Compared with the conventional casting process, digital pattern-less casting technology has many advantages such as good machining accuracy, a short processing cycle, and low production cost. It is a new rapid manufac...Compared with the conventional casting process, digital pattern-less casting technology has many advantages such as good machining accuracy, a short processing cycle, and low production cost. It is a new rapid manufacturing technology for castings, integrated with CAD/CAM, casting, CNC machining and many other advanced technologies. With this digital casting technology, no pattern is needed for making molds; it is precise, f lexible, and green. Usually, art castings have complex structures and are made in small batches or even made in a single-piece, especially for large-sized art castings. So it has the shortcomings of high cost, low eff iciency and long time for making a pattern to produce art castings with the conventional casting processes. However, the digital pattern-less casting technology can be applied to fabricate art castings, since it can greatly shorten the manufacturing cycle and lower the production cost, thus having a very good prospect. In this study, based on the digital pattern-less casting technology, a plaque casting with artistic Chinese characters(a Chinese poem) was designed and manufactured, and the production process was demonstrated in detail.展开更多
The influences of minor amounts of scandium on the microstructure and mechanical properties of as-cast ZA27 alloy have been experimentally investigated.The experimental results show that as far as the Sc addition is i...The influences of minor amounts of scandium on the microstructure and mechanical properties of as-cast ZA27 alloy have been experimentally investigated.The experimental results show that as far as the Sc addition is individually concerned,the refinement result of the as-cast ZA27 alloy with 0.5wt.%Sc addition is comparatively better.After alloying with minor amounts of Sc,the coarse dendrites of the ZA27 alloy are refined and transformed into the uniform and small equiaxed grain microstructure;also the eutectics among the grain boundaries become finer.The test results of mechanical properties show that the tensile strength and hardness of the as-cast ZA27 alloy containing 0.5wt.%Sc approach 495 MPa and 120.2 HB,increase by28.5%and 33.1%,respectively,compared with those of the ZA27 alloy with no addition of Sc element,while the elongation of the alloy is improved to 7.6%from 2.7%.The SEM,EDAX and XRD analyses show that in the ZA27 alloy,the trace element Sc combines with Al to form the square Al3Sc phase particles,which serve as heterogeneous nuclei,facilitating the refinement of the microstructure and the improvement of the mechanical properties of the alloy.展开更多
An investigation was made on the evolution of microstructures of hypoeutectic white cast iron slurry containing 2.5wt.%C and 1.8wt.%Si produced by rheocasting in which the solidifying alloy was vigorously agitated by ...An investigation was made on the evolution of microstructures of hypoeutectic white cast iron slurry containing 2.5wt.%C and 1.8wt.%Si produced by rheocasting in which the solidifying alloy was vigorously agitated by electromagnetic stirrer during isothermal cooling processes.The results indicated that under the proper agitating temperatures and speeds applied,the dendrite structures in white cast iron slurry were gradually evolved into spherical structures during a certain agitating time.It also revealed that the bent dendrites were formed by either convection force or by the growth of the dendrites themselves in the bending direction;then,as they were in solidifying,they were gradually being alternated into separated particles and into more spherical structures at the end of the isothermal cooling process.Especially,the dendrites were granulated as the bending process proceeding,which suggested that they were caused by unwanted elements such as sulfur and phosphor usually contained in engineering cast iron.Convective-ow of the melt caused corrosion on the dendritic segments where they were weaker in strength and lower in melting temperature because of higher concentration of sulfur or phosphor.And the granulation process for such dendrites formed in the melt became possible under the condition.Certainly,dendrite fragments are another factors considerable to function for spherical particles formation.A new mechanism,regarding to the rheocast structure formation of white cast iron,was suggested based on the structural evolution observed in the study.展开更多
Sn60Pb40 alloy powders were fabricated using the planar flow casting(PFC) atomization process. By using OM, SEM and EPMA, the characteristics of the morphologies and microstructures of the powders have been investigat...Sn60Pb40 alloy powders were fabricated using the planar flow casting(PFC) atomization process. By using OM, SEM and EPMA, the characteristics of the morphologies and microstructures of the powders have been investigated. It is observed that the environment of ambient gas in the atomization box has great effects on the morphology of the alloy powders. The microstructures of Sn60Pb40 alloy powders produced by the PFC atomization process are completely composed of eutectic, which is made up of both oversaturated α solid solution and β solid solution. The microstructures of small size powders are extraordinarily undeveloped dendritic eutectic, in which the large majority of the α phase appears nearly spherical, evidently since the cooling rate is higher and the under-cooling is larger. As for the large size powders, since the cooling rate and undercooling are relatively low, lamellar α phase apparently increases in the eutectic microstructures of these powders, and there is even typical lamellar eutectic structure clearly observed in some micro-areas. After remelting tests by DTA, the microstructures of small size powders are transformed, which become composed of large crumby α phase and eutectic(α+β), while those of large size powders change into classical tin-lead structures of primary α phase plus lamellar eutectic(α+β). By studying the microstructures of tin-lead alloy powders, a model has been proposed to predict the microstructure formation of Sn60Pb40 alloy powders.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51105257)
文摘Compared with the conventional casting process, digital pattern-less casting technology has many advantages such as good machining accuracy, a short processing cycle, and low production cost. It is a new rapid manufacturing technology for castings, integrated with CAD/CAM, casting, CNC machining and many other advanced technologies. With this digital casting technology, no pattern is needed for making molds; it is precise, f lexible, and green. Usually, art castings have complex structures and are made in small batches or even made in a single-piece, especially for large-sized art castings. So it has the shortcomings of high cost, low eff iciency and long time for making a pattern to produce art castings with the conventional casting processes. However, the digital pattern-less casting technology can be applied to fabricate art castings, since it can greatly shorten the manufacturing cycle and lower the production cost, thus having a very good prospect. In this study, based on the digital pattern-less casting technology, a plaque casting with artistic Chinese characters(a Chinese poem) was designed and manufactured, and the production process was demonstrated in detail.
基金financially supported by the Natural Science Foundation of Liaoning Province(No:20072043)
文摘The influences of minor amounts of scandium on the microstructure and mechanical properties of as-cast ZA27 alloy have been experimentally investigated.The experimental results show that as far as the Sc addition is individually concerned,the refinement result of the as-cast ZA27 alloy with 0.5wt.%Sc addition is comparatively better.After alloying with minor amounts of Sc,the coarse dendrites of the ZA27 alloy are refined and transformed into the uniform and small equiaxed grain microstructure;also the eutectics among the grain boundaries become finer.The test results of mechanical properties show that the tensile strength and hardness of the as-cast ZA27 alloy containing 0.5wt.%Sc approach 495 MPa and 120.2 HB,increase by28.5%and 33.1%,respectively,compared with those of the ZA27 alloy with no addition of Sc element,while the elongation of the alloy is improved to 7.6%from 2.7%.The SEM,EDAX and XRD analyses show that in the ZA27 alloy,the trace element Sc combines with Al to form the square Al3Sc phase particles,which serve as heterogeneous nuclei,facilitating the refinement of the microstructure and the improvement of the mechanical properties of the alloy.
基金supported by the Liaoning Education Bureau of China under grants No. 20061010
文摘An investigation was made on the evolution of microstructures of hypoeutectic white cast iron slurry containing 2.5wt.%C and 1.8wt.%Si produced by rheocasting in which the solidifying alloy was vigorously agitated by electromagnetic stirrer during isothermal cooling processes.The results indicated that under the proper agitating temperatures and speeds applied,the dendrite structures in white cast iron slurry were gradually evolved into spherical structures during a certain agitating time.It also revealed that the bent dendrites were formed by either convection force or by the growth of the dendrites themselves in the bending direction;then,as they were in solidifying,they were gradually being alternated into separated particles and into more spherical structures at the end of the isothermal cooling process.Especially,the dendrites were granulated as the bending process proceeding,which suggested that they were caused by unwanted elements such as sulfur and phosphor usually contained in engineering cast iron.Convective-ow of the melt caused corrosion on the dendritic segments where they were weaker in strength and lower in melting temperature because of higher concentration of sulfur or phosphor.And the granulation process for such dendrites formed in the melt became possible under the condition.Certainly,dendrite fragments are another factors considerable to function for spherical particles formation.A new mechanism,regarding to the rheocast structure formation of white cast iron,was suggested based on the structural evolution observed in the study.
基金supported by the Natural Science Foundation of Liaoning Province (No.20072043)
文摘Sn60Pb40 alloy powders were fabricated using the planar flow casting(PFC) atomization process. By using OM, SEM and EPMA, the characteristics of the morphologies and microstructures of the powders have been investigated. It is observed that the environment of ambient gas in the atomization box has great effects on the morphology of the alloy powders. The microstructures of Sn60Pb40 alloy powders produced by the PFC atomization process are completely composed of eutectic, which is made up of both oversaturated α solid solution and β solid solution. The microstructures of small size powders are extraordinarily undeveloped dendritic eutectic, in which the large majority of the α phase appears nearly spherical, evidently since the cooling rate is higher and the under-cooling is larger. As for the large size powders, since the cooling rate and undercooling are relatively low, lamellar α phase apparently increases in the eutectic microstructures of these powders, and there is even typical lamellar eutectic structure clearly observed in some micro-areas. After remelting tests by DTA, the microstructures of small size powders are transformed, which become composed of large crumby α phase and eutectic(α+β), while those of large size powders change into classical tin-lead structures of primary α phase plus lamellar eutectic(α+β). By studying the microstructures of tin-lead alloy powders, a model has been proposed to predict the microstructure formation of Sn60Pb40 alloy powders.
