Surface modifications can introduce natural gradients or structural hierarchy into human-made microlattices,making them simultaneously strong and tough.Herein,we describe our investigations of the mechanical propertie...Surface modifications can introduce natural gradients or structural hierarchy into human-made microlattices,making them simultaneously strong and tough.Herein,we describe our investigations of the mechanical properties and the underlying mechanisms of additively manufactured nickel–chromium superalloy(IN625)microlattices after surface mechanical attrition treatment(SMAT).Our results demonstrated that SMAT increased the yielding strength of these microlattices by more than 64.71%and also triggered a transition in their mechanical behaviour.Two primary failure modes were distinguished:weak global deformation,and layer-by-layer collapse,with the latter enhanced by SMAT.The significantly improved mechanical performance was attributable to the ultrafine and hard graded-nanograin layer induced by SMAT,which effectively leveraged the material and structural effects.These results were further validated by finite element analysis.This work provides insight into collapse behaviour and should facilitate the design of ultralight yet buckling-resistant cellular materials.展开更多
This work focuses on the structure and magnetic properties of Fe-50wt% Ni permalloy manufactured from the pre-alloyed powder by selective laser melting (SLM). The selective laser melted (SLMed) alloys were characteriz...This work focuses on the structure and magnetic properties of Fe-50wt% Ni permalloy manufactured from the pre-alloyed powder by selective laser melting (SLM). The selective laser melted (SLMed) alloys were characterized by a 3D profilometer,optical microscope, scanning electron microscope, X-ray diffraction, etc. The effects of the volume energy density of laser(LVED) on structure, and magnetic properties with coercivity ( H), remanence ( B), and power losses ( P), were evaluated and discussed systematically. The results show that the relative porosity rate and the surface roughness of the SLMed specimens decreased with the increase in LVED. Only the γ-(FeNi) phase was detected in the X-ray diffraction patterns of the SLMed permalloys fabricated from the different LVEDs. Statistical analysis of optical microscopy images indicated that the grain coarsened at higher LVED. Furthermore, the microstructure of the SLMed parts was a typical columnar structure with an oriented growth of building direction. The highest microhardness reached 198 HV. Besides, the magnetic properties including B, H, and Pof SLMed samples decreased when the LVED ranged from 33.3 to 60.0 J/mm ~3 firstly and then increased while LVED further up to 93.3 J/mm, which is related to the decrease in porosity and the increase in grain size, while the higher residual stress and microcracks presented in the samples manufactured using very high LVED. The observed evolution of magnetic properties and LVED provides a good compromise in terms of reduced porosity and crack formation for the fabrication of SLMed Fe-50 wt% Ni permalloy. The theoretical mechanism in this study can offer guidance to further investigate SLMed soft magnetic alloys.展开更多
Laser powder-bed fusion(LPBF)of Zn-0.8Cu(wt.%)alloys exhibits significant advantages in the customization of biodegradable bone implants.However,the formability of LPBFed Zn alloy is not sufficient due to the spheroid...Laser powder-bed fusion(LPBF)of Zn-0.8Cu(wt.%)alloys exhibits significant advantages in the customization of biodegradable bone implants.However,the formability of LPBFed Zn alloy is not sufficient due to the spheroidization during the interaction of powder and laser beam,of which the mechanism is still not well understood.In this study,the evolution of morphology and grain structure of the LPBFed Zn-Cu alloy was investigated based on single-track deposition experiments.As the scanning speed increases,the grain structure of a single track of Zn-Cu alloy gradually refines,but the formability deteriorates,leading to the defect’s formation in the subsequent fabrication.The Zn-Cu alloys fabricated by optimum processing parameters exhibit a tensile strength of 157.13 MPa,yield strength of 106.48 MPa and elongation of 14.7%.This work provides a comprehensive understanding of the processing optimization of Zn-Cu alloy,achieving LPBFed Zn-Cu alloy with high density and excellent mechanical properties.展开更多
Biodegradable polymer coatings are commonly used as protective barriers on magnesium(Mg) and its alloys.The properties of polymers,such as crystallinity and degradation properties,have a crucial impact on their corros...Biodegradable polymer coatings are commonly used as protective barriers on magnesium(Mg) and its alloys.The properties of polymers,such as crystallinity and degradation properties,have a crucial impact on their corrosion resistance.In this work,polyhydroxybutyrate(PHB) coatings are deposited on Mg sheets with a thickness similar to that of cardiovascular stents to assess the degradation behavior,and poly-lactic acid(PLA)-coated Mg is also investigated to compare the structure-propertyperformance relationship.The hydrogen evolution volume(HEV) of the PHB-coated sample decreases by 30% after immersion in artificial blood plasma(AP) for 7 days,whereas the PL A-coated sample shows an increase of 154%.The PHB coating also shows excellent durability at a constant voltage,compared to severe rupture of the PLA coating.The degradation behavior of the coated-Mg samples is evaluated in AP solution containing different concentrations of the bovine serum albumin(BSA).Corrosion is inhibited as the protein concentration increases.The degradation rates of the Mg,PLA-coated Mg,and PHBcoated Mg decrease by 65%,88%,and 75% for 5 g L^(-1)BSA,respectively.Our results reveal that higher crystallinity and less acidic degradation products give rise to better durability,while the acid self-catalytic effect leads to the failure of PLA.The protein-polymer interactions are determined and the empirical relationship of HEV is established.展开更多
Additive manufacturing enables processing of functionally graded materials(FGMs)with flexible spatial design and high bonding strength.A steel-copper FGM with high interfacial strength was developed using laser powder...Additive manufacturing enables processing of functionally graded materials(FGMs)with flexible spatial design and high bonding strength.A steel-copper FGM with high interfacial strength was developed using laser powder bed fusion(LPBF).The effect of laser process parameters on interfacial defects was evaluated by X-ray tomography,which indicates a low porosity level of 0.042%therein.Gradient/fine dendritic grains in the interface are incited by high cooling rates,which facilitates interface strengthening.Multiple mechanical tests evaluate the bonding reliability of interface;and the fatigue tests further substantiate the ultrahigh bonding strength in FGMs,which is superior to traditional manufacturing methods.Mechanisms of the high interfacial bond strength were also discussed.展开更多
Cold spray,as a solid-state additive manufacturing process,has been attracting increasing attention from both scientific and industrial communities.However,cold-sprayed deposits generally have unfavorable mechanical p...Cold spray,as a solid-state additive manufacturing process,has been attracting increasing attention from both scientific and industrial communities.However,cold-sprayed deposits generally have unfavorable mechanical properties in their as-fabricated state compared to conventionally manufactured and fusion-based additive-manufactured counterparts due to the inherent microstructural defects in the deposits(e.g.,porosity and incomplete interparticle bonding).This downside reduces its competitiveness and limits its wide applications as an additive manufacturing process.In the past years,many strengthening technologies have been developed or introduced to adjust the microstructure and improve the mechanical properties of cold-sprayed deposits.The term“strengthening”in this work specifically refers to improving the mechanical strength,particularly the tensile strength of the cold-sprayed bulk deposits.According to the stage that the strengthening technologies are used in the cold spray process,they can be classified into three categories:pre-process(e.g.,powder heat treatment),in-process(e.g.,powder heating,in-situ micro-forging,laser-assisted cold spray),and post-process(e.g.,post heat treatment,hot isostatic pressing,hot rolling,friction stir processing).Therefore,a comprehensive review of these strengthening technolo-gies is conducted to illuminate the possible correlations between the strengthening mechanisms and the resultant deposit microstructures and mechanical properties.This review paper aims to help researchers and engineers well understand the different strengthening methods and provide guidance for the cold spray community to develop new strengthening strategies for future high-quality mass production.展开更多
Fabrication of the Mg–9Al–1Zn–0.5Mn alloy with excellent mechanical performance using selective laser melting(SLM)technology is quite difficult owing to the poor weldability and low boiling point.To address these ch...Fabrication of the Mg–9Al–1Zn–0.5Mn alloy with excellent mechanical performance using selective laser melting(SLM)technology is quite difficult owing to the poor weldability and low boiling point.To address these challenges and seek the optimal processing parameters,response surface methodology was systematically utilized to determine the appropriate SLM parameter combinations.Mg–9Al–1Zn–0.5Mn sample with high relative density(99.5±0.28%)and favorable mechanical properties(microhardness=95.6±5.28 HV_(0.1),UTS=370.2 MPa,and At=10.4%)was achieved using optimized SLM parameters(P=120 W,v=500 mm/s,and h=45μm).Sample is dominated by a random texture and microstructure is primarily constituted by quantities offine equiaxed grains(α-Mg phase),a small amount ofβ-Al_(12)Mg_(17) structures(4.96 vol%,including spherical:[2110]_(α)//[111]_(β)and long lath-like:[2110]_(α)//[115]_(β)or[1011]_(α)//[321]_(β)),and some short rod-shaped Al8Mn5 nanoparticles.Benefiting from grain boundary strengthening,solid solution strengthening,and precipitation hardening of various nanoparticles(β-Al12Mg17 and Al8Mn5),high-performance Mg–9Al–1Zn–0.5Mn alloy biomedical implants can be fabricated.Precipitation hardening dominates the strengthening mechanism of the SLM Mg–9Al–1Zn–0.5Mn alloy.展开更多
The new designed high-velocity arc spray gun with three different nozzles is developed to match the DZ400 arc spray system, which can produce the coatings with the structure of superfine and low porosity. This system ...The new designed high-velocity arc spray gun with three different nozzles is developed to match the DZ400 arc spray system, which can produce the coatings with the structure of superfine and low porosity. This system can be used to spray three normal wires such as 4Cr13, FeCrAl and 7Cr13 （flux cored wires）. Using the scanning electron microscope （ SEM ） to analyze shape and particles size that sprayed by the nozzles with different parameters, as well as with the S-3500N SEM and the energy spectrum analytic （ESA） instrument to identify the content of the oxides, porosity and thickness of the coatings, we get the result that the porosity in the coatings of solid wire is less than 3%, of the flux-cored wires is less than 5%, and the distribution of the coatings sprayed by the nozzle with secondary supplementary airflow is typically shown in the form of highdensity lameUarsplat structure and the average lamellar thickness is around 5μm.展开更多
Selective laser melting(SLM)has attracted great attention in the fabrication of magnesium-based biodegradable implants.However,current SLMed magnesium alloys are generally suffered from rapid corrosion,which is deadly...Selective laser melting(SLM)has attracted great attention in the fabrication of magnesium-based biodegradable implants.However,current SLMed magnesium alloys are generally suffered from rapid corrosion,which is deadly detrimental to their use.Herein,we thoroughly revealed why they are so vulnerable to corrosion through a typical SLMed AZ91D material model.An abnormally spatiotemporal“bulk erosion”mechanism was found,not the well-known“surface corrosion”mode of traditionally plastic-deformed alloys.The unique microstructure derived from SLM possesses high chemical reactivity,which is favorable for interactional attacks of fast fluid penetration,severe local corrosion and intensive micro-galvanic corrosion.Thus,it brings two orders of magnitude in corrosion rates compared with its plastic-deformed counterparts.In vitro,such fast-corrosion induced apparent cytotoxicity,cell damage,and further apoptosis to rat and mouse derived mesenchymal stem cells.In vivo,the material disintegrates into small pieces in a short period,and results in unexpected bone destruction and long-lasting foreign body reactions in Sprague Dawley rats.Close attention should be paid to this issue before SLMed Mg-based implants being applied in patients.展开更多
The manufacturing of heterogeneous high-temperature material components is challenging for use in practical applications.Three-dimensional(3D)printing provides solutions to programmable constructing ceramic architectu...The manufacturing of heterogeneous high-temperature material components is challenging for use in practical applications.Three-dimensional(3D)printing provides solutions to programmable constructing ceramic architectures.However,the development of heterogeneous ceramics is limited by low flexibil-ity of heterogeneity,geometrical complexity,structural resolution,manufacturing efficiency,and mate-rial diversity.In this study,we demonstrated flexible and rapid approaches for fabricating complicated and precise heterogeneous ceramics by shape-changing(4D)or shape-keeping(3D)additive-subtractive manufacturing(ASM)methods.The shape-changing strategy for heterogeneous ceramics was achieved by global ceramization of heterogeneous precursors,while the shape-keeping strategy for heterogeneous ceramics was achieved by local receramization of homogeneous ceramics.Finite element analysis(FEA)simulations of the influence of the thermal shrinkage dominant in the shape-changing strategy on the shape deformation of heterogeneous ceramics could be valuable predictions of the experimental results.The 3D/4D ASM methods are generic for high-temperature materials and extendable to metallic and dia-mond materials.展开更多
The unique multilayer, multiscale structure of teakwood results in excellent mechanical and long-term environmental stability, providing inspiration for the biomimetic design of environmental barrier coating (EBC) str...The unique multilayer, multiscale structure of teakwood results in excellent mechanical and long-term environmental stability, providing inspiration for the biomimetic design of environmental barrier coating (EBC) structures. However, achieving the desired biomimetic structure control in high-temperature plasma spraying is a challenging task that requires new technological breakthroughs. In this study, a multiscale nano Yb_(2)Si_(2)O_(7)–Yb_(2)SiO_(5) (YbDS–YbMS) composite EBC with a teakwood-like lamellar structure was realized via a novel alternating vapor/liquid phase deposition method involving plasma spraying-physical vapor deposition (PS-PVD). Volatilized waste SiO_(2) from Yb_(2)Si_(2)O_(7) (YbDS) was reused and deposited on the coating surface during the spraying process, where a regularly arranged multilayer structure was formed in the coating by the alternate deposition of gaseous SiO_(2) and droplet YbDS. In addition, SiO_(2) on the coated surface formed nanoclusters and dome-shaped nanocrystals via homogeneous and heterogeneous nucleation, respectively, and some of them gradually formed a continuous nanofilm as the arc current increased. The deposited SiO_(2) reacted in situ with the decomposed phase YbMS in the coating to form YbDS, preserving its multiscale nanostructure after heat treatment and enabling the preparation of the YbDS–YbMS composite coating. This work provides a new design strategy and method for the preparation of coatings using YbDS and other spray powders with similar decomposition and volatilization characteristics during the plasma spraying process.展开更多
Environmental barrier coatings(EBCs)effectively protect the ceramic matrix composites(CMCs)from harsh engine environments,especially steam and molten salts.However,open pores inevitably formed during the deposition pr...Environmental barrier coatings(EBCs)effectively protect the ceramic matrix composites(CMCs)from harsh engine environments,especially steam and molten salts.However,open pores inevitably formed during the deposition process provide the transport channels for oxidants and corrosives,and lead to premature failure of EBCs.This research work proposed a method of pressure infiltration densification which blocked these open pores in the coatings.These results showed that it was difficult for aluminum to infiltrate spontaneously,but with the increase of external gas pressure and internal vacuum simultaneously,the molten aluminum obviously moved forward,and finally stopped infiltrating at a depth of a specific geometry.Based on the wrinkled zigzag pore model,a mathematical relationship between the critical pressure with the infiltration depth and the pore intrinsic geometry was established.The infiltration results confirmed this relationship,indicating that for a given coating,a dense thick film can be obtained by adjusting the internal and external gas pressures to drive a melt infiltration.展开更多
The laser shock processing implemented by a laser-induced high-pressure plasma which propagates into the sample as a shockwave is innovatively applied as a post-processing technique on HfO_(2)/SiO_(2) multilayer coati...The laser shock processing implemented by a laser-induced high-pressure plasma which propagates into the sample as a shockwave is innovatively applied as a post-processing technique on HfO_(2)/SiO_(2) multilayer coatings for the first time.The pure mechanical post-processing has provided evidence of a considerable promotion effect of the laser-induced damage threshold,which increased by a factor of about 4.6 with appropriate processing parameters.The promotion mechanism is confirmed to be the comprehensive modification of the intrinsic defects and the mechanical properties,which made the applicability of this novel post-processing technique on various types of coatings possible.Based on experiments,an interaction equation for the plasma pressure is established,which clarifies the existence of the critical pressure and provides a theoretical basis for selecting optimal processing parameters.In addition to the further clarification of the underlying damage mechanism,the laser shock post-processing provides a promising technique to realize the comprehensive and effective improvement of the laser-induced damage resistance of coatings.展开更多
Plasma spray-physical vapor deposition(PS-PVD)as a novel process was used to prepare feather-like columnar thermal barrier coatings(TBCs).This special microstructure shows good strain tolerance and non-line-of-sight(N...Plasma spray-physical vapor deposition(PS-PVD)as a novel process was used to prepare feather-like columnar thermal barrier coatings(TBCs).This special microstructure shows good strain tolerance and non-line-of-sight(NLOS)deposition,giving great potential application in aero-engine.However,due to serious service environment of aero-engine,particle erosion performance is a weakness for PS-PVD 7YSZ TBCs.As a solution,an Al-modification approach was proposed in this investigation.Through in-situ reaction of Al and ZrO2,anα-Al2O3 overlay can be formed on the surface of 7YSZ columnar coating.The results demonstrate that this approach can improve particle erosion resistance since hardness improvement of Al-modified TBCs.Meanwhile,as another important performance of thermal cycle,it has a better optimization with 350-cycle water-quenching,compared with the as-sprayed TBCs.展开更多
Thermal barrier coatings(TBCs)can effectively protect the alloy substrate of hot components in aeroengines or land-based gas turbines by the thermal insulation and corrosion/erosion resistance of the ceramic top coat....Thermal barrier coatings(TBCs)can effectively protect the alloy substrate of hot components in aeroengines or land-based gas turbines by the thermal insulation and corrosion/erosion resistance of the ceramic top coat.However,the continuous pursuit of a higher operating temperature leads to degradation,delamination,and premature failure of the top coat.Both new ceramic materials and new coating structures must be developed to meet the demand for future advanced TBC systems.In this paper,the latest progress of some new ceramic materials is first reviewed.Then,a comprehensive spalling mechanism of the ceramic top coat is summarized to understand the dependence of lifetime on various factors such as oxidation scale growth,ceramic sintering,erosion,and calcium–magnesium–aluminium–silicate(CMAS)molten salt corrosion.Finally,new structural design methods for high-performance TBCs are discussed from the perspectives of lamellar,columnar,and nanostructure inclusions.The latest developments of ceramic top coat will be presented in terms of material selection,structural design,and failure mechanism,and the comprehensive guidance will be provided for the development of next-generation advanced TBCs with higher temperature resistance,better thermal insulation,and longer lifetime.展开更多
The development of Si-HfO_(2)/Yb_(2)Si_(2)O_(7)/Yb_(2)SiO_(5)environmental barrier coatings(EBCs)aims to improve the operational temperature and longevity of ceramic matrix composites(CMCs)in turbine environments.Neve...The development of Si-HfO_(2)/Yb_(2)Si_(2)O_(7)/Yb_(2)SiO_(5)environmental barrier coatings(EBCs)aims to improve the operational temperature and longevity of ceramic matrix composites(CMCs)in turbine environments.Nevertheless,several critical questions remain unanswered,including the oxidation mechanism of Si-HfO_(2)bond coating,the compatibility of its mixed thermally grown oxide(m-TGO)with adjacent layers during thermal cycling,and the evolution pattern of vertical mud-cracks that impact the overall performance in service.Using plasma spraying physical vapor deposition(PS-PVD),we fabricated these EBCs on a CMC substrate,and thermal cycling tests at 1400,1450,and 1500℃ revealed that their durability reached 200 h.m-TGO growth followed a parabolic model,with the oxygen diffusion activation energy being 133.69 kJ/mol between 1400 and 1450℃ and 101.47 kJ/mol from 1450 to 1500℃,emphasizing that the transport of molecular oxygen is key to controlling the oxidation of m-TGO in this EBC system.Although residual stresses and stored elastic strain energy build up between m-TGO and adjacent layers,especially around the cristobalite phase transition temperature,causing interlaminar crack formation in later thermal cycles,the stored elastic strain energy remains lower than that of the silicon oxide-thermally grown oxide(SiO_(2)-TGO)formed in Si bond coating system.In addition to[110]dislocations,(001)twinning and interaction zones between twinning and dislocations were discovered for the first time,driving the bifurcation of mud cracks.Notably,controlling the mud-crack density is vital for protection of Yb_(2)SiO_(5)layer,as bifurcated mud-crack tips may converge with adjacent mud-cracks.展开更多
Zinc-based composites represent promising materials for orthopedic implants owing to their adjustable degradation rates and excellent biocompatibility.In this study,a series of Zn-10Mg-xHA(x=0-5 wt.%)composites with t...Zinc-based composites represent promising materials for orthopedic implants owing to their adjustable degradation rates and excellent biocompatibility.In this study,a series of Zn-10Mg-xHA(x=0-5 wt.%)composites with the core-shell structure were prepared through spark plasma sintering,and their microstructural,mechanical,and in vitro properties were systematically evaluated.Results showed that the doped hydroxyapatite(HA)is concentrated at the outer edge of the MgZn2 shell layer.The compression strength of the Zn-1oMg HA composite gradually decreased with the increase of the HA content,while its corrosion rate decreased initially and then increased.The corrosion resistance of the composite with the addition of 1 wt.%HA was improved compared to that of Zn-10Mg-0HA.However,the further increase of the HA content beyond 1 wt.%resulted in a faster degradation of the composite.Moreover,the Zn-10Mg-1HA composite significantly enhanced the activity of Mc3T3-E1 osteoblasts.Based on such findings,it is revealed that the composite containing 1 wt.%HA exhibits superior overall properties and is anticipated to serve as a promising candidate for bone implantmaterials.展开更多
基金support provided by Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone Shenzhen Park Project:HZQB-KCZYB-2020030the Hong Kong General Research Fund(GRF)Scheme(Ref:CityU 11216219)+2 种基金the Research Grants Council of Hong Kong(Project No:AoE/M-402/20)Shenzhen Science and Technology Program:JCYJ20220818101204010the Hong Kong Innovation and Technology Commission via the Hong Kong Branch of National Precious Metals Material Engineering Research Center.
文摘Surface modifications can introduce natural gradients or structural hierarchy into human-made microlattices,making them simultaneously strong and tough.Herein,we describe our investigations of the mechanical properties and the underlying mechanisms of additively manufactured nickel–chromium superalloy(IN625)microlattices after surface mechanical attrition treatment(SMAT).Our results demonstrated that SMAT increased the yielding strength of these microlattices by more than 64.71%and also triggered a transition in their mechanical behaviour.Two primary failure modes were distinguished:weak global deformation,and layer-by-layer collapse,with the latter enhanced by SMAT.The significantly improved mechanical performance was attributable to the ultrafine and hard graded-nanograin layer induced by SMAT,which effectively leveraged the material and structural effects.These results were further validated by finite element analysis.This work provides insight into collapse behaviour and should facilitate the design of ultralight yet buckling-resistant cellular materials.
基金financially supported by the Sciences Platform Environment and Capacity Building Projects of GDAS(No.2021GDASYL-20210102005)the Guangdong Special Support Program(No.2019BT02C629)+2 种基金the GuangDong Basic and Applied Basic Research Foundation(Nos.2020A1515111031 and 2021A515010939)the Guangzhou Major Projects of Industry University-Research(IUR)Collaborative Innovation“Surface Treatment and Repair for Key Components of Industrial Gas Turbine(IGT).”support from the program of CSC(No.201801810066)support from the program of CSC(No.201801810106)。
文摘This work focuses on the structure and magnetic properties of Fe-50wt% Ni permalloy manufactured from the pre-alloyed powder by selective laser melting (SLM). The selective laser melted (SLMed) alloys were characterized by a 3D profilometer,optical microscope, scanning electron microscope, X-ray diffraction, etc. The effects of the volume energy density of laser(LVED) on structure, and magnetic properties with coercivity ( H), remanence ( B), and power losses ( P), were evaluated and discussed systematically. The results show that the relative porosity rate and the surface roughness of the SLMed specimens decreased with the increase in LVED. Only the γ-(FeNi) phase was detected in the X-ray diffraction patterns of the SLMed permalloys fabricated from the different LVEDs. Statistical analysis of optical microscopy images indicated that the grain coarsened at higher LVED. Furthermore, the microstructure of the SLMed parts was a typical columnar structure with an oriented growth of building direction. The highest microhardness reached 198 HV. Besides, the magnetic properties including B, H, and Pof SLMed samples decreased when the LVED ranged from 33.3 to 60.0 J/mm ~3 firstly and then increased while LVED further up to 93.3 J/mm, which is related to the decrease in porosity and the increase in grain size, while the higher residual stress and microcracks presented in the samples manufactured using very high LVED. The observed evolution of magnetic properties and LVED provides a good compromise in terms of reduced porosity and crack formation for the fabrication of SLMed Fe-50 wt% Ni permalloy. The theoretical mechanism in this study can offer guidance to further investigate SLMed soft magnetic alloys.
基金Project(2022YFC2406000)supported by the National Key R&D Program,ChinaProject(2022GDASZH-2022010107)supported by the Guangdong Academy of Science,China+4 种基金Project(2019BT02C629)supported by the Guangdong Special Support Program,ChinaProject(2022GDASZH-2022010203-003)supported by the GDAS’project of Science and Technology Development,ChinaProjects(2023B1212120008,2023B1212060045)supported by the Guangdong Province Science and Technology Plan Projects,ChinaProject(2023TQ07Z559)supported by the Special Support Foundation of Guangdong Province,ChinaProject(52105293)supported by the National Natural Science Foundation of China。
文摘Laser powder-bed fusion(LPBF)of Zn-0.8Cu(wt.%)alloys exhibits significant advantages in the customization of biodegradable bone implants.However,the formability of LPBFed Zn alloy is not sufficient due to the spheroidization during the interaction of powder and laser beam,of which the mechanism is still not well understood.In this study,the evolution of morphology and grain structure of the LPBFed Zn-Cu alloy was investigated based on single-track deposition experiments.As the scanning speed increases,the grain structure of a single track of Zn-Cu alloy gradually refines,but the formability deteriorates,leading to the defect’s formation in the subsequent fabrication.The Zn-Cu alloys fabricated by optimum processing parameters exhibit a tensile strength of 157.13 MPa,yield strength of 106.48 MPa and elongation of 14.7%.This work provides a comprehensive understanding of the processing optimization of Zn-Cu alloy,achieving LPBFed Zn-Cu alloy with high density and excellent mechanical properties.
基金jointly supported by the National Natural Science Foundation of China(No.52171236)State Key Program of the National Natural Science Foundation of China(No.52231005)+5 种基金Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials,Southeast University(No.AMM2024A01)Suzhou Science and Technology Project(Nos.SJC2023005 and SZS2023023)City University of Hong Kong Donation Research Grants(Nos.DON-RMG 9229021 and 9220061)Hong Kong Innovation and Technology Fund(Nos.ITF GHP/212/22GD and CityU 440399)Hong Kong PDFS_RGC Postdoctoral Fellowship Scheme(Nos.PDFS2122-1S08 and CityU 9061014)Hong Kong HMRF(Health and Medical Research Fund)(Nos.2120972 and CityU 9211320)
文摘Biodegradable polymer coatings are commonly used as protective barriers on magnesium(Mg) and its alloys.The properties of polymers,such as crystallinity and degradation properties,have a crucial impact on their corrosion resistance.In this work,polyhydroxybutyrate(PHB) coatings are deposited on Mg sheets with a thickness similar to that of cardiovascular stents to assess the degradation behavior,and poly-lactic acid(PLA)-coated Mg is also investigated to compare the structure-propertyperformance relationship.The hydrogen evolution volume(HEV) of the PHB-coated sample decreases by 30% after immersion in artificial blood plasma(AP) for 7 days,whereas the PL A-coated sample shows an increase of 154%.The PHB coating also shows excellent durability at a constant voltage,compared to severe rupture of the PLA coating.The degradation behavior of the coated-Mg samples is evaluated in AP solution containing different concentrations of the bovine serum albumin(BSA).Corrosion is inhibited as the protein concentration increases.The degradation rates of the Mg,PLA-coated Mg,and PHBcoated Mg decrease by 65%,88%,and 75% for 5 g L^(-1)BSA,respectively.Our results reveal that higher crystallinity and less acidic degradation products give rise to better durability,while the acid self-catalytic effect leads to the failure of PLA.The protein-polymer interactions are determined and the empirical relationship of HEV is established.
基金financially supported by the Guangdong Basic and Applied Basic Research Foundation(No.2019A1515110542)the Guangdong Special Support Program(No.2019BT02C629)+5 种基金the National Natural Science Foundation of China(Nos.52005189and 51775196)the Chinese Postdoctoral Science Foundation(No.2020M672617)the Guangzhou Science and Technology Society Project(Nos.X20200301015,201907010008,202007020008and 201807010030)the Chinese Central Universities Funds(No.2018ZD30)supported by Guangdong province Science and Technology Plan Projects(No.2019A1515011841)GDAS Projects(Nos.2020GDASYL-20200402005,2019GDASYL-0501009,2019GDASYL-0502006,2018GDASCX-0111,2018GDASCX-0402 and 2019GDASYL-0402004)。
文摘Additive manufacturing enables processing of functionally graded materials(FGMs)with flexible spatial design and high bonding strength.A steel-copper FGM with high interfacial strength was developed using laser powder bed fusion(LPBF).The effect of laser process parameters on interfacial defects was evaluated by X-ray tomography,which indicates a low porosity level of 0.042%therein.Gradient/fine dendritic grains in the interface are incited by high cooling rates,which facilitates interface strengthening.Multiple mechanical tests evaluate the bonding reliability of interface;and the fatigue tests further substantiate the ultrahigh bonding strength in FGMs,which is superior to traditional manufacturing methods.Mechanisms of the high interfacial bond strength were also discussed.
基金the financial support from the following funding agency and projects:Science Foundation Ireland Frontiers for the Future Project(No.20/FFP-P/8815)National Natural Science Foundation of China(Nos.51875471,52001078,and 52061135101)+2 种基金China Scholarship Council-Trinity College Dublin Joint Scholarship Programme(No.201906460020)International Cooperation Project of Guangdong Province(No.2021A0505030052)Alexander von Humboldt Foundation.
文摘Cold spray,as a solid-state additive manufacturing process,has been attracting increasing attention from both scientific and industrial communities.However,cold-sprayed deposits generally have unfavorable mechanical properties in their as-fabricated state compared to conventionally manufactured and fusion-based additive-manufactured counterparts due to the inherent microstructural defects in the deposits(e.g.,porosity and incomplete interparticle bonding).This downside reduces its competitiveness and limits its wide applications as an additive manufacturing process.In the past years,many strengthening technologies have been developed or introduced to adjust the microstructure and improve the mechanical properties of cold-sprayed deposits.The term“strengthening”in this work specifically refers to improving the mechanical strength,particularly the tensile strength of the cold-sprayed bulk deposits.According to the stage that the strengthening technologies are used in the cold spray process,they can be classified into three categories:pre-process(e.g.,powder heat treatment),in-process(e.g.,powder heating,in-situ micro-forging,laser-assisted cold spray),and post-process(e.g.,post heat treatment,hot isostatic pressing,hot rolling,friction stir processing).Therefore,a comprehensive review of these strengthening technolo-gies is conducted to illuminate the possible correlations between the strengthening mechanisms and the resultant deposit microstructures and mechanical properties.This review paper aims to help researchers and engineers well understand the different strengthening methods and provide guidance for the cold spray community to develop new strengthening strategies for future high-quality mass production.
基金supported by the Sciences Platform Environment and Capacity Building Projects of GDAS(2021GDASYL-20210102005)the Guangdong Basic and Applied Basic Research Fund(2020A1515111031,2021A1515010939)+4 种基金the Young Elite Scientist Sponsorship Program by China Association for Science and Technology(CAST)(YESS20210269)Guangdong Provincial Special Support Program(2019BT02C629)Guangdong Academy of Sciences Development Special Fund Project(2022GDASZH-2022010107)Guangdong Academy of Sciences International Science and Technology Cooperation Platform Construction Project(2022GDASZH-2022010203-003)Guangzhou Key Field R&D Program(20200702008)。
文摘Fabrication of the Mg–9Al–1Zn–0.5Mn alloy with excellent mechanical performance using selective laser melting(SLM)technology is quite difficult owing to the poor weldability and low boiling point.To address these challenges and seek the optimal processing parameters,response surface methodology was systematically utilized to determine the appropriate SLM parameter combinations.Mg–9Al–1Zn–0.5Mn sample with high relative density(99.5±0.28%)and favorable mechanical properties(microhardness=95.6±5.28 HV_(0.1),UTS=370.2 MPa,and At=10.4%)was achieved using optimized SLM parameters(P=120 W,v=500 mm/s,and h=45μm).Sample is dominated by a random texture and microstructure is primarily constituted by quantities offine equiaxed grains(α-Mg phase),a small amount ofβ-Al_(12)Mg_(17) structures(4.96 vol%,including spherical:[2110]_(α)//[111]_(β)and long lath-like:[2110]_(α)//[115]_(β)or[1011]_(α)//[321]_(β)),and some short rod-shaped Al8Mn5 nanoparticles.Benefiting from grain boundary strengthening,solid solution strengthening,and precipitation hardening of various nanoparticles(β-Al12Mg17 and Al8Mn5),high-performance Mg–9Al–1Zn–0.5Mn alloy biomedical implants can be fabricated.Precipitation hardening dominates the strengthening mechanism of the SLM Mg–9Al–1Zn–0.5Mn alloy.
文摘The new designed high-velocity arc spray gun with three different nozzles is developed to match the DZ400 arc spray system, which can produce the coatings with the structure of superfine and low porosity. This system can be used to spray three normal wires such as 4Cr13, FeCrAl and 7Cr13 （flux cored wires）. Using the scanning electron microscope （ SEM ） to analyze shape and particles size that sprayed by the nozzles with different parameters, as well as with the S-3500N SEM and the energy spectrum analytic （ESA） instrument to identify the content of the oxides, porosity and thickness of the coatings, we get the result that the porosity in the coatings of solid wire is less than 3%, of the flux-cored wires is less than 5%, and the distribution of the coatings sprayed by the nozzle with secondary supplementary airflow is typically shown in the form of highdensity lameUarsplat structure and the average lamellar thickness is around 5μm.
基金supported by the National Natural Science Foundation of China(Nos.52101283 and U22A20121)the National Key R&D Program of China(Nos.2021YFC2400700 and 2022YFC2406000)+6 种基金the Science and Technology Planning Project of Guangzhou(No.202201011454)the NSFC Incubation Program of GDPH(No.KY012021165)the High-level Hospital Construction Project(No.KJ012019520)the Special Fund Project of Guangdong Academy of Sciences(Nos.2022GDASZH-2022010107 and 2021GDASYL-20210102005)the GDAS Projects of International Cooperation Platform of Science and Technology(No.2022GDASZH-2022010203-003)the Guangdong Basic and Applied Basic Research Foundation(No.2022B1515250004)the Young Elite Scientist Sponsorship Program by China Association for Science and Technology(CAST)(No.YESS20210269).
文摘Selective laser melting(SLM)has attracted great attention in the fabrication of magnesium-based biodegradable implants.However,current SLMed magnesium alloys are generally suffered from rapid corrosion,which is deadly detrimental to their use.Herein,we thoroughly revealed why they are so vulnerable to corrosion through a typical SLMed AZ91D material model.An abnormally spatiotemporal“bulk erosion”mechanism was found,not the well-known“surface corrosion”mode of traditionally plastic-deformed alloys.The unique microstructure derived from SLM possesses high chemical reactivity,which is favorable for interactional attacks of fast fluid penetration,severe local corrosion and intensive micro-galvanic corrosion.Thus,it brings two orders of magnitude in corrosion rates compared with its plastic-deformed counterparts.In vitro,such fast-corrosion induced apparent cytotoxicity,cell damage,and further apoptosis to rat and mouse derived mesenchymal stem cells.In vivo,the material disintegrates into small pieces in a short period,and results in unexpected bone destruction and long-lasting foreign body reactions in Sprague Dawley rats.Close attention should be paid to this issue before SLMed Mg-based implants being applied in patients.
基金supported by the Shenzhen-Hong Kong Sci-ence and Technology Innovation Cooperation Zone Shenzhen Park Project(grant No.HZQB-KCZYB-2020030)the Shenzhen Science and Technology Program:No.JCYJ20220818101204010+4 种基金the Re-search Grants Council of the Hong Kong Special Administrative Region,China(grant No.CityU PDFS2223-1S05)the Guangdong Provincial Department of Science and Technology(Key-Area Re-search and Development Program of Guangdong Province)(grant No.2020B090923002)the Major Program of Changsha Science and Technology Project(grant No.kh2003023)the Hong Kong In-novation and Technology Commission via the Hong Kong Branch of National Precious Metals Material Engineering Research Centerthe Research Grants Council of Hong Kong Special Administrative Region,China(grant No.AoE/M-402/20).
文摘The manufacturing of heterogeneous high-temperature material components is challenging for use in practical applications.Three-dimensional(3D)printing provides solutions to programmable constructing ceramic architectures.However,the development of heterogeneous ceramics is limited by low flexibil-ity of heterogeneity,geometrical complexity,structural resolution,manufacturing efficiency,and mate-rial diversity.In this study,we demonstrated flexible and rapid approaches for fabricating complicated and precise heterogeneous ceramics by shape-changing(4D)or shape-keeping(3D)additive-subtractive manufacturing(ASM)methods.The shape-changing strategy for heterogeneous ceramics was achieved by global ceramization of heterogeneous precursors,while the shape-keeping strategy for heterogeneous ceramics was achieved by local receramization of homogeneous ceramics.Finite element analysis(FEA)simulations of the influence of the thermal shrinkage dominant in the shape-changing strategy on the shape deformation of heterogeneous ceramics could be valuable predictions of the experimental results.The 3D/4D ASM methods are generic for high-temperature materials and extendable to metallic and dia-mond materials.
基金support from the National Natural Science Foundation of China(Nos.52322104,52172067,and 92160202)the Natural Science Foundation of Guangdong Province(No.2021B1515020038)+2 种基金the Guangdong Special Support Program(No.2019BT02C629)the Guangdong Provincial Science and Technology Program(No.2023A0505010017)the Science Center for Gas Turbine Project(No.P2023-C-IV-002-001).
文摘The unique multilayer, multiscale structure of teakwood results in excellent mechanical and long-term environmental stability, providing inspiration for the biomimetic design of environmental barrier coating (EBC) structures. However, achieving the desired biomimetic structure control in high-temperature plasma spraying is a challenging task that requires new technological breakthroughs. In this study, a multiscale nano Yb_(2)Si_(2)O_(7)–Yb_(2)SiO_(5) (YbDS–YbMS) composite EBC with a teakwood-like lamellar structure was realized via a novel alternating vapor/liquid phase deposition method involving plasma spraying-physical vapor deposition (PS-PVD). Volatilized waste SiO_(2) from Yb_(2)Si_(2)O_(7) (YbDS) was reused and deposited on the coating surface during the spraying process, where a regularly arranged multilayer structure was formed in the coating by the alternate deposition of gaseous SiO_(2) and droplet YbDS. In addition, SiO_(2) on the coated surface formed nanoclusters and dome-shaped nanocrystals via homogeneous and heterogeneous nucleation, respectively, and some of them gradually formed a continuous nanofilm as the arc current increased. The deposited SiO_(2) reacted in situ with the decomposed phase YbMS in the coating to form YbDS, preserving its multiscale nanostructure after heat treatment and enabling the preparation of the YbDS–YbMS composite coating. This work provides a new design strategy and method for the preparation of coatings using YbDS and other spray powders with similar decomposition and volatilization characteristics during the plasma spraying process.
基金supported by the National Natural Science Foundation of China(No.51901175)the Guangdong Province Outstanding Youth Foundation(No.2021B1515020038)+3 种基金the Guangzhou Technical Research Program(No.201906010015)the Industry University Research Project funded by Aero Engine Corporation of China(No.HFZL2019CXY015)the Postdoctoral Research Foundation of China(Nos.2020T130499 and 2019M653602)the National Program for Support of Top-notch Young Professionals.
文摘Environmental barrier coatings(EBCs)effectively protect the ceramic matrix composites(CMCs)from harsh engine environments,especially steam and molten salts.However,open pores inevitably formed during the deposition process provide the transport channels for oxidants and corrosives,and lead to premature failure of EBCs.This research work proposed a method of pressure infiltration densification which blocked these open pores in the coatings.These results showed that it was difficult for aluminum to infiltrate spontaneously,but with the increase of external gas pressure and internal vacuum simultaneously,the molten aluminum obviously moved forward,and finally stopped infiltrating at a depth of a specific geometry.Based on the wrinkled zigzag pore model,a mathematical relationship between the critical pressure with the infiltration depth and the pore intrinsic geometry was established.The infiltration results confirmed this relationship,indicating that for a given coating,a dense thick film can be obtained by adjusting the internal and external gas pressures to drive a melt infiltration.
基金the National Natural Science Foundation of China(NSFC)(No.11704285)the Natural Science Foundation of Zhejiang Province(No.LY20E050027)the Wenzhou Science and Technology Plan Projects(No.G20170012).
文摘The laser shock processing implemented by a laser-induced high-pressure plasma which propagates into the sample as a shockwave is innovatively applied as a post-processing technique on HfO_(2)/SiO_(2) multilayer coatings for the first time.The pure mechanical post-processing has provided evidence of a considerable promotion effect of the laser-induced damage threshold,which increased by a factor of about 4.6 with appropriate processing parameters.The promotion mechanism is confirmed to be the comprehensive modification of the intrinsic defects and the mechanical properties,which made the applicability of this novel post-processing technique on various types of coatings possible.Based on experiments,an interaction equation for the plasma pressure is established,which clarifies the existence of the critical pressure and provides a theoretical basis for selecting optimal processing parameters.In addition to the further clarification of the underlying damage mechanism,the laser shock post-processing provides a promising technique to realize the comprehensive and effective improvement of the laser-induced damage resistance of coatings.
基金We would like to acknowledge the financial support from the National Natural Science Foundation of China(52172067)Guangdong Province Outstanding Youth Foundation(2021B1515020038)+1 种基金Guangdong Special Support Program(2019BT02C629)Guangdong Academy of Sciences Program(2020GDASYL-20200104030).
文摘Plasma spray-physical vapor deposition(PS-PVD)as a novel process was used to prepare feather-like columnar thermal barrier coatings(TBCs).This special microstructure shows good strain tolerance and non-line-of-sight(NLOS)deposition,giving great potential application in aero-engine.However,due to serious service environment of aero-engine,particle erosion performance is a weakness for PS-PVD 7YSZ TBCs.As a solution,an Al-modification approach was proposed in this investigation.Through in-situ reaction of Al and ZrO2,anα-Al2O3 overlay can be formed on the surface of 7YSZ columnar coating.The results demonstrate that this approach can improve particle erosion resistance since hardness improvement of Al-modified TBCs.Meanwhile,as another important performance of thermal cycle,it has a better optimization with 350-cycle water-quenching,compared with the as-sprayed TBCs.
文摘Thermal barrier coatings(TBCs)can effectively protect the alloy substrate of hot components in aeroengines or land-based gas turbines by the thermal insulation and corrosion/erosion resistance of the ceramic top coat.However,the continuous pursuit of a higher operating temperature leads to degradation,delamination,and premature failure of the top coat.Both new ceramic materials and new coating structures must be developed to meet the demand for future advanced TBC systems.In this paper,the latest progress of some new ceramic materials is first reviewed.Then,a comprehensive spalling mechanism of the ceramic top coat is summarized to understand the dependence of lifetime on various factors such as oxidation scale growth,ceramic sintering,erosion,and calcium–magnesium–aluminium–silicate(CMAS)molten salt corrosion.Finally,new structural design methods for high-performance TBCs are discussed from the perspectives of lamellar,columnar,and nanostructure inclusions.The latest developments of ceramic top coat will be presented in terms of material selection,structural design,and failure mechanism,and the comprehensive guidance will be provided for the development of next-generation advanced TBCs with higher temperature resistance,better thermal insulation,and longer lifetime.
基金support from the National Major Science and Technology Projects of China(No.Y2022-1II-0004-0013)the National Natural Science Foundation of China(No.52272065),and the Program of the China Scholarships Council(No.202206830106)+1 种基金performed at the Hefei Advanced Computing Center.Moreover,we appreciate eceshi(www.eceshi.com)for SEM-FIB analysiswe acknowledge the Center for Microscopy and Analysis at Nanjing University of Aeronautics and Astronautics for SEMEDS analysis.
文摘The development of Si-HfO_(2)/Yb_(2)Si_(2)O_(7)/Yb_(2)SiO_(5)environmental barrier coatings(EBCs)aims to improve the operational temperature and longevity of ceramic matrix composites(CMCs)in turbine environments.Nevertheless,several critical questions remain unanswered,including the oxidation mechanism of Si-HfO_(2)bond coating,the compatibility of its mixed thermally grown oxide(m-TGO)with adjacent layers during thermal cycling,and the evolution pattern of vertical mud-cracks that impact the overall performance in service.Using plasma spraying physical vapor deposition(PS-PVD),we fabricated these EBCs on a CMC substrate,and thermal cycling tests at 1400,1450,and 1500℃ revealed that their durability reached 200 h.m-TGO growth followed a parabolic model,with the oxygen diffusion activation energy being 133.69 kJ/mol between 1400 and 1450℃ and 101.47 kJ/mol from 1450 to 1500℃,emphasizing that the transport of molecular oxygen is key to controlling the oxidation of m-TGO in this EBC system.Although residual stresses and stored elastic strain energy build up between m-TGO and adjacent layers,especially around the cristobalite phase transition temperature,causing interlaminar crack formation in later thermal cycles,the stored elastic strain energy remains lower than that of the silicon oxide-thermally grown oxide(SiO_(2)-TGO)formed in Si bond coating system.In addition to[110]dislocations,(001)twinning and interaction zones between twinning and dislocations were discovered for the first time,driving the bifurcation of mud cracks.Notably,controlling the mud-crack density is vital for protection of Yb_(2)SiO_(5)layer,as bifurcated mud-crack tips may converge with adjacent mud-cracks.
基金financially supported by the National Natural Science Foundation of China(No.52375370)the Natural Science Research General Program of Shanxi Province,China(No.202103021224048)+1 种基金the Shanxi Province Patent Transformation Project(No.202406019)the Shanxi-Zhejiang University New Materials and Chemical Research Institute Scientific Research Project(No.2022SXTD025).
文摘Zinc-based composites represent promising materials for orthopedic implants owing to their adjustable degradation rates and excellent biocompatibility.In this study,a series of Zn-10Mg-xHA(x=0-5 wt.%)composites with the core-shell structure were prepared through spark plasma sintering,and their microstructural,mechanical,and in vitro properties were systematically evaluated.Results showed that the doped hydroxyapatite(HA)is concentrated at the outer edge of the MgZn2 shell layer.The compression strength of the Zn-1oMg HA composite gradually decreased with the increase of the HA content,while its corrosion rate decreased initially and then increased.The corrosion resistance of the composite with the addition of 1 wt.%HA was improved compared to that of Zn-10Mg-0HA.However,the further increase of the HA content beyond 1 wt.%resulted in a faster degradation of the composite.Moreover,the Zn-10Mg-1HA composite significantly enhanced the activity of Mc3T3-E1 osteoblasts.Based on such findings,it is revealed that the composite containing 1 wt.%HA exhibits superior overall properties and is anticipated to serve as a promising candidate for bone implantmaterials.
