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The effect of Al or Cu content on the microstructure and mechanical properties of continuous casting and extrusion Zn alloys has been studied by a room temperature tensile test, X-ray diffraction, and scanning electron microscope. With the increase in Al content, the microstructure of continuous casting and extrusion Zn alloys slightly coarsens, and the lamellar eutectic structure increases. The changes in the above structural factors result in a slight decrease in strength and a significant increase in the elongation of Zn-Al alloys. The strength of Zn alloys increases as the Cu content increases due to the increased content and size of the second phase in the Zn alloys. This means that the mechanical properties of Zn alloys can be adjusted by a continuous casting and extrusion process, and the improvement of equipment capacity can improve the structure and morphology of the alloys. [ABSTRACT FROM AUTHOR]

The effect of Al or Cu content on the microstructure and mechanical properties of continuous casting and extrusion Zn alloys has been studied by a room temperature tensile test, X-ray diffraction, and scanning electron microscope. With the increase in Al content, the microstructure of continuous casting and extrusion Zn alloys slightly coarsens, and the lamellar eutectic structure increases. The changes in the above structural factors result in a slight decrease in strength and a significant increase in the elongation of Zn-Al alloys. The strength of Zn alloys increases as the Cu content increases due to the increased content and size of the second phase in the Zn alloys. This means that the mechanical properties of Zn alloys can be adjusted by a continuous casting and extrusion process, and the improvement of equipment capacity can improve the structure and morphology of the alloys.

A zinc-nutrient element alloy (Zn-1.0Cu-0.5Ca) was developed into subcuticular absorbable staples (SAS) as a robust alternative to the commercially available poly(l-lactide-co-glycolide) (PLGA) SAS for the first time. The fixation properties of the Zn SAS were measured via pull-out tests and in-situ lap-shear pull-out test comparatively against the PLGA SAS. The Zn SAS exhibited fixation force of 18.9±0.2 N, which was over three times higher than that of PLGA SAS (5.5±0.1 N). The Zn SAS was used to close incision wounds in a SD rat model for biodegradability and biocompatibility characterisation at 1, 4 and 12 weeks. The Zn SAS showed uniform degradation behaviour after in vivo implantation at the average rate of 198±54, 112±28, and 70±24 μm/y after 1, 4, and 12 weeks, which reduced the fixation force to 16.8±1.1 N, 15.4±0.9 N, 12.7±0.7 N, respectively. These findings showed the potential of the Zn SAS for the closure of heavy loading and slowing healing tissues. The Zn SAS enabled successful closure and healing of the incision wound, similar to the PLGA staples. However, the slow long-term degradation rate of the Zn SAS may lead to unnecessary implant retention. In addition, the alloy SAS resulted in higher local foreign body responses due to their stiffness. Reducing the implant cross-section profile and applying low stiffness and a corrosion-accelerating coating are suggested as possible approaches to reduce post-service implant retention and improve the biocompatibility of the Zn SAS. This work reports the fabrication of the first metallic subcuticular absorbable staples (SAS) made from Zn Cu Ca alloy for skin wound closure applications. The Zn-based SAS were characterised in vitro and in vivo (SD rat model) for biodegradability, fixation properties, biocompatibility and inflammatory responses, which were compared against the commercially available PLGA-based SAS. The Zn-based SAS provided a secure attachment of the full-thickness wounds on SD rats and allowed successful healing during the 12-week service period. In addition, the in vitro results showed that the Zn-based SAS provided more than three times higher fixation strength than the commercial PLGA, indicating the potential of the Zn-based SAS for load-bearing wound closure application. [Display omitted] [ABSTRACT FROM AUTHOR]

Zinc (Zn) and its alloys are considered as promising biodegradable metals due to its suitable degradability and important physiological functions. However, in the process of degradation, excessive release of Zn ions (Zn2+) will significantly affect the cytocompatibility and antibacterial properties. Surface modification technology can not only control the corrosion behavior of biodegradable metals but also improve its biocompatibility and antibacterial properties according to clinical requirements. In this study, an in-situ hopeite (HP, Zn3(PO4)2·4H2O) coating was prepared on Zn alloy by phosphate chemical conversion (PCC) method using Zn2+ provided by self-corrosion of the substrates. And the effect of phosphating time on the microstructure, phase composition, corrosion resistance, and wettability of HP coatings was investigated. The results showed that a complete HP coating was formed on the Zn alloy after reaction for 1 min, even if Zn2+ were supplied by self-corrosion without an additional Zn source. It also revealed that the reaction time had a marked impact on the morphologies and microstructures of the HP coating. The electrochemical test results proved that the prepared HP coatings had obvious protection on the Zn alloy and could regulate the corrosion rate of the substrate. Meanwhile, the Zn alloy modified by the PCC method also possessed excellent hydrophilicity. These primary findings might support new opportunities in the exploration of controllable coatings on biomedical Zn alloys.

This work aims to investigate the mechanisms responsible for changes in the microstructure and mechanical properties of a low-alloyed Zn–Mg–Ca alloy under two distinct processing techniques of equal-channel angular pressing (ECAP) and rolling. The Zn alloy was subjected to ECAP with various numbers of passes (1p, 4p, and 8p), and rolling with varying reductions (40 %, 60 %, and 80 %) at ambient temperature. The obtained results demonstrate that the Zn alloy exhibits the highest mechanical performance in terms of ultimate tensile strength (UTS) and elongation reaching 317 MPa and 34.5 % at 4p ECAP processing, while the rolled alloy shows enhanced UTS of 282 MPa and the optimum elongation of 42.2 % after 80 % reduction. Under two deformation processes, the differences in dynamic recrystallization (DRX) process are identified. During ECAP, the primary DRX mechanism is continuous dynamic recrystallization (CDRX), while in rolled alloys, the twinning-induced dynamic recrystallization (TDRX) also makes a significant contribution. [ABSTRACT FROM AUTHOR]

Although various biodegradable materials have been investigated for ligament reconstruction fixation in the past decades, only few of them possess a combination of high mechanical properties, appropriate degradation rate, good biocompatibility, and osteogenic effect, thus limiting their clinical applications. A high-strength Zn-0.8Mn-0.4Mg alloy (i.e., Zn08Mn04Mg) with yield strength of 317 MPa was developed to address this issue. The alloy showed good biocompatibility and promising osteogenic effect in vitro. The degradation effects of Zn08Mn04Mg interference screws on the interface between soft tissue and bone were investigated in anterior cruciate ligament (ACL) reconstruction in rabbits. Compared to Ti6Al4V, the Zn alloy screws significantly accelerated the formation of new bone and further induced partial tendon mineralization, which promoted tendon-bone integration. The newly developed screws are believed to facilitate early joint function recovery and rehabilitation training and also avoid screw breakage during insertion, thereby contributing to an extensive clinical prospect. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Zinc (Zn) alloys are receiving increasing attention in the field of biodegradable implant materials due to their unique combination of suitable biodegradability and good biological functionalities. However, the currently existing industrial Zn alloys are not necessarily biocompatible, nor sufficiently mechanically strong and wear-resistant. In this study, a Zn–1Cu–0.1Ti alloy is developed with enhanced mechanical strength, corrosion wear property, biocompatibility, and antibacterial ability for biodegradable implant material applications. HR and HR + CR were performed on the as-cast alloy and its microstructure, mechanical properties, frictional and wear behaviors, corrosion resistance, in vitro cytocompatibility, and antibacterial ability were systematically assessed. The microstructures of the Zn–1Cu–0.1Ti alloy after different deformation conditions included a η-Zn phase, a ε-CuZn 5 phase, and an intermetallic phase of TiZn 16. The HR+CR sample of Zn–1Cu–0.1Ti exhibited a yield strength of 204.2 MPa, an ultimate tensile strength of 249.9 MPa, and an elongation of 75.2%; significantly higher than those of the HR alloy and the AC alloy. The degradation rate in Hanks' solution was 0.029 mm/y for the AC alloy, 0.032 mm/y for the HR+CR alloy, and 0.034 mm/y for the HR alloy. The HR Zn–1Cu–0.1Ti alloy showed the best wear resistance, followed by the AC alloy and the alloy after HR + CR. The extract of the AC Zn–1Cu–0.1Ti alloy showed over 80% cell viability with MC3T3-E1 pre-osteoblast and MG-63 osteosarcoma cells at a concentration of ≤ 25%. The as-cast Zn–1Cu–0.1Ti alloy showed good blood compatibility and antibacterial ability. This work repots a Zn–1Cu–0.1Ti alloy with enhanced mechanical strength, corrosion wear property, biocompatibility, and antibacterial ability for biodegradable implant applications. Our findings showed that Zn–1Cu–0.1Ti after hot-rolling plus cold-rolling exhibited a yield strength of 204.2 MPa, an ultimate tensile strength of 249.9 MPa, an elongation of 75.2%, and a degradation rate of 0.032 mm/y in Hanks' Solution. The hot-rolled Zn–1Cu–0.1Ti showed the best wear resistance. The extract of the as-cast alloy at a concentration of ≤ 25% showed over 80% cell viability with MC3T3-E1 and MG-63 cells. The Zn–1Cu–0.1Ti alloy showed good hemocompatibility and antibacterial ability. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Zinc, as a promising biodegradable metal, has received the attention of many researchers in the medical field. However, zinc-based implants release excessive zinc ions when degraded in the human physiological environment, which in turn leads to high cytotoxicity and low osteogenic capacity. This study aims to further enhance the biocompatibility of zinc alloys while improving their osteogenic properties. For this purpose, calcium-containing phosphate (Ca P) interlayer and polylactic acid (PLA) composite layers with different sealing degrees are prepared on Zn–Mn–Mg alloys by hydrothermal (HT) and dip-coating methods. Results show that the PLA layer is tightly bonded to the Ca P intermediate layer, and it can effectively prevent early damage at the bone implantation site of the Ca P layer on the surface of the zinc alloy. Electrochemical and immersion tests show that the composite layer improves the corrosion resistance of the zinc alloy and that the HT/PLA (12 w / v) coatings show a large Ca P deposition on the surface, which suggests that the composite layer obtained from the preparation has good bioactivity. The HT/PLA (12 w / v) composite layer is the most cytocompatible and more suitable for the attachment of MC3T3-E1 cells among all tested samples. This superiority is manifested by increased survival of MC3T3-E1 cells, good attachment morphology, and highest spreading density. This study provides a certain reference value for surface modification of zinc-based materials, which is favorable for future application in degradable orthopedic surgery. • HT/PLA coatings were prepared on biodegradable Zn-Mn-Mg alloy surfaces by hydrothermal (HT) and dip-coating method. • Polylactic acid can effectively improve the scratch resistance of Ca P layer on Zn-Mn-Mg surface. • The Ca P layer further enhances the bioactivity, adhesion and osteogenic properties of the PLA layer. • The HT/PLA(12 w / v) coating exhibited good adhesion, corrosion resistance and excellent cytocompatibility. [ABSTRACT FROM AUTHOR]

Biodegradable Zn-0.05Mg-(0.5, 1 wt.%) Ag alloy was manufactured by indirectly extruding the alloy ingot at 200 °C with an extrusion ratio of 16:1. Dynamic recrystallization took place during the extrusion process, leading to the formation of equiaxed crystals with twins in both cross-sectional and longitudinal direction. There was no detectable Ag-related phase present except the Mg2Zn11 in the alloys. Tensile strength was increased with an increase in Ag content, reaching 202 MPa when Ag content is 1 wt.%. As-extruded Zn-0.05Mg-0.5Ag showed better corrosion performance with a low corrosion current density of 2.2 A/cm2 and low corrosion rate of 0.15 mm/year. The antibacterial property improved for both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) by addition of Ag. The antibacterial rates were more than 99% when Ag content is up to 1 wt.%. The biodegradable Zn-Mg-Ag alloys with high antibacterial behavior show great potential in medical devices. [ABSTRACT FROM AUTHOR]

The Zn-rich corner of the Zn-Cu-Ti-RE(Ce, La) quaternary systems at 450 °C have been experimentally investigated by scanning electron microscopy coupled with energy dispersive x-ray spectrometer and x-ray diffraction. The liquid containing phase regions have been well identified in these two systems. The ternary compound τ (Cu2TiZn20) can equilibrate with all phases in the Zn-rich corner of these two systems. Neither Ce nor La can dissolve into TiZn16, ε(CuZn4) and τ(Cu2TiZn20). While the solubility of Cu in CeZn11 and LaZn13 can reach 2.9 at.% and 5.0 at.%, respectively. The results can help to design and analyze the Zn-Cu-Ti-RE alloys. [ABSTRACT FROM AUTHOR]

Zn alloys reveal excellent biological degradability and compatibility, suitable mechanical properties, and unique anti-atherosclerotic properties, which make them suited for miniaturized medical implants. Superplastic forming is a promising method to fabricate high-performance microparts with difficult-to-deform materials. However, the effect of grain size on superplasticity in Zn alloys and the underlying mechanisms still need to be determined. In this research, Zn-0.033 Mg (in wt.%) alloy with different grain sizes from 1.53 to 36.17 μm was obtained by equal-channel angular pressing and heat treatment, and its mechanical performance was evaluated by uniaxial tensile tests in the temperature range of 453–533 K and the strain rate range of 0.001–0.01 s−1. Experimental results indicated that the flow stress is significantly reduced with increasing deformation temperature, and the elongation is effectively improved with the reduction in strain rate. Furthermore, the Zn-0.033 Mg alloy with a grain size of 1.53 μm exhibited a superplastic deformation with an elongation of 376 ± 79% at 453 K and 0.001 s−1. Two distinguishing deformation stages were observed during the superplastic deformation. In the early stage, the ∼85 ± 5°/ < 1 ‾ 1 ‾ 20 > twins significantly emerged, leading to subsequent dynamic recrystallization by high-angle grain boundary migration. In the steady-state stage, the non-basal dislocation slip was significantly activated via changing the grain orientation from hard to soft orientation with the aid of continuous dynamic recrystallization. The fracture mechanisms were further discussed based on the fracture surface analysis, indicating that the ultrafine-grained structures can accommodate the nucleation and growth of cavities by grain boundary sliding, enabling low-temperature superplasticity. These findings can grant a new insight and understanding of the superplastic mechanism of Zn alloys and shed light on the manufacture of high-performance Zn alloys for medical implants. [ABSTRACT FROM AUTHOR]

The simulation of heat flow, residual stress, and thermal distortion developed in A36 steel plate using a known volume of Zn brazing alloy for torch brazing technique is presented in this paper. FEHT software and GTstrudle codes were used for the heat transfer and residual stress simulation, respectively. The result of the heat flow simulation showed excessive cooling at the joints corner following convective heat loss to the ambient and maximum heat flux gradient thereby making the joint predisposed to underfill. Also the von misses stress and strain distribution in the plate showed that the residual stress is compressive and is limiting at 1800 N/mm, localized in the joint. This is a basic understanding for impedance to thermally induced cracking. [ABSTRACT FROM AUTHOR]

Zn alloy containing peritectic intermetallic compound usually has fine grains, so they show relatively high strength. But the intermetallic compound is coarse, which is blamed for the brittleness. In this work, a strategy to transform the peritectic intermetallic phase of Zn-Fe alloy into eutectic intermetallic phase is proposed by adding Mn. In detail, Mn co-precipitates with Fe and Zn to form a (Fe, Mn)Zn 13 phase, which provides nucleation substrate and increase the nucleation rate of the MnZn 13 eutectic phase because of their low interatomic and interplanar spacing misfit according to the edge-to-edge matching model. The intermetallic compound formed via eutectic reaction is finer than that formed by peritectic reaction. Results show that the intermetallic in Zn-Fe-Mn is refined by 79% compared with that of Zn-Fe. Moreover, the MnZn 13 phase forms a semi-coherent interface with negligible lattice misfit (0.09%) in (0 1 ¯ 1 1 ¯) orientation with Zn matrix, which is believed to decrease the intergranular fracture ratio. Consequently, Zn-Fe-Mn alloy has a compression yield strength, ultimate tensile strength and elongation of 135.98 MPa, 226.8 MPa, and 15.9%, respectively, which are 28%, 25% and 87% higher than those of Zn-Fe alloy. The strength is improved by dislocation shearing: lattice dislocations cut precipitates to advance through the alloy. The ductility is improved by significantly refined Zn grains, smaller second phase particles and their semi-coherent interfaces with the matrix. • The (Fe, Mn)Zn 13 provides nucleation sites for MnZn 13 phase due to their low interatomic and interplanar spacing misfit. • The MnZn 13 phase forms a semi-coherent interface with negligible lattice misfit in (0 1 ¯ 1 1 ¯) orientation with Zn matrix. • The strength and ductility are respectively improved by dislocation shearing and dislocation transmission. • The present paper put forward a strategy can be applied to other alloys for designing strong yet ductile materials. [ABSTRACT FROM AUTHOR]

Based on the unique properties, nanostructured ZnO could provide a stable immobilization for biomolecules retaining their biological activity. It has been recently developed as a nice candidate for the construction of biosensors with enhanced analytical performance. In this paper, we reviewed the progress in adapting nanostructured ZnO for several predominantly in biosensing applications based on enzymic reaction, immunoreaction, and molecular compitation. We also described several important considerations when working with nanostructured ZnO mainly centered on the fabrications of ZnO and appropriate strategies for biosensor construction (e.g. modified electrodes and multilayered immobilization) [ABSTRACT FROM AUTHOR]

AA7020 Al-Mg-Zn, a medium strength aluminium alloy, is used in welded structures in military and aerospace applications. As it may be subjected to extremes of environmental exposures, including high pressure liquid hydrogen, it could suffer hydrogen embrittlement. Hydrogen susceptibility of alloy AA7020 was evaluated by slow strain-rate tensile testing, and delayed failure testing of hydrogen-charged specimens of air-cooled, duplexaged, and water-quenched duplex agedmaterials. The resistance to hydrogen embrittlement of the alloy was found to be in the order of air-cooled duplex aged alloy > as-received (T6 condition) > water quenched duplex aged material. [ABSTRACT FROM AUTHOR]

Abstract: Novel Zn12Al based composite foams containing hybrid pores were fabricated by stirring technique followed by direct foaming of the composite melt using CaCO3 as a blowing agent. The structures of the composite foams contained pores in two forms. The first one of pores had close cell structure and was entirely contained within the microballoons, which were added into the Zn12Al matrix alloy. The second form of pores was due to releasing of gas because of the decomposing of blowing agent under the influence of heat. The microstructure of the composite foam showed that the interface between the microballoons and Zn12Al alloy matrix was sharp and free from micro porosities, indicating that a good interfacial bonding was developed between the microballoons and Zn12Al alloy. The compressive mechanical responses of Zn12Al and Zn12Al-microballoon foams were investigated at different strain rates (2×10−3, 4×10−3 and 6×10−3 s−1). All the produced foams showed ductile compressive deformation at room temperature. The experimental results showed that the yield, plateau and plastic stress of composite foams were higher than those of Zn12Al foam. The yield, plateau and plastic stress of the composite foams significantly increased with increasing the strain rate. The strain rate sensitivity of the yield and flow stress was noted to be high. The composite foams exhibited higher strain hardening exponent than those of the Zn12Al foams at all strain rates studied in the present work. The energy absorbed during plastic deformation of all the foams significantly increased with increasing the strain rate. The energy absorbed of the Zn12–30vol.% microballoons increased by about 90% with increasing strain rate from 2×10−3 to 6×10−3 s−1. The strain rate sensitivity and absorbed energy of the composite foams were larger than those of the conventional foams, indicating that the foams produced in the present work are suitable candidates for applications wherein the metallic foams are used primarily for their energy absorption capabilities. [Copyright &y& Elsevier]

• Zn-Mn-Mg alloy can effectively reduce the cytotoxicity of pure Zn. • Local corrosion can be avoided by MAO-PLA coatings immersion in SBF solution. • The affection of MC3T3-E1 cell showed that alloying and coating were beneficial to osteogenic properties. Zn has attracted increasing interests as a promising biodegradable metal in the medical field. However, in-vitro experiments show that the high cell cytotoxicity and low osteogenesis of Zn cannot match the requirements in many applications. In this study, a Zn-0.5Mn-0.5Mg alloy was surface modified using micro-arc oxidation (MAO) and sol-gel polylactic acid (PLA) methods to improve the osteogenesis and decrease the toxicity. In-vitro experiments show that the coating can effectively modify the corrosion resistance of the substrate, and substantially increases the viability of cells. In sum, the MAO-PLA surface modification of the Zn-0.5Mn-0.5Mg alloy seems a viable approach to enhance the biocompatibility. [ABSTRACT FROM AUTHOR]

The inhibitive effect of 2-aminothiazole on corrosion of Zn-Al-Cu alloy was investigated in acid, neutral and alkaline media by impedance and polarization techniques. The impedance data were fitted to a simple equivalent circuit model and indicated control by a diffusion process. Satisfactory inhibition was obtained in alkaline and neutral media. On the other hand, quite low inhibition efficiency was observed in acid medium. Increase in concentration of the inhibitor increased the inhibitive effect, whereas the reverse was observed when the temperature was increased. Different adsorption isotherms were tested in neutral and alkaline media, the best fit was obtained for the Freundlich isotherm. The highest value for the free energy change was recorded in alkaline medium in accordance with the high inhibition efficiency observed in this medium. [ABSTRACT FROM AUTHOR]

Poor mechanical strength and creep resistance limit the orthopedic application of biodegradable Zinc (Zn). In present work, cerium (Ce) was alloyed with Zn using laser additive manufacturing technique. As one kind of rare earth element, Ce possessed high surface activity, which effectively interrupted the grain growth and caused the formation of stable intermetallics, thus contributing to grain refinement strengthening and precipitate strengthening. More significantly, Ce alloying activated more pyramidal slip by means of reducing the critical resolved shear stress during plastic deformation, and resultantly formed the sessile dislocations, which caused the accumulated strain hardening and improved the creep resistance. As a result, Zn-Ce alloy exhibited a considerably improved ultimate tensile strength of 247.4 ± 7.2 MPa, and a reduced creep rate of 1.68 × 10−7 s−1. Moreover, it exhibited strong antibacterial activity, as well as favorable cytocompatibility and hemocompatibility. All these results demonstrated the great potential of Zn-Ce alloy as a candidate for bone repair application. [ABSTRACT FROM AUTHOR]

Zamak 3 alloy treatment by sliding-friction treatment (SFT) was investigated by nanoindentation to explore the influence of microstructure and strain rate on nanoscale deformation at room temperature. The results show that obvious material softening occurs in the ultrafine-grained (UFG) Zn alloy and strain-hardening happens in the twinning-deformed layer, respectively. It can be concluded that almost constant values of V in the UFG Zn alloy contribute to the dislocations moving along the grain boundary (GB) not cross the grain interior. In the twinning-deformed layer, the highly frequent dislocation–twinning boundary (TB) interactions are responsible for subsequent inverse Cottrell–Stokes at lower stress, which is quite different from dislocation–dislocation reaction inside the grain in their coarse-grained (CG) counterpart. [ABSTRACT FROM AUTHOR]

FeZn 13 intermetallic compound is the main second phase in recently developed biodegradable Fe-containing Zn alloys, including Zn-Fe, Zn-Mn-Fe and Zn-Cu-Fe alloys. However, knowledge of twinning in FeZn 13 is very limited. In this paper, full elements of {110} twinning in FeZn 13 are solved, including the twinning and the reciprocal twinning planes, the twinning and the reciprocal twinning directions, the shear plane and the shear magnitude. Only two of the former four elements are rational so that {110} twin belongs to Type I twin. The twinning system can be described as {110} < −1, 1, −2.81>. There exist two possible twin variants with a misorientation of <001> 70.94° with respect to the parent crystal. An outer twin leads to a mirror symmetrical shape of FeZn 13 particles, while an inner twin does not change their rhombus-like shape with an acute angle of 70.94°, enclosed by facets parallel to {110}. • Full elements of {110} twinning in FeZn 13 are calculated for the first time. • Twinning can lead to twinned shape of FeZn 13. • FeZn 13 in Zn matrix is enclosed by facets parallel to {110}. [ABSTRACT FROM AUTHOR]