Synchrotron X-ray radiography was used to carry out an in-situ observation of the hydrogen bubble evolution in the liquid Al/solid Ni interconnection. The individual bubble mainly grows in a stochastic way during heat...Synchrotron X-ray radiography was used to carry out an in-situ observation of the hydrogen bubble evolution in the liquid Al/solid Ni interconnection. The individual bubble mainly grows in a stochastic way during heating. The size distribution for groups of bubbles follows a Gaussian distribution in the early stage and Lifshitz-Slyozov-Wagner(LSW) diffusion controlled distribution in the final stage. The intermetallic compounds(IMCs) first form during solidification, following by the hydrogen bubbles. The bubbles between two adjacent Al3Ni grains grow unidirectionally along the liquid channel, with the bottom being impeded by the Al3Ni phase and the radius of the growth front being smaller. For the bubbles at triple junctions, they grow along the liquid channel and the crack with morphology transition.展开更多
The semi-solid slurry of an A356 Al alloy, which was grain-fined by yttrium, was manufactured by low temperature pouring, The effects of grain-refining on the morphology and the grain size of the primary α phase in t...The semi-solid slurry of an A356 Al alloy, which was grain-fined by yttrium, was manufactured by low temperature pouring, The effects of grain-refining on the morphology and the grain size of the primary α phase in the semi-solid A356 Al alloy were researched. The results indicate that the semi-solid A356 AI alloy with particle-like and rosette-like primary α-Al can be prepared by low temperature pouring from a liquid grain-refined A356 alloy. The grain size and particle morphology of primary α-Al in the A356 Al alloy are markedly improved by the addition of 0.5 wt,% Y. The fining mechanism of Y on the morphology and grain size of the primary α-Al in the semi-solid A356 Al alloy was delved.展开更多
The semi-solid slurry of A356 Al alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature on the slurry manufactured by weak electromagnetic stirring were r...The semi-solid slurry of A356 Al alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature on the slurry manufactured by weak electromagnetic stirring were researched. The results indicate that it is feasible to manufacture the slurry with particle-like primary phases by low superheat pouring and weak electromagnetic stirring, and there is an important effect of the pouring temperature (superheat temperature) on the morphology and the size of primaryα-Al in A356 Al alloy. By the action of suitable weak electromagnetic stirring, increasing pouring temperature to put low superheat pouring in practice is capable of obtaining semi-solid slurry of A356 Al alloy with particle-like primary phase. Compared with the samples made only by low superheat pouring without stirring, raising pouring temperature by 15-35 ℃ above the liquidus temperature under condition of weak electromagnetic stirring can ensure the same grain size and morphology of the primary phase.展开更多
The slurry of Al-20Sn alloy was prepared using electromagnetic-mechanical stirring method. The bonding of steel/mushy Al-20Sn was conducted using casting rolling technique. The bonding parameters were 505 ℃ for prehe...The slurry of Al-20Sn alloy was prepared using electromagnetic-mechanical stirring method. The bonding of steel/mushy Al-20Sn was conducted using casting rolling technique. The bonding parameters were 505 ℃ for preheat temperature of steel plate and 10 mm/s for rolling speed. The interfacial mechanical property and structure of steel/mushy Al-20Sn bonding plate were studied. The results show that the relationship between solid fraction of Al-20Sn slurry and interfacial shear strength of bonding plate is S=52.9+0.998φ s-0.014 4φ 2 s (where S is interfacial shear strength, φ s is solid fraction). The largest interfacial shear strength is 70.2 MPa when solid fraction is 34.6%. The interface of bonding plate is made up of Fe-Al compound and Fe-Al solid solution alternatively.展开更多
The influence of solid fraction of Al 28Pb alloy mushy on distribution of Pb in Al Pb ingot was studied. The special electromagnetic stirring apparatus was used to prepare Al 28Pb alloy mushy and the relationship betw...The influence of solid fraction of Al 28Pb alloy mushy on distribution of Pb in Al Pb ingot was studied. The special electromagnetic stirring apparatus was used to prepare Al 28Pb alloy mushy and the relationship between solid fraction and stirring temperature was gotten. The results show that when solid fraction of Al 28Pb alloy mushy is less than 45%, Pb precipitation usually happens in the ingot. However, Pb precipitation in casting reduces gradually with increasing solid fraction of mushy, and when solid fraction is larger than 45%, Pb precipitation in casting can be removed. [展开更多
The splat folis of Al-RE(RE=Y,La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Er and Yb) binary alloys of 0.04—0.06 mm thickness were made by are-melting and hammer-anvil technique,the.cooling rate is in 10~6 K/s order of magnitude.The m...The splat folis of Al-RE(RE=Y,La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Er and Yb) binary alloys of 0.04—0.06 mm thickness were made by are-melting and hammer-anvil technique,the.cooling rate is in 10~6 K/s order of magnitude.The metastable extended solid solubilities of these RE elements have been evaluated by measurements of the lattice spacings of the rapidly solidified(RS)Al-RE alloys,they are 0.4,0.15,0.21,0.21,0.3, 0.5,0.1,0.6,0.65,0.7,0.75,0.2 at.-% for above individual RE clements,respectively.The secondary phase in RS Al-RE alloys were identified to be Al_4RE for alloys containing light RE and Eu elements and Al_3 RE for alloys containing heavy RE and Y elements. Some factors influencing the extension of solid solubility of Al-RE alloy were discussed.展开更多
To explore the complex thermal-mechanical-chemical behavior in the solid-liquid cast-roll bonding(SLCRB) of Cu/Al cladding strip, numerical simulations were conducted from both macro and micro scales. In macro-scale, ...To explore the complex thermal-mechanical-chemical behavior in the solid-liquid cast-roll bonding(SLCRB) of Cu/Al cladding strip, numerical simulations were conducted from both macro and micro scales. In macro-scale, with birth and death element method, a thermo-mechanical coupled finite element model(FEM) was set up to explore the temperature and contact pressure distribution at the Cu/Al bonding interface in the SLCRB process. Taking these macro-scale simulation results as boundary conditions, we simulated the atom diffusion law of the bonding interface by molecular dynamics(MD) in micro-scale. The results indicate that the temperature in Cu/Al bonding interface deceases from 700 to 320 ℃ from the entrance to the exit of caster, and the peak of contact pressure reaches up to 140 MPa. The interfacial diffusion thickness depends on temperature and rolling reduction, higher temperature results in larger thickness, and the rolling reduction below kiss point leads to significant elongation deformation of cladding strip which yields more newborn interface with fresh metal and make the diffusion layer thinner. The surface roughness of Cu strip was found to be benefit to atoms diffusion in the Cu/Al bonding interface. Meanwhile, combined with the SEM-EDS observation on the microstructure and composition in the bonding interface of the experimental samples acquired from the castrolling bite, it is revealed that the rolling reduction and severe elongation deformation in the solid-solid contact zone below kiss point guarantee the satisfactory metallurgical bonding with thin and smooth diffusion layer. The bonding mechanisms of reactive diffusion, mechanical interlocking and crack bonding are proved to coexist in the SLCRB process.展开更多
A new technology thixo-die-forging of the composite in pseudo-semi-solid state was proposed based on the powder metallurgy technology combing with semi-solid metal process, and the cup shells with Al/Al2O3 composite w...A new technology thixo-die-forging of the composite in pseudo-semi-solid state was proposed based on the powder metallurgy technology combing with semi-solid metal process, and the cup shells with Al/Al2O3 composite was prepared successfully. The metallographic analysis and performance test show that the microstructure of parts is dense and mechanical properties axe excellent with the volume fraction of Al is 37%. The bend strength and fracture toughness of the composite are about 570- 690 MPa and 8.5-16.8 MPa·m^1/2, respectively. Comparing with reaction in situ and high temperature oxidation technologies the bending strength and fracture toughness are improved greatly. At the same time, it shows that the technology parameters have great influences on the properties. So it is feasible to prepare metal/ceramics composites by the proposed technology.展开更多
Preparation of semisolid slurry using a cooling slope is increasingly becoming popular,primarily because of the simplicity in design and ease control of the process.In this process,liquid alloy is poured down an incli...Preparation of semisolid slurry using a cooling slope is increasingly becoming popular,primarily because of the simplicity in design and ease control of the process.In this process,liquid alloy is poured down an inclined surface which is cooled from underneath.The cooling enables partial solidification and the incline provides the necessary shear for producing semisolid slurry.However,the final microstructure of the ingot depends on several process parameters such as cooling rate,incline angle of the cooling slope,length of the slope and initial melt superheat.In this work,a CFD model using volume of fluid(VOF) method for simulating flow along the cooling slope was presented.Equations for conservation of mass,momentum,energy and species were solved to predict hydrodynamic and thermal behavior,in addition to predicting solid fraction distribution and macrosegregation.Solidification was modeled using an enthalpy approach and a volume averaged technique for the different phases.The mushy region was modeled as a multi-layered porous medium consisting of fixed columnar dendrites and mobile equiaxed/fragmented grains.The alloy chosen for the study was aluminum alloy A356,for which adequate experimental data were available in the literature.The effects of two key process parameters,namely the slope angle and the pouring temperature,on temperature distribution,velocity distribution and macrosegregation were also studied.展开更多
The iron-rich solids formed during solidification of Al-Si alloys which are known to be detrimental to the mechanical,physical and chemical properties of the alloys should be removed.On the other hand,Al-Si hypereutec...The iron-rich solids formed during solidification of Al-Si alloys which are known to be detrimental to the mechanical,physical and chemical properties of the alloys should be removed.On the other hand,Al-Si hypereutectic alloys are used to extract the pure primary silicon which is suitable for photovoltaic cells in the solvent refining process.One of the important issues in iron removal and in solvent refining is the effective separation of the crystallized solids from the Al-Si alloy melts.This paper describes the separation methods of the primary solids from Al-Si alloy melts such as sedimentation,draining,filtration,electromagnetic separation and centrifugal separation,focused on the iron removal and on the separation of silicon in the solvent refining process.展开更多
Relationship between the processing parameters and the properties of semi-solid processed Al alloys were studied and microstructure and mechanical properties of semi-solid processed Al parts for automobile application...Relationship between the processing parameters and the properties of semi-solid processed Al alloys were studied and microstructure and mechanical properties of semi-solid processed Al parts for automobile application as a function of processing parameters were compared with those of die-cast parts and forged parts. In addition, the locations for the gate during the semi-solid processing were varied to elucidate the distribution of micro-porosities and resulting mechanical properties and the T6 heat tre...展开更多
The joint interface between semi-solid Zn-Al filler metal and SiCp/Al composites with applying vibration for different time was examined. With increasing vibrating time, the oxide layer was disrupted prior at the cent...The joint interface between semi-solid Zn-Al filler metal and SiCp/Al composites with applying vibration for different time was examined. With increasing vibrating time, the oxide layer was disrupted prior at the centre to the periphery of the interface. And the solid grains near the centre of interface in semi-solid filler metal aggregated into two solid regions and compressed the composites during vibration; the solid grains near the periphery of interface moved toward the edge and scraped the composites during vibration. The models of disrupting oxide layer under the vibration condition were developed. At the centre of interface, the oxide layer was tore and stripped during the solid grains in the semi-solid filler metal depressing the composites with a very high compressive stress. At the periphery of interface, the oxide layer was cut and stripped into the filler metal during the solid grains scraping the interface.展开更多
Structure evolution of an Al-Zn wrought alloy in remelting processing in thestrain induced melt activated (SIMA) serai-solid procedure was observed, and effects of factors, theremelting temperature, the holding time, ...Structure evolution of an Al-Zn wrought alloy in remelting processing in thestrain induced melt activated (SIMA) serai-solid procedure was observed, and effects of factors, theremelting temperature, the holding time, and the compression strain, on structures and grain sizesof the alloy were investigated. The results show that (1) the proper temperature of remelting is inthe range of 610 to 615℃; (2) the grain size in specimen with greater compression strain is smallerthan that with smaller compression strain in condition of the same remelting temperature andholding time, and the grain size in local area with great local equivalent strain is smaller thanthat with small one; (3) liquid occurs in form of cluster in matrix during remelting and itsquantity increases with remelting time increasing; liquid in specimen with great compression strainoccurs earlier than that with small one, and quantity of liquid in the center of specimen withgreater local equivalent strain is greater than that in the two ends of it; (4) distortion energyafter deforming in matrix of the alloy is the significant factor to activate melting of matrix atlocal area with great local equivalent strain.展开更多
Spray-formed Al-70%Si(mass fraction) alloys were deformed by compression in the semi-solid state. The effects of the deformation temperature, strain rate and the microstructure were studied. Two strain rates(1s -1an...Spray-formed Al-70%Si(mass fraction) alloys were deformed by compression in the semi-solid state. The effects of the deformation temperature, strain rate and the microstructure were studied. Two strain rates(1s -1and 0.1s -1) and six deformation temperatures (600℃, 720℃ , 780℃, 900℃, 1000℃ and 1100℃) were chosen. The stress—strain curve exhibits a peak at low strain and then decreases to a plateau before it starts to increase again as the strain increases. The stress required for deformation at lower strain rate and at higher deformation temperatures is less than those at higher strain rate and at lower deformation temperatures. Four mechanisms of semi-solid deformation can be used to explain the different behaviors of the stress—strain curves under different conditions.展开更多
The hypoeutectic Al-Si alloy billet with non-dendrite was reheated to meet the needs of the semi-solid thixoforming microstructure by four kinds of reheating power,achieving the same final temperature of 851 K.Subsequ...The hypoeutectic Al-Si alloy billet with non-dendrite was reheated to meet the needs of the semi-solid thixoforming microstructure by four kinds of reheating power,achieving the same final temperature of 851 K.Subsequently,under the same condition of thixoforming,the microstructure,surface hardness and tensile properties were observed.Afterwards,quantitative analysis was made for the microstructures of the reheated semi-solid of billet and the thixoforming parts.The results show that when the induction reheating power is 90 kW,the average grain size of the semi-solid billet is the minimum,the microstructures of the thixoforming samples also are the finest,and the mechanical properties of the relevant thixoforming samples are the best.Furthermore,after studying on the relationship between the microstructures of the semi-solid billet of aluminum alloy and the mechanical properties of the thixoforming samples,the reverse design of microstructure is primarily achieved.Finally,the effectiveness of the reverse design for semi-solid microstructure is confirmed by an actual automobile part with complex shape.展开更多
A new technology—the thixoforging of ceramics/metal composites in pseudo-semi-solid state was proposed based on the powder metallurgy technology combined with semi-solid metal forming process, and the cup shell of au...A new technology—the thixoforging of ceramics/metal composites in pseudo-semi-solid state was proposed based on the powder metallurgy technology combined with semi-solid metal forming process, and the cup shell of automobile piston with Al2O3/Al composites was prepared. It is proved through metallographic analyses and three-point bending tests that the technology is feasible for the ceramics/metal composites forming. The results show that the tough strength and the degree of hardness of the samples with certain plasticity are high. It will play a very large role in accelerating the ceramics composites and high melt point materials use in more fields and tamp the foundation for further studies of this technology.展开更多
In this study, the changing trend of crystal-lattice constant and the influential factors of the stability of supersaturated solid solutions with various alloying additions in the Al–X（Zn, Mg, Cu） binary alloys wer...In this study, the changing trend of crystal-lattice constant and the influential factors of the stability of supersaturated solid solutions with various alloying additions in the Al–X（Zn, Mg, Cu） binary alloys were investigated. The samples were analyzed using X-ray diffraction（XRD）,X-ray absorption fine structure（XAFS）, and scanning electron microscope（SEM）. It is found that the addition of Cu causes the largest change of crystal-lattice constant of the Al–xCu supersaturated solid solution binary alloy. The most dramatic change occurs in the initial stage of Cu addition.The change is stabilized thereafter. Also, at the same alloying element addition to the Al–X（X = Zn, Mg, Cu）binary alloys, the Al–xCu is the most unstable system.Influential factors of the stability include the lattice constant change and the type of alloying element. The larger the lattice constant changes, the more unstable the supersaturated solid solution is. The alloying element, easy to aggregate, often leads to the solid solution less stable.展开更多
The morphological instability of solid/liquid(S/L)interface during solidification will result in different patterns of microstructure.In this study,two dimension(2 D)and three dimension(3 D)in-situ observation of soli...The morphological instability of solid/liquid(S/L)interface during solidification will result in different patterns of microstructure.In this study,two dimension(2 D)and three dimension(3 D)in-situ observation of solid/liquid interfacial morphology transition in Al-Zn alloy during directional solidification were performed via X-ray imaging.Under a condition of increasing temperature gradient(G),the interface transition from dendritic pattern to cellular pattern,and then to planar growth with perturbation was captured.The effect of solidification parameter(the ratio of temperature gradient and growth velocity(v),G/v)on morphological instabilities was investigated and the experimental results were compared to classical"constitutional supercooling"theory.The results indicate that 2 D and 3 D evolution process of S/L interface morphology under the same thermal condition are different.It seems that the S/L interface in 2 D observation is easier to achieve planar growth than that in 3 D,implying higher S/L interface stability in 2 D thin plate samples.This can be explained as the restricted liquid flow under 2 D solidification which is beneficial to S/L interface stability.The in-situ observation in present study can provide coherent dataset for microstructural formation investigation and related model validation during solidification.展开更多
Six alloys with different compositions of Al 0.1%Sc, Al 0.3%Sc, Al 0.3%Zr, Al 0.1% Sc 0.1%Zr, Al 0.3%Sc 0.1%Zr and Al 0.3%Sc 0.3%Zr were prepared by casting in a wedge shaped copper mould. The hardness test, microstru...Six alloys with different compositions of Al 0.1%Sc, Al 0.3%Sc, Al 0.3%Zr, Al 0.1% Sc 0.1%Zr, Al 0.3%Sc 0.1%Zr and Al 0.3%Sc 0.3%Zr were prepared by casting in a wedge shaped copper mould. The hardness test, microstructure observation, and DSC thermal analysis were applied to fully investigate the solidification behavior of the wedge tip (whose cooling rate is 1 000 K/s) and the top surface (cooling rate 100 K/s) of each casting. The results show that the cast structures in the hypoeutectic region of Al Sc alloys are slightly affected by cooling rates during the solidification. In the case of hypereutectic alloy of Al 0.3%Sc 0.3%Zr , the cast grains were remarkably refined under the condition of a 100 K/s cooling rate, however, under a 1 000 K/s cooling rate condition, solute atoms contribute nothing to the grain refinement, due to the eutectic concentration becomes higher. The hardness can be improved to a greater degree by Sc single addition, compared to single Zr addition, but it can be improved even greater when Sc added together with Zr. It is sensitive to cooling rate, the higher the cooling rate, the greater the hardness. By combining the results of TEM examination and DSC analysis, it can be seen that a supersaturated Al solid solution forms during the solidification, and the solubility of Sc in Al solution can be improved by increasing the cooling rate.展开更多
基金supported by the National Key Research and Development Program (2017YFA0403800)the National Natural Science Foundation of China (51374144, 51727802)+2 种基金the Shanghai Municipal Natural Science Foundation (13ZR1420600)Shanghai Rising-Star Program (14QA1402300)The support of synchrotron radiation phase-contrast imaging by the BL13W1 beam line of Shanghai Synchrotron Radiation Facility (SSRF), China, is gratefully acknowledged
文摘Synchrotron X-ray radiography was used to carry out an in-situ observation of the hydrogen bubble evolution in the liquid Al/solid Ni interconnection. The individual bubble mainly grows in a stochastic way during heating. The size distribution for groups of bubbles follows a Gaussian distribution in the early stage and Lifshitz-Slyozov-Wagner(LSW) diffusion controlled distribution in the final stage. The intermetallic compounds(IMCs) first form during solidification, following by the hydrogen bubbles. The bubbles between two adjacent Al3Ni grains grow unidirectionally along the liquid channel, with the bottom being impeded by the Al3Ni phase and the radius of the growth front being smaller. For the bubbles at triple junctions, they grow along the liquid channel and the crack with morphology transition.
基金the Natural Science Foundation of Jiangxi Province, China (No. 0650047)
文摘The semi-solid slurry of an A356 Al alloy, which was grain-fined by yttrium, was manufactured by low temperature pouring, The effects of grain-refining on the morphology and the grain size of the primary α phase in the semi-solid A356 Al alloy were researched. The results indicate that the semi-solid A356 AI alloy with particle-like and rosette-like primary α-Al can be prepared by low temperature pouring from a liquid grain-refined A356 alloy. The grain size and particle morphology of primary α-Al in the A356 Al alloy are markedly improved by the addition of 0.5 wt,% Y. The fining mechanism of Y on the morphology and grain size of the primary α-Al in the semi-solid A356 Al alloy was delved.
基金Project (G2002AA336080) supported by Hi-tech Research and Development Program of China Project (50374012) supported by the National Natural Science Foundation of China
文摘The semi-solid slurry of A356 Al alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature on the slurry manufactured by weak electromagnetic stirring were researched. The results indicate that it is feasible to manufacture the slurry with particle-like primary phases by low superheat pouring and weak electromagnetic stirring, and there is an important effect of the pouring temperature (superheat temperature) on the morphology and the size of primaryα-Al in A356 Al alloy. By the action of suitable weak electromagnetic stirring, increasing pouring temperature to put low superheat pouring in practice is capable of obtaining semi-solid slurry of A356 Al alloy with particle-like primary phase. Compared with the samples made only by low superheat pouring without stirring, raising pouring temperature by 15-35 ℃ above the liquidus temperature under condition of weak electromagnetic stirring can ensure the same grain size and morphology of the primary phase.
文摘The slurry of Al-20Sn alloy was prepared using electromagnetic-mechanical stirring method. The bonding of steel/mushy Al-20Sn was conducted using casting rolling technique. The bonding parameters were 505 ℃ for preheat temperature of steel plate and 10 mm/s for rolling speed. The interfacial mechanical property and structure of steel/mushy Al-20Sn bonding plate were studied. The results show that the relationship between solid fraction of Al-20Sn slurry and interfacial shear strength of bonding plate is S=52.9+0.998φ s-0.014 4φ 2 s (where S is interfacial shear strength, φ s is solid fraction). The largest interfacial shear strength is 70.2 MPa when solid fraction is 34.6%. The interface of bonding plate is made up of Fe-Al compound and Fe-Al solid solution alternatively.
文摘The influence of solid fraction of Al 28Pb alloy mushy on distribution of Pb in Al Pb ingot was studied. The special electromagnetic stirring apparatus was used to prepare Al 28Pb alloy mushy and the relationship between solid fraction and stirring temperature was gotten. The results show that when solid fraction of Al 28Pb alloy mushy is less than 45%, Pb precipitation usually happens in the ingot. However, Pb precipitation in casting reduces gradually with increasing solid fraction of mushy, and when solid fraction is larger than 45%, Pb precipitation in casting can be removed. [
文摘The splat folis of Al-RE(RE=Y,La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Er and Yb) binary alloys of 0.04—0.06 mm thickness were made by are-melting and hammer-anvil technique,the.cooling rate is in 10~6 K/s order of magnitude.The metastable extended solid solubilities of these RE elements have been evaluated by measurements of the lattice spacings of the rapidly solidified(RS)Al-RE alloys,they are 0.4,0.15,0.21,0.21,0.3, 0.5,0.1,0.6,0.65,0.7,0.75,0.2 at.-% for above individual RE clements,respectively.The secondary phase in RS Al-RE alloys were identified to be Al_4RE for alloys containing light RE and Eu elements and Al_3 RE for alloys containing heavy RE and Y elements. Some factors influencing the extension of solid solubility of Al-RE alloy were discussed.
基金Funded by the General Program of National Natural Science Foundation of China(Nos.51474189 and 51674222)the Excellent Youth Foundation of Hebei Scientific Committee,China(No.E2018203446)the Scientific Research Foundation of the Higher Education Institutions of Hebei Province,China(No.QN2015214)
文摘To explore the complex thermal-mechanical-chemical behavior in the solid-liquid cast-roll bonding(SLCRB) of Cu/Al cladding strip, numerical simulations were conducted from both macro and micro scales. In macro-scale, with birth and death element method, a thermo-mechanical coupled finite element model(FEM) was set up to explore the temperature and contact pressure distribution at the Cu/Al bonding interface in the SLCRB process. Taking these macro-scale simulation results as boundary conditions, we simulated the atom diffusion law of the bonding interface by molecular dynamics(MD) in micro-scale. The results indicate that the temperature in Cu/Al bonding interface deceases from 700 to 320 ℃ from the entrance to the exit of caster, and the peak of contact pressure reaches up to 140 MPa. The interfacial diffusion thickness depends on temperature and rolling reduction, higher temperature results in larger thickness, and the rolling reduction below kiss point leads to significant elongation deformation of cladding strip which yields more newborn interface with fresh metal and make the diffusion layer thinner. The surface roughness of Cu strip was found to be benefit to atoms diffusion in the Cu/Al bonding interface. Meanwhile, combined with the SEM-EDS observation on the microstructure and composition in the bonding interface of the experimental samples acquired from the castrolling bite, it is revealed that the rolling reduction and severe elongation deformation in the solid-solid contact zone below kiss point guarantee the satisfactory metallurgical bonding with thin and smooth diffusion layer. The bonding mechanisms of reactive diffusion, mechanical interlocking and crack bonding are proved to coexist in the SLCRB process.
基金supported by National Natural Science Foundation of China(No50705018)Postdoctoral Foundation of China (No20070420847)
文摘A new technology thixo-die-forging of the composite in pseudo-semi-solid state was proposed based on the powder metallurgy technology combing with semi-solid metal process, and the cup shells with Al/Al2O3 composite was prepared successfully. The metallographic analysis and performance test show that the microstructure of parts is dense and mechanical properties axe excellent with the volume fraction of Al is 37%. The bend strength and fracture toughness of the composite are about 570- 690 MPa and 8.5-16.8 MPa·m^1/2, respectively. Comparing with reaction in situ and high temperature oxidation technologies the bending strength and fracture toughness are improved greatly. At the same time, it shows that the technology parameters have great influences on the properties. So it is feasible to prepare metal/ceramics composites by the proposed technology.
文摘Preparation of semisolid slurry using a cooling slope is increasingly becoming popular,primarily because of the simplicity in design and ease control of the process.In this process,liquid alloy is poured down an inclined surface which is cooled from underneath.The cooling enables partial solidification and the incline provides the necessary shear for producing semisolid slurry.However,the final microstructure of the ingot depends on several process parameters such as cooling rate,incline angle of the cooling slope,length of the slope and initial melt superheat.In this work,a CFD model using volume of fluid(VOF) method for simulating flow along the cooling slope was presented.Equations for conservation of mass,momentum,energy and species were solved to predict hydrodynamic and thermal behavior,in addition to predicting solid fraction distribution and macrosegregation.Solidification was modeled using an enthalpy approach and a volume averaged technique for the different phases.The mushy region was modeled as a multi-layered porous medium consisting of fixed columnar dendrites and mobile equiaxed/fragmented grains.The alloy chosen for the study was aluminum alloy A356,for which adequate experimental data were available in the literature.The effects of two key process parameters,namely the slope angle and the pouring temperature,on temperature distribution,velocity distribution and macrosegregation were also studied.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF),the Ministry of Education,Science and Technology of Korea(No.2012R1A1A2007476)supported by the Korea University of Technology and Education
文摘The iron-rich solids formed during solidification of Al-Si alloys which are known to be detrimental to the mechanical,physical and chemical properties of the alloys should be removed.On the other hand,Al-Si hypereutectic alloys are used to extract the pure primary silicon which is suitable for photovoltaic cells in the solvent refining process.One of the important issues in iron removal and in solvent refining is the effective separation of the crystallized solids from the Al-Si alloy melts.This paper describes the separation methods of the primary solids from Al-Si alloy melts such as sedimentation,draining,filtration,electromagnetic separation and centrifugal separation,focused on the iron removal and on the separation of silicon in the solvent refining process.
文摘Relationship between the processing parameters and the properties of semi-solid processed Al alloys were studied and microstructure and mechanical properties of semi-solid processed Al parts for automobile application as a function of processing parameters were compared with those of die-cast parts and forged parts. In addition, the locations for the gate during the semi-solid processing were varied to elucidate the distribution of micro-porosities and resulting mechanical properties and the T6 heat tre...
基金supported by the National Natural Science Foundation of China under grant No.50575057
文摘The joint interface between semi-solid Zn-Al filler metal and SiCp/Al composites with applying vibration for different time was examined. With increasing vibrating time, the oxide layer was disrupted prior at the centre to the periphery of the interface. And the solid grains near the centre of interface in semi-solid filler metal aggregated into two solid regions and compressed the composites during vibration; the solid grains near the periphery of interface moved toward the edge and scraped the composites during vibration. The models of disrupting oxide layer under the vibration condition were developed. At the centre of interface, the oxide layer was tore and stripped during the solid grains in the semi-solid filler metal depressing the composites with a very high compressive stress. At the periphery of interface, the oxide layer was cut and stripped into the filler metal during the solid grains scraping the interface.
文摘Structure evolution of an Al-Zn wrought alloy in remelting processing in thestrain induced melt activated (SIMA) serai-solid procedure was observed, and effects of factors, theremelting temperature, the holding time, and the compression strain, on structures and grain sizesof the alloy were investigated. The results show that (1) the proper temperature of remelting is inthe range of 610 to 615℃; (2) the grain size in specimen with greater compression strain is smallerthan that with smaller compression strain in condition of the same remelting temperature andholding time, and the grain size in local area with great local equivalent strain is smaller thanthat with small one; (3) liquid occurs in form of cluster in matrix during remelting and itsquantity increases with remelting time increasing; liquid in specimen with great compression strainoccurs earlier than that with small one, and quantity of liquid in the center of specimen withgreater local equivalent strain is greater than that in the two ends of it; (4) distortion energyafter deforming in matrix of the alloy is the significant factor to activate melting of matrix atlocal area with great local equivalent strain.
文摘Spray-formed Al-70%Si(mass fraction) alloys were deformed by compression in the semi-solid state. The effects of the deformation temperature, strain rate and the microstructure were studied. Two strain rates(1s -1and 0.1s -1) and six deformation temperatures (600℃, 720℃ , 780℃, 900℃, 1000℃ and 1100℃) were chosen. The stress—strain curve exhibits a peak at low strain and then decreases to a plateau before it starts to increase again as the strain increases. The stress required for deformation at lower strain rate and at higher deformation temperatures is less than those at higher strain rate and at lower deformation temperatures. Four mechanisms of semi-solid deformation can be used to explain the different behaviors of the stress—strain curves under different conditions.
文摘The hypoeutectic Al-Si alloy billet with non-dendrite was reheated to meet the needs of the semi-solid thixoforming microstructure by four kinds of reheating power,achieving the same final temperature of 851 K.Subsequently,under the same condition of thixoforming,the microstructure,surface hardness and tensile properties were observed.Afterwards,quantitative analysis was made for the microstructures of the reheated semi-solid of billet and the thixoforming parts.The results show that when the induction reheating power is 90 kW,the average grain size of the semi-solid billet is the minimum,the microstructures of the thixoforming samples also are the finest,and the mechanical properties of the relevant thixoforming samples are the best.Furthermore,after studying on the relationship between the microstructures of the semi-solid billet of aluminum alloy and the mechanical properties of the thixoforming samples,the reverse design of microstructure is primarily achieved.Finally,the effectiveness of the reverse design for semi-solid microstructure is confirmed by an actual automobile part with complex shape.
基金Project(50375035) supported by the National Natural Science Foundation of China
文摘A new technology—the thixoforging of ceramics/metal composites in pseudo-semi-solid state was proposed based on the powder metallurgy technology combined with semi-solid metal forming process, and the cup shell of automobile piston with Al2O3/Al composites was prepared. It is proved through metallographic analyses and three-point bending tests that the technology is feasible for the ceramics/metal composites forming. The results show that the tough strength and the degree of hardness of the samples with certain plasticity are high. It will play a very large role in accelerating the ceramics composites and high melt point materials use in more fields and tamp the foundation for further studies of this technology.
基金financially supported by the National Natural Science Foundation of China (No. 51274046)
文摘In this study, the changing trend of crystal-lattice constant and the influential factors of the stability of supersaturated solid solutions with various alloying additions in the Al–X（Zn, Mg, Cu） binary alloys were investigated. The samples were analyzed using X-ray diffraction（XRD）,X-ray absorption fine structure（XAFS）, and scanning electron microscope（SEM）. It is found that the addition of Cu causes the largest change of crystal-lattice constant of the Al–xCu supersaturated solid solution binary alloy. The most dramatic change occurs in the initial stage of Cu addition.The change is stabilized thereafter. Also, at the same alloying element addition to the Al–X（X = Zn, Mg, Cu）binary alloys, the Al–xCu is the most unstable system.Influential factors of the stability include the lattice constant change and the type of alloying element. The larger the lattice constant changes, the more unstable the supersaturated solid solution is. The alloying element, easy to aggregate, often leads to the solid solution less stable.
基金financially supported by National Natural Science Foundation of China(Grants 51690162,51604171 and 51701112)Shanghai Municipal Science and Technology Commission(No.17JC1400602)Shanghai Sailing Program(19YF1415900).
文摘The morphological instability of solid/liquid(S/L)interface during solidification will result in different patterns of microstructure.In this study,two dimension(2 D)and three dimension(3 D)in-situ observation of solid/liquid interfacial morphology transition in Al-Zn alloy during directional solidification were performed via X-ray imaging.Under a condition of increasing temperature gradient(G),the interface transition from dendritic pattern to cellular pattern,and then to planar growth with perturbation was captured.The effect of solidification parameter(the ratio of temperature gradient and growth velocity(v),G/v)on morphological instabilities was investigated and the experimental results were compared to classical"constitutional supercooling"theory.The results indicate that 2 D and 3 D evolution process of S/L interface morphology under the same thermal condition are different.It seems that the S/L interface in 2 D observation is easier to achieve planar growth than that in 3 D,implying higher S/L interface stability in 2 D thin plate samples.This can be explained as the restricted liquid flow under 2 D solidification which is beneficial to S/L interface stability.The in-situ observation in present study can provide coherent dataset for microstructural formation investigation and related model validation during solidification.
文摘Six alloys with different compositions of Al 0.1%Sc, Al 0.3%Sc, Al 0.3%Zr, Al 0.1% Sc 0.1%Zr, Al 0.3%Sc 0.1%Zr and Al 0.3%Sc 0.3%Zr were prepared by casting in a wedge shaped copper mould. The hardness test, microstructure observation, and DSC thermal analysis were applied to fully investigate the solidification behavior of the wedge tip (whose cooling rate is 1 000 K/s) and the top surface (cooling rate 100 K/s) of each casting. The results show that the cast structures in the hypoeutectic region of Al Sc alloys are slightly affected by cooling rates during the solidification. In the case of hypereutectic alloy of Al 0.3%Sc 0.3%Zr , the cast grains were remarkably refined under the condition of a 100 K/s cooling rate, however, under a 1 000 K/s cooling rate condition, solute atoms contribute nothing to the grain refinement, due to the eutectic concentration becomes higher. The hardness can be improved to a greater degree by Sc single addition, compared to single Zr addition, but it can be improved even greater when Sc added together with Zr. It is sensitive to cooling rate, the higher the cooling rate, the greater the hardness. By combining the results of TEM examination and DSC analysis, it can be seen that a supersaturated Al solid solution forms during the solidification, and the solubility of Sc in Al solution can be improved by increasing the cooling rate.
