Three kinds of Al-Si piston alloys were prepared and subjected to pulse electric current treatment (PECT)at different pouring temperatures.Some aspects of the solidification microstructures were examined including the...Three kinds of Al-Si piston alloys were prepared and subjected to pulse electric current treatment (PECT)at different pouring temperatures.Some aspects of the solidification microstructures were examined including the morphology and the distribution of the matrix and the secondary phases by using of optical microscopy(OM),SEM and EDS methods.Results indicate that PECT can refine the grains of a-Al in the alloys as effectively as chemical modification by sodium salt.The processing parameters of PECT on the multi-component Al-Si alloys were then optimized through the testing of tensile strength,elongation and microhardness of the prepared alloys.A new theory was put forward to explain the mechanism of PECT.展开更多
TiAl-based alloys are potentially used as high-temperature structural materials with a high specific strength in the range of^900°C.However,the mechanical properties of TiAl-based alloys are extremely anisotropic...TiAl-based alloys are potentially used as high-temperature structural materials with a high specific strength in the range of^900°C.However,the mechanical properties of TiAl-based alloys are extremely anisotropic with respect to the lamellar orientation of the microstructures.A balance combination of room-temperature ductility and strength can be achieved when the lamellar orientation are aligned parallel to the tensile stress direction.Lamellar orientation control of TiAl-based alloys by directional solidification technique has been widely studied in recent years.Two different directional solidification processes can be used to modify the lamellar orientation.One is a seeding technique and the other is adjusting the solidification path.This paper reviews the principles of the two methods and their progress.The influence of alloy composition and solidification parameters on lamellar orientation control is also discussed.展开更多
This article aims at building an electromagnetic and fluid model, based on the Maxwell equations and Navier-Stokes equations, in TiAl melt under two electric fields.FEM (Finite Element Method) and APDL (ANSYS Parametr...This article aims at building an electromagnetic and fluid model, based on the Maxwell equations and Navier-Stokes equations, in TiAl melt under two electric fields.FEM (Finite Element Method) and APDL (ANSYS Parametric Design Language) were employed to perform the simulation, model setup, loading and problem solving.The melt in molds of same cross section area with different flakiness ratio (i.e.width/depth) under the load of sinusoidal current or pulse current was analyzed to obtain the distribution of electromagnetic field and flow field.The results show that the induced magnetic field occupies sufficiently the domain of the melt in the mold with a flakiness ratio of 5:1.The melt is driven bipolarly from the center in each electric field.It is also found that the pulse electric field actuates the TiAl melt to flow stronger than what the sinusoidal electric field does.展开更多
A study on the interaction between TiAl alloy and zirconia was carried out in argon atmosphere. Themicrographic observations of the cross-section perpendicular to the interface were obtained using a scanning electronm...A study on the interaction between TiAl alloy and zirconia was carried out in argon atmosphere. Themicrographic observations of the cross-section perpendicular to the interface were obtained using a scanning electronmicroscope with a dedicated energy dispersive spectrometer (SEM/EDS). The results showed that firstly TiAl alloyspreads on the ceramic surface, and then infiltrates into the pores between ceramic particles accompanied by a chemicalreaction. The whole ceramic mold is broken into tiny blocks. A multiple fission reaction mechanism was developed toexplain the interaction between TiAl alloy and zirconia.展开更多
The solidified structure of the thin-walled and complicated Ti-6Al-4V castings produced by the vertical centrifugal casting process was studied in the present work.The results show that the wall thickness of the secti...The solidified structure of the thin-walled and complicated Ti-6Al-4V castings produced by the vertical centrifugal casting process was studied in the present work.The results show that the wall thickness of the section is featured with homogeneously distributed fine equiaxial grains,compared with the microstructure of the thick-walled section.The grain size of the castings has a tendency to decrease gradually with the increasing of the centrifugal radius.The inter-lamellar space in thick-walled casting parts is bigger than that of the thin-walled parts,and the profile of inter-lamellar space is not susceptible to the centrifugal radius.展开更多
基金supported by Heilongjiang Provincial Natural Science Foundation(Grant No.E200504)in China and the Harbin Institute of Technology Inter-disciplines Foundation(Grant No.HIT.MD2002.14).
文摘Three kinds of Al-Si piston alloys were prepared and subjected to pulse electric current treatment (PECT)at different pouring temperatures.Some aspects of the solidification microstructures were examined including the morphology and the distribution of the matrix and the secondary phases by using of optical microscopy(OM),SEM and EDS methods.Results indicate that PECT can refine the grains of a-Al in the alloys as effectively as chemical modification by sodium salt.The processing parameters of PECT on the multi-component Al-Si alloys were then optimized through the testing of tensile strength,elongation and microhardness of the prepared alloys.A new theory was put forward to explain the mechanism of PECT.
基金supported by the 973 project(2011CB610406,2011CB605504)NSFC project(51331005)Heilongjiang project(JC201209)
文摘TiAl-based alloys are potentially used as high-temperature structural materials with a high specific strength in the range of^900°C.However,the mechanical properties of TiAl-based alloys are extremely anisotropic with respect to the lamellar orientation of the microstructures.A balance combination of room-temperature ductility and strength can be achieved when the lamellar orientation are aligned parallel to the tensile stress direction.Lamellar orientation control of TiAl-based alloys by directional solidification technique has been widely studied in recent years.Two different directional solidification processes can be used to modify the lamellar orientation.One is a seeding technique and the other is adjusting the solidification path.This paper reviews the principles of the two methods and their progress.The influence of alloy composition and solidification parameters on lamellar orientation control is also discussed.
基金supported by the Program for New Century Excellent Talents in Universities of the Ministry of Education of China under Grant No.NCET-08-0164the Foundation of National Key Laboratory for Precision Heat Processing of Metals
文摘This article aims at building an electromagnetic and fluid model, based on the Maxwell equations and Navier-Stokes equations, in TiAl melt under two electric fields.FEM (Finite Element Method) and APDL (ANSYS Parametric Design Language) were employed to perform the simulation, model setup, loading and problem solving.The melt in molds of same cross section area with different flakiness ratio (i.e.width/depth) under the load of sinusoidal current or pulse current was analyzed to obtain the distribution of electromagnetic field and flow field.The results show that the induced magnetic field occupies sufficiently the domain of the melt in the mold with a flakiness ratio of 5:1.The melt is driven bipolarly from the center in each electric field.It is also found that the pulse electric field actuates the TiAl melt to flow stronger than what the sinusoidal electric field does.
基金This project (No. 50434030) was supported by the National Natural Science Foundation of China.
文摘A study on the interaction between TiAl alloy and zirconia was carried out in argon atmosphere. Themicrographic observations of the cross-section perpendicular to the interface were obtained using a scanning electronmicroscope with a dedicated energy dispersive spectrometer (SEM/EDS). The results showed that firstly TiAl alloyspreads on the ceramic surface, and then infiltrates into the pores between ceramic particles accompanied by a chemicalreaction. The whole ceramic mold is broken into tiny blocks. A multiple fission reaction mechanism was developed toexplain the interaction between TiAl alloy and zirconia.
基金by the National Natural Science Foundation of China under grant No. 50775050the State Key Laboratory of Solidif ication Processing in NWPU (200702)
文摘The solidified structure of the thin-walled and complicated Ti-6Al-4V castings produced by the vertical centrifugal casting process was studied in the present work.The results show that the wall thickness of the section is featured with homogeneously distributed fine equiaxial grains,compared with the microstructure of the thick-walled section.The grain size of the castings has a tendency to decrease gradually with the increasing of the centrifugal radius.The inter-lamellar space in thick-walled casting parts is bigger than that of the thin-walled parts,and the profile of inter-lamellar space is not susceptible to the centrifugal radius.
