Nb and Ti-13 Nb powders were used for improving the surface of Ti6Al4 V alloy.The deposition of the powders was carried out at various laser powers.The scanning electron microscopy（SEM）-EDS and optical microscopy we...Nb and Ti-13 Nb powders were used for improving the surface of Ti6Al4 V alloy.The deposition of the powders was carried out at various laser powers.The scanning electron microscopy（SEM）-EDS and optical microscopy were used for characterization.X-ray diffractometer（XRD） was used for analyzing the elemental composition and phase constituents.The hardness,wear and corrosion properties were achieved.The corrosion and the wear behaviours of the deposited layers were studied in a Hanks solution（simulated body fluid,SBF）.The microstructures of Nb coatings reveal the presence of orthorhombic,dendritic α″ and metastable β-Nb phases which produce uneven hardness with an average of HV 364.For Ti-13 Nb coatings,martensitic α′ and metastable β-Nb phases with an average hardness of HV 423 were observed.The resistance of wear on dry sliding of Ti-13 Nb coating is attributed to the increase in hardness.Experimental results indicate that deposition of Nb and Ti-13 Nb on Ti6Al4 V grossly reduces the mass fractions of Al and V in all coatings.In SBF,Nb reinforcement produces the best coating that reveals the best wear and corrosion resistances as compared with the substrate.Hence,this coating will perform best for orthopaedic implant material enhancement.展开更多
The leaching process of magnesiothermic self-propagating product generated during the multistage deep reduction process was investigated.The influence of magnesiothermic self-propagating product particle size,HCl solu...The leaching process of magnesiothermic self-propagating product generated during the multistage deep reduction process was investigated.The influence of magnesiothermic self-propagating product particle size,HCl solution concentration,and leaching solution temperature on the leaching behavior of elements Al and V was investigated.Results demonstrate that the leaching rate of Al and V is increased with the rise in leaching solution temperature,the increase in HCl solution concentration,and the enlargement of magnesiothermic self-propagating product particle size.The leaching processes of Al and V are consistent with the chemical reaction control model.When the magnesiothermic self-propagation product with D_(50) of 59.4μm is selected as the raw material,the leaching temperature is 40℃,and 1 mol/L HCl solution is employed,after leaching for 180 min,the leaching rates of Al and V are 24.8%and 12.6%,respectively.The acid-leached product exhibits a porous structure with a specific surface area of 3.5633 m^(2)/g.展开更多
Titanium/magnesium alloy bimetal composites show promising prospects for lightweight applications.The Ti/Mg bimetal composite was fabricated in Ti−6Al−4V pyramidal lattice structure via AZ91D melt infiltration.Compara...Titanium/magnesium alloy bimetal composites show promising prospects for lightweight applications.The Ti/Mg bimetal composite was fabricated in Ti−6Al−4V pyramidal lattice structure via AZ91D melt infiltration.Comparative analysis of the tensile and compressive properties was conducted between the composite and its constituent materials(Ti−6Al−4V lattice structure and AZ91D matrix).The tensile strength of the composite(95.9 MPa)was comparable to that of the Ti−6Al−4V lattice structure(94.4 MPa)but lower than that of the AZ91D alloy(120.8 MPa)due to gaps at the bimetal interfaces hindering load transfer during tension.The composite exhibited greater elongation(1.7%)compared to AZ91D(1.4%)alloy but less than the Ti−6Al−4V lattice structure(2.6%).The compressive performance of the composite outperformed that of the Ti−6Al−4V lattice structure,underscoring the significance of the AZ91D alloy in compressive deformation.Fracture analysis indicated that the predominant failure reasons in both the composite and lattice structures were attributed to the breakage of lattice struts at nodes caused by the stress concentration.展开更多
The poor wear resistance limits the applications of Ti6Al4V alloy.The additive manufactured Ti6Al4V alloy,particularly produced in the air,has issues with the poor forming quality.In this study,a rare earth compound(L...The poor wear resistance limits the applications of Ti6Al4V alloy.The additive manufactured Ti6Al4V alloy,particularly produced in the air,has issues with the poor forming quality.In this study,a rare earth compound(LaB_(6))was introduced to enhance both the forming quality and bio-tribological properties of Ti6Al4V alloy.The results show that adding an appropriate amount of LaB_(6)can reduce defects(pores).The micro structure is obviously refined due to pinning and heterogeneous nucleation effects,and the La_(2)O_(3)and TiB are formed through the in-situ reactions.The sample with 4 wt%LaB_(6)addition exhibits excellent microhardness and bio-tribological properties.Grain refinement,dispersion strengthening and solution strengthening can significantly improve the microhardness,and the bio-tribological properties are further improved when combined with the in-situ network-structured hard TiB whisker(TiBw).This work is expected to provide reference suggestions for the development of additive manufactured titanium alloys and its application in implants.展开更多
Experimental tests are essential for evaluating S-N curves and assessing the fatigue life of welded joints.However,in the case of complex geometries,experimental tests often cannot provide the necessary stress-strain ...Experimental tests are essential for evaluating S-N curves and assessing the fatigue life of welded joints.However,in the case of complex geometries,experimental tests often cannot provide the necessary stress-strain data for specific materials and welded joints.Therefore,finite element(FE)analyses are frequently utilized to assess fatigue behavior in complex geometries and address the discontinuities induced by welding processes.In this study,the fatigue properties of titanium welded joints,produced using an innovative laser source and welded without the use of filler materials,were analyzed through numerical methods.Two different FEmethodswere applied to T-specimens fabricated from Ti6Al4V sheets:the hot-spot stress and notch-stress approach.The FE fatigue life predictions were validated using experimental fatigue test results.The Hot-Spot Stress method yielded a fatigue limit slightly below 100 MPa,demonstrating a consistent slope in the S-N response.Conversely,the Notch Stress method,using a 1 mm fictitious notch radius,indicated a higher fatigue strength corresponding to a range between 225 and 250MPa,providing amore conservative and localized fatigue estimate.Fatigue resistance in welded joints of steel and aluminum is commonly assessed using specific fatigue classes called“Fatigue Strength Classes(FAT)curves”and their associated S-N curves as recommended by the International Institute of Welding(IIW).However,no such FAT class assignments currently exist for titanium alloys.To address this gap,strain-based FAT curves were proposed by normalizing steel FAT curves using titanium’s elastic properties.This strain-based framework enables direct comparison across materials and provides a foundation for fatigue evaluation of titanium weldments.The author proposed a procedure to normalize steel FAT curves considering the different elastic material properties,enabling a comparison with Ti6Al4V data in terms of hot spot strain or notch strain.This approach facilitates the development of a universal framework for strain-based fatigue evaluation across different materials.展开更多
基金financially supported by the National Research Foundation of South AfricaThe National Laser Centre,CSIR,Pretoria,South Africa,is appreciated for laser facilitythe support from Tshwane University of Technology,South Africa
文摘Nb and Ti-13 Nb powders were used for improving the surface of Ti6Al4 V alloy.The deposition of the powders was carried out at various laser powers.The scanning electron microscopy（SEM）-EDS and optical microscopy were used for characterization.X-ray diffractometer（XRD） was used for analyzing the elemental composition and phase constituents.The hardness,wear and corrosion properties were achieved.The corrosion and the wear behaviours of the deposited layers were studied in a Hanks solution（simulated body fluid,SBF）.The microstructures of Nb coatings reveal the presence of orthorhombic,dendritic α″ and metastable β-Nb phases which produce uneven hardness with an average of HV 364.For Ti-13 Nb coatings,martensitic α′ and metastable β-Nb phases with an average hardness of HV 423 were observed.The resistance of wear on dry sliding of Ti-13 Nb coating is attributed to the increase in hardness.Experimental results indicate that deposition of Nb and Ti-13 Nb on Ti6Al4 V grossly reduces the mass fractions of Al and V in all coatings.In SBF,Nb reinforcement produces the best coating that reveals the best wear and corrosion resistances as compared with the substrate.Hence,this coating will perform best for orthopaedic implant material enhancement.
基金Scientific and Technological Project of Nanyang(23KJGG017)Key Specialized Research&Development and Promotion Project(Scientific and Technological Project)of Henan Province(232102221022)+1 种基金College Students and Technology Innovation Fund Project of Nanyang Institute of Technology(2023139)Project of Doctoral Scientific Research Startup Fund of Nanyang Institute of Technology(NGBJ-2023-25)。
文摘The leaching process of magnesiothermic self-propagating product generated during the multistage deep reduction process was investigated.The influence of magnesiothermic self-propagating product particle size,HCl solution concentration,and leaching solution temperature on the leaching behavior of elements Al and V was investigated.Results demonstrate that the leaching rate of Al and V is increased with the rise in leaching solution temperature,the increase in HCl solution concentration,and the enlargement of magnesiothermic self-propagating product particle size.The leaching processes of Al and V are consistent with the chemical reaction control model.When the magnesiothermic self-propagation product with D_(50) of 59.4μm is selected as the raw material,the leaching temperature is 40℃,and 1 mol/L HCl solution is employed,after leaching for 180 min,the leaching rates of Al and V are 24.8%and 12.6%,respectively.The acid-leached product exhibits a porous structure with a specific surface area of 3.5633 m^(2)/g.
基金the financial support from the National Natural Science Foundation of China(Nos.51875062,52205336)。
文摘Titanium/magnesium alloy bimetal composites show promising prospects for lightweight applications.The Ti/Mg bimetal composite was fabricated in Ti−6Al−4V pyramidal lattice structure via AZ91D melt infiltration.Comparative analysis of the tensile and compressive properties was conducted between the composite and its constituent materials(Ti−6Al−4V lattice structure and AZ91D matrix).The tensile strength of the composite(95.9 MPa)was comparable to that of the Ti−6Al−4V lattice structure(94.4 MPa)but lower than that of the AZ91D alloy(120.8 MPa)due to gaps at the bimetal interfaces hindering load transfer during tension.The composite exhibited greater elongation(1.7%)compared to AZ91D(1.4%)alloy but less than the Ti−6Al−4V lattice structure(2.6%).The compressive performance of the composite outperformed that of the Ti−6Al−4V lattice structure,underscoring the significance of the AZ91D alloy in compressive deformation.Fracture analysis indicated that the predominant failure reasons in both the composite and lattice structures were attributed to the breakage of lattice struts at nodes caused by the stress concentration.
基金Project supported by the National Natural Science Foundation of China(52405176)the Guangdong Province Natural Science Foundation(2023A1515011558)+2 种基金the State Key Laboratory of Solid Lubrication Fund(LSL-2204)the Fundamental Research Funds for the Central Universities(N2403019)the Tribology Science Fund of the State Key Laboratory of Tribology in Advanced Equipment(SKLTKF24B15)。
文摘The poor wear resistance limits the applications of Ti6Al4V alloy.The additive manufactured Ti6Al4V alloy,particularly produced in the air,has issues with the poor forming quality.In this study,a rare earth compound(LaB_(6))was introduced to enhance both the forming quality and bio-tribological properties of Ti6Al4V alloy.The results show that adding an appropriate amount of LaB_(6)can reduce defects(pores).The micro structure is obviously refined due to pinning and heterogeneous nucleation effects,and the La_(2)O_(3)and TiB are formed through the in-situ reactions.The sample with 4 wt%LaB_(6)addition exhibits excellent microhardness and bio-tribological properties.Grain refinement,dispersion strengthening and solution strengthening can significantly improve the microhardness,and the bio-tribological properties are further improved when combined with the in-situ network-structured hard TiB whisker(TiBw).This work is expected to provide reference suggestions for the development of additive manufactured titanium alloys and its application in implants.
基金supported by the project PRIN_2022PNRR_P2022Y3PBY_001“MADLEINE,CUP:J53D23015830001”.Project funded under the National Recovery and Resilience Plan(NRRP),Mission 4 Component C2 Investment 1.1 by the European Union-NextGenerationEU.
文摘Experimental tests are essential for evaluating S-N curves and assessing the fatigue life of welded joints.However,in the case of complex geometries,experimental tests often cannot provide the necessary stress-strain data for specific materials and welded joints.Therefore,finite element(FE)analyses are frequently utilized to assess fatigue behavior in complex geometries and address the discontinuities induced by welding processes.In this study,the fatigue properties of titanium welded joints,produced using an innovative laser source and welded without the use of filler materials,were analyzed through numerical methods.Two different FEmethodswere applied to T-specimens fabricated from Ti6Al4V sheets:the hot-spot stress and notch-stress approach.The FE fatigue life predictions were validated using experimental fatigue test results.The Hot-Spot Stress method yielded a fatigue limit slightly below 100 MPa,demonstrating a consistent slope in the S-N response.Conversely,the Notch Stress method,using a 1 mm fictitious notch radius,indicated a higher fatigue strength corresponding to a range between 225 and 250MPa,providing amore conservative and localized fatigue estimate.Fatigue resistance in welded joints of steel and aluminum is commonly assessed using specific fatigue classes called“Fatigue Strength Classes(FAT)curves”and their associated S-N curves as recommended by the International Institute of Welding(IIW).However,no such FAT class assignments currently exist for titanium alloys.To address this gap,strain-based FAT curves were proposed by normalizing steel FAT curves using titanium’s elastic properties.This strain-based framework enables direct comparison across materials and provides a foundation for fatigue evaluation of titanium weldments.The author proposed a procedure to normalize steel FAT curves considering the different elastic material properties,enabling a comparison with Ti6Al4V data in terms of hot spot strain or notch strain.This approach facilitates the development of a universal framework for strain-based fatigue evaluation across different materials.
