关键词： CSBD   cerabone   magnesium alloy   bone regeneration   osteoconduction  

摘要： Xenogeneic biomaterials Cerbone(R) and OsteoBiol(R) are widely used in oral implantology. In dental practice, xenogeneic biomaterial is usually combined with autologous bone to provide bone volume stability needed for long-term dental implants. Magnesium alloy implants dissolve and form mineral corrosion layer that is directly in contact with bone tissue, allowing deposition of the newly formed bone. CSBD heals by intramembranous ossification and therefore is a convenient model for analyses of ostoconductive and osteoinductive properties of different type of biomaterials. Magnesium alloy-enriched biomaterials have not yet been applied in oral implantology. Therefore, the aim of the current study was to investigate biological properties of potentially new bovine xenogeneic biomaterial enriched with magnesium alloy in a 5 mm CSBD model. Osteoconductive properties of Cerabone(R), Cerabone(R) + Al. bone, and OsteoBiol(R) were also analyzed. Dynamics of bone healing was followed up on the days 3, 7, 15, 21, and 30. Calvary bone samples were analyzed by micro-CT, and values of the bone morphometric parameters were assessed. Bone samples were further processed for histological and immunohistochemical analyses. Histological observation revealed CSBD closure at day 30 of the given xenogeneic biomaterial groups, with the exception of the control group. TNF-alpha showed high intensity of expression at the sites of MSC clusters that underwent ossification. Osx was expressed in pre-osteoblasts, which were differentiated into mature osteoblasts and osteocytes. Results of the micro-CT analyses showed linear increase in bone volume of all xenogeneic biomaterial groups and also in the control. The highest average values of bone volume were found for the Cerabone(R) + Mg group. In addition, less residual biomaterial was estimated in the Cerabone(R) + Mg group than in the Cerabone(R) group, indicating its better biodegradation during CSBD healing. Overall, the magnesium alloy xenogene

关键词： AZ31 magnesium alloy   Extrusion   Shearing   Tube   Finite element method   Microstructure   Experiment and simulation   Grain refinement  

摘要： This paper presents a new forming technology for manufacturing the AZ31 magnesium alloy thin-wall tube. The direct extrusion process and continuous shearing-bending process are combined to produce thin-wall magnesium tube, abbreviated as "TESB" (tube extrusion-shearing-bending). The process has been studied based on the combination of experiments and numerical simulations, and the influences of temperatures, extrusion stresses, and friction factors on the forming process have been studied by Deform-3D simulation. And the mechanical properties and the grain size of the formed product have been tested. TESB technology has been proved to refine the grains of magnesium alloy tube effectively, and the mechanical property of the product can be improved. The better experimental extrusion conditions were also obtained by simulation, and the properties of the products under the condition of lubrication were better when the temperature was 400 degrees C. Three-dimensional finite element modeling is used to investigate the plastic deformation behaviors of wrought magnesium alloy during TESB process. Numerical results indicate TES could increase the cumulative strains effectively by direct extrusion and additional shearings. Experiments show that microstructures of magnesium alloy fabricated by TESB process can be refined to 50% of the original grain size with more uniform distribution. TES process could improve hardness of magnesium alloy obviously by comparing with which fabricated by direct extrusion.

关键词： Novel CECAP process   AM60 alloy   Grain refinement   Mechanical properties   Microstructure  

摘要： The mechanical properties and microstructure of AM60 Magnesium alloy processed by a new cyclic extrusion channel angular pressing (CECAP) technique were investigated in this research. In this novel method, a low extrusion ratio stage was added at the end of the CECAP process to enhance the hydrostatic stresses and equivalent strain. The structure was refined from the average grain size of similar to 76 mu m for the annealed samples to 2.63 mu m in the new CECAP after four passes. While for the CECAP and ECAP processes, it was 3.43 and 6.98 mu m, respectively. Experimental results of the proposed CECAP process showed an improvement in the mechanical properties after the second pass that were stopped for the ECAP process. However, the hardness of the CECAP-processed and proposed samples was constantly increasing. This increase in hardness was 196% and 175% for the proposed CECAP and CECAP processes after four passes compared to the unprocessed sample, respectively. Moreover, the compressive yield stress and ultimate compressive strength of the CECAP-processed samples were higher in all passes;however, they were smaller than those of the proposed CECAP process. The hydrostatic compressive stresses and higher plastic strain in the proposed technique helped in further refining of the grains, which can effectively improve the mechanical properties.

关键词： Magnesium alloys  

摘要： In this research, cast magnesium alloys AZ31-xGd are assessed as anode material candidates for primary Mg-air batteries. The effects of Gd content in the microstructure, discharge behavior and electrochemical properties of cast AZ31 as an anode are studied through microstructure characterization, electrochemical measurements and battery discharge tests. Results indicate that the introduction of Gd can refine alpha-Mg grains. The discharge and electrochemical properties of magnesium alloys are improved by optimizing its composition. We confirm that the Al2Gd can restrain the kinetics of hydrogen evolution reaction. The acicular structure can connect the magnesium alloy matrix and reduce the chunk spalling. The data suggest that AZ31-5.8Gd alloy has the best self-corrosion resistance performance and discharge behavior among all prepared AZ31-xGd alloys. AZ31-5.8Gd can output a high specific capacity of 1411.8 mAh g(-1) and a high energy density of 1153 mWh g(-1) at the current density of 40 mA cm(-2). The anode efficiency can reach up to 63.21%. The addition of Gd properly can optimize magnesium alloy microstructure and improve the discharge performance. [GRAPHICS] .

关键词： Room temperature  

摘要： Magnesium (Mg) alloys, as one of the lightest structural metallic materials, have attracted considerable attention in the automotive, aerospace, and microelectronic industries. However, wrought Mg alloys are easy to form a strong basal texture with the basal planes of hexagonal close-packed unit cells being parallel to the processing direction during hot processing. This extremely deteriorates the stretch formability of Mg alloy sheets at room temperature (RT) and limits their widespread industrial applications. To overcome this drawback, many studies have been devoted to controlling microstructures including grain sizes, texture characteristics and precipitates to achieve high-performance Mg alloy sheets via alloying and new processing techniques. In this review, we briefly summarize recent advances in enhancing the stretch formability of Mg alloy sheets at RT from two major aspects: (1) by the design of new alloy systems and (2) by the exploitation of advanced processing techniques. Both strategies hold great promise for developing high-performance and low-cost Mg alloy sheets with a superior combination of strength, ductility and stretch formability. Additionally, future research directions for the development of such high-performance Mg alloy sheets are suggested. We hope that this review can provide some insightful information for researchers who are committed to fabricating high-performance Mg alloys for lightweight structural applications in the transportation industry, so as to improve fuel efficiency and reduce climate-changing and health-compromising emissions.

关键词： AZ91D mg alloy substrate   cold-sprayed al coating   corrosion resistance   friction stir-spot-processing   intermetallic compounds   microhardness  

摘要： Magnesium-based alloys are appropriate materials for transportation applications owing to their high strength-to-weight ratio. However, the poor corrosion performance of Mg alloy limits its lifetime. In this study, the pure Al coating was deposited onto an AZ91D substrate by cold spraying, and then modified by friction stir-spot-processing. The interfacial microstructure and phase were studied in detail, and the effect of the intermetallic compounds on the microhardness and corrosion properties of the coatings was investigated. Results show that the sound and dense coatings were obtained after friction stir-spot-processing at 2400 and 2700 rpm. Al12Mg17 was found in the upper part of the 1/2 radius zone in the processed coating. The thin and thick IMCs were identified at the interface in the center and 1/2 radius areas, respectively. In the thick IMCs, mainly two types of multi-phase coexistence structures were observed. The four-phase coexistence structure dominated by Al3Mg2 revealed a higher microhardness than the three-phase coexistence structure dominated by Al12Mg17. In the processed coating, the upper part of the 1/2 radius zone containing Al12Mg17 exhibited a higher microhardness than the center zone. Moreover, the cold-sprayed Al coating provided more effective corrosion protection for the AZ91D substrate after FSSP.

关键词： Annealed extruded magnesium alloy   Proportional loading   Non-proportional loading   Subsequent yield loci   Kinematic & isotropic hardening  

摘要： This investigation reports for the first time, the subsequent yield loci after finite plastic deformation based on 10 mu epsilon offset definition yield of an annealed extruded AZ31 magnesium alloy under proportional and non-proportional loading paths. The proportional loading paths comprise uniaxial tension, free end torsion, and combined tension-torsion radial paths. The tension loading followed by torsion, and torsion followed by tension are the non-proportional loading paths. Subsequent yield loci under proportional loading paths show a prominent nose in the loading direction and are almost flat in the unloading direction with evolution of significant isotropic hardening under tension and visible kinematic hardening under torsion loading path. Strong path-dependency is observed in subsequent yield loci under non-proportional loading directions along with hardening effects. All the yield loci are investigated in tension-torsion (sigma 11-root 3 sigma 12) stress space. The results are significantly different than observed for other metals, especially for aluminum alloys by Khan et al. (2009) and Iftikhar et al. (2021). Elastic moduli within each subsequent yield loci are also measured during these experiments with the increase in plastic strain. The observed small decreases in the elastic moduli with increasing plastic strains are very similar to the ones reported earlier (Iftikhar et al., 2021;Khan et al., 2009).

关键词： Initial orientation   AZ80 magnesium alloy   Simulated body fluid   Corrosion behavior   Texture  

摘要： Three different orientation specimens (P-ND30, P-ND60 and P-TD) prepared from the rolled AZ80 magnesium alloy plates were immersed in simulated body fluid (SBF) for 384 h. Electrochemical impedance spectroscopy (EIS) tests were measured at 24 h, 96 h, 192 h, 288 h, and 384 h during immersion. The corrosion morphology and chemical composition of the three orientation specimens were investigated using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). X-ray diffractometer (XRD) was used to evaluate the phase composition of the surface of the specimen at different immersion stages. The results indicated that the P-ND30 and P-ND60 specimens had similar corrosion behavior. The P-TD specimen showed the best corrosion resistance. A degradation evolution model was established, and the effect of initial orientation on corrosion behavior was discussed.

关键词： composite coating   corrosion resistance   hydrothermal reaction   magnesium alloy   superhydrophobic  

摘要： A superhydrophobic ceria-based composite coating is developed to improve anticorrosion properties of AZ61 magnesium alloy, fabricating via chemical conversion method followed by hydrothermal treatment. The cerium conversion coating has a block structure with microcracks. After the hydrothermal treatment, a dense CeO2 layer, porous CeO2 nanorods, and stearic absorbing layers are grown stepwise on the conversion coating. And the composite coating is hydrophobic or even superhydrophobic and has almost no microcracks. As the hydrothermal reaction time increases, the water contact angle of the composite coating first increases and then decreases, and it reaches the maximum value of 152 degrees after hydrothermal treatment for 4 h. Both the dense CeO2 layer and the superhydrophobic stearic absorbing layer can effectively prevent the electrolyte from contacting the substrate;the corrosion current density of the superhydrophobic composite coating is lower than that of the hydrophilic composite coating and the cerium conversion coating, and has the best corrosion resistance.

关键词： WE43   Magnesium alloy   Chitosan   Bioactive glass   Mesoporous nano bioactive glass   Electrophoretic deposition  

摘要： Mg-based materials are good candidates for biodegradable bone regeneration implants due to their favorable mechanical properties and an excellent compatibility with human bone. However, too high corrosion/degradation rate in body fluids still limits their applicability. Coatings based on chitosan (CS) and bioactive glass (BG) particles fabricated by electrophoretic deposition (EPD) on Dulbecco's Modified Eagle Medium (DMEM) pretreated magnesium alloys have promising potential to suppress the substrate corrosion and additionally to incorporate bioactivity. However, the impact of processing parameters or type of coating components on the long-term substrate corrosion behavior and cell response have not been investigated previously. In this study, two types of composite coatings based on a high molecular weight CS (M-w 340-360 kDa, DDA >= 95%) and embedded particles: solid BG (2 mu m) and a mixture of BG and mesoporous bioactive glass nanoparticles (MBGN, 100-300 nm with mesopores 2.3-5.6 nm) were fabricated by EPD on DMEM pre-treated WE43 magnesium alloy. It was found that partial replacement of BG particles with MBGN (ratio 3:1) in the composite coating increases the water contact angle, surface roughness and induces a positive cell response. Although the acidic CS-based solutions and applied EPD conditions may decrease the stability of the temporary barrier formed during the DMEM pre-treatment on WE43 substrate therewith slightly increasing its corrosion sensitivity, the composite coating with a mixture of different sizes of particles (BG, MBGN) is a promising candidate for bone regeneration applications.