Magnesium alloys remain critical in the context of light-weighting and advanced devices. The increased utilisation of magnesium(Mg)each year reveals growing demand for its Mg-based alloys. Additive manufacturing(AM) p...Magnesium alloys remain critical in the context of light-weighting and advanced devices. The increased utilisation of magnesium(Mg)each year reveals growing demand for its Mg-based alloys. Additive manufacturing(AM) provides the possibility to directly manufacture components in net-shape, providing new possibilities and applications for the use of Mg-alloys, and new prospects in the utilisation of novel physical structures made possible from ‘3D printing’. The review herein seeks to holistically explore the additive manufacturing of Mg-alloys to date, including a synopsis of processes used and properties measured(with a comparison to conventionally prepared Mg-alloys). The challenges and possibilities of AM Mg-alloys are critically elaborated for the field of mechanical metallurgy.展开更多
In this study,the influence of a plasma electrolytic oxidation(PEO)surface treatment on a medical-grade WE43-based magnesium alloy is examined through an experimental and computational framework that considers the eff...In this study,the influence of a plasma electrolytic oxidation(PEO)surface treatment on a medical-grade WE43-based magnesium alloy is examined through an experimental and computational framework that considers the effects of localised corrosion features and mechanical properties throughout the corrosion process.First,a comprehensive in-vitro immersion study was performed on WE43-based tensile specimens with and without PEO surface modification,which included fully automated spatial reconstruction of the phenomenological features of corrosion through micro-CT scanning,followed by uniaxial tensile testing.Then the experimental data of both unmodified and PEO-modified groups were used to calibrate parameters of a finite element-based surface corrosion model.In-vitro,it was found that the WE43-PEO modified group had a significantly lower corrosion rate and maintained significantly higher mechanical properties than the unmodified.While corrosion rates were~50%lower in the WE43-PEO modified specimens,the local geometric features of corroding surfaces remained similar to the unmodified WE43 group,however evolving after almost the double amount of time.We were also able to quantitatively demonstrate that the PEO surface treatment on magnesium continued to protect samples from corrosion throughout the entire period tested,and not just in the early stages of corrosion.Using the results from the testing framework,the model parameters of the surface-based corrosion model were identified for both groups.This enabled,for the first time,in-silico prediction of the physical features of corrosion and the mechanical performance of both unmodified and PEO modified magnesium specimens.This simulation framework can enable future in-silico design and optimisation of bioabsorbable magnesium devices for load-bearing medical applications.展开更多
Silk fibroin is a biomaterial with multiple beneficial properties for use in regenerative medicine and tissue engineering.When dissolving and processing the reconstituted silk fibroin solution by electrospinning,the a...Silk fibroin is a biomaterial with multiple beneficial properties for use in regenerative medicine and tissue engineering.When dissolving and processing the reconstituted silk fibroin solution by electrospinning,the arrangement and size of fibers can be manifold varied and according fiber diameters reduced to the nanometer range.Such nonwovens show high porosity as well as potential biocompatibility.Usually,electrospinning of most biomaterials demands for the application of additives,which enable stable electrospinning by adjusting viscosity,and are intended to evaporate during processing or to be washed out afterwards.However,the use of such additives increases costs and has to be taken into account in terms of biological risks when used for biomedical applications.In this study,we explored the possibilities of additive-free electrospinning of pure fibroin nonwovens and tried to optimize process parameters to enable stable processing.We used natural silk derived from the mulberry silkworm Bombyx mori.After degumming,the silk fibroin was dissolved and the viscosity of the spinning solution was controlled by partial evaporation of the initial solving agent.This way,we were able to completely avoid the use of additives and manufacture nonwovens,which potentially offer higher biocompatibility and reduced immunogenicity.Temperature and relative humidity during electrospinning were systematically varied(25–35°C,25–30%RH).In a second step,the nonwovens optionally underwent methanol treatment to initiate beta-sheet formation in order to increase structural integrity and strength.Comprehensive surface analysis on the different nonwovens was performed using scanning electron microscopy and supplemented by additional mechanical testing.Cytotoxicity was evaluated using BrdU-assay,XTT-assay,LDH-assay and live-dead staining.Our findings were,that an increase of temperature and relative humidity led to unequal fiber diameters and defective nonwovens.Resistance to penetration decreased accordingly.The most uniform fiber diameters of 998±63 nm were obtained at 30°C and 25%relative humidity,also showing the highest value for resistance to penetration(0.20 N).The according pure fibroin nonwoven also showed no signs of cytotoxicity.However,while the biological response showed statistical evidence,the material characteristics showed no statistically significant correlation to changes of the ambient conditions within the investigated ranges.We suggest that further experiments should explore additional ranges for temperature and humidity and further focus on the repeatability of material properties in dependency of suitable process windows.展开更多
This study develops a three-dimensional automated detection framework(PitScan)that systematically evaluates the severity and phenomenology of pitting corrosion.This framework uses a python-based algorithm to analyse m...This study develops a three-dimensional automated detection framework(PitScan)that systematically evaluates the severity and phenomenology of pitting corrosion.This framework uses a python-based algorithm to analyse microcomputer-tomography scans(μCT)of cylindrical specimens undergoing corrosion.The approach systematically identifies several surface-based corrosion features,enabling full spatial characterisation of pitting parameters,including pit density,pit size,pit depth as well as pitting factor according to ASTM G46-94.Furthermore,it is used to evaluate pitting formation in tensile specimens of a Rare Earth Magnesium alloy undergoing corrosion,and relationships between key pitting parameters and mechanical performance are established.Results demonstrated that several of the parameters described in ASTM G46-94,including pit number,pit density and pitting factor,showed little correlation to mechanical performance.However,this study did identify that other parameters showed strong correlations with the ultimate tensile strength and these tended to be directly linked to the reduction of the cross-sectional area of the specimen.Specifically,our results indicate,that parameters directly linked to the loss of the cross-sectional area(e.g.minimum material width),are parameters that are most suited to provide an indication of a specimen’s mechanical performance.The automated detection framework developed in this study has the potential to provide a basis to standardise measurements of pitting corrosion across a range of metals and future prediction of mechanical strength over degradation time.展开更多
This study presents a computational framework that investigates the effect of localised surface-based corrosion on the mechanical performance of a magnesium-based alloy.A finite element-based phenomenological corrosio...This study presents a computational framework that investigates the effect of localised surface-based corrosion on the mechanical performance of a magnesium-based alloy.A finite element-based phenomenological corrosion model was used to generate a wide range of corrosion profiles,with subsequent uniaxial tensile test simulations to predict the mechanical response to failure.The python-based detection framework PitScan provides detailed quantification of the spatial phenomenological features of corrosion,including a full geometric tracking of corroding surface.Through this approach,this study is the first to quantitatively demonstrate that a surface-based non-uniform corrosion model can capture both the geometrical and mechanical features of a magne-sium alloy undergoing corrosion by comparing to experimental data.Using this verified corrosion modelling approach,a wide range of corrosion scenarios was evaluated and enabled quantitative relationships to be established between the mechanical integrity and key phenomenological corrosion features.In particular,we demonstrated that the minimal cross-sectional area parameter was the strongest predictor of the remaining mechanical strength(R2=0.98),with this relationship being independent of the severity or spatial features of localised surface corrosion.Interestingly,our analysis demonstrated that parameters described in ASTM G46-94 showed weaker correlations to the mechanical integrity of corroding specimens,compared to parameters determined by Pitscan.This study establishes new mechanistic insight into the performance of the magnesium-based materials undergoing corrosion.展开更多
基金support from Australian National University Futures Schemethe support from the first Singapore-Germany Academic-Industry (2 + 2) international collaboration grant (Grant No.: A1890b0050)。
文摘Magnesium alloys remain critical in the context of light-weighting and advanced devices. The increased utilisation of magnesium(Mg)each year reveals growing demand for its Mg-based alloys. Additive manufacturing(AM) provides the possibility to directly manufacture components in net-shape, providing new possibilities and applications for the use of Mg-alloys, and new prospects in the utilisation of novel physical structures made possible from ‘3D printing’. The review herein seeks to holistically explore the additive manufacturing of Mg-alloys to date, including a synopsis of processes used and properties measured(with a comparison to conventionally prepared Mg-alloys). The challenges and possibilities of AM Mg-alloys are critically elaborated for the field of mechanical metallurgy.
基金Funding support was also provided by the Irish Research Council(IRC)Government of Ireland Postgraduate Scholarship(GOIPG/2017/2102).
文摘In this study,the influence of a plasma electrolytic oxidation(PEO)surface treatment on a medical-grade WE43-based magnesium alloy is examined through an experimental and computational framework that considers the effects of localised corrosion features and mechanical properties throughout the corrosion process.First,a comprehensive in-vitro immersion study was performed on WE43-based tensile specimens with and without PEO surface modification,which included fully automated spatial reconstruction of the phenomenological features of corrosion through micro-CT scanning,followed by uniaxial tensile testing.Then the experimental data of both unmodified and PEO-modified groups were used to calibrate parameters of a finite element-based surface corrosion model.In-vitro,it was found that the WE43-PEO modified group had a significantly lower corrosion rate and maintained significantly higher mechanical properties than the unmodified.While corrosion rates were~50%lower in the WE43-PEO modified specimens,the local geometric features of corroding surfaces remained similar to the unmodified WE43 group,however evolving after almost the double amount of time.We were also able to quantitatively demonstrate that the PEO surface treatment on magnesium continued to protect samples from corrosion throughout the entire period tested,and not just in the early stages of corrosion.Using the results from the testing framework,the model parameters of the surface-based corrosion model were identified for both groups.This enabled,for the first time,in-silico prediction of the physical features of corrosion and the mechanical performance of both unmodified and PEO modified magnesium specimens.This simulation framework can enable future in-silico design and optimisation of bioabsorbable magnesium devices for load-bearing medical applications.
文摘Silk fibroin is a biomaterial with multiple beneficial properties for use in regenerative medicine and tissue engineering.When dissolving and processing the reconstituted silk fibroin solution by electrospinning,the arrangement and size of fibers can be manifold varied and according fiber diameters reduced to the nanometer range.Such nonwovens show high porosity as well as potential biocompatibility.Usually,electrospinning of most biomaterials demands for the application of additives,which enable stable electrospinning by adjusting viscosity,and are intended to evaporate during processing or to be washed out afterwards.However,the use of such additives increases costs and has to be taken into account in terms of biological risks when used for biomedical applications.In this study,we explored the possibilities of additive-free electrospinning of pure fibroin nonwovens and tried to optimize process parameters to enable stable processing.We used natural silk derived from the mulberry silkworm Bombyx mori.After degumming,the silk fibroin was dissolved and the viscosity of the spinning solution was controlled by partial evaporation of the initial solving agent.This way,we were able to completely avoid the use of additives and manufacture nonwovens,which potentially offer higher biocompatibility and reduced immunogenicity.Temperature and relative humidity during electrospinning were systematically varied(25–35°C,25–30%RH).In a second step,the nonwovens optionally underwent methanol treatment to initiate beta-sheet formation in order to increase structural integrity and strength.Comprehensive surface analysis on the different nonwovens was performed using scanning electron microscopy and supplemented by additional mechanical testing.Cytotoxicity was evaluated using BrdU-assay,XTT-assay,LDH-assay and live-dead staining.Our findings were,that an increase of temperature and relative humidity led to unequal fiber diameters and defective nonwovens.Resistance to penetration decreased accordingly.The most uniform fiber diameters of 998±63 nm were obtained at 30°C and 25%relative humidity,also showing the highest value for resistance to penetration(0.20 N).The according pure fibroin nonwoven also showed no signs of cytotoxicity.However,while the biological response showed statistical evidence,the material characteristics showed no statistically significant correlation to changes of the ambient conditions within the investigated ranges.We suggest that further experiments should explore additional ranges for temperature and humidity and further focus on the repeatability of material properties in dependency of suitable process windows.
基金funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 813869.
文摘This study develops a three-dimensional automated detection framework(PitScan)that systematically evaluates the severity and phenomenology of pitting corrosion.This framework uses a python-based algorithm to analyse microcomputer-tomography scans(μCT)of cylindrical specimens undergoing corrosion.The approach systematically identifies several surface-based corrosion features,enabling full spatial characterisation of pitting parameters,including pit density,pit size,pit depth as well as pitting factor according to ASTM G46-94.Furthermore,it is used to evaluate pitting formation in tensile specimens of a Rare Earth Magnesium alloy undergoing corrosion,and relationships between key pitting parameters and mechanical performance are established.Results demonstrated that several of the parameters described in ASTM G46-94,including pit number,pit density and pitting factor,showed little correlation to mechanical performance.However,this study did identify that other parameters showed strong correlations with the ultimate tensile strength and these tended to be directly linked to the reduction of the cross-sectional area of the specimen.Specifically,our results indicate,that parameters directly linked to the loss of the cross-sectional area(e.g.minimum material width),are parameters that are most suited to provide an indication of a specimen’s mechanical performance.The automated detection framework developed in this study has the potential to provide a basis to standardise measurements of pitting corrosion across a range of metals and future prediction of mechanical strength over degradation time.
基金Irish Research Council(IRC)Government of Ireland Postgraduate Scholarship(GOIPG/2017/2102).
文摘This study presents a computational framework that investigates the effect of localised surface-based corrosion on the mechanical performance of a magnesium-based alloy.A finite element-based phenomenological corrosion model was used to generate a wide range of corrosion profiles,with subsequent uniaxial tensile test simulations to predict the mechanical response to failure.The python-based detection framework PitScan provides detailed quantification of the spatial phenomenological features of corrosion,including a full geometric tracking of corroding surface.Through this approach,this study is the first to quantitatively demonstrate that a surface-based non-uniform corrosion model can capture both the geometrical and mechanical features of a magne-sium alloy undergoing corrosion by comparing to experimental data.Using this verified corrosion modelling approach,a wide range of corrosion scenarios was evaluated and enabled quantitative relationships to be established between the mechanical integrity and key phenomenological corrosion features.In particular,we demonstrated that the minimal cross-sectional area parameter was the strongest predictor of the remaining mechanical strength(R2=0.98),with this relationship being independent of the severity or spatial features of localised surface corrosion.Interestingly,our analysis demonstrated that parameters described in ASTM G46-94 showed weaker correlations to the mechanical integrity of corroding specimens,compared to parameters determined by Pitscan.This study establishes new mechanistic insight into the performance of the magnesium-based materials undergoing corrosion.
