ZK60 Alloy Research Articles

Micromechanics Modeling on Mechanical Properties in Mg Alloys with Bimodal Grain Size Distribution

Bimodal grain structure (BGS) Mg alloys containing a high fraction of fine grains (FGs) and a low fraction of coarse grains (CGs) show a good combination of strength and plasticity. Here, taking the ZK60 alloy as an example, the influences of CG size, volume fraction, and texture intensity on mechanical properties and the hetero-deformation-induced (HDI) effect were examined using the Mori–Tanaka mean-field method combined with strain gradient theory of plasticity. The results indicate that the overall mechanical properties decrease with an increase in CG size because the limited HDI effect cannot compensate for the strength and plasticity decrease derived from larger CGs. A higher aspect ratio of CG along the loading direction can weaken the HDI effect and subsequently reduce the overall mechanical properties. Optimal comprehensive mechanical properties can be achieved when the CG volume fraction is approximately 30%. Furthermore, an increasing basal texture intensity in CG results in higher yield strength and lower ultimate tensile strength, while the uniform elongation reaches a maximum value when ~60% of CGs possess hard orientations with Euler angles of (0~30°, 0°, 0°).

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.

Investigating the Effects of Transition Metals and Activated Carbon on Hydrogenation Characteristics of Severely Deformed ZK60 Processed by High-Energy Ball Milling.

The synergic effects of activated carbon and transition metals on the hydrogenation characteristics of commercial ZK60 magnesium alloy were investigated. Severe plastic deformation was performed using equal-channel angular pressing with an internal die angle of 120° and preheating at 300 °C. The ZK60 alloy samples were processed for 12 passes using route BA. The deformed ZK60 alloy powder was blended with activated carbon and different concentrations of transition metals (Ag, Pd, Co, Ti, V, Ti) using high-energy ball milling for 20 h at a speed of 1725 rpm. The amount of hydrogen absorbed and its kinetics were calculated using Sievert's apparatus at the higher number of cycles at a 300 °C ab/desorption temperature. The microstructure of the powder was analyzed using an X-ray diffractometer and scanning electron microscope. The results indicated that 5 wt% activated carbon presented the maximum hydrogen absorption capacity of 6.2 wt%. The optimal hydrogen absorption capacities were 7.1 wt%, 6.8 wt%, 6.7 wt%, 6.64 wt%, 6.65 wt%, and 7.06 wt% for 0.5 Ag, 0.3 Co, 0.1 Al, 0.5 Pd, 2 Ti, and 0.5 V, respectively. The hydrogen absorption capacities were reduced by 35.21%, 26.47%, 41.79%, 21.68%, 26.31%, and 26.34% after 100 cycles for 5C0.5Ag, 5C0.3Co, 5C0.1Al, 5C0.5Pd, 2Ti, and 5C0.5V, respectively. Hydrogen absorption kinetics were significantly improved so that more than 90% of hydrogen was absorbed within five minutes.

Corrosion Behavior and Biological Properties of ZK60/HA Composites Prepared by Laser Powder Bed Fusion.

Magnesium alloy ZK60 shows great promise as a medical metal material, but its corrosion resistance in the body is inadequate. Hydroxyapatite (HA), the primary inorganic component of human and animal bones, can form chemical bonds with body tissues at the interface, promoting the deposition of phosphorus products and creating a dense calcium and phosphorus layer. To enhance the properties of ZK60, HA was added to create HA/ZK60 composite materials. These composites, fabricated using the advanced technique of LPBF, demonstrated superior corrosion resistance and enhanced bone inductive capabilities compared to pristine ZK60. Notably, the incorporation of 3 wt% led to a significant reduction in bulk porosity, achieving a value of 0.8%. The Ecorr value increased from -1.38 V to -1.32 V, while the minimum Icorr value recorded at 33.9 μA·cm-2. Nano-HA achieved the lowest volumetric porosity and optimal corrosion resistance. Additionally, these composites significantly promoted osteogenic differentiation in bone marrow stromal cells (BMSCs), as evidenced by increased alkaline phosphatase (ALP) activity and robust calcium nodule formation, highlighting their excellent biocompatibility and osteo-inductive potential. However, when increasing the HA content to 6 wt%, the bulk porosity rose significantly to 3.3%. The Ecorr value was -1.3 V, with the Icorr value being approximately 50 μA·cm-2. This increase in porosity and weaker interfacial bonding, ultimately accelerated electrochemical corrosion. Therefore, a carefully balanced amount of HA significantly enhances the performance of the ZK60 magnesium alloy, while excessive amounts can be detrimental.

Laser powder bed fusion of Mg–Zn–Zr alloy: Formability, microstructure evolution and biodegradation behavior

Laser powder bed fusion (LPBF) was used to fabricate Mg–Zn–Zr (ZK60) parts, with a thorough investigation of processability by varying laser power and scanning rate. The combined effect of these parameters, which determines laser energy density, significantly impacted the forming quality of LPBF ZK60. Dense parts (over 99%) free of visible defects such as pores and cracks were achieved at a laser energy density of 74.1 J/mm2. The formation mechanisms of pores and cracks were extensively analyzed concerning the characteristics of the molten pool and subsequent cooling behavior. The LPBF ZK60 parts exhibited extremely fine grains, with an average grain size of 3.2 μm. Both equiaxed and columnar grains were observed, with a central equiaxed zone in the melt pool and a perpendicular lamellar zone along its boundary. Additionally, the Mg7Zn3 eutectic phase precipitated within the α-Mg matrix of ZK60. Immersion and electrochemical tests indicated that the XZ plane displayed superior corrosion resistance, attributed to fewer deformation regions and lower dislocation density. Furthermore, in vitro cell experiments confirmed that the ZK60 alloy possesses good biocompatibility.

Effect of lanthanum oxide on microstructure and mechanical properties of ZK60 magnesium alloy

Different amounts of La2O3 were added to ZK60 alloy to observe the changes in microstructure and mechanical properties of ZK60-XLa2O3 (X = 0, 0.2 wt%, 0.5 wt%) composites. Our findings reveal that within the as-cast ZK60 alloy, the Mg-Zn binary phase is manifested as rod-shaped precipitates, exhibiting a dispersed distribution predominantly along the grain boundary regions. With the increase of La2O3 addition, the rod-like Mg-Zn binary phases are gradually replaced by Mg-Zn-La ternary phases, and these Mg-Zn-La ternary phases are semi-continuously distributed around the grain boundaries. Both ZK602 and ZK605 alloys result in a corresponding improvement in ductility after extrusion. It is noteworthy that the ductility of the as-extruded ZK605 alloy is increased by 59.4% compared to ZK60 at the expense of a reduction of only 3.9% in yield strength. Taken together, the significant increase in ductility of ZK605 is mainly due to the weakening of the basal texture, which is weakened by the redox reaction of La2O3 with the α-Mg matrix, generating the La element. The decrease in yield strength of ZK605 in the extruded state is closely related to the observed grain coarsening phenomenon and the basal texture weakening. At the same time, the ultimate tensile strength of ZK605 shows a slight increase, which is mainly due to the second phase strengthening. The Mg-Zn-La ternary phase exhibits a notably hard character, and it is evident that the distribution of this phase becomes progressively denser as the La2O3 content increases.

Enhancement of PEO-coated ZK60 Mg alloy: Curcumin-enriched mesoporous silica and PLA/bioglass for antibacterial properties, bioactivity and biocorrosion resistance

The corrosion resistance and antibacterial properties of ZK60 magnesium alloy implants have been enhanced via Plasma Electrolytic Oxidation (PEO) and electrospinning techniques. A robust, porous oxide coating was created on the ZK60 alloy using the PEO process, with characterization performed via SEM and XRD. Improved corrosion resistance of the PEO-coated samples was demonstrated through electrochemical analyses, including EIS and polarization tests. In addition to the PEO treatment, composite electrospun nanofibrous coatings were developed, incorporating curcumin-loaded mesoporous silica nanoparticles and bioactive glass. The electrospun nanofibers, which exhibited a diameter of 350 nm without beads, were characterized by Dynamic Light Scattering, Zeta Potential, Infrared Spectroscopy, BET, and XRD, confirming a curcumin loading of 10 wt%. Significant antibacterial activity against Escherichia coli and Staphylococcus aureus was shown by these fibers, and high bioactivity was observed after 14 days of immersion in simulated body fluid (SBF). The combination of PEO coatings and electrospun nanofibers highlights an enhancement in both corrosion resistance and antibacterial properties for implant applications.

Corrosion behavior of ternary HA-NrGO-CS composite coatings via cathodic electrophoretic deposited on ZK60 Mg alloy combining with thermal annealing

In this paper, effect of various contents of chitosan (1.0, 1.5 and 2.0 wt%) on corrosion/degradation behavior of ternary HA-NrGO-CS prepared on ZK60 alloy substrates were investigated. The samples were prepared by combining cathodic electrophoretic deposition and thermal argon atmosphere annealing for 120 min at 200 °C to regulate corrosion and quick degradation of ZK60 Mg alloy surface. After immersion for 30 min, HA-NrGO-1.5CS coated sample exhibited highest |Z|0.1Hz value, trailed by the HA-NrGO-2.0CS, HA-NrGO-1.0CS and ZK60 alloy samples. After immersion for 2 days, |Z|0.1Hz values moved to higher Bode modulus for HA-NrGO-CS coated samples, indicating poles and defects were filled due to the formation of apatite layer on the HA-NrGO-CS surface. FT-IR and Raman spectra proved the successful doping of N atoms into the rGO nanosheet skeleton to form NrGO. The SEM images and EDS plane-scan results for the samples after immersion for 2 days verified the existence of an apatite layer. The experimental results indicated that the existence of CS, HA and NrGO in the composite coatings can regulate the pH values and supply a sustained release of Mg2+ ions and O2 due to the synergistic effect of the protonation/deprotonation of -NH2 groups in CS and the dissolution/recrystallization of HA. Furthermore, the production of MgO2 film can convert corrosion behavior of ZK60 alloy from pitting corrosion to uniform corrosion, which provided a potential strategy for bone biomedical applications.

ZK60 alloy deformation and damage at different temperatures using unified constitutive model

The deformation behaviour and damage mechanism of ZK60 magnesium alloy under temperatures of 25–140 °C and strain rates of 0.01–0.0001 s−1 were investigated by uniaxial hot tensile and characterization experiments. The results suggested that the main factor for damage in ZK60 magnesium alloy was the nucleation, growth and coalescence of microdefects such as microvoids and cracks around the second-phase particles and/or grain boundaries. Then, a unified constitutive model including damage evolution, work hardening and recovery mechanisms was established. The model, verified by experimental data, shows good predictability. It was implemented into ABAQUS software through the VUMAT subroutine, which then predicted and analyzed the microstructure evolution.

Effect of Annealing Time on the Microstructure, Mechanical and Damping Properties of an As-Rolled ZK60 Alloy

Effect of Annealing Time on the Microstructure, Mechanical and Damping Properties of an As-Rolled ZK60 Alloy

Zinc oxide coating impact on corrosion of ZK60 magnesium alloys in simulated body fluid

Magnesium alloys offer an alternative for applications in biodegradable implant devices within human body, eliminating the need for subsequent surgeries to remove metallic parts. Nevertheless, the uniform degradation rate of magnesium (Mg) alloys must be enhanced by applying surface coatings, preferably incorporating bactericidal and biocompatible agents, to improve the implant properties. In this study, magnesium alloys ZK60 (Mg, Zn, and Zr) and ZK60-Mm (Mg, Zn, and Zr with 1.5 % mass of rare-earth elements - mischmetal), both having a specific mass close to the bone, were investigated. The surfaces were coated with ZnO using physical vapor deposition (PVD) in the HiPIMS (High Power Impulse Magnetron Sputtering) mode. The corrosion resistance and degradation of the alloys were studied using electrochemical and immersion tests in simulated body fluid. Surface analysis and microstructures were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD). The results showed that the ZnO coating favors osseointegration with hydroxyapatite formation after immersion in SBF. Moreover, electrochemical analysis indicates an enhancement in corrosion resistance. On average, the corrosion current density decreases by a factor of four for the ZK60 alloy and two for the ZK60-Mm alloy post-coating. The corrosion rate of ZnO-coated alloys is lower compared to that of uncoated alloys, showcasing the promising utility of this coating.

Corrosion Activity of Ultrafine-Grained Pure Magnesium and ZK60 Magnesium Alloy in Phosphate Buffered Saline Solution.

The magnesium alloy ZK60 is a promising candidate as a material for biodegradable implants. One of the most important factors for biodegradable implants is the modification of their corrosion behavior to match the requirements for the healing bone or tissue. The corrosion behavior can be influenced by different factors, among them the grain size, which can be changed by severe plastic deformation processes such as High Pressure Torsion Extrusion (HPTE). This study focuses on the corrosion behavior of samples of pure magnesium and ZK60 before and after HPTE, and the influence of the microstructure on the corrosion activity. The samples are subjected to immersion tests in phosphate buffered saline solution (PBS). The corrosion activity is defined by the emerging hydrogen volume from the corrosion process which is collected and by subsequently observing the resulting sample surfaces. The findings of this study suggest that pure magnesium shows lower corrosion activities than ZK60 and that HPTE processing leads to higher corrosion activities in PBS.

Towards implementation of alloy-specific thermo-fluid modelling for laser powder-bed fusion of Mg alloys

Multi-physics thermo-fluid modeling has been extensively used as an approach to understand melt pool dynamics and defect formation as well as optimizing the process-related parameters of laser powder-bed fusion (L-PBF). However, its capabilities for being implemented as a reliable tool for material design, where minor changes in material-related parameters must be accurately captured, is still in question. In the present research, first, a thermo-fluid computational fluid dynamics (CFD) model is developed and validated against experimental data. Considering the predicted material properties of the pure Mg and commercial ZK60 and WE43 Mg alloys, parametric studies are done attempting to elucidate how the difference in some of the material properties, i.e., saturated vapor pressure, viscosity, and solidification range, can influence the melt pool dynamics. It is found that a higher saturated vapor pressure, associated with the ZK60 alloy, leads to a deeper unstable keyhole, increasing the keyhole-induced porosity and evaporation mass loss. Higher viscosity and wider solidification range can increase the non-uniformity of temperature and velocity distribution on the keyhole walls, resulting in increased keyhole instability and formation of defects. Finally, the WE43 alloy showed the best behavior in terms of defect formation and evaporation mass loss, providing theoretical support to the extensive use of this alloy in L-PBF. In summary, this study suggests an approach to investigate the effect of materials-related parameters on L-PBF melting and solidification, which can be extremely helpful for future design of new alloys suitable for L-PBF.

Achieving excellent oxidation resistance in a Mg alloy by grain boundary adhesion and in-situ phase transformation

The oxidation resistance of Mg–Zn–Zr (ZK60) alloys with the addition of minor rare-earth element (RE) oxides (CeO2, La2O3) was investigated in 420 °C in air and pure O2 environments. It was revealed that the oxidation behavior of ZK60, ZK60-La2O3 and ZK60-CeO2 is different. In comparison to typical intergranular oxidation in ZK60 alloy, owing to diverse phase transformations between La and Mg, the La–Mg phase is continuously distributed in the grain boundaries, and furthermore, a dense and protective layer consisting La–Mg intermetallic phase is coated on the surface, which can effectively inhibit the oxidation of the Mg substrate, exhibiting excellent oxidation resistance. However, the presence of discontinuously distributed Ce-rich phases at the grain boundaries and the chain reaction during high-temperature exposure are the reasons for the deterioration of the oxidation resistance in ZK60-CeO2. It is anticipated that our findings will inspire the development of next-generation low-cost and excellent high-temperature performance Mg alloys.

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 solutes on texture evolution during grain growth in ZK60 alloy by phase field simulation

A three-dimensional (3D) multiscale phase field model was proposed to investigate the effect of Ca, Y and Al solutes on the texture evolution of ZK60 alloy during grain growth at 573 K under an applied compression stress of 270 MPa, in which the characteristics of the elastic anisotropy and grain boundary (GB) segregation caused by the solutes were taken into account. The results show that either Ca or Y addition can weaken the basal texture of ZK60, while Al addition enhances it. The deviation of the grain size distribution from the Hillert model becomes greater with the addition of Al, while Ca or Y addition reduces the deviation. The solute segregation-induced GB energy change has a very limited effect on the texture evolution compared with elastic anisotropy. The revealed mechanism is of great significance for the microstructure design of the ZK60 alloy by an appropriate alloying strategy.

Effects of differential speed rolling and H2S poison on hydrogen storage performance of ZK60 alloys ball-milled with C, Pd, Ag, and Zr

The commercial ZK60 magnesium alloy was used to investigate hydrogen absorption performance. The ZK60 alloy was severely deformed via differential speed rolling with differential speeds of 6:3 and 9:3. High energy ball milling was used to blend deformed ZK60 powder with 5 wt% activated carbon(C), 0.5 wt% silver (Ag), 0.5 wt%palladium (Pd), and 1 wt% zirconium (Zr) for 20h at 1725 rpm. Hydrogen absorption characteristics at different low temperatures and number of cycles were analyzed using Sievert's apparatus with hydrogen supplied with H2S impurities. The microstructure of the powder was analyzed field emission scanning electron microscope (FESEM). The hydrogen absorption capacity increases with the temperature rise, and maximum capacity(6.02 wt%) was observed in 5C1Zr deformed at 9:3DSR at 200 °C after five cycles. Hydrogen absorption capacity increases after each hydrogenation cycle in 5C0.5Ag and 5C1Zr but remains the same in 5C0.5Pd. The increase in H2S concentration decreases the hydrogen capacity, and increase in the number of cycles further deteriorates absorption capacity when the differential speed ratio is 6:3. The H2S concentration variation has almost no effect at the differential speed of 9:3. The maximum hydrogen absorption kinetics (74.7%) in 10min was observed in 5C1Zr. A more refined dendritic microstructure was observed in ZK60 alloy deformed with a differential speed ratio of 9:3.

Degradation protection and enhanced biocompatibility of Mg alloys pretreated with plasma proteins.

After implantation of the Mg alloy in the human body, the adsorption of plasma protein on surface will cause a series of cell reactions and affect the degradation of Mg alloys. Herein, in vitro biological reactions of the ZK60 and AZ31 Mg alloys are analyzed in plasma protein environment. Combined with mass spectrometry analysis of the type of adsorbed proteins, it is shown that proteins such as fibrinogen, vitronectin, fibronectin, and prothrombin are prone to get adsorbed on the surface of the alloys than other proteins, leading to the promotion of MG63 cell adhesion and proliferation. The effect of selected proteins (fibrinogen, fibronectin, and prothrombin) on degradation of ZK60 and AZ31 Mg alloys is investigated using immersion tests. The degradation of AZ31 Mg alloy is significantly restrained with the presence of proteins. This is due to the protein adsorption effect on the sample surface. The molecular dynamics simulation results indicate that both fibrinogen and fibronectin tend to adsorb onto the AZ31 rather than ZK60, forming a stable protein layer on the AZ31 Mg alloy retarding the degradation of the samples. As to ZK60 alloy, the addition of protein inhibits the degradation in the short term, however, the degradation increases after a long time of immersion. This phenomenon is particularly pronounced in fibronectin solution.

Effect of Multidirectional Forging and Aging Treatment on Wear Properties of ZK61 Alloy.

This study investigated the effects of multidirectional forging (MDF) and aging treatments on the wear properties of ZK61 magnesium alloy. Dry sliding wear tests were performed on homogenized, MDF, and aged samples using a friction wear machine to analyze the surface morphology by scanning electron microscopy (SEM) and white light interferometry, as well as the hardness and tensile mechanical properties. The ZK61 magnesium alloy has higher sliding wear properties after MDF due to higher strength, hardness, and work hardening. Grain refinement affects the wear resistance of the material, but aging increases the hardness and tensile strength and decreases the wear resistance.

Effect of Ce on microstructure and dynamic compression properties of ZK60 alloy

The Mg–6Zn– xCe–0.6Zr ( x = 1, 2) alloys were subjected to a dynamic compression experiment, and the change in microstructure was noticed and studied. The primary components of two alloys are α-Mg matrix, Mg7Zn3 phase, and (Mg1− xZn x)11Ce phase. The two alloys have grain diameters of 2.8 and 3.2 μm, respectively. The dynamic compressive mechanical characteristics of the two alloys show a positive strain-strengthening effect, with Mg–6Zn–1Ce–0.6Zr alloy having somewhat higher values than Mg–6Zn–2Ce–0.6Zr alloy. At a strain rate of 500 s−1, {10[Formula: see text]2} tensile twin is the dominant deformation mechanism for two alloys, but the Mg–6Zn–2Ce–0.6Zr alloy is more prone to produce {10[Formula: see text]2} tensile twin. With the increase of the strain rate, the dominant deformation mechanism changes from {10[Formula: see text]2} tensile twin to pyramidal slip.