-DYNA 3D. The experiments were conducted at 250 °C. This paper elucidated the deformation characteristics, forming defects and forming limit of ZM21 tubes. Their deformation behavior in the taper-cavity die was affected by the axial compressive direction. Additionally, the occurrence of tube buckling could be inferred by changes of the axial compression force, which were measured by the load cell during the processing. In addition, grain with twin boundaries and refined grain were observed at the bended areas of tapered tubes. The hydroformed samples could have a high strength. Moreover, wrinkles, which are caused under a lower internal pressure condition, were employed to avoid tube fractures during the axial feeding. The tube with wrinkles was expanded by a straightening process after the axial feed. It was found that the process of warm THF of the tubes in the cylinder-cavity die was successful.