The application of investment casting auto-pouring system can improve the efficiency of manual-pouring system to a certain extent.The judgment of start-stop time depends on the preprocessing of original image collecte...The application of investment casting auto-pouring system can improve the efficiency of manual-pouring system to a certain extent.The judgment of start-stop time depends on the preprocessing of original image collected by the CCD camera.Several methods are presented to denoise the liquid column image.The method of morphological image processing is feasible in theory,and it is important whether to choose the structural element or not.The method of pouring image projection is less affected the image of spure cup.The complexity of image window algorithm is minimal.展开更多
A novel micro fused-casting(MFC)process is developed for semisolid aluminum alloy slurry.The microstructure evolution and properties of semisolid ZL101 aluminum alloy slurry with difierent pouring temperature by MFC a...A novel micro fused-casting(MFC)process is developed for semisolid aluminum alloy slurry.The microstructure evolution and properties of semisolid ZL101 aluminum alloy slurry with difierent pouring temperature by MFC are investigated in this paper.During the cooling process,the effects of the pouring temperature on microstructure and properties is primarily analyzed.The microstructure of the semisolid ZL101 aluminum alloy is more homogeneous and the grain is smaller under proper pouring temperature.Temperature of liquids and solids of ZL101 aluminum alloy is measured by difierential scanning calorimetry(DSC).Distribution and characteristics of the microstructure of samples are examined by optical microscope(OM),scanning electron microscopy(SEM)equipped with energy dispersive spectrometer(EDS).The results show that the ZL101 semisolid slurry fabricated by MFC presents uniform shape and good grain size under the pouring temperature of 594°C and the stirring velocity of 600 r/min,and the fine grains of the primary a-Al phase with average grain size of 55μm and shape factor up to 0.67 were obtained.Besides,the ultimate tensile strength and the average Vickers hardness for semisolid ZL101 aluminum slurry are 178.19±1.37 MPa and 86.15±1.16 HV,respectively.展开更多
Pouring and mold temperatures are two important parameters during casting magnesium components. The present study examined their influence on hot tearing susceptibility （HTS） of commercial AZ91D and newly developed ...Pouring and mold temperatures are two important parameters during casting magnesium components. The present study examined their influence on hot tearing susceptibility （HTS） of commercial AZ91D and newly developed Mg-3Nd-0.2Zn-Zr （mass fraction, %; NZ30K） magnesium alloys in gravity permanent mold casting condition. The results indicate that mold temperature shows much more significant influence on the HTS of both alloys than pouring temperature whose influence only can be distinguished at low mold temperature （341 K for AZ91D alloy and 423 K for NZ30K alloy）. Hot tearing susceptibility prediction model concerning feeding parameters, grain size and solidification range, is more suitable to estimate the HTS of different magnesium alloys than the model only concerning feeding parameters. In order to achieve better hot tearing resistance, the ranges of pouring and mold temperatures are suggested to be 961-991 K and≥641 K for AZ91D alloy, 1003-1033 K and≥623 K for NZ30K alloy, respectively.展开更多
Over the past few decades,one of the most significant advances in dam construction has been the inven-tion of the rock-filled concrete(RFC)dam,which is constructed by pouring high-performance self-compacting concrete(...Over the past few decades,one of the most significant advances in dam construction has been the inven-tion of the rock-filled concrete(RFC)dam,which is constructed by pouring high-performance self-compacting concrete(HSCC)to fill the voids in preplaced large rocks.The innovative use of large rocks in dam construction provides engineers with a material that requires less cement consumption and hydration heat while enhancing construction efficiency and environmental friendliness.However,two fundamental scientific issues related to RFC need to be addressed:namely,the pouring compactness and the effect of large rocks on the mechanical and physical properties of RFC.This article provides a timely review of fundamental research and innovations in the design,construction,and quality control of RFCdams.Prospects for next-generation concrete dams are discussed from the perspectives of envi-ronmental friendliness,intrinsic safety,and labor savings.展开更多
An advanced rheomoulder,which is a device in the integration of melting metal,storage,slurry preparation,transportation and injection forming,was introduced and used to manufacture rheomoulding AZ91 D alloy.Effects of...An advanced rheomoulder,which is a device in the integration of melting metal,storage,slurry preparation,transportation and injection forming,was introduced and used to manufacture rheomoulding AZ91 D alloy.Effects of pouring temperature and cylinder temperature on microstructures and mechanical properties of rheomoulding AZ91 D alloy were investigated.The results show that the process can obtain such rheomoulding AZ91 D in which primary α-Mg particles are fine,spherical and uniformly distributed in the matrix.With the decrease of pouring temperature,the morphology of primary α-Mg particles changes from coarse rosette-like to fine spherical shape gradually.As the cylinder temperature decreases,the average size of primary α-Mg particles decreases firstly and then substantially maintains stable while the sphericity and solid fraction increase continuously.Also,decreasing pouring temperature or cylinder temperature properly contributes to improving mechanical properties of rheomoulding AZ91 D for the refinement of α-Mg particles and the decrease of porosity fraction.Furthermore,rheomoulding AZ91 D performs much better than thixomoulding,rheo-diecasting and high pressure die-casting（HPDC） in terms of mechanical properties.Compared with HPDC,the tensile strength,yield strength and elongation are increased by 27.8%,15.7% and 121%,respectively.展开更多
The semi-solid slurry of a hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouting temperature and stirring power on the semi-solid slurry were inve...The semi-solid slurry of a hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouting temperature and stirring power on the semi-solid slurry were investigated. The results indicated that the semi-solid slurry to satisfy rheocasting can be manufactured by low superheat pouring and weak electromagnetic stirring. The pouring temperature （or superheat） and the stirring power remarkably affected the morphology of primary α-Al and the size of primary α-Al, and there is no obvious effect of stirring time on primary α-Al. Compared with the samples made by low superheat pouring with no stirring, the nucleation rate, particle morphology and grain size of primary α-Al in A356 were markedly improved by low superheat pouring and weak electromagnetic stirring. On the condition of weak electromagnetic stirring, the pouring temperature with low superheat can be suitably raised to reach the effectiveness obtained from the lower pouring temperature without stirring.展开更多
The semi-solid slurry of hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature and stirring power on the semi-solid slurry making proc...The semi-solid slurry of hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature and stirring power on the semi-solid slurry making process were investigated. The results indicate that the semi-solid slurry to satisfy rheocasting requirement can be made by a combination of low superheat pouring and weak electromagnetic stirring. The pouring temperature (or superheat) and the stirring power significantly affect the morphology and the size of primary α-Al, while there is no obvious effect of the stirring time on primary α-Al. Compared with the samples made by low superheat pouring without stirring, the nucleation rate, particle morphology and grain size of primary α-Al in A356 Al alloy are markedly improved by a process of applying both low superheat pouring and weak electromagnetic stirring. Under the condition of weak electromagnetic stirring applied, the pouring temperature with low superheat can be equivalently to reach the effectiveness obtained from the even lower pouring temperature without stirring.展开更多
The semi-solid slurry of A356 alloy, which is grain-refined by Al-Ti-B master alloy, is prepared by low superheat pouring and slight electromagnetic stirring. The effects of grain refining on the morphology and the gr...The semi-solid slurry of A356 alloy, which is grain-refined by Al-Ti-B master alloy, is prepared by low superheat pouring and slight electromagnetic stirring. The effects of grain refining on the morphology and the grain size of the primary α phase in the slurry manufactured are researched. The results indicate that the slurry with particle-like and rosette-like primary α phases can be prepared by low superheat pouring and slight electromagnetic stirring from liquid A356 alloy grain-refined, in which the pouring temperature can be suitably raised. Compared with the A356 samples without grain refining, the grain size and particle morphology of primary α phase as well as the distribution of the grain with particle-like or rosette-like along radial in the ingot in A356 are markedly improved by grain refining.展开更多
A ladle-tundish-mould transportation model considering the entire multiple pouring(MP) process is proposed. Numerical simulation is carried out to study the carbon distribution and variation in both the tundish and th...A ladle-tundish-mould transportation model considering the entire multiple pouring(MP) process is proposed. Numerical simulation is carried out to study the carbon distribution and variation in both the tundish and the mould for making a 292 t steel ingot. Firstly, the fluid flow as well as the heat and mass transfer of the molten steel in the tundish is simulated based on the multiphase transient turbulence model. Then, the carbon mixing in the mould is calculated by using the species concentration at the tundish outlet as the inlet condition during the teeming process. The results show a high concentration of carbon at the bottom and a low concentration of carbon at the top of the mould after a MP process with carbon content high in the first ladle and low in the last ladle. Such carbon concentration distribution would help reduce the negative segregation at the bottom and the positive segregation at the top of the solidified ingot.展开更多
The Cu?Al composite casts were prepared by the method of pouring molten aluminum. The solidification process and themicrostructure of the transition layer were investigated during the recombination process of the liqu...The Cu?Al composite casts were prepared by the method of pouring molten aluminum. The solidification process and themicrostructure of the transition layer were investigated during the recombination process of the liquid Al and the solid Cu. The results reveal that the microstructure of the transition layer in the Cu?Al composite cast consists of α(Al)+α(Al)?CuAl2 eutectic,α(Al)?CuAl2 eutectic, CuAl2+α(Al)?CuAl2 eutectic and Cu9Al4. Additionally, the pouring temperature, cooling mode of the Cu platesurface and start time of the forced cooling after pouring have no effect on the microstructure species. But the proportion of thevarious microstructures in the transition layer changes with the process parameters. The pure Al at the top of the transition layer startsto solidify first and then the α(Al) phase grows in a dendritic way, while the CuAl2 phase exhibits plane or cellular crystal growth from the two sides of the transition layer towards its interior. The stronger the cooling intensity of the Cu plate outer surface, the more developed the dendrite, and the easier it is for the CuAl2 phase to grow into a plane crystal.展开更多
The semi-solid slurry of ZL101 alloy is prepared by a combination technology of low superheat pouring and slightly electromagnetic stirring. The effects of pouring temperature on the slurry prepared by the technology ...The semi-solid slurry of ZL101 alloy is prepared by a combination technology of low superheat pouring and slightly electromagnetic stirring. The effects of pouring temperature on the slurry prepared by the technology are investigated. The results indicate that it is feasible to prepare the slurry with globular primary phases by low superheat pouring and slightly electromagnetic stirring, and that the pouring temperature has an important effect on the morphology and the size of primary α-AI in ZL101 alloy. By applying suitable slightly electromagnetic stirring combining with relatively increased pouring temperature, i.e., in a practical way to apply low superheat pouring technology, is capable of obtaining appropriate semi-solid slurry of ZL101 alloy with globular shape of primary phase. Compared with the samples made by low superheat pouring only without stirring, the samples prepared by applying both slightly electromagnetic stirring and low superheat pouring can enable to achieve the same grain size and morphology of the primary phase with that of pouring at 15-35℃ higher.展开更多
A novel semisolid micro fused-casting(MFC) for preparing A356 alloy strips is proposed, and the effects of process parameters of pouring temperature on the microstructure and properties of A356 alloy strips are invest...A novel semisolid micro fused-casting(MFC) for preparing A356 alloy strips is proposed, and the effects of process parameters of pouring temperature on the microstructure and properties of A356 alloy strips are investigated. MFC means that the semisolid metal slurry was pressed out from the outlet of bottom of crucible to the movable plate, and directly solidified and formed layer by layer. The microstructure and properties of A356 semisolid alloy slurry were influenced by the cooling conditions. Results show that the aluminu alloy A356 strip samples fabricated by micro fused-casting had good performances and uniform structures with the pouring temperature at 595 ℃ and the substrate movement speed at 18 mm/s. The fine grains of the primary a-Al phase with average grain size of 53 μm and shape factor up to 0.72 was obtained, the ultimate tensile strength of the aluminum alloy A356 strip reaches 243.79±3.91 MPa, while the average vickers hardness is 82.65±1.86 HV.展开更多
The effect of different pouring temperatures and different pouring heights, the distance between the mouth of the pouring ladle and the top of the mold, on the microstructure of AlSi7Mg alloy have been researched in t...The effect of different pouring temperatures and different pouring heights, the distance between the mouth of the pouring ladle and the top of the mold, on the microstructure of AlSi7Mg alloy have been researched in the paper. When the pouring temperature is close to the liquidus temperature, the primary alpha -Al in 'the billets of AlSi7Mg alloy solidified into spherical and nodular fine grains distributed homogeneously. The optimum pouring temperature for semi-solid AlSi7Mg billet with spherical or nodular primary alpha -Al is 615 degreesC. At the same pouring temperature, the higher the pouring ladle, the more easily the spherical and nodular primary alpha -Al obtained in the semi-solid AlSi7Mg billet. When the pouring temperature is close to the liquidus temperature and the pouring ladle is relatively high, it is the great cooling rate, the flow of the molten allay caused by pouring and the large simultaneous solidification region induced by the near liquidus temperature, that promote the formation of spherical or nodular primary cr-Al.展开更多
Pouring position as the input heat source has great infl uence on the temperature fi eld evolution. In this study, the Flow3 D simulation software was applied to investigate the infl uence of pouring methods(with fi x...Pouring position as the input heat source has great infl uence on the temperature fi eld evolution. In this study, the Flow3 D simulation software was applied to investigate the infl uence of pouring methods(with fi xed or moving pouring channel) on AZ91 Mg alloy horizontal centrifugal casting(HCC) process. The simulation results show that the moving pouring channel method can effectively increase the cooling rate and formability of casting pipe. The casting experiment shows that an AZ91 Mg alloy casting pipe with homogeneous microstructure and clear contour was obtained by the moving pouring channel method, and the grain size of the casting pipe is signifi cantly decreased. Meanwhile, serious macro-segregation appeared in the AZ91 casting pipe by the fi xed pouring channel HCC process. Compared with the fi xed pouring channel, the moving pouring channel can remarkably improve the ultimate tensile strength and elongation of the AZ91 HCC pipe from 142.2 MPa to 201.5 MPa and 6.2% to 6.7%, respectively.展开更多
In this study, a serpentine channel pouring process was used to prepare the semi-solid A1-20%Si alloy slurry and refine primary Si grains in the alloy. The effects of the pouring temperature, number of curves in the s...In this study, a serpentine channel pouring process was used to prepare the semi-solid A1-20%Si alloy slurry and refine primary Si grains in the alloy. The effects of the pouring temperature, number of curves in the serpentine channel, and material of the serpentine channel on the size of primary Si grains in the semi-solid A1-20%Si alloy slurry were investigated. The results showed that the pouting temperature, number of the curves, and material of the channel strongly affected the size and distribution of the primary Si grains. The pouring tempera- ture exerted the strongest effect, followed by the number of the curves and then the material of the channel. Under experimental conditions of a four-curve copper channel and a pouring temperature of 701℃, primary Si grains in the semi-solid A1-20%Si alloy slurry were refined to the greatest extent, and the lath-like grains were changed into granular grains. Moreover, the equivalent grain diameter and the average shape coefficient of primary Si grains in the satisfactory semi-solid A1-20%Si alloy slurry were 24.4 μm and 0.89, respectively. Finally, the re- finement mechanism and distribution rule of primary Si grains in the slurry prepared through the serpentine channel pouring process were analyzed and discussed.展开更多
In this paper, the serpentine channel pouring process for preparing a semi-solid A390 alloy slurry and refining the primary Si grains of the A390 alloy, was used. The effects of the pouring temperature, the cooling wa...In this paper, the serpentine channel pouring process for preparing a semi-solid A390 alloy slurry and refining the primary Si grains of the A390 alloy, was used. The effects of the pouring temperature, the cooling water flow and the number of the curves on the size of the primary Si grains in the semi-solid A390 alloy slurry were investigated. The results show that the pouring temperature, the cooling water flow and the number of the curves have a major effect on the size and the distribution of primary Si grains. Under the experimental condition of the four-curve copper channel whose cooling water flow was 500 L·h-1 and the pouring temperature was 690 oC, the primary Si grains of the semi-solid A390 alloy slurry were refined to the greatest extent and the lath-like grains were changed into granular ones. Additionally, the equivalent grain diameter and the average shape factor of the primary Si grains of the satisfactory semi-solid A390 alloy slurry are 18.6 μm and 0.8, respectively. Further, the refinement mechanism of the primary Si grains through the serpentine channel pouring process was analyzed and discussed. In summary, the primary Si nuclei could be easily precipitated due to the chilling effect of the channel inner wall, thus the primary Si grains were greatly refined. Meanwhile, the subsequent alloy melt fluid also promoted the separation of primary Si grains from the inner wall, further refining the primary Si grains.展开更多
The effect of different pouring heights and evenly soaking process in the liquidus and solidus range on the solidified microstructure of AlSi7Mg alloy has been studied. The results show that if the pouring temperature...The effect of different pouring heights and evenly soaking process in the liquidus and solidus range on the solidified microstructure of AlSi7Mg alloy has been studied. The results show that if the pouring temperature is 630 or 650℃ and the pouring height is 40 mm, the microstructure of the solidified melt is not homogeneous and there are many rosette-like primary α-Al grains. But if the pouring height is increased to 400 mm, the solidified microstructure becomes more homogeneous and favorable to obtain spherical primary α-Al grains in the solidified melt. With further being evenly soaked in the liquidus and solidus range for some time, the temperature difference between the melt center and the melt periphery can be controlled within ±2℃ and the primary α-Al grains will evolve into more spherical grains. The theoretical analysis indicates that the higher pouring height promotes the melt flow motion and makes the temperature field in the melt more homogeneous and restrains the large rosette primary α-Al grains. This flow motion can also promote the ripening effect and the primary α-Al grains in the melt are gradually changed into spherical grains. It can be concluded from the experiments that pouring at an appropriate superheat and from a proper height is a good new method for preparing the semisolid slurry of AlSi7Mg alloy, its process control is easy and the preparation cost is lower.展开更多
To control the morphology and size of the primary and eutectic Mg2Si phases in in situ Mg2Si/Al-Si composite and achieve a feasible and reliable technique to produce appropriate feedstock for the thixo-casting and rhe...To control the morphology and size of the primary and eutectic Mg2Si phases in in situ Mg2Si/Al-Si composite and achieve a feasible and reliable technique to produce appropriate feedstock for the thixo-casting and rheo-casting of this type of material, three AI-Si matrix composites reinforced by 5wt.%, 9wt.% and 17wt.% Mg2Si with hypoeutectic, eutectic and hypereutectic compositions were prepared by the low superheat pouring （LSP） process. The effects of the pouring temperature （superheat） on the morphology and size distribution of primary phases （primary e-AI and Mg2Si）, binary （a-AI ＋ Mg2Si） eutectic cell and eutectic Mg2Si were investigated. The experimental results show that low pouring temperature （superheat） not only refines the grain structure of the primary e-AI and binary （e-AI ＋ Mg2Si） eutectic cell in three composites and promotes the formation of more non- dendritic structural semi-solid metal （SSM） slurry of these phases; but also refines the primary and eutectic Mg2Si phases, which seems to be attributed to the creation of an ideal condition for the nucleation and the acquisition of a high survival of nuclei caused by the LSP process.展开更多
Based on the background of navigation lock structure engineering in Changsha Integrated Hub, this study used Parametric Design Language （APDL） compilation command on the t＇mite element program ANSAYS platforms to s...Based on the background of navigation lock structure engineering in Changsha Integrated Hub, this study used Parametric Design Language （APDL） compilation command on the t＇mite element program ANSAYS platforms to simulate the temperature field of the layered pouring process about the lower lock head. The temperature contour map and the change laws of temperature field with time in each different levels of the floor were obtained. And compared with the actual instrument measurement data, the feasibility of the simulation analysis was concluded. Then, this study optimized the pouring process, obtained the suitable methods of layered pouring and put forward the measures to reduce the concrete temperature crack.展开更多
The preparation of semisolid slurry of A356 aluminum alloy using an oblique plate was investigated. A356 alloy melt undergoes partial solidification when it flows down on an oblique plate cooled from underneath by cou...The preparation of semisolid slurry of A356 aluminum alloy using an oblique plate was investigated. A356 alloy melt undergoes partial solidification when it flows down on an oblique plate cooled from underneath by counter flowing water. It results in continuous formation of columnar dendrites on plate wall. Due to forced convection, these dendrites are sheared off into equiaxed/fragmented grains and then washed away continuously to produce semisolid slurry at plate exit. Melt pouring temperature provides required condition of solidification whereas plate inclination enables necessary shear for producing semisolid slurry of desired quality. Slurry obtained was solidified in metal mould to produce semisolid-cast billets of desired microstructure. Furthermore, semisolid-cast billets were heat treated to improve surface quality. Microstructures of both semisolid-cast and heat-treated billets were analyzed. Effects of melt pouring temperature and plate inclination on solidification and microstructure of billets produced using oblique plate were described. The investigations involved four different melt pouring temperatures (620, 625, 630 and 635 °C) associated with four different plate inclinations (30°, 45°, 60° and 75°). Melt pouring temperature of 625 °C with plate inclination of 60° shows fine and globular microstructures and it is the optimum.展开更多
文摘The application of investment casting auto-pouring system can improve the efficiency of manual-pouring system to a certain extent.The judgment of start-stop time depends on the preprocessing of original image collected by the CCD camera.Several methods are presented to denoise the liquid column image.The method of morphological image processing is feasible in theory,and it is important whether to choose the structural element or not.The method of pouring image projection is less affected the image of spure cup.The complexity of image window algorithm is minimal.
基金Funded by the National Natural Science Foundation of China(No.51341009)。
文摘A novel micro fused-casting(MFC)process is developed for semisolid aluminum alloy slurry.The microstructure evolution and properties of semisolid ZL101 aluminum alloy slurry with difierent pouring temperature by MFC are investigated in this paper.During the cooling process,the effects of the pouring temperature on microstructure and properties is primarily analyzed.The microstructure of the semisolid ZL101 aluminum alloy is more homogeneous and the grain is smaller under proper pouring temperature.Temperature of liquids and solids of ZL101 aluminum alloy is measured by difierential scanning calorimetry(DSC).Distribution and characteristics of the microstructure of samples are examined by optical microscope(OM),scanning electron microscopy(SEM)equipped with energy dispersive spectrometer(EDS).The results show that the ZL101 semisolid slurry fabricated by MFC presents uniform shape and good grain size under the pouring temperature of 594°C and the stirring velocity of 600 r/min,and the fine grains of the primary a-Al phase with average grain size of 55μm and shape factor up to 0.67 were obtained.Besides,the ultimate tensile strength and the average Vickers hardness for semisolid ZL101 aluminum slurry are 178.19±1.37 MPa and 86.15±1.16 HV,respectively.
基金Project (2009AA033501) supported by the High-tech Research and Development Program of China
文摘Pouring and mold temperatures are two important parameters during casting magnesium components. The present study examined their influence on hot tearing susceptibility （HTS） of commercial AZ91D and newly developed Mg-3Nd-0.2Zn-Zr （mass fraction, %; NZ30K） magnesium alloys in gravity permanent mold casting condition. The results indicate that mold temperature shows much more significant influence on the HTS of both alloys than pouring temperature whose influence only can be distinguished at low mold temperature （341 K for AZ91D alloy and 423 K for NZ30K alloy）. Hot tearing susceptibility prediction model concerning feeding parameters, grain size and solidification range, is more suitable to estimate the HTS of different magnesium alloys than the model only concerning feeding parameters. In order to achieve better hot tearing resistance, the ranges of pouring and mold temperatures are suggested to be 961-991 K and≥641 K for AZ91D alloy, 1003-1033 K and≥623 K for NZ30K alloy, respectively.
基金the support from the Key Program Grant from National Natural Science Foundation of China (52039005)Grant from State Key Laboratory of Hydroscience and Engineering (2022-KY-01).
文摘Over the past few decades,one of the most significant advances in dam construction has been the inven-tion of the rock-filled concrete(RFC)dam,which is constructed by pouring high-performance self-compacting concrete(HSCC)to fill the voids in preplaced large rocks.The innovative use of large rocks in dam construction provides engineers with a material that requires less cement consumption and hydration heat while enhancing construction efficiency and environmental friendliness.However,two fundamental scientific issues related to RFC need to be addressed:namely,the pouring compactness and the effect of large rocks on the mechanical and physical properties of RFC.This article provides a timely review of fundamental research and innovations in the design,construction,and quality control of RFCdams.Prospects for next-generation concrete dams are discussed from the perspectives of envi-ronmental friendliness,intrinsic safety,and labor savings.
基金Project(2011CB606302-1)supported by the National Basic Research Program of ChinaProject(2013AA031001)supported by High-tech Research and Development Program of China
文摘An advanced rheomoulder,which is a device in the integration of melting metal,storage,slurry preparation,transportation and injection forming,was introduced and used to manufacture rheomoulding AZ91 D alloy.Effects of pouring temperature and cylinder temperature on microstructures and mechanical properties of rheomoulding AZ91 D alloy were investigated.The results show that the process can obtain such rheomoulding AZ91 D in which primary α-Mg particles are fine,spherical and uniformly distributed in the matrix.With the decrease of pouring temperature,the morphology of primary α-Mg particles changes from coarse rosette-like to fine spherical shape gradually.As the cylinder temperature decreases,the average size of primary α-Mg particles decreases firstly and then substantially maintains stable while the sphericity and solid fraction increase continuously.Also,decreasing pouring temperature or cylinder temperature properly contributes to improving mechanical properties of rheomoulding AZ91 D for the refinement of α-Mg particles and the decrease of porosity fraction.Furthermore,rheomoulding AZ91 D performs much better than thixomoulding,rheo-diecasting and high pressure die-casting（HPDC） in terms of mechanical properties.Compared with HPDC,the tensile strength,yield strength and elongation are increased by 27.8%,15.7% and 121%,respectively.
基金The project was financially supported by the Hi-tech Research and Development Program of China (No. G2002AA336080) and the National Natural Science Foundation of China (No. 50374012)
文摘The semi-solid slurry of a hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouting temperature and stirring power on the semi-solid slurry were investigated. The results indicated that the semi-solid slurry to satisfy rheocasting can be manufactured by low superheat pouring and weak electromagnetic stirring. The pouring temperature （or superheat） and the stirring power remarkably affected the morphology of primary α-Al and the size of primary α-Al, and there is no obvious effect of stirring time on primary α-Al. Compared with the samples made by low superheat pouring with no stirring, the nucleation rate, particle morphology and grain size of primary α-Al in A356 were markedly improved by low superheat pouring and weak electromagnetic stirring. On the condition of weak electromagnetic stirring, the pouring temperature with low superheat can be suitably raised to reach the effectiveness obtained from the lower pouring temperature without stirring.
基金The paper is supported by the Hi-tech Research and Develop-ment Program of China (Authorized No.: G2002AA336080), andthe National Natural Science Foundation of China (AuthorizedNo.: 50374012).
文摘The semi-solid slurry of hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature and stirring power on the semi-solid slurry making process were investigated. The results indicate that the semi-solid slurry to satisfy rheocasting requirement can be made by a combination of low superheat pouring and weak electromagnetic stirring. The pouring temperature (or superheat) and the stirring power significantly affect the morphology and the size of primary α-Al, while there is no obvious effect of the stirring time on primary α-Al. Compared with the samples made by low superheat pouring without stirring, the nucleation rate, particle morphology and grain size of primary α-Al in A356 Al alloy are markedly improved by a process of applying both low superheat pouring and weak electromagnetic stirring. Under the condition of weak electromagnetic stirring applied, the pouring temperature with low superheat can be equivalently to reach the effectiveness obtained from the even lower pouring temperature without stirring.
基金financially supported by National High Technical Research and Development Program of China(No.G2002AA336080)National Natural Science Foundation of China(No.50374012)Natural Science Foundation of Jiangxi Province(No.0650047).
文摘The semi-solid slurry of A356 alloy, which is grain-refined by Al-Ti-B master alloy, is prepared by low superheat pouring and slight electromagnetic stirring. The effects of grain refining on the morphology and the grain size of the primary α phase in the slurry manufactured are researched. The results indicate that the slurry with particle-like and rosette-like primary α phases can be prepared by low superheat pouring and slight electromagnetic stirring from liquid A356 alloy grain-refined, in which the pouring temperature can be suitably raised. Compared with the A356 samples without grain refining, the grain size and particle morphology of primary α phase as well as the distribution of the grain with particle-like or rosette-like along radial in the ingot in A356 are markedly improved by grain refining.
基金financially supported by the National Basic Research Program of China(No.2011CB012900)the National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2012ZX04012011)
文摘A ladle-tundish-mould transportation model considering the entire multiple pouring(MP) process is proposed. Numerical simulation is carried out to study the carbon distribution and variation in both the tundish and the mould for making a 292 t steel ingot. Firstly, the fluid flow as well as the heat and mass transfer of the molten steel in the tundish is simulated based on the multiphase transient turbulence model. Then, the carbon mixing in the mould is calculated by using the species concentration at the tundish outlet as the inlet condition during the teeming process. The results show a high concentration of carbon at the bottom and a low concentration of carbon at the top of the mould after a MP process with carbon content high in the first ladle and low in the last ladle. Such carbon concentration distribution would help reduce the negative segregation at the bottom and the positive segregation at the top of the solidified ingot.
基金Project(LJQ2014062)supported by the Outstanding Young Scholars in Colleges and Universities of Liaoning Province,China
文摘The Cu?Al composite casts were prepared by the method of pouring molten aluminum. The solidification process and themicrostructure of the transition layer were investigated during the recombination process of the liquid Al and the solid Cu. The results reveal that the microstructure of the transition layer in the Cu?Al composite cast consists of α(Al)+α(Al)?CuAl2 eutectic,α(Al)?CuAl2 eutectic, CuAl2+α(Al)?CuAl2 eutectic and Cu9Al4. Additionally, the pouring temperature, cooling mode of the Cu platesurface and start time of the forced cooling after pouring have no effect on the microstructure species. But the proportion of thevarious microstructures in the transition layer changes with the process parameters. The pure Al at the top of the transition layer startsto solidify first and then the α(Al) phase grows in a dendritic way, while the CuAl2 phase exhibits plane or cellular crystal growth from the two sides of the transition layer towards its interior. The stronger the cooling intensity of the Cu plate outer surface, the more developed the dendrite, and the easier it is for the CuAl2 phase to grow into a plane crystal.
基金supported by the Hi-tech Research and Development Program of China(Authorized No.G2002AA336080)the National Natural Science Foundation of China(Authorized No.50374012)the Natural Science Foundation of Jiangxi Province(Authorized No.0650047).
文摘The semi-solid slurry of ZL101 alloy is prepared by a combination technology of low superheat pouring and slightly electromagnetic stirring. The effects of pouring temperature on the slurry prepared by the technology are investigated. The results indicate that it is feasible to prepare the slurry with globular primary phases by low superheat pouring and slightly electromagnetic stirring, and that the pouring temperature has an important effect on the morphology and the size of primary α-AI in ZL101 alloy. By applying suitable slightly electromagnetic stirring combining with relatively increased pouring temperature, i.e., in a practical way to apply low superheat pouring technology, is capable of obtaining appropriate semi-solid slurry of ZL101 alloy with globular shape of primary phase. Compared with the samples made by low superheat pouring only without stirring, the samples prepared by applying both slightly electromagnetic stirring and low superheat pouring can enable to achieve the same grain size and morphology of the primary phase with that of pouring at 15-35℃ higher.
文摘A novel semisolid micro fused-casting(MFC) for preparing A356 alloy strips is proposed, and the effects of process parameters of pouring temperature on the microstructure and properties of A356 alloy strips are investigated. MFC means that the semisolid metal slurry was pressed out from the outlet of bottom of crucible to the movable plate, and directly solidified and formed layer by layer. The microstructure and properties of A356 semisolid alloy slurry were influenced by the cooling conditions. Results show that the aluminu alloy A356 strip samples fabricated by micro fused-casting had good performances and uniform structures with the pouring temperature at 595 ℃ and the substrate movement speed at 18 mm/s. The fine grains of the primary a-Al phase with average grain size of 53 μm and shape factor up to 0.72 was obtained, the ultimate tensile strength of the aluminum alloy A356 strip reaches 243.79±3.91 MPa, while the average vickers hardness is 82.65±1.86 HV.
基金The authors would like to thank the National 863 Plan of China for financial support under Grant No 715-012-0040.
文摘The effect of different pouring temperatures and different pouring heights, the distance between the mouth of the pouring ladle and the top of the mold, on the microstructure of AlSi7Mg alloy have been researched in the paper. When the pouring temperature is close to the liquidus temperature, the primary alpha -Al in 'the billets of AlSi7Mg alloy solidified into spherical and nodular fine grains distributed homogeneously. The optimum pouring temperature for semi-solid AlSi7Mg billet with spherical or nodular primary alpha -Al is 615 degreesC. At the same pouring temperature, the higher the pouring ladle, the more easily the spherical and nodular primary alpha -Al obtained in the semi-solid AlSi7Mg billet. When the pouring temperature is close to the liquidus temperature and the pouring ladle is relatively high, it is the great cooling rate, the flow of the molten allay caused by pouring and the large simultaneous solidification region induced by the near liquidus temperature, that promote the formation of spherical or nodular primary cr-Al.
基金financially supported by the National Natural Foundation of China(Grant No.51605307)Liaoning Provincial Natural Science Foundation(Grant No.201501084)
文摘Pouring position as the input heat source has great infl uence on the temperature fi eld evolution. In this study, the Flow3 D simulation software was applied to investigate the infl uence of pouring methods(with fi xed or moving pouring channel) on AZ91 Mg alloy horizontal centrifugal casting(HCC) process. The simulation results show that the moving pouring channel method can effectively increase the cooling rate and formability of casting pipe. The casting experiment shows that an AZ91 Mg alloy casting pipe with homogeneous microstructure and clear contour was obtained by the moving pouring channel method, and the grain size of the casting pipe is signifi cantly decreased. Meanwhile, serious macro-segregation appeared in the AZ91 casting pipe by the fi xed pouring channel HCC process. Compared with the fi xed pouring channel, the moving pouring channel can remarkably improve the ultimate tensile strength and elongation of the AZ91 HCC pipe from 142.2 MPa to 201.5 MPa and 6.2% to 6.7%, respectively.
基金financially supported by the National Basic Research Program of China (No. 2011CB606300)the National Natural Science Foundation of China (No. 5077400)
文摘In this study, a serpentine channel pouring process was used to prepare the semi-solid A1-20%Si alloy slurry and refine primary Si grains in the alloy. The effects of the pouring temperature, number of curves in the serpentine channel, and material of the serpentine channel on the size of primary Si grains in the semi-solid A1-20%Si alloy slurry were investigated. The results showed that the pouting temperature, number of the curves, and material of the channel strongly affected the size and distribution of the primary Si grains. The pouring tempera- ture exerted the strongest effect, followed by the number of the curves and then the material of the channel. Under experimental conditions of a four-curve copper channel and a pouring temperature of 701℃, primary Si grains in the semi-solid A1-20%Si alloy slurry were refined to the greatest extent, and the lath-like grains were changed into granular grains. Moreover, the equivalent grain diameter and the average shape coefficient of primary Si grains in the satisfactory semi-solid A1-20%Si alloy slurry were 24.4 μm and 0.89, respectively. Finally, the re- finement mechanism and distribution rule of primary Si grains in the slurry prepared through the serpentine channel pouring process were analyzed and discussed.
基金supported by the National Basic Research Program of China(2011CB606300)the National Natural Science Foundation of China(5077400)
文摘In this paper, the serpentine channel pouring process for preparing a semi-solid A390 alloy slurry and refining the primary Si grains of the A390 alloy, was used. The effects of the pouring temperature, the cooling water flow and the number of the curves on the size of the primary Si grains in the semi-solid A390 alloy slurry were investigated. The results show that the pouring temperature, the cooling water flow and the number of the curves have a major effect on the size and the distribution of primary Si grains. Under the experimental condition of the four-curve copper channel whose cooling water flow was 500 L·h-1 and the pouring temperature was 690 oC, the primary Si grains of the semi-solid A390 alloy slurry were refined to the greatest extent and the lath-like grains were changed into granular ones. Additionally, the equivalent grain diameter and the average shape factor of the primary Si grains of the satisfactory semi-solid A390 alloy slurry are 18.6 μm and 0.8, respectively. Further, the refinement mechanism of the primary Si grains through the serpentine channel pouring process was analyzed and discussed. In summary, the primary Si nuclei could be easily precipitated due to the chilling effect of the channel inner wall, thus the primary Si grains were greatly refined. Meanwhile, the subsequent alloy melt fluid also promoted the separation of primary Si grains from the inner wall, further refining the primary Si grains.
基金This work was financially supported by the National High-Tech Research and Development Program of China (No.G2002AA336080) and the National Natural Science Foundation of China (No.50374012).
文摘The effect of different pouring heights and evenly soaking process in the liquidus and solidus range on the solidified microstructure of AlSi7Mg alloy has been studied. The results show that if the pouring temperature is 630 or 650℃ and the pouring height is 40 mm, the microstructure of the solidified melt is not homogeneous and there are many rosette-like primary α-Al grains. But if the pouring height is increased to 400 mm, the solidified microstructure becomes more homogeneous and favorable to obtain spherical primary α-Al grains in the solidified melt. With further being evenly soaked in the liquidus and solidus range for some time, the temperature difference between the melt center and the melt periphery can be controlled within ±2℃ and the primary α-Al grains will evolve into more spherical grains. The theoretical analysis indicates that the higher pouring height promotes the melt flow motion and makes the temperature field in the melt more homogeneous and restrains the large rosette primary α-Al grains. This flow motion can also promote the ripening effect and the primary α-Al grains in the melt are gradually changed into spherical grains. It can be concluded from the experiments that pouring at an appropriate superheat and from a proper height is a good new method for preparing the semisolid slurry of AlSi7Mg alloy, its process control is easy and the preparation cost is lower.
文摘To control the morphology and size of the primary and eutectic Mg2Si phases in in situ Mg2Si/Al-Si composite and achieve a feasible and reliable technique to produce appropriate feedstock for the thixo-casting and rheo-casting of this type of material, three AI-Si matrix composites reinforced by 5wt.%, 9wt.% and 17wt.% Mg2Si with hypoeutectic, eutectic and hypereutectic compositions were prepared by the low superheat pouring （LSP） process. The effects of the pouring temperature （superheat） on the morphology and size distribution of primary phases （primary e-AI and Mg2Si）, binary （a-AI ＋ Mg2Si） eutectic cell and eutectic Mg2Si were investigated. The experimental results show that low pouring temperature （superheat） not only refines the grain structure of the primary e-AI and binary （e-AI ＋ Mg2Si） eutectic cell in three composites and promotes the formation of more non- dendritic structural semi-solid metal （SSM） slurry of these phases; but also refines the primary and eutectic Mg2Si phases, which seems to be attributed to the creation of an ideal condition for the nucleation and the acquisition of a high survival of nuclei caused by the LSP process.
文摘Based on the background of navigation lock structure engineering in Changsha Integrated Hub, this study used Parametric Design Language （APDL） compilation command on the t＇mite element program ANSAYS platforms to simulate the temperature field of the layered pouring process about the lower lock head. The temperature contour map and the change laws of temperature field with time in each different levels of the floor were obtained. And compared with the actual instrument measurement data, the feasibility of the simulation analysis was concluded. Then, this study optimized the pouring process, obtained the suitable methods of layered pouring and put forward the measures to reduce the concrete temperature crack.
基金financial support received from Ministry of Mines, TIFAC, and Department of Science and Technology
文摘The preparation of semisolid slurry of A356 aluminum alloy using an oblique plate was investigated. A356 alloy melt undergoes partial solidification when it flows down on an oblique plate cooled from underneath by counter flowing water. It results in continuous formation of columnar dendrites on plate wall. Due to forced convection, these dendrites are sheared off into equiaxed/fragmented grains and then washed away continuously to produce semisolid slurry at plate exit. Melt pouring temperature provides required condition of solidification whereas plate inclination enables necessary shear for producing semisolid slurry of desired quality. Slurry obtained was solidified in metal mould to produce semisolid-cast billets of desired microstructure. Furthermore, semisolid-cast billets were heat treated to improve surface quality. Microstructures of both semisolid-cast and heat-treated billets were analyzed. Effects of melt pouring temperature and plate inclination on solidification and microstructure of billets produced using oblique plate were described. The investigations involved four different melt pouring temperatures (620, 625, 630 and 635 °C) associated with four different plate inclinations (30°, 45°, 60° and 75°). Melt pouring temperature of 625 °C with plate inclination of 60° shows fine and globular microstructures and it is the optimum.
