Two kinds of high strength-damping aluminum alloys （LZ7） were fabricated by rapid solidification and powder metallurgy （RS-PM） process. One material was extruded to profile aluminum directly and the other was extr...Two kinds of high strength-damping aluminum alloys （LZ7） were fabricated by rapid solidification and powder metallurgy （RS-PM） process. One material was extruded to profile aluminum directly and the other was extruded to bar and then rolled to sheet. The damping capacity over a temperature range of 25-300 ℃was studied with damping mechanical thermal analyzer （DMTA） and the microstructures were investigated by optical microscopy （OM）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results show that the damping capacity increases with the test temperature elevating. Internal friction value of rolled sheet aluminum is up to 11.5×10^-2 and that of profile aluminum is as high as 6.0×10^-2 and 7.5×10^-2 at 300 ℃, respectively. Microstructure analysis shows the shape of precipitation phase of rolled alloy is more regular and the distribution is more homogeneous than that of profile alloy. Meanwhile, the interface between particulate and matrix of rolled sheet alloy is looser than that of profile alloy. Maybe the differences at interface can explain why damping capacity of rolled sheet alloy is higher than that of profile alloys at high temperature （above 120 ℃）.展开更多
Rapidly solidified hypereutectic Al-Si alloys were prepared by powder hot extrusion. By eliminating vacuum degassing procedure, the fabrication routine was simplified. The tensile fracture mechanisms at room temperatu...Rapidly solidified hypereutectic Al-Si alloys were prepared by powder hot extrusion. By eliminating vacuum degassing procedure, the fabrication routine was simplified. The tensile fracture mechanisms at room temperature and elevated temperature were investigated by SEM fractography. Compared with KS282 casting material, the tensile strength of rapidly solidified Al-Si alloy is greatly improved due to silicon particles refining while its density and coefficient of thermal expansion are lower than those of KS282. The wear resistance of RS AlSi is better than that of KS282.展开更多
Sn60Pb40 al oy 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 investi...Sn60Pb40 al oy 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 al oy powders. The microstructures of Sn60Pb40 al oy powders produced by the PFC atomization process are completely composed of eutectic, which is made up of both oversaturated αsolid solution and β solid solution. The microstructures of smal 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, lamel ar 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 smal 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 al oy powders.展开更多
The effects of additions of Ti and W on microstructure and mechanical properties of rapidly solidified Al-Fe-V-Si alloys were investigated. Alloy powders were produced by the centrifugal rotary atomization process. Af...The effects of additions of Ti and W on microstructure and mechanical properties of rapidly solidified Al-Fe-V-Si alloys were investigated. Alloy powders were produced by the centrifugal rotary atomization process. After atomization, powders were screened to various mesh sizes to see the effect of powder size on the mechanical properties.These Powders were consolidated into billets using conventional powder metallurgy process, and then extruded into bar form.Microstructural analysis shows that the W addition results in the heterogeneous microstructure.On the other hand, the Ti addition refines the microstructure.Alloy containing both Ti and W has the highest thermal stability of the dispersoid. These variations in the microstructure are well reflected in the mechanical properties in that the Ti containtng alloys (with or without W) have the higher strength and ductility than the W containing alloy. It also shows that the alloys made of the coarser powders have better combinations of strength and ductility than those made of the finer powders.展开更多
This study investigated the microstructures and mechanical properties of ZK60 alloy prepared by a simplified rapid solidification powder metallurgy （RS P/M） processing system （S-RS P/M）, which consists of warm pre...This study investigated the microstructures and mechanical properties of ZK60 alloy prepared by a simplified rapid solidification powder metallurgy （RS P/M） processing system （S-RS P/M）, which consists of warm press in dry air and hot extrusion. Microstructure characterizations showed that S-RS P/M alloy consisted of magnesium matrix and oxide stringers of ~1 #m in width. TEM （transmission electron microscopy） observations illustrated nano-size magnesia particles （10-30 nm） constituted oxide stringer in detail. Due to a relatively higher volume of nano-size magnesia particle produced during S-RS P/M process, 0.2% yield strength of S-RS P/M ZKO0 alloy was found to be as high as 382 MPa, which is 10% higher than that of RS P/M alloy. The improvement in mechanical properties is mainly attributed to the combination effects of Orowan mechanism and coefficient of thermal expansion （CTE） mismatch because of the approximately same average grain size.展开更多
Aluminum silicon alloy of composition (Al-25%Si-3%Ni-1%Fe-2%Cu) was atomized using water atomization. The powders were cold compacted in a die to produce green cylinder compacts. Four consolidation processes were appl...Aluminum silicon alloy of composition (Al-25%Si-3%Ni-1%Fe-2%Cu) was atomized using water atomization. The powders were cold compacted in a die to produce green cylinder compacts. Four consolidation processes were applied, namely;conventional sintering at 500℃, sintering followed by hot forging to obtain pistons, one step hot forging into pistons, and hot pressing. The microstructure of the sintered specimens showed inter-granular pores and oxide layers on particle interfaces of 84% relative density. When the sintered specimens were hot forged, both the inter-granular pores and oxide layers on particle interfaces almost disappeared and the relative densities increased up to about 95%. The same microstructure is also obtained for the one step forged specimens, but the relative densities increased to about 97%. However, the hot pressing specimens showed the presence of oxide layers on particle surfaces as well as few isolated pores. The relative density of the hot pressed specimens was about 90%. Hardness and ultimate compression strength were measured. It is noted that the strongest bulk materials are those made by hot forging, followed by those made by hot pressing and the weakest bulk materials are those made by conventional sintering.展开更多
Bascd on serires authors study ofAl—Li alloys in recent years,the formation theory of powders,characteristics,powder compaction,the microstructures and the mechanical behaviors of RSP Al-Li based alloys analyzed and ...Bascd on serires authors study ofAl—Li alloys in recent years,the formation theory of powders,characteristics,powder compaction,the microstructures and the mechanical behaviors of RSP Al-Li based alloys analyzed and discussed in this paper.展开更多
Al-20Sn-1Cu powders were prepared by gas atomization in an argon atmosphere with atomizing pressures of 1.1 and 1.6 MPa. The characteristics of the powders are determined by means of dry sieving, scanning electron mic...Al-20Sn-1Cu powders were prepared by gas atomization in an argon atmosphere with atomizing pressures of 1.1 and 1.6 MPa. The characteristics of the powders are determined by means of dry sieving, scanning electron microscopy （SEM）, optical microscopy （OM）, and X-ray diffractometry （XRD）. The results show that the powders exhibit a bimodal size distribution and a higher gas pressure results in a broad size distribution. All particles in both cases are spherical or nearly spherical and satellites form on the surface of coarse particles. Dendritic and cellular structures coexist in the particle. With decreasing particle diameter, the secondary dendrite arm spacing （SDAS） decreases and the cooling rate increases. The particles processed under high gas atomization pressure （1.6 MPa） exhibit a lower SDAS value and a higher cooling rate than those of the same size under low gas atomization pressure （1.1 MPa）. The XRD results show that the Sn content increases with decreasing particle size.展开更多
Conventional planar flow casting(PFC) is one of rapid solidification processes for the fabrication of microcrystalline or amorphous ribbons.Based on the conventional PFC process,the planar flow casting atomization(PFC...Conventional planar flow casting(PFC) is one of rapid solidification processes for the fabrication of microcrystalline or amorphous ribbons.Based on the conventional PFC process,the planar flow casting atomization(PFCA) process has been developed,which is a new rapid solidification process for the production of metal powder directly from alloy melts.A prototype experimental apparatus was designed and manufactured.With the apparatus,Sn60Pb40 alloy solder powders were prepared,and the effects of the main technological parameters on the powder size distribution and morphology were experimentally studied.The experimental investigations indicate that the metal powders produced by the PFCA process can be classified by velocity;and fine spherical tin-lead alloy solder powders can be fabricated by adjusting the technical parameters.The new PFCA process has such features as high productivity and efficiency,low energy consumption,simple operation,short technological process,and large gross yield.展开更多
Al-based quasicrystalline powders were consolidated by a new technique.This paper describes the consolidation process and the properties of bulk quasicrystalline materials.The bulk,dense,full quasicrystalline samples ...Al-based quasicrystalline powders were consolidated by a new technique.This paper describes the consolidation process and the properties of bulk quasicrystalline materials.The bulk,dense,full quasicrystalline samples were obuined by means of consolidating quasicrystalline powders at superhigh pressure below their crystallizing temperature or at low temperture.At superhigh pressure,the thermal stability of the quasicrystalline powders increased,while the quasicrystalline powders containing some crystalline phases,were purified,that the crystalline phases disappeared and the amount of quasicrystalling phases increased.Besides,the consolidated materials possessed high strength and were free from flaws and Mach holes caused by shock waves;therefore,this method is better than the explosion consolidation technique.展开更多
A novel solid atomization technology, which using high velocity gas jet stream rich in solid salt particles as atomization medium, was developed. The results show that using this novel atomization process can produce ...A novel solid atomization technology, which using high velocity gas jet stream rich in solid salt particles as atomization medium, was developed. The results show that using this novel atomization process can produce various metal and alloy powders with finer particle size, finer microstructures and higher cooling rate than those powders produced by the conventional gas atomization technology.展开更多
基金Project (50971012) supported by the National Natural Science Foundation of China
文摘Two kinds of high strength-damping aluminum alloys （LZ7） were fabricated by rapid solidification and powder metallurgy （RS-PM） process. One material was extruded to profile aluminum directly and the other was extruded to bar and then rolled to sheet. The damping capacity over a temperature range of 25-300 ℃was studied with damping mechanical thermal analyzer （DMTA） and the microstructures were investigated by optical microscopy （OM）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results show that the damping capacity increases with the test temperature elevating. Internal friction value of rolled sheet aluminum is up to 11.5×10^-2 and that of profile aluminum is as high as 6.0×10^-2 and 7.5×10^-2 at 300 ℃, respectively. Microstructure analysis shows the shape of precipitation phase of rolled alloy is more regular and the distribution is more homogeneous than that of profile alloy. Meanwhile, the interface between particulate and matrix of rolled sheet alloy is looser than that of profile alloy. Maybe the differences at interface can explain why damping capacity of rolled sheet alloy is higher than that of profile alloys at high temperature （above 120 ℃）.
文摘Rapidly solidified hypereutectic Al-Si alloys were prepared by powder hot extrusion. By eliminating vacuum degassing procedure, the fabrication routine was simplified. The tensile fracture mechanisms at room temperature and elevated temperature were investigated by SEM fractography. Compared with KS282 casting material, the tensile strength of rapidly solidified Al-Si alloy is greatly improved due to silicon particles refining while its density and coefficient of thermal expansion are lower than those of KS282. The wear resistance of RS AlSi is better than that of KS282.
基金supported by the Natural Science Foundation of Liaoning Province (No.20072043)
文摘Sn60Pb40 al oy 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 al oy powders. The microstructures of Sn60Pb40 al oy powders produced by the PFC atomization process are completely composed of eutectic, which is made up of both oversaturated αsolid solution and β solid solution. The microstructures of smal 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, lamel ar 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 smal 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 al oy powders.
文摘The effects of additions of Ti and W on microstructure and mechanical properties of rapidly solidified Al-Fe-V-Si alloys were investigated. Alloy powders were produced by the centrifugal rotary atomization process. After atomization, powders were screened to various mesh sizes to see the effect of powder size on the mechanical properties.These Powders were consolidated into billets using conventional powder metallurgy process, and then extruded into bar form.Microstructural analysis shows that the W addition results in the heterogeneous microstructure.On the other hand, the Ti addition refines the microstructure.Alloy containing both Ti and W has the highest thermal stability of the dispersoid. These variations in the microstructure are well reflected in the mechanical properties in that the Ti containtng alloys (with or without W) have the higher strength and ductility than the W containing alloy. It also shows that the alloys made of the coarser powders have better combinations of strength and ductility than those made of the finer powders.
文摘This study investigated the microstructures and mechanical properties of ZK60 alloy prepared by a simplified rapid solidification powder metallurgy （RS P/M） processing system （S-RS P/M）, which consists of warm press in dry air and hot extrusion. Microstructure characterizations showed that S-RS P/M alloy consisted of magnesium matrix and oxide stringers of ~1 #m in width. TEM （transmission electron microscopy） observations illustrated nano-size magnesia particles （10-30 nm） constituted oxide stringer in detail. Due to a relatively higher volume of nano-size magnesia particle produced during S-RS P/M process, 0.2% yield strength of S-RS P/M ZKO0 alloy was found to be as high as 382 MPa, which is 10% higher than that of RS P/M alloy. The improvement in mechanical properties is mainly attributed to the combination effects of Orowan mechanism and coefficient of thermal expansion （CTE） mismatch because of the approximately same average grain size.
文摘Aluminum silicon alloy of composition (Al-25%Si-3%Ni-1%Fe-2%Cu) was atomized using water atomization. The powders were cold compacted in a die to produce green cylinder compacts. Four consolidation processes were applied, namely;conventional sintering at 500℃, sintering followed by hot forging to obtain pistons, one step hot forging into pistons, and hot pressing. The microstructure of the sintered specimens showed inter-granular pores and oxide layers on particle interfaces of 84% relative density. When the sintered specimens were hot forged, both the inter-granular pores and oxide layers on particle interfaces almost disappeared and the relative densities increased up to about 95%. The same microstructure is also obtained for the one step forged specimens, but the relative densities increased to about 97%. However, the hot pressing specimens showed the presence of oxide layers on particle surfaces as well as few isolated pores. The relative density of the hot pressed specimens was about 90%. Hardness and ultimate compression strength were measured. It is noted that the strongest bulk materials are those made by hot forging, followed by those made by hot pressing and the weakest bulk materials are those made by conventional sintering.
文摘Bascd on serires authors study ofAl—Li alloys in recent years,the formation theory of powders,characteristics,powder compaction,the microstructures and the mechanical behaviors of RSP Al-Li based alloys analyzed and discussed in this paper.
基金the Major State Ba-sic Research Development Program of China (Nos. 2006CB605203 and 2006CB605204)
文摘Al-20Sn-1Cu powders were prepared by gas atomization in an argon atmosphere with atomizing pressures of 1.1 and 1.6 MPa. The characteristics of the powders are determined by means of dry sieving, scanning electron microscopy （SEM）, optical microscopy （OM）, and X-ray diffractometry （XRD）. The results show that the powders exhibit a bimodal size distribution and a higher gas pressure results in a broad size distribution. All particles in both cases are spherical or nearly spherical and satellites form on the surface of coarse particles. Dendritic and cellular structures coexist in the particle. With decreasing particle diameter, the secondary dendrite arm spacing （SDAS） decreases and the cooling rate increases. The particles processed under high gas atomization pressure （1.6 MPa） exhibit a lower SDAS value and a higher cooling rate than those of the same size under low gas atomization pressure （1.1 MPa）. The XRD results show that the Sn content increases with decreasing particle size.
文摘Conventional planar flow casting(PFC) is one of rapid solidification processes for the fabrication of microcrystalline or amorphous ribbons.Based on the conventional PFC process,the planar flow casting atomization(PFCA) process has been developed,which is a new rapid solidification process for the production of metal powder directly from alloy melts.A prototype experimental apparatus was designed and manufactured.With the apparatus,Sn60Pb40 alloy solder powders were prepared,and the effects of the main technological parameters on the powder size distribution and morphology were experimentally studied.The experimental investigations indicate that the metal powders produced by the PFCA process can be classified by velocity;and fine spherical tin-lead alloy solder powders can be fabricated by adjusting the technical parameters.The new PFCA process has such features as high productivity and efficiency,low energy consumption,simple operation,short technological process,and large gross yield.
基金supported by the National Natural Science Foundation of China
文摘Al-based quasicrystalline powders were consolidated by a new technique.This paper describes the consolidation process and the properties of bulk quasicrystalline materials.The bulk,dense,full quasicrystalline samples were obuined by means of consolidating quasicrystalline powders at superhigh pressure below their crystallizing temperature or at low temperture.At superhigh pressure,the thermal stability of the quasicrystalline powders increased,while the quasicrystalline powders containing some crystalline phases,were purified,that the crystalline phases disappeared and the amount of quasicrystalling phases increased.Besides,the consolidated materials possessed high strength and were free from flaws and Mach holes caused by shock waves;therefore,this method is better than the explosion consolidation technique.
文摘A novel solid atomization technology, which using high velocity gas jet stream rich in solid salt particles as atomization medium, was developed. The results show that using this novel atomization process can produce various metal and alloy powders with finer particle size, finer microstructures and higher cooling rate than those powders produced by the conventional gas atomization technology.
基金Natural Science Foundation of China(No.51871244)Hunan Provincial Innovation Foundation for Postgraduate,China(No.CX20200172)Fundamental Research Funds for the Central Universities of Central South University,China(No.1053320190103)。
