MgZn2 Phase Research Articles

Characteristics of Mg-Zn-Ca-Pr Alloy Synthesized by Mechanical Alloying.

Magnesium-based materials are an interesting solution in terms of medical applications. Alloys that are hard to obtain via standard means may be manufactured via mechanical alloying (MA), which allows the production of materials with complex a chemical composition and non-equilibrium structures. This work aimed to investigate materials obtained by the MA process for 5, 8, 13, and 20 h in terms of their phase composition and changes during heating. The results of thermal XRD analysis were in the temperature range between 25 and 360 °C, which revealed MgZn2, PrZn11, Ca2Mg5Zn13, and Ca phases as well as α-Mg and α-Zn solid solution. The structural analysis features the powder morphology of the analyzed samples, showing cold-welding and fracturing processes leading to their homogenization, which is supported by the EDS results. The base Mg-Zn-Ca alloy was modified by different additions, but a thorough analysis of the influence of praseodymium on its thermal properties has not yet been performed. We chose to focus on Pr addition because it belongs to low-toxicity rare earth metals, which is an essential feature of biomaterials. Also, the Ca2Mg5Zn13 phase is not fully known, as there are no crystallographic data (hkl). Therefore, the investigation is important and scientifically justified.

Effects of processing parameters on microstructure and mechanical properties of friction stir additive manufactured Al-Zn-Mg-Cu alloy

Abstract A multilayered build was fabricated by friction stir additive manufacturing (FSAM) with different parameters, using 4-mm thick 7A04-T6 aluminum alloy sheets in this study. The parameters effect on the microstructure and mechanical properties of the builds were investigated combined scanning electron microscopy (SEM), transmission electron microscopy (TEM), vickers hardness and tensile tests. Macro-softening phenomenon was observed in the builds. The precipitation and growth of the Mg (Zn, Cu, Al)2 or MgZn2 phase with the effect of the effective thermal cycles during the FSAM process mainly attributed to the formation of the macro-softening. The more effective thermal cycles experienced during the FSAM process, the more Mg (Zn, Cu, Al)2 or MgZn2 phase precipitated and coarsened, resulting in a more pronounced decrease in the mechanical properties of the build. Heat input affected the macro-softening behavior of the build by influencing the degree of dissolution, re-precipitation and coarsening of the precipitates during the FSAM process. Too low or too high heat input resulted in the incomplete dissolution or further precipitation and growth of the precipitates, aggravating the macro-softening phenomenon, and reducing the precipitation strengthening ability of the build. The mechanical properties of the build fabricated at the rotation speed of 700 rpm and travelling speed of 160 mm/min were the best in this study.

High-strength and high-plasticity ZK60 magnesium alloy prepared by rapid solidification and high-speed extrusion

The extrusion speed of ZK60 magnesium alloy is usually lower than 5 m/min. The rapidly solidified (RS) ZK60 magnesium alloy extruded at 350 ℃ with die-exit speeds of 10 m/min, 20 m/min and 30 m/min was investigated. The results reveal that after the RS ZK60 alloy was extruded at different die-exit speeds, the average size of dynamically recrystallized grains is 1.19–1.40 μm, the percent of high-angle grain boundaries (HAGBs) become larger with the average orientation degree of 57.83 ° to 54.81 °, the intensity of texture at (0001)<1̅100> is below 3.4, and the Schmid factors of the prismatic and pyramidal planes reach the high value of no lower than 0.42 overall, while no coarse MgZn phase was observed. The yield tensile strength, ultimate tensile strength and elongation of the RS as-extruded ZK60 magnesium alloy change slowly from 321 to 299 MPa, -355–348 MPa, and -23–27 % when the die-exit speed increase from 10 to 30 m/min, respectively. The ultra-fine grains and disappearance of the coarse low melting-point MgZn phase are the main reasons for the high-speed extrusion, high strength, high plasticity and low texture of the RS as-extruded ZK60 magnesium alloy.

Study on dynamic recrystallization and precipitation behavior of hot compressed Al-20Zn-0.5Mg-0.5Sc alloy

The dynamic recrystallization (DRX) behavior of the Al-20Zn-0.5Mg-0.5Sc alloy was investigated under specific conditions using a Gleeble-3500 thermal simulator. The resultant grain size, recrystallization degree and precipitated phases were studied. The results indicate that the sensitivity of DRX grain size is highly affected by temperature, feebly influenced by strain and intermediately affected by strain rate. The DRX grains are grown by an average of 3.49 μm with increasing temperature. The DRX behavior is sensitive to temperature, strain and strain rate, resulting in changes in average grain size, percentage of HAGBs and degree of recrystallization under different parameters. At 400 ℃ / 40 % / 0.1 s−1, the average grain size is refined to 12.90 μm, and the corresponding HAGBs and recrystallization degree are approximately 46.2 % and 34.3 %, respectively. The Al3Sc, Zn and η (MgZn2) phases are precipitated in the hot-compressed alloy. The Al3Sc phase promotes the precipitation of the Zn and η phases. The size, amount and morphology of Al3Sc, Zn and η phases at different parameters have an important influence on the movement of dislocations and nucleation of grains, which leads to changes in DRX grain size and the degree of recrystallization. The fine precipitated phase particles Al3Sc and η inhibit the growth of recrystallized grain by pinning grain boundaries and exerting a blocking force on dislocations. Dynamic precipitation is the dominant mechanism for the changes in DRX grain size and degree of recrystallization. To achieve the refined grains and homogeneous microstructures, the optimum parameters are recommended as 400 ℃, 0.1 s−1 and 50 %.

3D X-ray Tomography Analysis of Mg–Si–Zn Alloys for Biomedical Applications: Elucidating the Morphology of the MgZn Phase

Temporary metal implants, made from materials like titanium (Ti) or stainless steel, can cause metabolic issues, raise toxicity levels within the body, and negatively impact the patient’s long-term health. This necessitates a subsequent operation to extract these implants once the healing process is complete or when they are outgrown by the patient. In contrast, medical devices fabricated from absorbable alloys have the advantage of being biodegradable, allowing them to be naturally absorbed by the body once they have fulfilled their role in facilitating tissue healing. Among the various absorbable alloy systems studied, magnesium (Mg) alloys stand out due to their biocompatibility, mechanical properties, and corrosion behavior. The existing literature on absorbable Mg alloys highlights the effectiveness of silicon (Si) and zinc (Zn) additions in improving mechanical properties and controlling corrosion susceptibility; however, there is a lack of comprehensive quantitative morphological analysis of the intermetallic phases within these alloy systems. The quantification of the complex morphology of intermetallic particles is a challenging task and has significant implications for the micromechanical properties of the alloys. This study, therefore, aims to introduce a robust set of morphometric parameters for evaluating the morphology of intermetallic phases within two as-cast Mg alloys with Si and Zn additions. X-ray Computed Tomography (XCT) was used to capture the 3D tomographic data of the alloys, and a novel pair of morphological parameters (ratio of convex hull to particle volume and convex hull sphericity) was applied to the 3D tomographic data to assess the MgZn phase formed in the two alloys. In addition to the impact of composition, the effect of solidification rate on the morphological parameters was also studied. Furthermore, Scanning Electron Microscopy (SEM) and Energy-Dispersive Spectroscopy (EDS) were employed to gather detailed 2D microstructural and compositional information on the intermetallics. The comprehensive characterization reveals that the morphological complexity and size distribution of the MgZn phase are influenced by both compositional changes and the solidification rate. However, the change in MgZn intermetallic particle morphology with size was found to follow a predictable trend, which was relatively agnostic of the chosen casting conditions.

Mechanical properties and stability of hot rolled Zn-0.8Mg alloy

Insufficient mechanical strength and mechanical instability are important factors limiting the application of zinc-based alloys as biodegradable materials. Currently, alloying and plastic deformation are effective methods to improve material properties. Therefore, this paper investigates the effect of hot rolling process on the mechanical properties and stability of Zn-0.8Mg alloys. The results show that after hot rolling, the internal grain of Zn-0.8Mg alloy is refined, the second phase is precipitated, the weaving strength is enhanced, and the overall mechanical properties are significantly improved. The contribution of deformation strengthening can reach about 90 %. The tensile strength, yield strength, and elongation of the alloy were 312.3 MPa, 249.5 MPa, and 15.6 % (141.72 %, 155.96 %, and 189.96 %, respectively) at a rolling volume of 70 %, which meets the clinical criteria for degradable material implants. However, this treatment reduced the stability of the mechanical properties of the Zn-0.8Mg alloy. During natural ageing, a small amount of Mg2Zn11 phase precipitated inside the alloy, reducing the elongation. Compared with cast alloys, hot rolled alloys have higher grain boundary density, which accelerates the precipitation of secondary phases, leading to more pronounced changes in the mechanical properties of the alloys after hot rolling.

Corrosion behavior, antibacterial properties and in vitro and in vivo biocompatibility of biodegradable Zn-5Cu-xMg alloy for bone-implant applications

Reasonable optimization of degradation rate, antibacterial performance and biocompatibility is crucial for the development of biodegradable zinc alloy medical implant devices with antibacterial properties. In this study, various amounts of Mg elements were incorporated into Zn5Cu alloy to modulate the degradation rate, antibacterial properties and biocompatibility. The effects of Mg contents on the microstructure, corrosion behavior, antibacterial properties and biocompatibility of Zn-5Cu-xMg alloy were extensively investigated. The results revealed that with an increase of Mg content, the amount of Mg2Zn11 phase increased and its galvanic effect with the Zn matrix was enhanced, which accelerated the corrosion process and led to higher corrosion rate and high degradation rate of the alloy. Additionally, there was an increased release of Mg2+ and Zn2+ ions from the alloy which imparted excellent resistance against Escherichia coli and Staphylococcus aureus bacteria and improved biocompatibility, subcutaneous antibacterial and immune microenvironment regulation properties. Zn-5Cu-2 Mg exhibited superior antibacterial ability, cell compatibility, proliferation effect, subcutaneous antibacterial and immune microenvironment regulation performances, which can work as a promising candidate of biodegradable antibacterial medical implants.

Substantial Improvement in Mechanical Properties and Anti‐corrosion Properties of Rolled Zn–Mg–Sr Alloys as an Orthopedic Implant

This study investigates a Zn–Mg alloy, enhanced for biodegradability and biocompatibility, by introducing trace amounts of Sr and subjecting it to hot‐rolling. The resulting Zn–Mg–Sr alloy shows a reduced average grain size to 3.35 μm and a transformed Mg2Zn11 phase from lamellar to finely dispersed particles, while maintaining a uniform SrZn13 phase distribution. The as‐rolled alloy exhibits significantly improved mechanical properties, with a tensile strength of 340 MPa and 40% of elongation, attributed to grain‐boundary strengthening, reinforcement by second‐phase particles, and the presence of intragranular dislocations and nanoscale precipitates. This microstructural refinement enhances the elongation by hindering crack propagation. Corrosion resistance tests reveal the superior performance of the as‐rolled alloy, owing to the finely distributed eutectic particles, which mitigated localized corrosion and altered the corrosion morphology from localized to finer corrosion pits. In vitro biocompatibility assessments show over 80% cell viability in C3H10 cultures with 50% Zn–Mg–Sr alloy extract, indicating low cytotoxicity. Furthermore, the alloy exhibits promising bone‐promoting properties, highlighting its potential for biomedical applications.

The Activation of Magnesium Sintering by Zinc Addition

Light alloys based on magnesium are widely used in most areas of science and technology. However, magnesium powder alloys are quite difficult to sinter due to the stable film of oxides that counteracts diffusion. Therefore, finding a method to activate magnesium sintering is urgent. This study examines the effect of adding 5 wt. % and 10 wt. % zinc to the sintering pattern of magnesium powders at 430 °C; a dwell of 30 min was used to homogenize at the densification’s temperature. Scanning electron microscopy (SEM) was used to characterize the alloy’s microstructure, while the phase composition was characterized using X-ray diffraction (XRD) and energy dispersion spectroscopy (EDS). The sintering densities of Mg–5Zn and Mg–10Zn were found to be 88% and 92%, respectively. The results show that after sintering, a heterophase structure of the alloy is formed based on a solid solution and phases MgZn and Mg50Zn21. To establish the sintering mechanism, the interaction at the MgO and Zn melt phase interface was analyzed using the sessile drop method. The minimum contact angle—65°—was discovered at 500 °C with a 20 min holding time. It was demonstrated that the sintering process in the Mg–Zn system proceeds through the following stages: (1) penetration of zinc into oxide-free surfaces; (2) crystallization of a solid solution, intermetallics; and (3) the removal of magnesium oxide from the particle surface, with oxide particles deposited on the surface of the sample.

Assessment of biodegradability and biocompatibility: An experimental and comparative analysis of magnesium and magnesium-(zinc-tin)/hydroxyapatite composites

This study presents the fabrication and comparative assessment of biodegradation and biocompatibility behaviors of pure Mg, Mg/HA (Hydroxyapatite), Mg-Zn/HA, and Mg-Sn/HA composites with fixed 5 wt% HA and 1 wt% each of Zn and Sn, using novel ultrasonic-assisted rheo casting technology. Characterization techniques, including X-ray diffractometry and scanning electron microscopy integrated with energy dispersive spectroscopy, were employed to analyze phase formation, surface morphology, and elemental composition. Microhardness tests were conducted to assess indentation resistance, while in vitro corrosion performance was evaluated in simulated bodily fluid to compare degradation behavior. Results indicate a uniform distribution of reinforced particles within the matrix with minimal casting defects. Intermetallic phases MgZn and Mg2Sn precipitated along grain boundaries in Mg-Zn/HA and Mg-Sn/HA composites. The Mg-Sn/HA composite exhibited peak microhardness (94.8 HV) due to precipitation strengthening. In contrast, Mg-Zn/HA samples showed a low degradation rate (0.19 mm/yr) and H2 gas evolution rate (0.035 ml/mm2), attributed to uniform distribution of secondary phases and fine grains that mitigate galvanic cell formation and control degradation. Cell viability assay results demonstrated that Mg-Zn/HA composite outperformed all other samples, showing a 94% relative cell growth rate of osteosarcoma MG-63 cells after 2 h of incubation, attributed to strong apatite formation (rich in Ca and P) on the surface post-immersion, promoting cell proliferation.

Influence of heat treatment on the microstructure evolution and corrosion performance of biodegradable Zn-Mg alloys

Zinc and zinc-based alloys have garnered increasing attention as biodegradable materials due to their excellent mechanical properties, lower degradation rates compared to magnesium, and favorable biocompatibility. This study investigates the impact of homogenization treatment on the microstructure and corrosion behavior of Zn-Mg alloys using scanning electron microscopy, X-ray diffraction, hardness testing, and accelerated corrosion immersion tests. The results reveal that homogenization treatment induces the fusion of eutectic cells within the alloys, causing significant morphological alternations in the eutectic structure and varying proportions of the Mg2Zn11 phase, These changes notably affect material properties. The raised content of Mg2Zn11 phase in the eutectic structure correlates with higher hardness but reduced corrosion resistance, whereas the reduced Mg2Zn11 phase content leads to enhanced corrosion resistance. Furthermore, in-situ corrosion observations demonstrate that corrosion initiates at the eutectic phase, with corrosion pits forming due to the ion release as corrosion progresses, leading to gradual enlargement of the corrosion pits. In summary, this study provides comprehensive insights into the microstructural changes in Zn-Mg alloys and their impact on corrosion resistance, offering valuable references for their engineering applications.

Effect of different homogenization times on the mechanical properties of 7075 aluminum alloy

The effects of homogenization temperature at 465 °C and different homogenization times (6h/12h/24h/36/h/48h) on the microstructure and mechanical properties of as-cast 7075 aluminum alloy were studied using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), hardness testing, and tensile testing. The results show that during the initial stage of homogenization, the continuous bright white network of σ-Mg (Zn, Cu, Al)2 phase transforms into a white broken flocculent S–Al2CuMg phase with the dissolution of Zn. In the middle stage, the S–Al2CuMg phase dissolves and Cu diffuses into primary Al7Cu2Fe, accompanied by precipitation of a large amount of dispersed nanoscale MgZn2 phase. With the homogenization time, the Al7Cu2Fe and MgZn2 phase are coarsened. The strength and plasticity of the alloy show a trend of first increase and then decrease. When the homogenization time is 24 h, the ultimate tensile strength (UTS), yield strength (YS), and elongation reach the peak values of 231.1 MPa, 134.2 MPa, and 4.0%, respectively. The phase transformation and dissolution mechanism during the homogenization process of 7075 aluminum alloy provides a scientific theoretical basis for improving the mechanical properties of the alloy.

Impact of cooling rates on the microstructure and cracking susceptibility of hot-dip galvanized Zn-12 wt% Al-5 wt% Mg coatings

Zinc-Aluminum-Magnesium (ZnAlMg) alloy coatings, applied through the hot-dip galvanizing process, are renowned for their superior corrosion resistance. This study investigated how different cooling rates affect the microstructure and cracking tendency of Zn-12Al-5Mg (in wt%) coatings. It was found that faster cooling rates lead to a more refined microstructure with primary MgZn2 grains but also increase the likelihood of cracking. This is primarily attributed to the finer distribution of primary MgZn2 grains and ternary eutectic (Zn/MgZn2/Al) regions, which allows micro-cracks originating from hard and brittle MgZn2 grains to easily propagate through the surrounding eutectic regions and develop into macro-cracks. Notably, we observed an epitaxial relationship between the primary and binary eutectic MgZn2 phases, shedding light on their crystallographic orientation and morphology. Additionally, our investigation revealed that cracking susceptibility depends on the crystallographic orientation of MgZn2 grains relative to the tensile axis. Fiber-like MgZn2 grains tend to crack along their basal planes, while hexagonal grains crack along other crystallographic planes. This insight into cracking behavior is crucial for designing ZnAlMg coatings with enhanced corrosion resistance and mechanical integrity. Overall, while faster cooling rates refine the microstructure, they can also increase the susceptibility to cracking in ZnAlMg coatings with Mg contents exceeding 3 wt%, emphasizing the need for a balanced approach in optimizing coating properties for different applications.

Thermodynamic Simulation Calculations of Phase Transformations in Low-Aluminum Zn-Al-Mg Coatings.

This study delves into the formation, transformation, and impact on coating performance of MgZn2 and Mg2Zn11 phases in low-aluminum Zn-Al-Mg alloy coatings, combining thermodynamic simulation calculations with experimental verification methods. A thermodynamic database for the Zn-Al-Mg ternary system was established using the CALPHAD method, and this alloy's non-equilibrium solidification process was simulated using the Scheil model to predict phase compositions under varying cooling rates and coating thicknesses. The simulation results suggest that the Mg2Zn11 phase might predominate in coatings under simulated production-line conditions. However, experimental results characterized using XRD phase analysis show that the MgZn2 phase is the main phase existing in actual coatings, highlighting the complexity of the non-equilibrium solidification process and the decisive effect of experimental conditions on the final phase composition. Further experiments confirmed that cooling rate and coating thickness significantly influence phase composition, with faster cooling and thinner coatings favoring the formation of the metastable phase MgZn2.

Microstructure, mechanical properties and multiphase synergistic strengthening mechanisms of LPBF fabricated AlZnMgZr alloy with high Zn content

In this work, a novel aluminum alloy with high Zn content was designed for laser powder bed fusion (LPBF) forming process. Aluminum alloy powder containing 14 wt% Zn and 2 wt% Zr was produced to conduct LPBF experiments with different process parameters. The analysis of the specimens revealed that the up facing surface exhibited an average microhardness peak value of 170.6 HV, achieving the ultimate tensile strength (UTS) of 573 MPa and the elongation of 11.6 %. There was no significant change in grain size and a large amount of plate-like η' (a metastable precipitate MgZn2 phase) phase precipitated within the grains after aging treatment (120°C, 21 h). The specimen reached the average microhardness peak of 181.7 HV and the UTS of 605 MPa. The principal strengthening mechanisms in the LPBF-formed samples were solid solution strengthening and grain refinement strengthening. After aging treatment, the precipitation of the second phase from solute atoms led to grain refinement strengthening and second-phase strengthening becoming the predominant factors to enhance the sample's strength. Al14ZnMgZr alloy have great application prospect in high strength and tough service environment.

Microstructure evolution and ductility improvement of additively manufactured biodegradable zinc–magnesium alloys via annealing

Zinc&amp;ndash;magnesium (Zn&amp;ndash;Mg) alloys, fabricated by laser powder bed fusion (LPBF) additive manufacturing techniques, have emerged as promising candidates for biomedical implants due to their biodegradation capability, superior mechanical strength, and excellent biocompatibility. However, LPBF-fabricated Zn&amp;ndash;Mg alloys still face challenges related to extremely low ductility and limited exploration of degradation characteristics. In this study, the impact of Mg incorporation on the printability, degradation properties, microstructure, and mechanical properties of LPBF-fabricated Zn&amp;ndash;Mg alloys was primarily investigated. Furthermore, we proposed a viable annealing post-processing route for the first time to tailor the microstructural characteristics of the fabricated Zn&amp;ndash;Mg alloy and enhanced its limited ductility. The results demonstrated that by applying a laser power of 80 W and a scanning speed of 600 mm/s, the relative density of LPBF-fabricated Zn&amp;ndash;Mg alloy reached 98.62%. Increasing the Mg amount from 1 to 5 wt% refined the grain size while promoting an increase in Mg2Zn11 and MgZn2 phases. Among these compositions, the Zn&amp;ndash;1Mg alloy exhibited the greatest degradation rate at 0.126 mm/year. The annealing treatment facilitated the microstructure evolution of the Zn&amp;ndash;1Mg alloy, resulting in equiaxed grains, increased average grain size, high-angle grain boundaries, and enrichment of Mg at grain boundaries. After annealing at 300&amp;deg;C for 0.5 h, the tensile strength of Zn&amp;ndash; 1Mg alloy decreased from 254.92 to 170.93 MPa, while the elongation significantly increased by a factor of 14.3 from 0.55% to 8.43%. These findings provide valuable insights into an effective post-processing approach for tailoring the microstructure and resultant mechanical properties of LPBF-fabricated Zn and its alloys.

Simultaneously improving thermal conductivity, mechanical properties and metal fluidity through Cu alloying in Mg-Zn-based alloys

Mg-Zn-based alloys have been widely used in computer, communication, and consumer (3C) products due to excellent thermal conductivity. However, it is still a challenge to balance their mechanical performance and thermal conductivity. Here, we investigate microstructure, mechanical performance, thermal conductivity and metal fluidity of Mg-5Zn (wt.%) alloy after Cu alloying by experimental and simulation methods. First, Mg-5Zn alloy consist of α-Mg matrix and interdendritic MgZn phases. As the Cu content increases, however, MgZn phases disappear but intragranular Mg2Cu and interdendritic MgZnCu phases appear in Mg-5Zn-Cu alloys. Besides, the grain size of α-Mg phase is refined and the volume fraction of MgZnCu phase increases as the Cu content increases. Second, Cu addition is found to improve thermal conductivity of Mg-5Zn alloy remarkably. Especially, Mg-5Zn-4Cu alloy exhibits the best thermal conductivity of 124 W/(m·K), which is mainly due to the significant reduction in both solid solubility of Zn in the α-Mg matrix and lattice distortion of α-Mg matrix. Moreover, a stable crystal structure of MgZnCu phase also contributes to an increased thermal conductivity based on first principles and molecular dynamics simulations. Third, Cu addition simultaneously enhances strength and ductility of Mg-5Zn alloy. Tensile yield strength and elongation of Mg-5Zn-6Cu alloy reach 117 MPa and 18.0 %, respectively, which is a combined result of refinement, solution, second phase, and dislocation strengthening. Finally, combined with a phase field simulation, we found that Cu addition enhances metal fluidity of Mg-5Zn alloy. On the one hand, Cu alloying not only delays dendrite growth but also prolongs solidification time. On the other hand, MgZnCu phase stabilizes the dendrite growth of the α-Mg phases by reducing energy consumption during solidification of liquid metal. This work demonstrates that Cu alloying is an ideal strategy for synergistically improving the thermal conductivity, mechanical performance and metal fluidity of Mg-based alloys.

Study on the quenching sensitivity of corrosion properties in 7199 aluminum alloy

This study used electrochemical corrosion, intergranular corrosion (IGC), and exfoliation corrosion tests, as well as microscopic observations of the microstructure and first-principles calculations, to investigate the effect of different quenching rates on the microstructure and corrosion properties of the 7199 alloy. The results show that as the quenching rate decreases, the size, Zn, and Mg content of precipitated phases at grain boundaries (GBs), as well as the width of the precipitation-free zone (PFZ), increase, resulting in a decrease in corrosion properties. During slow quenching, the η phase (MgZn2) at the GBs continuously absorbs surrounding Zn and Mg atoms, causing Zn and Mg atom depletion near the GBs. This results in the formation of a wide PFZ. Enlargement of the η phase and PFZ at the GBs leads to anodic dissolution channels, allowing for rapid corrosion expansion along the GBs. Additionally, at slow quenching rates, not only does the η phase precipitate at the subgrain boundaries (SGBs) but also the T and S phases. In corrosive environments, the η phase is more prone to corrosion than the T and S phases. Electron work function calculations show that the S phase has the highest corrosion potential, whereas the η phase has the lowest. As a result, SGBs containing T and S phases are unlikely to serve as corrosion pathways. Corrosion preferentially extends along SGBs containing η phases.

Effects of Nd content on the microstructures and mechanical properties of ZK60 Mg alloy and corresponding strengthening mechanisms

The aim of this research was to develop high-strength Mg alloys and investigate the microstructural evolution and corresponding strengthening mechanisms of ZK60 Mg alloys with different Nd content. The results indicated that the Nd-free ZK60 alloy was mainly composed of the α-Mg matrix and MgZn, MgZn2 and Zn2Zr phases, while a new phase, Nd3Zn11, formed after the addition of Nd. The addition of Nd enhanced the precipitation. The grain size first decreased and then increased with increasing Nd content. The texture component parallel to the ED in the [1‾ 100] direction remained unchanged after the addition of Nd, but the texture intensities sharply increased. The as-extruded Mg-6Zn-0.5Zr-3Nd (wt.%) alloy exhibited the best mechanical properties among all the as-extruded alloys, with the YS, UTS, and EL of 355 MPa, 369 MPa, and 8.9 %, respectively. The YS increased by 77 MPa compared with that of the as-extruded ZK60 Mg alloy, which was mainly attributed to the texture strengthening and precipitation strengthening mechanisms.

Effect of cooling rate on microstructure, mechanical and wear properties of Mg-2Zn and Mg-2Zn-1Mn alloys

ABSTRACT In this study, the wear characteristics of Mg-2Zn and Mg2Zn-1Mn alloys in both dry and corrosive conditions, as well as their mechanical properties dependent on cooling rate, were examined. It has been determined that MgZn, Mg2Zn3 and MgZn2 phases are formed together with the α-Mg main matrix in the microstructure of the alloys. The highest tensile strength (188.6 MPa) was observed in section B of Mg-2Zn alloy. With this, section A of the Mg-2Zn-1Mn alloy showed the lowest wear value (0.00144 mm3/N.m) following dry wear. However, under corrosive wear conditions, the lowest wear rate (0.0008 mm3/N.m) was exhibited at B section in Mg-2Zn-1Mn alloy. In the SEM images of the abrasive tips used in the wear tests, it was determined that the scratches occurred along the wear direction, and as a result of the EDX analysis, alloying elements were transferred from the alloys to the abrasive tip.