Pure WC-6%Co nanosized composite powders were synthesized via a low-temperature method.The effects of carbon source on microstructure characteristic of composite powders were investigated,and the effects of heat-treat...Pure WC-6%Co nanosized composite powders were synthesized via a low-temperature method.The effects of carbon source on microstructure characteristic of composite powders were investigated,and the effects of heat-treatment parameter on carbon content of composite powders were also discussed.The results of SEM and XRD revealed that the carbon decomposing from glucose was more active than carbon black.Therefore,WC-Co nanosized composite powders could be synthesized at 900°C for 1 h under a hydrogen atmosphere.The individual WC grains were bonded together into a long strip under the action of cobalt.The results of carbon analysis revealed that the total carbon content decreased with the increase of the temperature in the range of 800-1000°C.Moreover,the total carbon content and the compounded carbon increased with the increase of the flow rate of H2 in the range of 1.1-1.9 m3/h.展开更多
Ti6Al4V powders with three different particle size distributions(0–20, 20–45, and 45–75 μm) were used to evaluate the effect of the particle size distribution on the solid-state sintering and their mechanical prop...Ti6Al4V powders with three different particle size distributions(0–20, 20–45, and 45–75 μm) were used to evaluate the effect of the particle size distribution on the solid-state sintering and their mechanical properties. The sintering kinetics was determined by dilatometry at temperatures from 900 to 1260°C. The mechanical properties of the sintered samples were evaluated by microhardness and compression tests. The sintering kinetics indicated that the predominant mechanism depends on the relative density irrespective of the particle size used. The mechanical properties of the sintered samples are adversely affected by increasing pore volume fraction. The elastic Young's modulus and yield stress follow a power law function of the relative density. The fracture behavior after compression is linked to the neck size developed during sintering, exhibiting two different mechanisms of failure: interparticle neck breaking and intergranular cracking in samples with relative densities below and above of 90%, respectively. The main conclusion is that relative density is responsible for the kinetics, mechanical properties, and failure behavior of Ti6 Al4 V powders.展开更多
Ti-6 Al-4 V alloy powder was processed by electrode induction melting gas atomization(EIGA)at high gas pressure(5.5-7.0 MPa).The effects of atomizing gas pressure on the powder characteristics and the microstructure,a...Ti-6 Al-4 V alloy powder was processed by electrode induction melting gas atomization(EIGA)at high gas pressure(5.5-7.0 MPa).The effects of atomizing gas pressure on the powder characteristics and the microstructure,along with the mechanical properties of the as-fabricated block by laser melting deposition(LMD),were investigated.The results indicate that the diameters of powders are distributed in a wide range of sizes from 1 to 400μm,and the median powder size(d50)decreases with increasing gas pressure.The powders with a size fraction of 100-150μm obtained at gas pressures of 6.0 and 6.5 MPa have better flowability.The oxygen content is consistent with the change trend of gas pressure within a low range of 0.06%-0.20%.Specimens fabricated by LMD are mainly composed ofα+βgrains with a fine lamellar Widmanstatten structures and have the ultimate tensile strength(UTS)and yield strength of approximately 1100 and 1000 MPa,respectively.Furthermore,the atomized powders have a favorable 3 D printing capability,and the mechanical properties of Ti-6 Al-4 V alloys manufactured by LMD typically exceed those of their cast or wrought counterparts.展开更多
Taking Ti6Al4V titanium alloy powder as the research object,on the basis of single layer scanning and single channel scanning experiment,this paper studies the influence of selective laser melting(SLM)process paramete...Taking Ti6Al4V titanium alloy powder as the research object,on the basis of single layer scanning and single channel scanning experiment,this paper studies the influence of selective laser melting(SLM)process parameters on Ti6Al4V alloy material formability,and block forming experiment is carried out.Through the design of orthogonal experiment,morphology observation of sample and density analysis,results show that the best block molding parameters of SLM technology in Ti6Al4V alloy powder are laser power of 400 W,lap rate of 1 and the scanning speed of 750 mm/min,density can up to 96.17%.展开更多
Ti6Al4V powder compaction was performed by using magnetic pulse compaction in air at 200℃.Effects of process parameters such as voltage,capacitance,discharge times on the microstructure,compressive strength,hardness ...Ti6Al4V powder compaction was performed by using magnetic pulse compaction in air at 200℃.Effects of process parameters such as voltage,capacitance,discharge times on the microstructure,compressive strength,hardness and relative density of compacts were investigated.The experimental results show that the relative density,hardness and compressive strength of compacted specimens increase with increasing voltage.In addition,the relative density and compressive strength of compacted specimens increase with the augmentation of capacitance in the range investigated.The relative density increases,the hardness firstly increases and then tends to be a fixed value;and the compressive strength firstly increases and then decreases from one to five times compaction.Both values of the hardness and compressive strength reach the maxima of HRA 69.1 and 1 062.31 MPa,at three times compaction,respectively.There are pores in and between particles.展开更多
This study was carried out to determine the effect of the age of the leaves and fermentation on in vitro protein digestibility and biochemical properties of leaves powder of Moringa oleifera. A 6 × 2 × 2 fac...This study was carried out to determine the effect of the age of the leaves and fermentation on in vitro protein digestibility and biochemical properties of leaves powder of Moringa oleifera. A 6 × 2 × 2 factorial design with two ages of the leaves (one and seven-month-old leaves), six times of fermentation and two fermentation temperatures was used for this purpose. One and seven-month-old fresh leaves were dried at 45 ℃ for 24 h, crushed to 1000 μm then fermented at 30℃ and 37℃ for 120 hours with Lactobacillus plantarum A6 at 108 CFU/g. Samples were withdrawn every 24 hours for physico-chemical analyses. Results showed that 7 month-old leaves were richer in iron, proteins, polyphenols and phytates than one month old leaves. The phytates content dropped from 66.92% and 61.95% in the seven and one month-old leaves powders respectively fermented at 37℃, and from 54.15% and 67.95% in the seven and one month-old leaves powders respectively fermented at 30℃. Protein content increased by 26.34% and 24.48% for the 1and 7-month-old leaves powders respectively fermented at 37℃, and by 13.06% and 13.97% for the 1and 7month-old leaves powders respectively, fermented at 30℃. Iron availability increased from 35.97% to 40.57% and 20.74% to 30.98% for the 1and 7-month-old leaves powders respectively, fermented at 37℃ and from 35.97% to 39.79% and 20.76% to 23.72% for the 1and 7-month-old leaves powders respectively, fermented at 30℃. There was a negative correlation between pH, total and reducing sugar contents, time as well as fermentation temperature, whereas there was a positive correlation between total protein content and pepsic digestibility of protein and fermentation time. From these results, fermentation of M. oleifera leaf powder by Lactobacillus plantarum A6 increases protein content, pepsic digestibility of protein and availability of iron and reduces the phytates content of these powders.展开更多
The Ti−6Al−4V(TC4)alloy powder and forged solid were diffusion bonded by hot isostatic pressing(HIP)to fabricate a powder−solid part.The microstructure of the powder−solid part was observed by scanning electron micros...The Ti−6Al−4V(TC4)alloy powder and forged solid were diffusion bonded by hot isostatic pressing(HIP)to fabricate a powder−solid part.The microstructure of the powder−solid part was observed by scanning electron microscope(SEM).The microhardness and tensile tests were conducted to investigate the mechanical properties.The results showed that the powder compact was near-fully dense,and the powder/solid interface was tight and complete.The microhardness of the interface was higher than that of the powder compact and solid.The fractures of all powder−solid tensile specimens were on the solid side rather than at the interface,which indicated that a good interfacial strength was obtained.The tensile strength and elongation of the powder compact were higher than those of the solid.It is concluded that the HIP process can successfully fabricate high-quality Ti−6Al−4V powder−solid parts,which provides a novel near net shape technology for titanium alloys.展开更多
SiCf/Ti-6Al-4V composites were fabricated by the powder-coated fiber method. The precursor fiber was prepared under the optimized parameter, and the composites were made using the vacuum hot pressure method. The influ...SiCf/Ti-6Al-4V composites were fabricated by the powder-coated fiber method. The precursor fiber was prepared under the optimized parameter, and the composites were made using the vacuum hot pressure method. The influence of heat exposure time on products of thelinterfacial reaction was investigated using scanning electron microscope （SEM） and analytical transmission electron microscope （TEM） with energy dispersive spectrometer （EDS）. The main products are TiC and Ti5Si3 after vacuum exposing the samples at 700℃ for 50 h. The growth dynamics of interracial reaction products was analyzed quantitatively, which fitted the parabola rule. The activity energy of the reaction was 252 kJ·mol^-1.展开更多
The potential of powder metallurgy processing for the manufacture of Al?SrB6 composites was explored. Al4Sr particles fractured extensively during the ball milling of Al?15Sr/Al?4B powder mixtures. There was no intera...The potential of powder metallurgy processing for the manufacture of Al?SrB6 composites was explored. Al4Sr particles fractured extensively during the ball milling of Al?15Sr/Al?4B powder mixtures. There was no interaction between the Al4Sr and AlB2 compounds across the section of the aluminium grains in the as-milled state. SrB6 formed, when the ball milled powder blends were subsequently annealed at sufficiently high temperatures. Ball milling for 1 h was sufficient for SrB6 to become the major constituent in powder blends annealed at 700 °C while it took 2 h of ball milling for powder blends annealed at 600 °C. Higher annealing temperatures and longer ball milling time encouraged the formation of the SrB6 compound while the latter made a great impact on the microstructural features of the Al?SrB6 composite. The SrB6 compound particles were much smaller and more uniformly distributed across the aluminium matrix grains in powder grains ball milled for 2 h before the annealing treatments at 600 °C and 700 °C.展开更多
Direct LMD （laser metal deposition） was used to fabricate thin-wall Ti-6Al-4V using the powder mixture of Ti-6 wt.%Al-4 wt.%V. SEM （scanning electron microscopy）, OM （optical microscopy） and EDS （energy dispers...Direct LMD （laser metal deposition） was used to fabricate thin-wall Ti-6Al-4V using the powder mixture of Ti-6 wt.%Al-4 wt.%V. SEM （scanning electron microscopy）, OM （optical microscopy） and EDS （energy dispersive spectroscopy） were employed to examine the chemical composition and microstructure of the as-deposited sections. Vickers hardness tests were then applied to characterize the mechanical properties of the deposit samples which were fabricated using pre-mixed elemental powders. The EDS line scans indicated that the chemical composition of the samples was homogenous across the deposit. After significant analysis, some differences were observed among two sets of deposit samples which varied in the particle size of the mixing Ti-6wt.%Al-4wt.%V powder. It could be found that the set with similar particle number for Ti, Al and V powder made composition much more stable and could easily get industry qualified Ti-6Al-4V components.展开更多
基金Project(51274107)supported by the National Natural Science Foundation of ChinaProject(2015FB127)supported by the Yunnan Natural Science Foundation,ChinaProject(2016P20151130003)supported by Analysis Foundation of Kunming University of Science and Technology,China
文摘Pure WC-6%Co nanosized composite powders were synthesized via a low-temperature method.The effects of carbon source on microstructure characteristic of composite powders were investigated,and the effects of heat-treatment parameter on carbon content of composite powders were also discussed.The results of SEM and XRD revealed that the carbon decomposing from glucose was more active than carbon black.Therefore,WC-Co nanosized composite powders could be synthesized at 900°C for 1 h under a hydrogen atmosphere.The individual WC grains were bonded together into a long strip under the action of cobalt.The results of carbon analysis revealed that the total carbon content decreased with the increase of the temperature in the range of 800-1000°C.Moreover,the total carbon content and the compounded carbon increased with the increase of the flow rate of H2 in the range of 1.1-1.9 m3/h.
基金the National Laboratory SEDEAM-National Council for Science and Technology (CONACYT)ECOS M15P01 for the financial support and the facilities to develop this study
文摘Ti6Al4V powders with three different particle size distributions(0–20, 20–45, and 45–75 μm) were used to evaluate the effect of the particle size distribution on the solid-state sintering and their mechanical properties. The sintering kinetics was determined by dilatometry at temperatures from 900 to 1260°C. The mechanical properties of the sintered samples were evaluated by microhardness and compression tests. The sintering kinetics indicated that the predominant mechanism depends on the relative density irrespective of the particle size used. The mechanical properties of the sintered samples are adversely affected by increasing pore volume fraction. The elastic Young's modulus and yield stress follow a power law function of the relative density. The fracture behavior after compression is linked to the neck size developed during sintering, exhibiting two different mechanisms of failure: interparticle neck breaking and intergranular cracking in samples with relative densities below and above of 90%, respectively. The main conclusion is that relative density is responsible for the kinetics, mechanical properties, and failure behavior of Ti6 Al4 V powders.
基金Project(2017YFB0305801)supported by the National Key R&D Program of ChinaProject(U1508213)supported by the Joint-Fund of NSFC-Liaoning,ChinaProject(51771051)supported by the National Natural Science Foundation of China.
文摘Ti-6 Al-4 V alloy powder was processed by electrode induction melting gas atomization(EIGA)at high gas pressure(5.5-7.0 MPa).The effects of atomizing gas pressure on the powder characteristics and the microstructure,along with the mechanical properties of the as-fabricated block by laser melting deposition(LMD),were investigated.The results indicate that the diameters of powders are distributed in a wide range of sizes from 1 to 400μm,and the median powder size(d50)decreases with increasing gas pressure.The powders with a size fraction of 100-150μm obtained at gas pressures of 6.0 and 6.5 MPa have better flowability.The oxygen content is consistent with the change trend of gas pressure within a low range of 0.06%-0.20%.Specimens fabricated by LMD are mainly composed ofα+βgrains with a fine lamellar Widmanstatten structures and have the ultimate tensile strength(UTS)and yield strength of approximately 1100 and 1000 MPa,respectively.Furthermore,the atomized powders have a favorable 3 D printing capability,and the mechanical properties of Ti-6 Al-4 V alloys manufactured by LMD typically exceed those of their cast or wrought counterparts.
文摘Taking Ti6Al4V titanium alloy powder as the research object,on the basis of single layer scanning and single channel scanning experiment,this paper studies the influence of selective laser melting(SLM)process parameters on Ti6Al4V alloy material formability,and block forming experiment is carried out.Through the design of orthogonal experiment,morphology observation of sample and density analysis,results show that the best block molding parameters of SLM technology in Ti6Al4V alloy powder are laser power of 400 W,lap rate of 1 and the scanning speed of 750 mm/min,density can up to 96.17%.
文摘Ti6Al4V powder compaction was performed by using magnetic pulse compaction in air at 200℃.Effects of process parameters such as voltage,capacitance,discharge times on the microstructure,compressive strength,hardness and relative density of compacts were investigated.The experimental results show that the relative density,hardness and compressive strength of compacted specimens increase with increasing voltage.In addition,the relative density and compressive strength of compacted specimens increase with the augmentation of capacitance in the range investigated.The relative density increases,the hardness firstly increases and then tends to be a fixed value;and the compressive strength firstly increases and then decreases from one to five times compaction.Both values of the hardness and compressive strength reach the maxima of HRA 69.1 and 1 062.31 MPa,at three times compaction,respectively.There are pores in and between particles.
文摘This study was carried out to determine the effect of the age of the leaves and fermentation on in vitro protein digestibility and biochemical properties of leaves powder of Moringa oleifera. A 6 × 2 × 2 factorial design with two ages of the leaves (one and seven-month-old leaves), six times of fermentation and two fermentation temperatures was used for this purpose. One and seven-month-old fresh leaves were dried at 45 ℃ for 24 h, crushed to 1000 μm then fermented at 30℃ and 37℃ for 120 hours with Lactobacillus plantarum A6 at 108 CFU/g. Samples were withdrawn every 24 hours for physico-chemical analyses. Results showed that 7 month-old leaves were richer in iron, proteins, polyphenols and phytates than one month old leaves. The phytates content dropped from 66.92% and 61.95% in the seven and one month-old leaves powders respectively fermented at 37℃, and from 54.15% and 67.95% in the seven and one month-old leaves powders respectively fermented at 30℃. Protein content increased by 26.34% and 24.48% for the 1and 7-month-old leaves powders respectively fermented at 37℃, and by 13.06% and 13.97% for the 1and 7month-old leaves powders respectively, fermented at 30℃. Iron availability increased from 35.97% to 40.57% and 20.74% to 30.98% for the 1and 7-month-old leaves powders respectively, fermented at 37℃ and from 35.97% to 39.79% and 20.76% to 23.72% for the 1and 7-month-old leaves powders respectively, fermented at 30℃. There was a negative correlation between pH, total and reducing sugar contents, time as well as fermentation temperature, whereas there was a positive correlation between total protein content and pepsic digestibility of protein and fermentation time. From these results, fermentation of M. oleifera leaf powder by Lactobacillus plantarum A6 increases protein content, pepsic digestibility of protein and availability of iron and reduces the phytates content of these powders.
基金the National Natural Science Foundation of China(No.51675029).
文摘The Ti−6Al−4V(TC4)alloy powder and forged solid were diffusion bonded by hot isostatic pressing(HIP)to fabricate a powder−solid part.The microstructure of the powder−solid part was observed by scanning electron microscope(SEM).The microhardness and tensile tests were conducted to investigate the mechanical properties.The results showed that the powder compact was near-fully dense,and the powder/solid interface was tight and complete.The microhardness of the interface was higher than that of the powder compact and solid.The fractures of all powder−solid tensile specimens were on the solid side rather than at the interface,which indicated that a good interfacial strength was obtained.The tensile strength and elongation of the powder compact were higher than those of the solid.It is concluded that the HIP process can successfully fabricate high-quality Ti−6Al−4V powder−solid parts,which provides a novel near net shape technology for titanium alloys.
文摘SiCf/Ti-6Al-4V composites were fabricated by the powder-coated fiber method. The precursor fiber was prepared under the optimized parameter, and the composites were made using the vacuum hot pressure method. The influence of heat exposure time on products of thelinterfacial reaction was investigated using scanning electron microscope （SEM） and analytical transmission electron microscope （TEM） with energy dispersive spectrometer （EDS）. The main products are TiC and Ti5Si3 after vacuum exposing the samples at 700℃ for 50 h. The growth dynamics of interracial reaction products was analyzed quantitatively, which fitted the parabola rule. The activity energy of the reaction was 252 kJ·mol^-1.
文摘The potential of powder metallurgy processing for the manufacture of Al?SrB6 composites was explored. Al4Sr particles fractured extensively during the ball milling of Al?15Sr/Al?4B powder mixtures. There was no interaction between the Al4Sr and AlB2 compounds across the section of the aluminium grains in the as-milled state. SrB6 formed, when the ball milled powder blends were subsequently annealed at sufficiently high temperatures. Ball milling for 1 h was sufficient for SrB6 to become the major constituent in powder blends annealed at 700 °C while it took 2 h of ball milling for powder blends annealed at 600 °C. Higher annealing temperatures and longer ball milling time encouraged the formation of the SrB6 compound while the latter made a great impact on the microstructural features of the Al?SrB6 composite. The SrB6 compound particles were much smaller and more uniformly distributed across the aluminium matrix grains in powder grains ball milled for 2 h before the annealing treatments at 600 °C and 700 °C.
文摘Direct LMD （laser metal deposition） was used to fabricate thin-wall Ti-6Al-4V using the powder mixture of Ti-6 wt.%Al-4 wt.%V. SEM （scanning electron microscopy）, OM （optical microscopy） and EDS （energy dispersive spectroscopy） were employed to examine the chemical composition and microstructure of the as-deposited sections. Vickers hardness tests were then applied to characterize the mechanical properties of the deposit samples which were fabricated using pre-mixed elemental powders. The EDS line scans indicated that the chemical composition of the samples was homogenous across the deposit. After significant analysis, some differences were observed among two sets of deposit samples which varied in the particle size of the mixing Ti-6wt.%Al-4wt.%V powder. It could be found that the set with similar particle number for Ti, Al and V powder made composition much more stable and could easily get industry qualified Ti-6Al-4V components.
