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Stamping processing is commonly used to form medical devices and implant. However, for biodegradable Mg alloy, the stamping will influence the degradation behavior because of the change in microstructure after stamping. So in this study, the As-rolled Mg-2Zn-0.5Nd alloy (ZN20) was processed by stamping. The microstructure, crystallographic orientat...
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... plates, and then uniformly rolled at a speed of 2 mm/min. The Rolled sheets of 0.7 mm thickness were obtained from the 2 mm thick plate after 2 h preheating at 300 °C. The rolled sheets were placed in a blank form into a stamping press where a tool and die surface transformed the rolled sheet into circular samples of 10 mm diameter, as shown in Fig. 1.The stamping was carried out at a force of 3 KN and speed of 200 mm/min. Finally, the stamped samples were annealed at 400 °C for 3 h. The rolled, stamped and annealed samples were named Rolled ZN20, Stamped ZN20 and HT-stamped ZN20 respectively. The chemical compositions of the Mg-2Zn-0.5Nd alloys are listed in Table ...
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... Corrosion penetrated into the specimen interior. In contrast, there were few obvious deep pits on the surface of the rolled Sample. Corrosion of the HT-stamped sample was less severe. The corrosion morphology also indicated a ranking of the corrosion severity similar to that from the polarization curves and mass loss measurements. The EDS results (Fig. 10d-f) reveal that the surface corrosion products (rectangular area in Fig. 10 a-c) were rich in O, Mg, Zn, Nd, P and Ca. The corrosion product on the rolled sample is less loose as compared to the Stamped sample while the HT-stamped sample has a more compact corrosion product ...
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... obvious deep pits on the surface of the rolled Sample. Corrosion of the HT-stamped sample was less severe. The corrosion morphology also indicated a ranking of the corrosion severity similar to that from the polarization curves and mass loss measurements. The EDS results (Fig. 10d-f) reveal that the surface corrosion products (rectangular area in Fig. 10 a-c) were rich in O, Mg, Zn, Nd, P and Ca. The corrosion product on the rolled sample is less loose as compared to the Stamped sample while the HT-stamped sample has a more compact corrosion product ...
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Stress corrosion cracking (SCC) may lead to brittle, unexpected failure of medical devices. However, available researches are limited to Mg-based biodegradable metals (BM) and pure Zn. The stress corrosion behaviors of newly-developed Zn alloys remain unclear. In the present work, we conducted slow strain rate testing (SSRT) and constant-load immer...
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... They offer a unique combination of biocompatibility and mechanical properties akin to natural bone, making them an ideal choice for bone screws and plates [4]. Moreover, the biodegradability of Mg alloys eliminates the need for surgical removal and promotes beneficial bone metabolism and apatite formation [5][6][7]. ...
This study investigated the effects of Zinc (Zn) content, specifically in the range of 1 wt.% to 7 wt.%, on the powder characteristics, porosity, microstructure, and corrosion behavior of Mg-xZn-0.2Mn alloys produced using selective laser melting (SLM). To evaluate the porosity of the printed parts and various powder attributes, such as size, circularity, void spaces between powders, and inherent imperfections, scanning electron microscopy (SEM) and optical microscopy (OM) were employed. The alloy microstructure, composition, and phase were examined using energy dispersive X-ray (SEM-EDX) and X-ray Diffraction (XRD). The corrosion resistance and degradation behavior were assessed through electrochemical corrosion tests and immersion tests in Hanks’ solution at 37.5 °C, respectively. Finally, OM and SEM-EDX were used to characterize the corrosion products. The findings of this study indicated that the powder size increased with Zn content, maintaining a 0.8 circularity. Powder defects were minimal, with occasional satellite particles. For the SLM-printed samples, it was evident that porosity characteristics could be influenced by Zn content. As Zn content increased, the pore fraction rose from 1.0% to 5.3%, and the pore size grew from 2.2 μm to 3.0 μm. All printed samples consisted of an α-Mg matrix. Additionally, a higher Zn content resulted in more distinct grain boundaries. Corrosion resistance decreased with Zn, leading to more pronounced localized corrosion after immersion in Hanks’ solution. Ca-P was found as white corrosion products on all samples.
... Mg alloys have a low electrode potential (−2.37 V) as well as strong chemical activity. They can be gradually degraded and absorbed after implantation in the body, avoiding the implant removal operation [6]. Meanwhile, Mg is an essential element to the human body and beneficial to the growth of new bone tissue [7]. ...
The Mg-6Zn-0.5Zr (ZK60) alloy has attracted extensive attention as one of the hopeful biomedical material candidates for bone implant applications on account of its unique degradability, favorable biocompatibility as well as mechanical compatibility. Nevertheless, the rapid degradation rate in the biological environment is the major hurdle for its clinical application in the field of bone implants. In this study, nanodiamond (ND) was incorporated into ZK60 alloy via selective laser melting technology to enhance its degradation resistance. The results showed that compared with selective laser-melted ZK60 (SLMed ZK60), the selective laser-melted ZK60 with 6 wt.% ND (SLMed ZK60−6ND) possessed the better degradation resistance with the lower degradation rate of 0.5 ± 0.1 mm/year. The enhancement of the degradation resistance was attributed to the fact that ND could promote the deposition of apatite and build up a dense and insoluble protective layer through the dissociation of the carboxyl groups on the ND surface, which could effectively hinder the further degradation of the Mg matrix. Meanwhile, the compressive strength and hardness were improved mainly due to grain refinement strengthening and ND dispersion strengthening. In addition, the SLMed ZK60−6ND possessed good cytocompatibility. These results suggested that the SLMed ZK60−6ND, with enhanced degradation resistance, improved mechanical properties, and good cytocompatibility, was an excellent biomedical material candidate for bone implant applications.
... They have considerable potential for application in transportation, aerospace, electronic technology, and especially biomedicine [3][4][5]. Magnesium alloys have a similar density to human bones and good biocompatibility to be used as human implant materials, which is why they are known as revolutionary metal materials [6][7][8][9][10]. However, the corrosion rate is so fast that many hydrogen bubbles are generated in the human tissue, and the Mg(OH) 2 surface film formed is loose and porous, meaning it has no protective effect during the soaking process [11]. ...
As a kind of potential biomedical material, Mg–Ca alloy has attracted much attention. However, the role of Ca-containing intermetallics in microgalvanic corrosion is still controversial. In 0.6 mol/L NaCl and Na2SO4 solutions, the microgalvanic corrosion behavior of the second phase and Mg matrix of Mg–Ca and Mg–Al–Ca alloys was examined. It was confirmed that the Mg2Ca phase acts as a microanode in microgalvanic corrosion in both NaCl and Na2SO4 solutions, with the Mg matrix acting as the cathode and the Al2Ca phase acting as the microcathode to accelerate corrosion of the adjacent Mg matrix. It was also found that Cl− and SO42− have different sensibilities to microgalvanic corrosion.
... Since the compressive direction is parallel to ED, the c axes of most of the grains are close to being perpendicular to the compressive direction. Thus {1012} extension twins are easy to be activated, which leads to a low CYS value [59][60][61]. Although alloy A3 shows stronger basal texture before the compressive test, its DRXed grains are much smaller than alloy A1 and A2, thus extension twinning is not easy to be activated in these DRXed grains in alloy A3, which lead to a higher CYS value of alloy A3 than alloy A1 and A2. ...
A new type of Mg-Zn-Y-Nd alloy for degradable orthopedic implants was developed. In the present study, the Zn and Y content was adjusted and their influences on the microstructures and mechanical behaviors were discussed in depth. The results showed that the as-extruded Mg-Zn-Y-Nd alloys are mainly composed of fine dynamic recrystallized grains (DRXed grains), large unDRXed grains and linearly distributed secondary phases. The change of Zn content exerts little influence on the grain structure of the extruded Mg-Zn-Y-Nd alloy, while the increase of Y content would hinder the dynamic recrystallization process and the growth of the DRXed grains, thus the size and volume fraction of the equiaxed DRXed grains decrease. The tensile and compressive properties are very little affected by Zn content because of the similar grain structure. As Y content increases, the tensile yield strength (TYS) and ultimate strength (TUS) increase while the elongation decreases, this is caused by a combined strengthening effect of grain refinement, texture, precipitation and twinning. The compressive yield strength (CYS) and ultimate strength (CUS) of Mg-Zn-Y-Nd alloy with different Y content exhibit a similar tendency as the tensile test.
... Today, magnesium (Mg) and its alloys are implantable materials due to their superior biocompatibility and biodegradable properties [1][2][3][4][5]. However, Mg and its alloys degrade too fast due to their lower electrochemical potentials [6,7], limiting their use as implants. ...
Protein exerts a critical influence on the degradation behavior of absorbable magnesium (Mg)-based implants. However, the interaction mechanism between protein and a micro-arc oxidation (MAO) coating on Mg alloys remains unclear. Hereby, a MAO coating was fabricated on AZ31 Mg alloy. And its degradation behavior in phosphate buffer saline (PBS) containing bovine serum albumin (BSA) was investigated and compared with that of the uncoated alloy. Surface morphologies and chemical compositions were studied using Field-emission scanning electron microscope (FE-SEM), Fourier transform infrared spectrophotometer (FT-IR) and X-ray diffraction (XRD). The degradation behavior of the bare Mg alloy and its MAO coating was studied through electrochemical and hydrogen evolution tests. Cytotoxicity assay was applied to evaluate the biocompatibility of Mg alloy substrate and MAO coating. Results indicated that the presence of BSA decreased the degradation rate of Mg alloy substrate because BSA (RCH(NH2)COO‾) molecules combined with Mg²⁺ ions to form (RCH(NH2)COO)2Mg and thus inhibited the dissolution of Mg(OH)2 by impeding the attack of Cl‾ ions. In the case of MAO coated Mg alloy, the adsorption of BSA on MAO coating and the formation of (RCH(NH2)COO)2Mg exhibited a synergistic effect and enhanced the corrosion resistance of the coated alloy significantly. Furthermore, cell bioactive assay suggested that the MAO coating had good viability for MG63 cells due to its high surface area.
Based on first-principles density functional theory, the adhesion, stability and bonding properties of the interfaces between (0001) plane of Mg and (111) plane of oxide (MgO and CaO) were investigated systematically. Meanwhile, the heterogeneous nucleation ability of these oxide particles in Mg melt were elucidated. The results demonstrated that the stability of the O-terminated surface was higher than that of the X-termination of XO(111) surface under high oxidation potential, and the stability of the X-terminated surface gradually increased with decreasing the oxidation potential. The interfacial adhesion work of Mg/XO-O was higher than that of Mg/XO-X in the same stacking order, indicating that the interface stability of Mg/XO-O was higher than Mg/XO-X. In addition, the results of interface local charge function and Bader charge showed that the atomic charges on the Mg(0001) surface would transfer to the oxygen atoms on the o-termination of XO(111) surface to form ionic bond. The ionic bond strength at the Mg/MgO-O interface was higher than ionic bond strength in Mg/CaO-O interface. Therefore, MgO can be used as a more effective nucleation substrate in Mg melt than CaO.
Magnesium alloys have become promising biomedical metal materials because of their biocompatibility, degradability, and good mechanical properties. However, the rapid degradation of magnesium alloys and its associated effects have limited the applications of magnesium alloys. Alloying and preparation processes can reduce the degradation rate by changing the microstructure of magnesium alloys, such as grain size, porosity, formation of intermetallic compounds/second phases, etc. In this paper, the in vitro and in vivo degradation of magnesium alloys were reviewed in terms of degradation mechanism, influencing factors, and corrosion products. Composition design and manufacturing process were mainly discussed for controlling the degradation, and surface treatment and structural design were briefly described as control methods of degradation. This helps achieve the goal of controlled and predictable degradation rate of magnesium alloys.
