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Additively manufactured (AM) biodegradable zinc (Zn) alloys have recently emerged as promising porous bone-substituting materials, due to their moderate degradation rates, good biocompatibility, geometrically ordered microarchitectures, and bone-mimicking mechanical properties. While AM Zn alloy porous scaffolds mimicking the mechanical properties of trabecular bone have been previously reported, mimicking the mechanical properties of cortical bone remains a formidable challenge. To overcome this challenge, we developed the AM Zn-3Mg alloy. We used laser powder bed fusion to process Zn-3Mg and compared it with pure Zn. The AM Zn-3Mg alloy exhibited significantly refined grains and a unique microstructure with interlaced α-Zn/Mg 2 Zn 11 phases. The compressive properties of the solid Zn-3Mg specimens greatly exceeded their tensile properties, with a compressive yield strength of up to 601 MPa and an ultimate strain of >60 %. We then designed and fabricated functionally graded porous structures with a solid core and achieved cortical bone-mimicking mechanical properties, including a compressive yield strength of >120 MPa and an elastic modulus of ≈20 GPa. The biodegradation rates of the Zn-3Mg specimens were lower than those of pure Zn and could be adjusted by tuning the AM process parameters. The Zn-3Mg specimens also exhibited improved biocompatibility as compared to pure Zn, including higher metabolic activity and enhanced osteogenic behavior of MC3T3 cells cultured with the extracts from the Zn-3Mg alloy specimens. Altogether, these results marked major progress in developing AM porous biodegradable metallic bone substitutes, which paved the way toward clinical adoption of Zn-based scaffolds for the treatment of load-bearing bony defects. STATEMENT OF SIGNIFICANCE: Our study presents a significant advancement in the realm of biodegradable metallic bone substitutes through the development of an additively manufactured Zn-3Mg alloy. This novel alloy showcases refined grains and a distinctive microstructure, enabling the fabrication of functionally graded porous structures with mechanical properties resembling cortical bone. The achieved compressive yield strength and elastic modulus signify a critical leap toward mimicking the mechanical behavior of load-bearing bone. Moreover, our findings reveal tunable biodegradation rates and enhanced biocompatibility compared to pure Zn, emphasizing the potential clinical utility of Zn-based scaffolds for treating load-bearing bony defects. This breakthrough opens doors for the wider adoption of zinc-based materials in regenerative orthopedics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

In this study, Zn-xCu (-0.1 Mg) wires with a diameter of 0.3 mm were obtained by hot extrusion and cold drawing. The microstructures, mechanical properties, and degradation behaviour were investigated to evaluate their feasibility as biodegradable metals. During the drawing process of the Zn-xCu alloys, many granular CuZn 5 phases were dynamically precipitated, and the grains were significantly refined, along with a significant work softening with the tensile strength decreasing and the elongation increasing (from 161 MPa to 92 MPa and 22%-103% for Zn-0.2Cu). With the increase of Cu additions, the phenomenon of work softening was more intense and there was an opposite trend in the strength changes between the as-extruded rods (increase) and as-drawn wires (decrease). With 0.1 wt.% Mg added, the stable rod-like Mg 2 Zn 11 phase was formed in as-extruded Zn-xCu-0.1 Mg rods, which obviously improved the strength, and inhibited the dynamic precipitation of granular CuZn 5 phase and work softening phenomenon in the drawing process (from 332 MPa to 313 MPa and 11%-46% for Zn-0.2Cu-0.1 Mg). In addition, due to the micro-galvanic effect induced by the precipitates, alloying accelerated the degradation of Zn alloy wires, especially Zn-1Cu-0.1 Mg, which was related to the shape, distribution, and potential of the phases.

Zinc (Zn)-based composites have received extensive attention as promising biodegradable materials due to their unique combination of moderate biodegradability, biocompatibility, and functionality. Nevertheless, the low mechanical strength of as-cast Zn-based composites impedes their practical clinical application. Here we reported the mechanical properties, corrosion behavior, wear properties, and cytotoxicity of in situ synthesized biodegradable Zn-xMg 2 Ge (x = 1, 3, and 5 wt.%) composites for bone-implant applications. The mechanical properties of Zn-xMg 2 Ge composites were effectively improved by alloying and hot-rolling due to particle reinforcement of the Mg 2 Ge intermetallic phase and dynamic recrystallization. The hot-rolled (HR) Zn-3Mg 2 Ge composite exhibited the best mechanical properties, including a yield strength of 162.3 MPa, an ultimate tensile strength of 264.3 MPa, an elongation of 10.9%, and a Brinell hardness of 83.9 HB. With an increase in Mg 2 Ge content, the corrosion and degradation rates of the HR Zn-xMg 2 Ge composites gradually increased, while their wear rate decreased and then increased in Hanks' solution. The diluted extract (12.5% concentration) of the HR Zn-3Mg 2 Ge composite showed the highest cell viability compared to the other HR composites and their as-cast pure Zn counterparts. Overall, the HR Zn-3Mg 2 Ge composite can be considered a promising biodegradable Zn-based composite for bone-implant applications. STATEMENT OF SIGNIFICANCE: This paper reports the mechanical properties, corrosion behavior, wear properties, and cytotoxicity of in situ synthesized biodegradable Zn-xMg 2 Ge (x = 1, 3, and 5 wt.%) composites for bone-implant applications. Our findings demonstrated that the mechanical properties of Zn-xMg 2 Ge composites were effectively improved by alloying and hot-rolling due to Mg 2 Ge particle reinforcement and dynamic recrystallization. The hot-rolled Zn-3Mg 2 Ge composite showed superior cytocompatibility, satisfying corrosion and degradation rates, and the best mechanical properties including a yield strength of 162.3 MPa, an ultimate tensile strength of 264.3 MPa, and an elongation of 10.9%., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Fe is considered as a potential candidate for implant materials, but its application is impeded by the low degradation rate. Herein, a dual-phase Fe30Mn6Si alloy was prepared by mechanical alloying (MA). During MA, the motion of dislocations driven by the impact stress promoted the solid solution of Mn in Fe, which transformed α-ferrite into γ-austenite since Mn was an austenite-stabilizing element. Meanwhile, the incorporation of Si decreased the stacking fault energy inside austenite grains, which tangled dislocations into stacking faults and acted as nucleation sites for ε-martensite. Resultantly, Fe30Mn6Si powder had a dual-phase structure composed of 53% γ-austenite and 47% ε-martensite. Afterward, the powders were prepared into implants by selective laser melting. The Fe30Mn6Si alloy had a more negative corrosion potential of -0.76 ± 0.09 V and a higher corrosion current of 30.61 ± 0.41 μA/cm 2 than Fe and Fe30Mn. Besides, the long-term weight loss tests also proved that Fe30Mn6Si had the optimal degradation rate (0.25 ± 0.02 mm/year).

Zinc (Zn) and its alloys have been considered promising absorbable metals for medical implants. However, the dynamic interaction between Zn-based materials and human blood after implantation remains unclear. In this study, a modified Chandler-Loop system was applied to assess the blood compatibility and initial degradation behavior of a Zn-4.0Cu (wt%) alloy (Zn-4Cu) and Zn with human peripheral blood under circulation conditions. In this dynamic in vitro model, the Zn-4Cu and Zn showed sufficient blood compatibility. The numbers of erythrocytes, platelets, and leukocytes were not significantly altered, and appropriate activations of the coagulation and complement system were observed. Concerning initial degradation behavior, the product layers formed on the surfaces comprise a mixture of organic and inorganic compounds while the inorganic constituents decrease toward the outer surface. Considering the corrosion morphology and electrochemical behaviors, Zn-4Cu exhibited milder and more uniform degradation than Zn. Additionally, long-term degradation tests of 28 days in human peripheral blood, human serum, and Dulbecco's phosphate-buffered saline (DPBS) demonstrated that the Zn-4Cu showed relatively uniform degradation in blood and serum. On the contrary, in DPBS, severe localized corrosion appeared along the grain boundary of the secondary phase, which was likely attributed to the acceleration of galvanic corrosion. The Zn was found with localized corrosion impeded in the blood albeit with apparently developed deep pitting holes in the serum and DPBS., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Zn-0.8 wt.% Li-0.1 wt.% Mn wire with the diameter of 0.3 mm was fabricated and further processed into gastrointestinal staple, and its in vitro and in vivo biodegradation behavior and biocompatibility were studied systematically. The experimental Zn-Li-Mn alloy staple could deform from the original U-shape to B-shape without fracture, indicating its good mechanical property. Due to the residual stress concentration caused by anastomosis deformation, the feet and leg arc part of the staple were more prone to degradation. The Zn-Li-Mn alloy staple sustained integrity after immersion in Hanks' solution and simulated gastric fluid (SGF) for 28 days, and the degradation rate in SGF was about 4 times of that in Hanks' solution. Furthermore, Zn-Li-Mn alloy staples were utilized for gastrointestinal anastomosis in pig models, with clinically-used titanium alloy staples as a comparison. No anastomotic leakage and severe inflammation were observed after operation. The Zn-Li-Mn alloy staple maintained mechanical integrity within 8 weeks' implantation. The gastrointestinal tissue healed after 12 weeks, and no obvious side effects were detected during the whole implantation period, demonstrating the good biocompatibility of Zn-Li-Mn alloy staple. Thus, Zn-Li-Mn alloy staple fabricated in this work displayed the promising potential in the gastrointestinal anastomosis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

Zinc (Zn) and its alloys are receiving great attention as promising biodegradable materials due to their suitable corrosion resistance, good biocompatibility, and highly desirable biofunctionality. Nevertheless, the low mechanical strength of pure Zn impedes its practical clinical application and there have been calls for further research into the Zn alloys and thermomechanical processes to enhance their mechanical properties and biocompatibility. Here, we report on the alloying efficacy of rare earth elements (REEs) including erbium (Er), dysprosium (Dy), and holmium (Ho) on the microstructure, mechanical properties, corrosion and wear behavior, and in vitro biological properties of Zn-1Mg-0.1RE alloys. Microstructural characterization revealed that the addition of 0.1 wt.% REEs had a significant refining effect on the grain size of the α-Zn matrix and the second phases of the alloys. Alloying of the REEs and hot-rolling effectively improved the mechanical properties due to both precipitation strengthening of the second phases of ErZn 5 , DyZn 5 , and Ho 2 Zn 17 and grain-refinement strengthening. The highest ultimate tensile strength of 259.4 MPa and yield strength of 234.8 MPa with elongation of 16.8% were achieved in the hot-rolled Zn-1Mg-0.1Ho. Alloying of REEs also improved the wear and corrosion resistance, and slowed down the degradation rate in Hanks' solution. Zn-1Mg-0.1Er showed the highest cytocompatibility of MC3T3-E1 cells cultured directly on the alloy surface and of MG-63 cells cultured in the alloy extract. Zn-1Mg-0.1Dy showed the best anticoagulant property among all the alloys. Overall, these Zn-1Mg-0.1RE (Er, Dy, and Ho) alloys can be considered promising biodegradable metallic materials for orthopedic applications., Competing Interests: Declaration of competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

An Mg-Zn-Ca-Y alloy operative clip was developed to overcome the drawbacks of the Ti clips such as ion dissolution inflammation, interference imaging diagnosis, and the potential harm that permanent retention brings to the patient. The structure optimization design of the hemostatic clip was carried out by the finite element numerical simulation method to realize the matching between the structure design and the material properties. Hot extrusion and wire cutting process was used to prepare the Mg-Zn-Ca-Y alloy operative clip. Corrosion degradation behavior of Mg-Zn-Ca-Y alloy in vitro was investigated using electrochemical noise (EN) and immersion test in Simulated body fluid (SBF). The carotid artery of SD rats was clipped using the Mg-Zn-Ca-Y operative clip to evaluate occlusion safety and the complete corrosion degradation behavior and biocompatibility of Mg-Zn-Ca-Y alloy clip in vivo were investigated using micro-computed tomography, histological analysis, and blood biochemical indicators. It was found that the newly designed Mg-Zn-Ca-Y clip can successfully ligate the carotid artery, and no blood leakage occurred after surgery. After eight months, the Mg-Zn-Ca-Y clip degraded utterly. Histological analysis and various blood biochemical parameters in SD rat serum samples collected at different time periods showed no tissue inflammation around the clips., Competing Interests: Declaration of competing interest The authors declared that they have no conflicts of interest to this work. We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Biodegradable zinc (Zn) and its alloys have great potential to be used for orthopedic applications due to their suitable degradation rate and good biocompatibility. However, pure Zn has insufficient mechanical properties, such as low strength and hardness, and poor plasticity, which limits its clinical applications. Here, we report on a new series of ternary Zn-3Ge-0.5X (X=Cu, Mg, and Fe) alloys aiming to achieve good corrosion resistance and biocompatibility, and enhanced mechanical properties via micro-alloying with copper (Cu), magnesium (Mg), and iron (Fe). Hot-rolling has also been applied to the new ternary alloys to further enhance their mechanical properties. Mechanical testing results indicate that both the strength and hardness of hot-rolled Zn-3Ge are significantly improved with micro-alloying of Cu, Mg, and Fe; of which the hot-rolled Zn-3Ge-0.5Mg exhibits the highest ultimate tensile strength of 253.4 MPa and yield strength of 208.5 MPa among all the alloys, 25.9% and 44.7% higher than those of the hot-rolled Zn-3Ge. The degradation rate of the as-cast alloys is lower than that of the hot-rolled alloys in Hanks' solution for 1 month and the hot-rolled Zn-3Ge-0.5Mg alloy exhibits the highest degradation rate of 0.075 mm/y. CCK-8 assay using MG-63 cells indicates that the diluted extracts of Zn-3Ge-0.5X (X=Cu, Mg, and Fe) alloys with concentrations of 12.5% and 25% exhibit no or slight cytotoxicity, and the diluted extracts of Zn-3Ge-0.5Cu alloys show high cell viability of over 100%, showing the best cytocompatibility., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

The degradation behavior of Mg-4 wt% Zn alloy with three different microstructures was examined in Hank's solution at 37 °C by electrochemical measurements and immersion tests in this study. The results show that the sample with cellular structure exhibits a more positive corrosion potential, lower corrosion current density, larger impedance and more protective film than samples with columnar dendritic and equiaxed dendritic structure. The higher corrosion resistance is attributed to the preferred orientation, eliminating susceptible grain boundaries and reduced secondary phases., (Copyright © 2019. Published by Elsevier B.V.)

Zn-based alloys as biodegradable materials for cardiovascular stents have drawn more and more attention in recent years. However, the hot plastic deformation of Zn-based alloys does not get enough attention. In this study, Zn-3Cu-0.5Fe alloy was prepared and then hot extruded at 140, 180, 220 and 260 °C. Effects of extrusion temperature on the microstructure, mechanical properties and degradation behavior were investigated. Nano-scaled particles precipitated during extrusion and the quantity decreased with the increasing of extrusion temperature. As the extrusion temperature increased from 140 to 260 °C, the grain size increased from 1.15 to 4.38 μm, the yield strength and ultimate tensile strength increased from 203 ± 3.23 and 221 ± 1.56 MPa to 269 ± 2.65 and 302 ± 8.01 MPa, increased by 32.5% and 45%, while the degradation rate was decreased gradually from 62.8 ± 0.72 μm/year to 49.9 ± 3.35 μm/year, decreased by 20.5%. In addition, the degradation behavior changes from a relatively uniform degradation mode to a localized degradation mode with the increase of the grain size. Dislocation gliding is replaced by grain-boundary movement and dynamic recrystallization (DRX) in the room temperature tensile deformation process. Lower extrusion temperature is beneficial for higher elongation and degradation rate as well as relatively uniform degradation mode, which is better suitable for the clinical application of cardiovascular stents., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The orthopedic application of Zn is limited owing to the poor strength and low plasticity. In this study, a novel strategy by combining rapid solidification obtained by selective laser melting (SLM) and alloying with Mg was proposed to improve the mechanical properties of Zn. The microstructures, mechanical properties, as well as in vitro cytocompatibility of SLM processed Zn-xMg (x = 0-4 wt%) were studied systematically. Results shown that SLM processed Zn-xMg alloys consisted of fine equiaxed α-Zn grains with homogeneously precipitated Mg 2 Zn 11 along grain boundaries. More importantly, the grains size of α-Zn was decreased from 104.4 ± 30.4 µm to 4.9 ± 1.4 µm with Mg increasing. And Mg mainly dissolved in α-Zn developing into supersaturated solid solution due to rapid solidification effect. As a consequence, the ultimate tensile strength and elongation were enhanced by 361% and 423%, respectively, with Mg containing up to 3 wt%. Meanwhile, alloying with Mg enhanced the corrosion resistance of Zn, with the degradation rate decreasing from 0.18 ± 0.03 mm year -1 to 0.10 ± 0.04 mm year -1 . Furthermore, SLM processed Zn-xMg exhibited good biocompatibility. This research suggested that SLM processed Zn-3Mg alloy was a potential biomaterial for orthopedic applications., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objectives: As promising alternative to current metallic biomaterials, the porous Mg scaffold with a 3-D open-pore framework has drawn much attention in recent years due to its suitable biodegradation, biocompatibility, and mechanical properties for human bones. This experiment's aim is to study the mechanical properties, biosafety, and osteogenesis of porous Mg-Zn alloy., Methods: A porous Mg-2Zn-0.3Ca (wt%) alloy was successfully prepared by infiltration casting, and the size of NaCl particles was detected by a laser particle size analyzer. The microstructure of the Mg-2Zn-0.3Ca alloy was characterized by the stereoscopic microscope and Sirion Field emission scanning electron microscope. X-ray computerized tomography scanning (x-CT) was used to create the 3-D image. The degradation rate was measured using the mass loss method and the pH values were determined together. The engineering stress-strain curve, compressive modulus, and yield strength were tested next. The bone marrow stromal cells (BMSC) were cultured in vitro. The CCK-8 method was used to detect the proliferation of the BMSC. Alkaline phosphatase (ALP) and alizarin red staining were used to reflect the differentiation effects. After co-culturing, cell growth on the material's surface was observed by scanning electron microscope (SEM). The cell adhesion was tested by confocal microscopy., Results: The obtained results showed that by using near-spherical NaCl filling particles, the porous Mg alloy formed complete open-cell foam with a very uniform size of pores in the range of 500-600 μm. Benefitting from the small size and uniform distribution of pores, the present porous alloy exhibited a very high porosity, up to 80%, and compressive yield strength up to 6.5 MPa. The degradation test showed that both the pH and the mass loss rate had similar change tendency, with a rapid rise in the early stage for 1-2 day's immersion and subsequently remaining smooth after 3 days. In vitro cytocompatibility trials demonstrated that in comparison with Ti, the porous alloy accelerated proliferation in 1, 3, 5, and 7 days (P < 0.001), and the osteogenic differentiation test showed that the ALP activity in the experimental group was significantly higher (P = 0.017) and has more osteogenesis nodules. Cell adhesion testing showed good osteoconductivity by more BMSC adhesion around the holes. The confocal microscopy results showed that cells in porous Mg-based alloy had better cytoskeletal morphology and were larger in number than in titanium., Conclusions: These results indicated that this porous Mg-based alloy fabricated by infiltration casting shows great mechanical properties and biocompatibilities, and it has potential as an ideal bone tissue engineering scaffold material for bone regeneration., (© 2018 Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.)

Mg–Ag alloy has potential as a material for bone tissue repair, but the faster degradation rate in vivo limits its use in medical applications. In this study, pure Mg and Mg99.5Ag0.5 alloy with a porous structure are prepared using the metal/gas eutectic unidirectional solidification method (Gasar process). The influence of introducing Ag on the degradation behavior of porous Mg99.5Ag0.5 and pure Mg is investigated. The addition of Ag increases the compressive strength and elastic modulus of the material. The corrosion resistance of as‐cast Mg99.5Ag0.5 alloy decreases due to localized aggregation of Ag in the alloys. Therefore, the T4 (solution treatment) is chosen for the Mg99.5Ag0.5 alloy. After T4 treatment, due to the uniform distribution of Ag atoms in the alloy, the corrosion behavior on the alloy surface is more uniform, and a denser Mg(OH)2 passivation layer is formed on the surface, which reduces the degradation rate of Mg99.5Ag0.5. Importantly, insoluble Ca–P compounds in the form of hydroxyapatite (HA) phases gradually grown on passivated layers of porous T4 Mg99.5Ag0.5 contribute to bone growth. This indicates the feasibility of using the T4 Gasar porous Mg99.5Ag0.5 alloy as a potential tissue engineering scaffold. [ABSTRACT FROM AUTHOR]

• Radial compressive stress was introduced in the degradation test of mg microtubes. • Dynamic medium and radial compressive stress accelerate mg microtubes degradation. • The degradation mechanism of mg microtube under different environments was proposed. The degradation of Mg alloys relates to the service performance of Mg alloy biodegradable implants. In order to investigate the degradation behavior of Mg alloys as vascular stent materials in the near service environment, the hot-extruded fine-grained Mg-Zn-Y-Nd alloy microtubes, which are employed to manufacture vascular stents, were tested under radial compressive stress in the dynamic Hanks' Balanced Salt Solution (HBSS). The results revealed that the high flow rate accelerates the degradation of Mg alloy microtubes and its degradation is sensitive to radial compressive stress. These results contribute to understanding the service performance of Mg alloys as vascular stent materials. [ABSTRACT FROM AUTHOR]

In this paper, in order to achieve the development of a novel biodegradable dual-phase alloy in a Ca–Mg–Zn system, the establishment of the control strategy of degradation behavior of alloys composed of two phases was attempted by the control of alloy composition, constituent phases, and microstructure. By combining two phases with different dissolution behavior, biodegradable alloys are expected to exhibit multiple functions. For example, combining a suitable slow dissolving phase with a faster dissolving second phase may allow for dynamical concavities formation during immersion on the surface of the alloy, assisting the invasion and establishment of bone cells. Without the careful control of the microstructure, however, there is a risk that such dual-phase alloy rapidly collapses before the healing of the affected area. In this study, ten two-phase alloys consisting of various different phases were prepared and their degradation behaviors were examined. Consequently, it was found that by combining the IM3 and IM1 intermetallic phases with the compositions of Ca2Mg5Zn13 and Ca3Mg4.6Zn10.4, the expected degradation behavior can be obtained. [ABSTRACT FROM AUTHOR]

Zn alloys have attracted considerable attention owing to their favorable biocompatibility, mechanical strength, and corrosion resistance. Such outstanding biodegradable metallic materials may also have potential practical applications in biomedicine. By means of microstructure characterization, immersion corrosion tests, and electrochemical measurement, this study researched into the effect of homogenization treatment on the microstructure and in vitro degradation behavior of a novel biodegradable Zn-Mg-Sr alloy. The experimental results indicated serious dendritic segregation in the as-cast Zn-Mg-Sr alloy. The metallic phases in the as-cast Zn-Mg-Sr alloy were non-equilibrium MgZn2, Sr-rich SrZn13, and equilibrium Mg2Zn11. By raising the homogenization temperature or lengthening soaking time, the non-equilibrium MgZn2 and SrZn13 gradually dissolved into the Zn matrix, and the dendritic segregation was mostly eliminated. Compared with as-cast Zn-Mg-Sr alloys, homogenized alloys exhibited a slower degradation rate and better pitting corrosion resistance. Based on the experimental results and homogenization kinetic analysis, the optimum homogenizing parameters for the biodegradable Zn-Mg-Sr alloy were 350 °C and 24 h, so the corresponding degradation rate was 0.083 mm/year. [ABSTRACT FROM AUTHOR]

The real physiological environment of the human body is complicated, with different degrees and forms of loads applied to biomedical implants caused by the daily life of the patients, which will definitely influence the degradation behaviors of Mg-based biodegradable implants. In the present study, the degradation behaviors of modified WE43 alloys under the combination of torsional and tensile stress were systematically investigated. Slow strain rate tensile tests revealed that the simulated body fluid (SBF) solution could deteriorate the ultimate tensile stress of WE43 alloy from 210.1 MPa to 169.2 MPa. In the meantime, the fracture surface of the specimens tested in the SBF showed an intergranular corrosion morphology in the marginal region, while the central area appeared not to have been affected by the corrosive media. The bio-degradation performances under the combination of torsional and tensile stressed conditions were much more severe than those under unstressed conditions or single tensile stressed situations. The combination of 40 MPa tensile and 40 MPa torsional stress resulted in a degradation rate over 20 mm/y, which was much higher than those under 80 MPa single tensile stress (4.5 mm/y) or 80 MPa single torsional stress (13.1 mm/y). The dynamic formation and destruction mechanism of the protective corrosion products film on the modified WE43 alloy could attribute to the exacerbated degradation performance and the unique corrosion morphology. The dynamic environment and multi-directional loading could severely accelerate the degradation process of modified WE43 alloy. Therefore, the SCC susceptibility derived from a single directional test may be not suitable for practical purposes. Complex external stress was necessary to simulate the in vivo environment for the development of biodegradable Mg-based implants for clinical applications. [ABSTRACT FROM AUTHOR]

Zinc (Zn)-based metals and alloys are emerging as promising biodegradable implant materials due to their inherent biodegradability and good biocompatibility. However, this class of materials exhibits low mechanical strength and a slow degradation rate, which hinders their clinical application. Here we report the development of a new biodegradable Fe/Zn–3Cu composite fabricated by infiltration casting of a Zn–3Cu alloy into an Fe foam followed by hot-rolling. Our results indicate that the hot-rolled (HR) Fe/Zn–3Cu composite exhibited an α-Zn matrix phase, a secondary CuZn 5 phase, and an α-Fe phase. The HR Fe/Zn–3Cu composite exhibited an ultimate tensile strength of 269 MPa, a tensile yield strength of 210 MPa, and an elongation of 27%. The HR Fe/Zn–3Cu composite showed a degradation rate of 228 µm/year after immersion in Hanks' solution for 30 d The diluted extract of the HR Fe/Zn–3Cu composite exhibited a higher cell viability than that of the HR Zn–3Cu alloy in relation to MC3T3-E1 and MG-63 cells. Furthermore, the HR Fe/Zn–3Cu composite showed significantly better antibacterial ability than that of the HR Zn–3Cu alloy in relation to S. aureus. Overall, the HR Fe/Zn–3Cu composite can be anticipated to be a promising biodegradable implant material for bone-fixation applications. This work reports a new biodegradable Fe/Zn–3Cu composite fabricated by infiltration casting and followed by hot-rolling for biodegradable bone-fixation application. Our findings demonstrated that the hot-rolled (HR) Fe/Zn–3Cu composite exhibited an ultimate tensile strength of 269.1 MPa, a tensile yield strength of 210.3 MPa, and an elongation of 26.7%. HR Fe/Zn–3Cu composite showed a degradation rate of 227.6 µm/a, higher than HR Zn–3Cu alloy after immersion in Hanks' solution for 30 d The diluted extracts of the HR Fe/Zn–3Cu composite exhibited a higher cell viability than HR Zn–3Cu alloy toward MC3T3-E1 cells. Furthermore, the HR Fe/Zn–3Cu composite showed significantly better antibacterial ability than the HR Zn–3Cu alloy toward S. aureus. [Display omitted] [ABSTRACT FROM AUTHOR]

Degradable materials with low density exhibit unique applications in the petroleum equipment field. Herein, hollow glass microspheres (HGM)‐reinforced Mg alloy degradable composites are fabricated. The microstructure and degradation behavior of the composites are investigated using scanning electron microscopy, immersion tests, and electrochemical measurements. Then the influence mechanisms of the HGM on the degradation property of composites are further revealed. The results show that the addition of the HGM significantly reduces the density of the composites. Different degrees of chemical reaction between the Mg alloy melt and HGM wall happen during the fabrication of the composites, resulting in the formation of MgO and Mg2Si. From the corrosive morphologies of the composites, Mg2Si phase can serve as a microgalvanic cathode consequently inducing more galvanic corrosion. The interface between HGM and matrix alloy can serve as the initiation site for pitting corrosion and increase the exposed area of the matrix in the aggressive medium. The electrochemical measurements prove that the HGM can act a part in facilitating the exfoliation of degradation products. Consequently, the HGM greatly increases the degradation rate of the composites in the KCl solution. The current study provides a new insight for developing lightweight Mg‐based composites with quickly degradable performance. [ABSTRACT FROM AUTHOR]

• Boron affects the metabolism of sugar, protein and fat and has estrogenic effects. • This paper adopts the metal mold gravity casting to prepare Zn-4Al-xB alloy. • The η (Zn) and α (Al) + η (Zn) layered structure are refined. • The elongation of Zn-4Al-0.15B is 0.92%, about three times of without B addition. • The corrosion rate is 32.7 μm/year, 1/3 of the value of alloy without B addition. The effect of B addition on the microstructure, mechanical properties, and in vitro degradation behavior of Zn-3.5Al alloy was studied using Zn-3.5Al as the matrix alloy. The results indicate that the dendrites η (Zn) and eutectic structure α (Al) + η (Zn) layered structure are refined with B addition. As the amount of B element addition increases, the tensile strength and corrosion rate of zinc alloy decrease, while the elongation increases. When the amount of B element added is 0.15 wt%, the tensile strength of zinc alloy is 182 MPa, and the elongation is 0.92 %, which is about three times that of the zinc alloy without B addition. The corrosion rate is 32.7 μm/year, approximately one-third of the value of alloy without B addition. [ABSTRACT FROM AUTHOR]

Considering the remarkable function of silicon in the development and growth of connective tissue and bone, building the immune system, and tissue healing, together with its positive effects on improving mechanical and degradation behavior of magnesium alloys, Mg–Si alloys can be a promising alloying system for making biodegradable implants. However, the morphology, size, and distribution of Mg 2 Si particles, as the only intermetallic phase in Mg–Si alloys, can affect the corrosion behavior of these alloys significantly. Therefore, in this investigation, the effects of Y addition (0.5 wt%) and heat treatment (HT, at 420 °C for 24 h) on degradation behavior of two hypo-eutectic Mg–1Si and hyper-eutectic Mg–2Si alloys are studied by hydrogen evolution, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) tests, all done in phosphate-buffered saline (PBS) solution. Also, the appearance of the corroded surfaces of the studied alloys after electrochemical and immersion tests was evaluated by scanning electron microscopy equipped with electron disperse spectroscopy. It was found that Y addition to the as-cast Mg–1Si alloy increased the corrosion resistance, corresponding to a decrease in the corrosion current density (I corr) from 5.60 to 3.24 μA/cm2. On the contrary, the addition of Y to the as-cast Mg–2Si alloy did not significantly change the corrosion resistance. In addition, it was found that after applying HT on the as-cast Mg–1Si and Mg–2Si alloys, corrosion resistance was improved, which was mainly attributed to the modified eutectic Mg 2 Si particles. • Y addition and heat treatment could modify the coarse laminated eutectic Mg 2 Si phase to very short rods. • Y addition could enhance the corrosion resistance of the as-cast Mg–1Si alloy. • Corrosion resistance of both the as-cast Mg–1Si and Mg–2Si alloys was improved after heat treatment. [ABSTRACT FROM AUTHOR]

Binary Zn–Mg alloys have great potential as biodegradable implants due to their good biological safety and moderate degradation rates. Herein, a new combined process of ECAP plus cold rolling of as-cast Zn–0.6Mg alloy was developed to address its application problem of insufficient mechanical properties and serious localized corrosion. Cold rolling process can break the eutectic phase and refine grains, while deformed grains were dominant with a lot of dislocations. 8-pass ECAP process can refine grains by recrystallization, and the grains were equiaxed with less dislocations. The strength and ductility were greatly improved after cold rolling (CR) or ECAP processing compared with that of as-cast alloy, but the strength still cannot meet the requirement of orthopedic implant materials. After 8-pass ECAP+CR75% (ER) processing, the strength was further improved, which benefited from fine grain strengthening, second phase strengthening, and strain strengthening mechanisms. Tensile yield strength (σ YS), ultimate tensile strength (σ UTS), and fractured elongation of ER alloy were 301.2 MPa, 411.8 MPa, and 28.5%, respectively, which can meet the requirement of orthopedic implants. The eutectic phase fragmentation and grain refinement caused by cold rolling and ECAP process can reduce the galvanic corrosion tendency of the Zn–0.6Mg alloy. The corrosion resistance was further improved after 8-pass ECAP+CR75% processing with the degradation rate of 0.025 mm/y, and the alloy tended to corrode uniformly. • A new combined process of ECAP plus cold rolling (CR) of as-cast Zn-0.6Mg alloy was developed. • 8-pass ECAP+CR75% processing can refine grains and break eutectic phase of Zn-0.6Mg alloy greatly. • The mechanical properties of 8-pass ECAP+CR75% processed Zn-0.6Mg alloy were superior in Zn-Mg alloys. • The 8-pass ECAP+CR75% processed Zn-0.6Mg alloy tended to corrode uniformly. [ABSTRACT FROM AUTHOR]

• AlCrFeMnTiZr 0.5 HEA powder photocatalyst is prepared by mechanical alloying. • AlCrFeMnTiZr 0.5 catalyst exhibits good malachite green degradation under light. • Nano-reactants are mainly oxides or hydroxides of Al and Mn after catalysis. • Nanoparticles and nanosheets covering surface promote adsorption and degradation of MG. • Exfoliated nano-reactants and exposed fresh surface enhance degradation reusability. This work reports that the mechanical alloyed AlFeMnCrTiZr 0.5 high-entropy alloy (HEA) powder was used as catalyst for malachite green (MG) degradation. The HEA with dual solid solutions shows good catalytic performance under visible light. Its efficiency of reaching degradation saturation and maximum degradation rate are much greater than those of Fe0 powder. The oxides or hydroxides of Al and Mn nucleate and grow on the powder surface, existing in the form of initial nanoparticles and growing nanosheets, which promote the adsorption and catalytic degradation of MG. The exfoliated nanoreactants and exposed fresh powder surface of catalyst enhance the reusability and sustainability of degradation. The catalytic mechanism is mainly visualized by the synergy of chemical dye decomposition and physical dye adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • Design degradable Mg-2Zn-0.2Zr- x Sc (ZK- x Sc, x = 0, 0.2, 0.4, 0.6, 0.8, wt.%) alloys as potential implants. • Investigate the effect of alloying element (Sc) on microstructure, degradation behavior and mechanical property of as-extruded ZK alloy. • The addition of Sc in ZK alloy decreases the degradation rate and improves the ultimate tensile strength. • Provide a better understanding on Sc as alloying elements for biomedical Mg alloys with superior mechanical property, slower degradation rate and good biocompatibility. Microstructure, degradation behavior in vitro and mechanical property of as-extruded Mg-2Zn-0.2Zr- x Sc (x = 0, 0.2, 0.4, 0.6, 0.8, wt.%) alloys was investigated. Fine rod-like Mg(Zn,Sc,Zr) phase in as-extruded ZK-(0.4–0.8)Sc alloys inhibits recrystallized grains growth, resulting in grain refinement. The addition of Sc decreases the degradation rate in vitro and improves the mechanical property of ZK20 alloy. All tested alloys had no cytotoxicity effect on HUVEC and MC3T3-E1 cells. This work provides a better understanding on adding Sc as alloying element for biomedical Mg alloys with superior mechanical property, slower degradation rate and good biocompatibility. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemical degradation behavior of new Ca-Sr-Mg alloy is studied in Hanks' solution. • Silicate anodized surface increases the alloy total resistance (R t) in the blank (H0) solution. • Addition of 4.0 g L−1 BSA (H4.0 solution) accelerates the corrosion rate and decreases R t. • Compared to H4.0, in the H6.0 solution R t value of the pristine surface is improved. • Anodization can slow down the corrosion rate in H4.0 solution after 24 h immersion. Recently, magnesium alloys have been intensively studied for their potential usage as bioabsorbable medical implants. Herein, in vitro degradation behavior of a new Mg alloy (AXJ530) was investigated under different conditions in Hanks' solution at 37 °C and pH 7.4 using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP). Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques were also applied to characterize the morphological and chemical composition of the alloy surface immersed in different solutions. The alloy was first examined as abraded surface, and after it was anodized in 0.1 mol L−1 Na 2 SiO 3 at a controlled potential of 1.0 V (vs. SCE) for 10 min. The results confirmed that anodization is sufficient to obtain a protective biocompatible thin film from silicate coating with better corrosion resistance of 0.67 ± 0.03 kΩ cm2, almost twice higher than of the pristine surface after 24 h immersion. Secondly, the influence of bovine serum albumin (BSA) at two different doses on the degradation behavior of the bare alloy surface was also studied. The results revealed a decrease in the degradation rate with raising the protein content from 4.0 g L−1 to 6.0 g L−1. Finally, the synergetic influence of the thin silicate anodic coating on the degradation behavior of the alloy was scrutinized in Hanks' solution containing the lower BSA dose. The results suggested that silicate coating could be effective in suppressing the high degradation rate of AXJ530 Mg alloy as an absorbable implant. [ABSTRACT FROM AUTHOR]