A new method for corrosion protection of Al-based metal matrix composites (MMC) was developed using two-step process, which involves anodizing in H2SO4 solution and sealing in rare earth solution. Corrosion resistance...A new method for corrosion protection of Al-based metal matrix composites (MMC) was developed using two-step process, which involves anodizing in H2SO4 solution and sealing in rare earth solution. Corrosion resistance of the treated surface was evaluated with polarization curves. The results showed that the effect of the protection using rare earth sealing is equivalent to that using chromate sealing for A16061/SiCp. The rare earth metal salt can be an alternative to the toxic chromate for sealing anodized Al MMC.展开更多
Diamond grinding wheel were prepared with Al-based bonding agent.The microstructure of Al-based diamond grinding wheel was observed by SEM.The fracture morphology,interface between bonding agent and diamond,and the el...Diamond grinding wheel were prepared with Al-based bonding agent.The microstructure of Al-based diamond grinding wheel was observed by SEM.The fracture morphology,interface between bonding agent and diamond,and the elemental distribution in bonding agent were studied.The results showed that there were some Al-based agents retained on the diamond surface.Ti,Ni formed intermetallurgy phase with Al in the agent and reduced the plasticity of bonding agent.The service life of this Al-based diamond grinding wheel is proved by the grinding experiments to be three times as long as that of resin-bonded grinding wheel.展开更多
The effect of hot-rolling processing on microstructure as well as the relationship between the elongated grain structure and tensile properties are investigated. The results indicate that the elongated grain structure...The effect of hot-rolling processing on microstructure as well as the relationship between the elongated grain structure and tensile properties are investigated. The results indicate that the elongated grain structure influences the tensile properties and creep rupture life of Fe3Al alloy significantly. For the better strength and ductility at RT,a thinner elongated grain structure is desirable. When the elongated grain size is increased, the tensile properties will be decreased. On the other hand, the creeP rupture life at 600℃ is increased with the increase of elongated grain size.展开更多
The Proccss of gascous hydrogcn charging into a Ti_3Al- based alloy in the temperature range of 500-650℃isinvcstigatcd. The rcsnlls snoxvc that in rclatiollshil, between the average hydrogen concentration at constant...The Proccss of gascous hydrogcn charging into a Ti_3Al- based alloy in the temperature range of 500-650℃isinvcstigatcd. The rcsnlls snoxvc that in rclatiollshil, between the average hydrogen concentration at constant tempreature and charging time reveals a parabolie rate law Applying the theory of lattice constant tcnlpcralurc and hrgillg tin rcvcals a parabolic riltc laiv. Applyillg tbcthcoly oftatticc dillbsio to allalyzc the hydrogcll diethesioll they andthat cncrgy of hydrogcn diffusion is 90.40 kJ/mol. and the equilibrium hydrogen content in the alloy depends on the temperature of the gaseous hydrogen charging process展开更多
Whether you leave business school to become a corporate manager, a professional high performer or an entrepreneur, you will spend much of your time on tasks unrelated to your expertise. Only the most senior executives...Whether you leave business school to become a corporate manager, a professional high performer or an entrepreneur, you will spend much of your time on tasks unrelated to your expertise. Only the most senior executives now have dedicated personal assistants and so the more mundane work of emails.展开更多
For the bonding couple of S31042 steel and Ni3Al-based superalloy,joint microstructure regulation plays a pivotal role in improving joint performance.Different pretreatment approaches including solution and cold rolli...For the bonding couple of S31042 steel and Ni3Al-based superalloy,joint microstructure regulation plays a pivotal role in improving joint performance.Different pretreatment approaches including solution and cold rolling treatments were severally applied to the two substrates before vacuum diffusion bonding.Cold rolling treatment in S31042 steel substrate before bonding promoted the coarsening and precipitation behaviors of large amounts of Z(NbCrN)phases during the bonding process so that the AlN phase decreased in the joint area because of the consumption of N atom in the Z phase.And solution treatment for Ni3Al-based superalloy increased the grain boundary mobility and led to the occurrence of dynamic recrystallization in the diffusion area of the joint by reducing segregation and homogenizing the microstructure within the substrate.As a result,the bonded sample with two substrates that are pretreated exhibited a better tensile strength and elongation at 700℃.展开更多
The Ni3Al-based superalloy was rapidly solidified in the form of droplets with varying diameters.The cooling rate(Rc)is a function of diameter(D)of droplet.With the decrease in droplet sizes(increase in the cooling ra...The Ni3Al-based superalloy was rapidly solidified in the form of droplets with varying diameters.The cooling rate(Rc)is a function of diameter(D)of droplet.With the decrease in droplet sizes(increase in the cooling rates),the volume fraction ofγ’+γeutectic structure increases from 21.31(D=1400 lm,Rc=3.6 9 102 K s-1)to 36.31%(D=270 lm,Rc-=2.3 9 103 K s-1).Moreover,unimodal size distribution of nano-γ’exists in the droplets instead of bimodal dual-size distributions ofγprecipitates that are normal in as-cast alloys.展开更多
Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings were prepared using cold gas kinetic spray technology.The results show that Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings are achieved with the porosit...Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings were prepared using cold gas kinetic spray technology.The results show that Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings are achieved with the porosity about 3.2%,thickness about 893 μm,the amount of amorphous phase about 82.5%,the hardness about 300 HV0.2.The corrosion potential and anti-corrosion life of 7075 T6 alloy aluminum are about-0.78 V and 72 h,respectively.The electrochemical analysis and neutral salt spray are about-0.69 V corrosion potential and 274 h anti-corrosion life for amorphous Al-based coatings,respectively.Therefore,the life of the Albased amorphous coatings is about 3.8 times that of 7075 T6 aluminum alloy.Besides,the failure mechanism was analyzed using TEM in this investigation.In a word,Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) coatings keep dense structure,high amorphous content,favorable amorphous phase stabilizing ability and longer anticorrosion life.That is,Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) coatings have better comprehensive properties.Therefore,these findings indicate that the present Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings prepared using cold gas kinetic spray technique can protect aluminum alloy very well and they can be considered to be used in aviation field.展开更多
As-cast Microstructure of A Designed Polycrystalline Ni3 Al-based Superalloy Is Characterized Using Optical Microscope,scanning Electron Microscope, Transmission Electron Microscope Equipped with Selected Area Diffrac...As-cast Microstructure of A Designed Polycrystalline Ni3 Al-based Superalloy Is Characterized Using Optical Microscope,scanning Electron Microscope, Transmission Electron Microscope Equipped with Selected Area Diffraction System,and the Intermetallic Phase Transformations Involved During Solidification Process Are Determined Based on Thermal Analysis Measurements. the As-cast Microstructure Is Mainly Composed of 80.63 Vol% Dendritic and 19.37 Vol% Interdendritic Phases,and the Dendrite Is Identified As Quasi-cuboidal γ'i Phase Connected by γ-channels Where Ultrafine γ'Ⅱ Particles Are Distributed,and the Interdendritic Phases Are Determined As γ'-γ Eutectic Structure Consisting of Ye Phase with Dotted Quasi-spherical γ'e Particles. During Solidification, the Dendrite Firstly Nucleates from Liquid Melt Near 1348 ℃; Subsequently, the Residual Liquidoid Is Transformed into Interdendritic Phases Around 1326 ℃. Afterward, γ' Phase Will Precipitate from Dendritic Ymatrix with Two-stage Characteristics, Resulting in the Distinct Precipitation of γ'Ⅰ and γ'Ⅱ Phases When Approaching to 1190 And 1043 ℃, Respectively. the Corresponding Transformations Involved During the Solidification Process Can Be Translated As:Liquidoid{Dendrite(γD)(80.63)%→γ'Ⅰ+γ(channel)→γ'Ⅰ+γ'Ⅱ+γ(channel) Residual liquidoid(19.37%)→Interdendrite(γ'E-γE eutectic)}As-cast展开更多
The corrosion-induced crystallization of Al94 exNixGd6(x=6 and 10, in at.%) metallic glasses as well as phase separation, oxidation and cracking in good conductivity solution has been investigated by various techniq...The corrosion-induced crystallization of Al94 exNixGd6(x=6 and 10, in at.%) metallic glasses as well as phase separation, oxidation and cracking in good conductivity solution has been investigated by various techniques.The transmission electronic microscopy(TEM) result reveals that crystalline intermetallics and oxides present on the electrochemically thinned hole edge, and the phase separation occurs in the matrix of the as-spun ribbons with the circumferential speed Rcof 29.3 m/s. In addition, the bending and cracking of the samples occur after corrosion. The influence of Ni content on the phase separation, bending and cracking can be explained by the fact that the percolation of the backbone clusters in the amorphous alloy melts and glasses is enhanced by increasing the composition of Ni.展开更多
The brazing of SiCp/Al composites is limited owing to the unavailability of suitable commercial intermediate temperature brazes. Adding a third constituent of copper to aluminum-silicon brazing alloy can depress the m...The brazing of SiCp/Al composites is limited owing to the unavailability of suitable commercial intermediate temperature brazes. Adding a third constituent of copper to aluminum-silicon brazing alloy can depress the melting point sharply. While, it generates a large volume fraction of the hard Al2Cu intermetallic compounds (IMCs), which makes the alloy brittle and reduces its corrosion resistance. A quaternary addition of nickel that partly substitute for copper can refine grain size significantly, improve the mechanical properties, and without altering the melting range of aluminum-silicon-copper alloy. Al-Cu-Ni-Si braze alloy has been prepared and a fluxless process has been employed to braze SiCp/Al composites that leads to a good bonding strength of brazing joint.展开更多
In this work,water cooling,air cooling(AC)and furnace cooling(FC)were applied to investigate the effect of cooling rate on microstructure evolution of primaryγ′in a newly designed Ni3Al-based alloy.The results showe...In this work,water cooling,air cooling(AC)and furnace cooling(FC)were applied to investigate the effect of cooling rate on microstructure evolution of primaryγ′in a newly designed Ni3Al-based alloy.The results showed that nucleation rate of primaryγ′increased with increasing cooling rate.In addition,higher cooling rate shortened growth period of primaryγ′,which made its morphology close to the initial precipitatedγ′.For AC and FC specimens,due to the lower cooling rate,primaryγ′possessed longer growth period and its morphology was mainly due to the evolution of lattice misfit betweenγand primaryγ′.Meanwhile,growth of primaryγ′depended on lattice misfit distribution between its corner and edge area.Moreover,primaryγ′morphologies of sphere,cube and concave cube with tip corners were illustrated by considering interaction between elemental diffusion and elastic strain energy.展开更多
The influence of a longitudinal static magnetic field on microstructures and mechanical properties of Ni_(3)Al-based alloy during directional solidification at the growth speed of 25μm/s and 100μm/s has been experim...The influence of a longitudinal static magnetic field on microstructures and mechanical properties of Ni_(3)Al-based alloy during directional solidification at the growth speed of 25μm/s and 100μm/s has been experimentally investigated.Results reflected that the utilization of a 0.5 T magnetic field refines the Ni Al dendrites at both speeds of growth.When applying a high magnetic field,the columnar-to-equiaxed transition(CET)occurred at growth speed of 25μm/s and dendrite networks formed at growth speed of 100μm/s.Tensile property results indicated that the refinement of dendrites enhanced both plasticity and ultimate tensile strength of Ni-Al alloy.The change of microstructures and mechanical properties should be attributed to the combined action of the thermoelectric magnetic convection(TEMC)in mushy zone together with the thermoelectric magnetic force(TEMF)acting on the solid.When applying a low magnetic field(0.5 T),the TEMF is too small to fragment the dendrites,and the refined dendrites is mainly due to the TEMC in the interdendritic regions.At a lower growth speed,the TEMF is supposed to strong enough to fragment the dendrites and induce the occurrence of CET under 2 or 4 T.When the growth speed increased to 100μm/s,no obvious CET was observed,but a vertical secondary convection is induced by the circulation in the parallel plane,which promotes the growth of secondary and tertiary branches,leading to the formation of abnormally developed high order dendrites.The hierarchical dendritic structure was suggested to provide a channel for rapid crack propagation and thus degraded the mechanical properties.展开更多
Al-BTC MOFs were prepared in a facile manner via a solvothermal reaction and characterized using FT-IR, XRD, and SEM. The compound was then evaluated as an adsorbent to remove Congo red(CR) from an aqueous solution. T...Al-BTC MOFs were prepared in a facile manner via a solvothermal reaction and characterized using FT-IR, XRD, and SEM. The compound was then evaluated as an adsorbent to remove Congo red(CR) from an aqueous solution. The adsorption kinetics was evaluated using the pseudo-first-order and pseudo-second-order, and it was found that the adsorption of CR onto the MOFs was well described by the pseudo-second-order equation. The as-prepared MOFs adsorbent seems to be a promising material in practice for dyes removal from aqueous solution.展开更多
A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatm...A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatments,wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt.In order to perform a comparison with conventional Ni Al and(Ni,Pt)Al coatings,the cyclic oxidation performance of the Ni Re Pt Al coating was evaluated at 1100 and 1150℃.We observed that the oxidation resistance of the Ni Re Pt Al coating was significantly improved by the greater presence of the residualβ-Ni Al phase in the outer layer and the lesser outward-diffusion of Mo from the substrate.In addition,the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate,where the thickness of the second reaction zone(SRZ)in the substrate alloy decreased by 25%.The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed,in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.展开更多
The phase transformation and deformation mechanism of the alloy based on composition Ti_3Al with addition of Nb,V,Mo have been studied by use of transmission electron microscopy (TEM).It has been shown that the orient...The phase transformation and deformation mechanism of the alloy based on composition Ti_3Al with addition of Nb,V,Mo have been studied by use of transmission electron microscopy (TEM).It has been shown that the orientation relationship of α_2 phase transformed from β phase is:(0001)α_2// (l10)β,[1210]α_2//[111]β.The present dislocation slip systems in α_2 phase are (1100)[0001] and (1100)<1120>.There also exist α_2 twins which have new twin relationship and the twin plane is (2021).展开更多
In the present paper, the relations between the microstructure and the properties of Ti-14Al-21Nb and Ti-14Al-20Nb-3.5V-2Mo alloys at different temperatures and different cooling rates of heat treatment were re-vealed...In the present paper, the relations between the microstructure and the properties of Ti-14Al-21Nb and Ti-14Al-20Nb-3.5V-2Mo alloys at different temperatures and different cooling rates of heat treatment were re-vealed by X-ray , optical microscope , HVTEM , auto-graphical-analyser and mechanical properties test at roomand high temperature. The experimental results show as follows: at 1040~1120℃ 14h WQ, the microstruc-ture of Ti-14Al-21Nb bar is primary phaseα_2+B2. With temperature increasing, the primary α_2 phase de-crease and the mechanical properties ultimate tensile strength (UTS), yield strength (YS) and elongation(EL) at room temperature increase. When it has reduced the α_2 phase by 50% (at 1080℃/4h WQ) , the me-chanical properties at room temperature are excellent , EL being 10. 5%. Following the α_2 phase reduces contin-uously , UTS, YS are going up, but EL is going down. After heated at two phases range and cooled down tothe room temperature with furnace, the microstructure of Ti-14Al-20Nb-3.5V-2Mo alloy is the equiaxed α_2+needle-like α_2+βphase. The mechanical properties at room temperature and 700℃ are fairly good.展开更多
We report a process route to fabricate an Al–Al interpenetrating-phase composite by combining the Al–Mg–Mn–Sc–Zr lattice structure and Al_(84)Ni_(7)Gd_(6)Co_(3)nanostructured structure. The lattice structure was ...We report a process route to fabricate an Al–Al interpenetrating-phase composite by combining the Al–Mg–Mn–Sc–Zr lattice structure and Al_(84)Ni_(7)Gd_(6)Co_(3)nanostructured structure. The lattice structure was produced by the selective laser melting and subsequently filled with the Al_(84)Ni_(7)Gd_(6)Co_(3)amorphous powder, and finally the mixture was used for hot extrusion to produce bulk samples. The results show that the composites achieve a high densification and good interface bonding due to the element diffusion and plastic deformation during hot extrusion.The bulk samples show a heterogeneous structure with a combination of honeycomb lattice structure with an average grain size of less than1 μm and nanostructured area with a high volume fraction of nanometric intermetallics and nanograin α-Al. The heterogeneous structure leads to a bimodal mechanical zone with hard area and soft area giving rise to high strength and acceptable plasticity, where the compressive yield strength and the compressive plasticity can reach ~745 MPa and ~30%, respectively. The high strength can be explained by the rule of mixture,the grain boundary strengthening, and the back stress, while the acceptable plasticity is mainly owing to the confinement effect of the nanostructured area retarding the brittle fracture behavior.展开更多
文摘A new method for corrosion protection of Al-based metal matrix composites (MMC) was developed using two-step process, which involves anodizing in H2SO4 solution and sealing in rare earth solution. Corrosion resistance of the treated surface was evaluated with polarization curves. The results showed that the effect of the protection using rare earth sealing is equivalent to that using chromate sealing for A16061/SiCp. The rare earth metal salt can be an alternative to the toxic chromate for sealing anodized Al MMC.
文摘Diamond grinding wheel were prepared with Al-based bonding agent.The microstructure of Al-based diamond grinding wheel was observed by SEM.The fracture morphology,interface between bonding agent and diamond,and the elemental distribution in bonding agent were studied.The results showed that there were some Al-based agents retained on the diamond surface.Ti,Ni formed intermetallurgy phase with Al in the agent and reduced the plasticity of bonding agent.The service life of this Al-based diamond grinding wheel is proved by the grinding experiments to be three times as long as that of resin-bonded grinding wheel.
文摘The effect of hot-rolling processing on microstructure as well as the relationship between the elongated grain structure and tensile properties are investigated. The results indicate that the elongated grain structure influences the tensile properties and creep rupture life of Fe3Al alloy significantly. For the better strength and ductility at RT,a thinner elongated grain structure is desirable. When the elongated grain size is increased, the tensile properties will be decreased. On the other hand, the creeP rupture life at 600℃ is increased with the increase of elongated grain size.
文摘The Proccss of gascous hydrogcn charging into a Ti_3Al- based alloy in the temperature range of 500-650℃isinvcstigatcd. The rcsnlls snoxvc that in rclatiollshil, between the average hydrogen concentration at constant tempreature and charging time reveals a parabolie rate law Applying the theory of lattice constant tcnlpcralurc and hrgillg tin rcvcals a parabolic riltc laiv. Applyillg tbcthcoly oftatticc dillbsio to allalyzc the hydrogcll diethesioll they andthat cncrgy of hydrogcn diffusion is 90.40 kJ/mol. and the equilibrium hydrogen content in the alloy depends on the temperature of the gaseous hydrogen charging process
文摘Whether you leave business school to become a corporate manager, a professional high performer or an entrepreneur, you will spend much of your time on tasks unrelated to your expertise. Only the most senior executives now have dedicated personal assistants and so the more mundane work of emails.
基金supported by the National Natural Science Foundation of China(Grant Nos.52034004 and 52075373).
文摘For the bonding couple of S31042 steel and Ni3Al-based superalloy,joint microstructure regulation plays a pivotal role in improving joint performance.Different pretreatment approaches including solution and cold rolling treatments were severally applied to the two substrates before vacuum diffusion bonding.Cold rolling treatment in S31042 steel substrate before bonding promoted the coarsening and precipitation behaviors of large amounts of Z(NbCrN)phases during the bonding process so that the AlN phase decreased in the joint area because of the consumption of N atom in the Z phase.And solution treatment for Ni3Al-based superalloy increased the grain boundary mobility and led to the occurrence of dynamic recrystallization in the diffusion area of the joint by reducing segregation and homogenizing the microstructure within the substrate.As a result,the bonded sample with two substrates that are pretreated exhibited a better tensile strength and elongation at 700℃.
基金supported by the National Natural Science Foundation of China (Nos. 51774212 and 51674175)
文摘The Ni3Al-based superalloy was rapidly solidified in the form of droplets with varying diameters.The cooling rate(Rc)is a function of diameter(D)of droplet.With the decrease in droplet sizes(increase in the cooling rates),the volume fraction ofγ’+γeutectic structure increases from 21.31(D=1400 lm,Rc=3.6 9 102 K s-1)to 36.31%(D=270 lm,Rc-=2.3 9 103 K s-1).Moreover,unimodal size distribution of nano-γ’exists in the droplets instead of bimodal dual-size distributions ofγprecipitates that are normal in as-cast alloys.
基金Project supported by the AVIC Unite Fund(KZ041605114)Civil Aircraft(MJ-2016-F-16)。
文摘Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings were prepared using cold gas kinetic spray technology.The results show that Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings are achieved with the porosity about 3.2%,thickness about 893 μm,the amount of amorphous phase about 82.5%,the hardness about 300 HV0.2.The corrosion potential and anti-corrosion life of 7075 T6 alloy aluminum are about-0.78 V and 72 h,respectively.The electrochemical analysis and neutral salt spray are about-0.69 V corrosion potential and 274 h anti-corrosion life for amorphous Al-based coatings,respectively.Therefore,the life of the Albased amorphous coatings is about 3.8 times that of 7075 T6 aluminum alloy.Besides,the failure mechanism was analyzed using TEM in this investigation.In a word,Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) coatings keep dense structure,high amorphous content,favorable amorphous phase stabilizing ability and longer anticorrosion life.That is,Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) coatings have better comprehensive properties.Therefore,these findings indicate that the present Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings prepared using cold gas kinetic spray technique can protect aluminum alloy very well and they can be considered to be used in aviation field.
基金financially supported by the National Natural Science Foundation of China (Nos.U1660201 and 51474156)the China National Funds for Distinguished Young Scientists (No.51325401)the National High Technology Research and Development Program of China (No.2015AA042504)
文摘As-cast Microstructure of A Designed Polycrystalline Ni3 Al-based Superalloy Is Characterized Using Optical Microscope,scanning Electron Microscope, Transmission Electron Microscope Equipped with Selected Area Diffraction System,and the Intermetallic Phase Transformations Involved During Solidification Process Are Determined Based on Thermal Analysis Measurements. the As-cast Microstructure Is Mainly Composed of 80.63 Vol% Dendritic and 19.37 Vol% Interdendritic Phases,and the Dendrite Is Identified As Quasi-cuboidal γ'i Phase Connected by γ-channels Where Ultrafine γ'Ⅱ Particles Are Distributed,and the Interdendritic Phases Are Determined As γ'-γ Eutectic Structure Consisting of Ye Phase with Dotted Quasi-spherical γ'e Particles. During Solidification, the Dendrite Firstly Nucleates from Liquid Melt Near 1348 ℃; Subsequently, the Residual Liquidoid Is Transformed into Interdendritic Phases Around 1326 ℃. Afterward, γ' Phase Will Precipitate from Dendritic Ymatrix with Two-stage Characteristics, Resulting in the Distinct Precipitation of γ'Ⅰ and γ'Ⅱ Phases When Approaching to 1190 And 1043 ℃, Respectively. the Corresponding Transformations Involved During the Solidification Process Can Be Translated As:Liquidoid{Dendrite(γD)(80.63)%→γ'Ⅰ+γ(channel)→γ'Ⅰ+γ'Ⅱ+γ(channel) Residual liquidoid(19.37%)→Interdendrite(γ'E-γE eutectic)}As-cast
基金financially supported by the National Natural Science Foundation of China (No. 51171091, 51471099)the Excellent Youth Project of Shandong Natural Science Foundation (No. JQ201012)the National Basic Research Program of China ("973 Program", No. 2012CB825702)
文摘The corrosion-induced crystallization of Al94 exNixGd6(x=6 and 10, in at.%) metallic glasses as well as phase separation, oxidation and cracking in good conductivity solution has been investigated by various techniques.The transmission electronic microscopy(TEM) result reveals that crystalline intermetallics and oxides present on the electrochemically thinned hole edge, and the phase separation occurs in the matrix of the as-spun ribbons with the circumferential speed Rcof 29.3 m/s. In addition, the bending and cracking of the samples occur after corrosion. The influence of Ni content on the phase separation, bending and cracking can be explained by the fact that the percolation of the backbone clusters in the amorphous alloy melts and glasses is enhanced by increasing the composition of Ni.
基金National Science Foundation of China (50774005)National "973" Program (2006CB605207)
文摘The brazing of SiCp/Al composites is limited owing to the unavailability of suitable commercial intermediate temperature brazes. Adding a third constituent of copper to aluminum-silicon brazing alloy can depress the melting point sharply. While, it generates a large volume fraction of the hard Al2Cu intermetallic compounds (IMCs), which makes the alloy brittle and reduces its corrosion resistance. A quaternary addition of nickel that partly substitute for copper can refine grain size significantly, improve the mechanical properties, and without altering the melting range of aluminum-silicon-copper alloy. Al-Cu-Ni-Si braze alloy has been prepared and a fluxless process has been employed to braze SiCp/Al composites that leads to a good bonding strength of brazing joint.
基金financially supported by the Natural Science Foundation of Hebei Province(No.E2019202161)the Highlevel Talent Funding Project of Hebei Province(No.A201902008)+2 种基金the Key R&D Program of Hebei Province(No.19251013D)the College Student Innovation and Entrepreneurship Training Program of Hebei University of Technology(No.S201910080035)the National Key R&D Program of China(No.2018YFB2001805)。
文摘In this work,water cooling,air cooling(AC)and furnace cooling(FC)were applied to investigate the effect of cooling rate on microstructure evolution of primaryγ′in a newly designed Ni3Al-based alloy.The results showed that nucleation rate of primaryγ′increased with increasing cooling rate.In addition,higher cooling rate shortened growth period of primaryγ′,which made its morphology close to the initial precipitatedγ′.For AC and FC specimens,due to the lower cooling rate,primaryγ′possessed longer growth period and its morphology was mainly due to the evolution of lattice misfit betweenγand primaryγ′.Meanwhile,growth of primaryγ′depended on lattice misfit distribution between its corner and edge area.Moreover,primaryγ′morphologies of sphere,cube and concave cube with tip corners were illustrated by considering interaction between elemental diffusion and elastic strain energy.
基金supported by National Science and Technology Major Project“Aero engine and Gas Turbine”(2017-VII-00080102)National Key Research and Development Program of China(No.2019YFA0705300)+2 种基金National Nature Science Foundation of China(No.51701112 and No.51690162)Shanghai Rising-Star Program(20QA1403800 and 21QC1401500)Shanghai Science and Technology Committee(19DZ1100704)。
文摘The influence of a longitudinal static magnetic field on microstructures and mechanical properties of Ni_(3)Al-based alloy during directional solidification at the growth speed of 25μm/s and 100μm/s has been experimentally investigated.Results reflected that the utilization of a 0.5 T magnetic field refines the Ni Al dendrites at both speeds of growth.When applying a high magnetic field,the columnar-to-equiaxed transition(CET)occurred at growth speed of 25μm/s and dendrite networks formed at growth speed of 100μm/s.Tensile property results indicated that the refinement of dendrites enhanced both plasticity and ultimate tensile strength of Ni-Al alloy.The change of microstructures and mechanical properties should be attributed to the combined action of the thermoelectric magnetic convection(TEMC)in mushy zone together with the thermoelectric magnetic force(TEMF)acting on the solid.When applying a low magnetic field(0.5 T),the TEMF is too small to fragment the dendrites,and the refined dendrites is mainly due to the TEMC in the interdendritic regions.At a lower growth speed,the TEMF is supposed to strong enough to fragment the dendrites and induce the occurrence of CET under 2 or 4 T.When the growth speed increased to 100μm/s,no obvious CET was observed,but a vertical secondary convection is induced by the circulation in the parallel plane,which promotes the growth of secondary and tertiary branches,leading to the formation of abnormally developed high order dendrites.The hierarchical dendritic structure was suggested to provide a channel for rapid crack propagation and thus degraded the mechanical properties.
基金supported by the Natural Science Foundation of Fujian Province (No. 2017J01420 and 2018H0030)Education Bureau of Fujian Province (JZ160453)Fujian Provincial Key Laboratory of Featured Materials in Biochemical Industry (FJKL_FBCM201902)。
文摘Al-BTC MOFs were prepared in a facile manner via a solvothermal reaction and characterized using FT-IR, XRD, and SEM. The compound was then evaluated as an adsorbent to remove Congo red(CR) from an aqueous solution. The adsorption kinetics was evaluated using the pseudo-first-order and pseudo-second-order, and it was found that the adsorption of CR onto the MOFs was well described by the pseudo-second-order equation. The as-prepared MOFs adsorbent seems to be a promising material in practice for dyes removal from aqueous solution.
基金the Key-Area Research and Development Program of Guangdong Province(2019B010936001)financially supported by the National Natural Science Foundation of China(Grant Nos.51671202 and 51301184)。
文摘A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatments,wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt.In order to perform a comparison with conventional Ni Al and(Ni,Pt)Al coatings,the cyclic oxidation performance of the Ni Re Pt Al coating was evaluated at 1100 and 1150℃.We observed that the oxidation resistance of the Ni Re Pt Al coating was significantly improved by the greater presence of the residualβ-Ni Al phase in the outer layer and the lesser outward-diffusion of Mo from the substrate.In addition,the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate,where the thickness of the second reaction zone(SRZ)in the substrate alloy decreased by 25%.The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed,in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.
文摘The phase transformation and deformation mechanism of the alloy based on composition Ti_3Al with addition of Nb,V,Mo have been studied by use of transmission electron microscopy (TEM).It has been shown that the orientation relationship of α_2 phase transformed from β phase is:(0001)α_2// (l10)β,[1210]α_2//[111]β.The present dislocation slip systems in α_2 phase are (1100)[0001] and (1100)<1120>.There also exist α_2 twins which have new twin relationship and the twin plane is (2021).
文摘In the present paper, the relations between the microstructure and the properties of Ti-14Al-21Nb and Ti-14Al-20Nb-3.5V-2Mo alloys at different temperatures and different cooling rates of heat treatment were re-vealed by X-ray , optical microscope , HVTEM , auto-graphical-analyser and mechanical properties test at roomand high temperature. The experimental results show as follows: at 1040~1120℃ 14h WQ, the microstruc-ture of Ti-14Al-21Nb bar is primary phaseα_2+B2. With temperature increasing, the primary α_2 phase de-crease and the mechanical properties ultimate tensile strength (UTS), yield strength (YS) and elongation(EL) at room temperature increase. When it has reduced the α_2 phase by 50% (at 1080℃/4h WQ) , the me-chanical properties at room temperature are excellent , EL being 10. 5%. Following the α_2 phase reduces contin-uously , UTS, YS are going up, but EL is going down. After heated at two phases range and cooled down tothe room temperature with furnace, the microstructure of Ti-14Al-20Nb-3.5V-2Mo alloy is the equiaxed α_2+needle-like α_2+βphase. The mechanical properties at room temperature and 700℃ are fairly good.
基金financially supported by the High-end Foreign Experts Recruitment Program (No. G2021163004L)the Guangdong International Science and Technology Cooperation Program (No. 2021A0505050002)+1 种基金National Key Research and Development Program of China (Nos. 2020YFB 2008300, 2020YFB2009301, and 2020YFB2008305)Guangdong Natural Science Foundation (No. 2020A1515 011242)。
文摘We report a process route to fabricate an Al–Al interpenetrating-phase composite by combining the Al–Mg–Mn–Sc–Zr lattice structure and Al_(84)Ni_(7)Gd_(6)Co_(3)nanostructured structure. The lattice structure was produced by the selective laser melting and subsequently filled with the Al_(84)Ni_(7)Gd_(6)Co_(3)amorphous powder, and finally the mixture was used for hot extrusion to produce bulk samples. The results show that the composites achieve a high densification and good interface bonding due to the element diffusion and plastic deformation during hot extrusion.The bulk samples show a heterogeneous structure with a combination of honeycomb lattice structure with an average grain size of less than1 μm and nanostructured area with a high volume fraction of nanometric intermetallics and nanograin α-Al. The heterogeneous structure leads to a bimodal mechanical zone with hard area and soft area giving rise to high strength and acceptable plasticity, where the compressive yield strength and the compressive plasticity can reach ~745 MPa and ~30%, respectively. The high strength can be explained by the rule of mixture,the grain boundary strengthening, and the back stress, while the acceptable plasticity is mainly owing to the confinement effect of the nanostructured area retarding the brittle fracture behavior.