An improved wax-based binder was developed for powder injection molding of pure titanium. A critical powder loading of 69 vol.% and a pseudo-plastic flow behavior were obtained by the feedstock based on the binder. Th...An improved wax-based binder was developed for powder injection molding of pure titanium. A critical powder loading of 69 vol.% and a pseudo-plastic flow behavior were obtained by the feedstock based on the binder. The injection molding, debinding, and sintering process were studied. An ideal control of carbon and oxygen contents was achieved by thermal debinding in vacuum atmosphere （10^-3 Pa）. The mechanical properties of as-sintered specimens were less than those of titanium made by the conventional press-sintering process. Good shape retention and ±0.04 mm dimension deviation were achieved.展开更多
The thermal debinding of new binder in cemented carbide's extruding compacts and its debinding mechanism have been studied here. When the low molecular mass components (LMMC) in these new binder systems are change...The thermal debinding of new binder in cemented carbide's extruding compacts and its debinding mechanism have been studied here. When the low molecular mass components (LMMC) in these new binder systems are changed, their thermogravimetric analysis (TGA) curves are very different. As the paraffin wax is the main LMMC, the new binder has been removed in two different temperature zones; while the temperature is at 240 ℃, the LMMC have been almost totally debinded. When a kind of short time polymer X is the main LMMC, there are no zones of low temperature debinding in the TGA curves. The differential thermal analysis curves show that a new single phase microstructural material composing with X and polymer A has been made in these cases.展开更多
Ti3AlC2 has the properties of ceramics and metals. These excellent properties indicate that Ti3AlC2 is a very promising material to extensive applications. Ti3AlC2 ceramic material was prepared by mechanical alloying....Ti3AlC2 has the properties of ceramics and metals. These excellent properties indicate that Ti3AlC2 is a very promising material to extensive applications. Ti3AlC2 ceramic material was prepared by mechanical alloying. The effects of milling time and sintering temperature on the fracture, microstmctttre and mechanical properties of Ti3AlC2 ceramic material were analyzed by laser particle analyzer, X-ray diffraction, and scanning electron microscopy. The experimental results showed that Ti3AlC2 had the best comprehensive properties after the composite powder was milled for 3 h and sintered at 1630℃ for 2 h. The relative density, bending strength, and hardness of the sample reached 92.23%, 345.2 MPa, and HRA 34.1, respectively. The fracture surface indicated that the fracture of the material belonged to ductile rapture.展开更多
The aim of this research was to examine the effect of microstructural parameters on the tensile properties of different compositions of tungsten heavy alloys. The microstructural parameters （grain size, connectivity,...The aim of this research was to examine the effect of microstructural parameters on the tensile properties of different compositions of tungsten heavy alloys. The microstructural parameters （grain size, connectivity, contiguity, and solid volume fraction） were measured and were found to have a significant effect on the tensile properties of tungsten-based heavy alloys. The microstructural parameters of W-Ni-Fe alloys are sufficiently different to present a range of mechanical properties. It is concluded that the mechanical properties of tungsten heavy alloys largely depend on the microstructural parameters and their ductility is particularly harmed when grains are contiguous.展开更多
Anisotropic bonded magnets were prepared by warm compaction using anisotropic Nd-Fe-B powder. The forming process, magnetic properties, and temperature stability were studied. The results indicate that the optimal tem...Anisotropic bonded magnets were prepared by warm compaction using anisotropic Nd-Fe-B powder. The forming process, magnetic properties, and temperature stability were studied. The results indicate that the optimal temperature of the process, which was decided by the vis-cosity of the binders, was 110°C. With increasing pressure, the density of the magnets increased. When the pressure was above 700 MPa, the powder particles were destroyed and the magnetic properties decreased. The magnetic properties of the anisotropic bonded magnets were as follows： remanence Br=0.98 T, intrinsic coercivity iHc=1361 kA/m, and maximum energy product BHmax=166 kJ/m3. The magnets had excellent thermal stability because of the high coercivity and good squareness of demagnetization curves. The flux density of the magnets was 35% higher than that of isotropic bonded Nd-Fe-B magnets at 120°C for 1000 h. The flux density of the bonded magnets showed little change with regard to temperature.展开更多
The effects of two different heat-treatment atmospheres,nitrogen atmosphere and reducing nitrogen atmosphere with carbon,on the properties of Y2O3-doped aluminum nitride（AlN） ceramics were investigated.The AlN powde...The effects of two different heat-treatment atmospheres,nitrogen atmosphere and reducing nitrogen atmosphere with carbon,on the properties of Y2O3-doped aluminum nitride（AlN） ceramics were investigated.The AlN powder as a raw material was synthesized by self-propagating high-temperature synthesis（SHS） and compacts were fabricated by employing powder injection molding technique.The polymer-wax binder consisted of 60 wt.% paraffin wax（PW）,35 wt.% polypropylene（PP）,and 5 wt.% stearic acid（SA）.After the removal of binder,specimens were sintered at 1850°С in nitrogen atmosphere under atmospheric pressure.To improve the thermal conductivity,sintered samples were reheated.The result reveals that the heat-treatment atmosphere has significant effect on the properties and secondary phase of AlN ceramics.The thermal conductivity and density of AlN ceramics reheated in nitrogen gas are 180 W·m^-1·K^-1 and 3.28 g·cm^-3 and the secondary phase is yttrium aluminate.For the sample reheated in reducing nitrogen atmosphere with carbon,the thermal conductivity and density are 173 W·m^-1·K^-1 and 3.23 g·cm^-3,respectively,and the secondary phase is YN.展开更多
The structure and characteristics of dislocation networks in Ti50 Al ordered alloy deformed at room temperature were studied by means of TEM diffraction contrast analysis technique. The results show that the observed...The structure and characteristics of dislocation networks in Ti50 Al ordered alloy deformed at room temperature were studied by means of TEM diffraction contrast analysis technique. The results show that the observed dislocation networks consist of three展开更多
The dislocation structures of arc-melted,near-equiatomic TiAl alloys containing 1.5-2.0 wt.-%manga-nese were analysed and compared with those of binary TiAl alloy processed in a similar fashion.It was found that the p...The dislocation structures of arc-melted,near-equiatomic TiAl alloys containing 1.5-2.0 wt.-%manga-nese were analysed and compared with those of binary TiAl alloy processed in a similar fashion.It was found that the pinning effect of a/6[112]partial dislocations was eliminated by Mn addition,as a result,the movement of a[101]and a/2[112]superdislocations and twinning and played an important role in the plastic deformation and increased the ductility of TiAl alloys.In addition,the workability of the Mn-ductilized TiAl alloy was evaluated with hot extrusion and forging.展开更多
ZrC coatings were deposited on graphite substrates by low pressure chemical vapor deposition（LPCVD） with the Br2-Zr-C3H6-H2-Ar system. The effects of deposition time on the microstructures and growth behavior of ZrC...ZrC coatings were deposited on graphite substrates by low pressure chemical vapor deposition（LPCVD） with the Br2-Zr-C3H6-H2-Ar system. The effects of deposition time on the microstructures and growth behavior of ZrC coatings were investigated. ZrC coating grew in an island-layer mode. The formation of coating was dominated by the nucleation of ZrC in the initial 20 minutes, and the rapid nucleation generated a fine-grained structure of ZrC coating. When the deposition time was over 30 min, the growth of coating was dominated by that of crystals, giving a column-arranged structure. Energy dispersive X-ray spectroscopy showed that the molar ratio of carbon to zirconium was near 1：1 in ZrC coating, and X-ray photoelectron spectroscopy showed that ZrC was the main phase in coatings, accompanied by about 2.5mol% ZrO2 minor phase.展开更多
The continuing miniaturization of electronic devices in microelectronics and semiconductors drives the development of new packaging materials with enhanced thermal conductivity to dissipate the heat generated in elect...The continuing miniaturization of electronic devices in microelectronics and semiconductors drives the development of new packaging materials with enhanced thermal conductivity to dissipate the heat generated in electronic packages. In recent years, several promising composite materials with high thermal conductivity have been developed successfully for high performance electronic equipment to replace the traditional Kovar and Cu/W or Cu/Mo alloys, such as SiCp/Al, SICp/Cu, diamond/Al and diamond/Cu. However, these materials with high content of reinforcements have not been widely used in packaging field because they are hard to be machined into complex-shaped parts due to their greater hardness and brittleness. So, it is necessary to explore a near-net shape forming technology for these composites. In this paper, a novel technology of powder injection molding-infiltration is introduced to realize the near-net shaped preparation of the composite packages with high thermal conductivity.展开更多
Micro powder injection molding (μPIM),a miniaturized variant of powder injection molding,has advantages of shape complexity,applicability to many materials and good mechanical properties. Co-injection molding has bee...Micro powder injection molding (μPIM),a miniaturized variant of powder injection molding,has advantages of shape complexity,applicability to many materials and good mechanical properties. Co-injection molding has been realized between met-als and ceramics on micro components,which become the first breakthrough within the PIM field. Combined with the prominent characteristics of high features/cost ratio,micro powder injection molding becomes a potential technique for large scale production of intricate and three-dimensional micro components or micro-structured components in microsystems technology (MST) field.展开更多
文摘An improved wax-based binder was developed for powder injection molding of pure titanium. A critical powder loading of 69 vol.% and a pseudo-plastic flow behavior were obtained by the feedstock based on the binder. The injection molding, debinding, and sintering process were studied. An ideal control of carbon and oxygen contents was achieved by thermal debinding in vacuum atmosphere （10^-3 Pa）. The mechanical properties of as-sintered specimens were less than those of titanium made by the conventional press-sintering process. Good shape retention and ±0.04 mm dimension deviation were achieved.
文摘The thermal debinding of new binder in cemented carbide's extruding compacts and its debinding mechanism have been studied here. When the low molecular mass components (LMMC) in these new binder systems are changed, their thermogravimetric analysis (TGA) curves are very different. As the paraffin wax is the main LMMC, the new binder has been removed in two different temperature zones; while the temperature is at 240 ℃, the LMMC have been almost totally debinded. When a kind of short time polymer X is the main LMMC, there are no zones of low temperature debinding in the TGA curves. The differential thermal analysis curves show that a new single phase microstructural material composing with X and polymer A has been made in these cases.
文摘Ti3AlC2 has the properties of ceramics and metals. These excellent properties indicate that Ti3AlC2 is a very promising material to extensive applications. Ti3AlC2 ceramic material was prepared by mechanical alloying. The effects of milling time and sintering temperature on the fracture, microstmctttre and mechanical properties of Ti3AlC2 ceramic material were analyzed by laser particle analyzer, X-ray diffraction, and scanning electron microscopy. The experimental results showed that Ti3AlC2 had the best comprehensive properties after the composite powder was milled for 3 h and sintered at 1630℃ for 2 h. The relative density, bending strength, and hardness of the sample reached 92.23%, 345.2 MPa, and HRA 34.1, respectively. The fracture surface indicated that the fracture of the material belonged to ductile rapture.
文摘The aim of this research was to examine the effect of microstructural parameters on the tensile properties of different compositions of tungsten heavy alloys. The microstructural parameters （grain size, connectivity, contiguity, and solid volume fraction） were measured and were found to have a significant effect on the tensile properties of tungsten-based heavy alloys. The microstructural parameters of W-Ni-Fe alloys are sufficiently different to present a range of mechanical properties. It is concluded that the mechanical properties of tungsten heavy alloys largely depend on the microstructural parameters and their ductility is particularly harmed when grains are contiguous.
文摘Anisotropic bonded magnets were prepared by warm compaction using anisotropic Nd-Fe-B powder. The forming process, magnetic properties, and temperature stability were studied. The results indicate that the optimal temperature of the process, which was decided by the vis-cosity of the binders, was 110°C. With increasing pressure, the density of the magnets increased. When the pressure was above 700 MPa, the powder particles were destroyed and the magnetic properties decreased. The magnetic properties of the anisotropic bonded magnets were as follows： remanence Br=0.98 T, intrinsic coercivity iHc=1361 kA/m, and maximum energy product BHmax=166 kJ/m3. The magnets had excellent thermal stability because of the high coercivity and good squareness of demagnetization curves. The flux density of the magnets was 35% higher than that of isotropic bonded Nd-Fe-B magnets at 120°C for 1000 h. The flux density of the bonded magnets showed little change with regard to temperature.
基金supported by the National Natural Science Foundation of China(Nos.50025412 and 60576011)the National Key Basic Research and Development Program of China(No.TG2000067203).
文摘The effects of two different heat-treatment atmospheres,nitrogen atmosphere and reducing nitrogen atmosphere with carbon,on the properties of Y2O3-doped aluminum nitride（AlN） ceramics were investigated.The AlN powder as a raw material was synthesized by self-propagating high-temperature synthesis（SHS） and compacts were fabricated by employing powder injection molding technique.The polymer-wax binder consisted of 60 wt.% paraffin wax（PW）,35 wt.% polypropylene（PP）,and 5 wt.% stearic acid（SA）.After the removal of binder,specimens were sintered at 1850°С in nitrogen atmosphere under atmospheric pressure.To improve the thermal conductivity,sintered samples were reheated.The result reveals that the heat-treatment atmosphere has significant effect on the properties and secondary phase of AlN ceramics.The thermal conductivity and density of AlN ceramics reheated in nitrogen gas are 180 W·m^-1·K^-1 and 3.28 g·cm^-3 and the secondary phase is yttrium aluminate.For the sample reheated in reducing nitrogen atmosphere with carbon,the thermal conductivity and density are 173 W·m^-1·K^-1 and 3.23 g·cm^-3,respectively,and the secondary phase is YN.
文摘The structure and characteristics of dislocation networks in Ti50 Al ordered alloy deformed at room temperature were studied by means of TEM diffraction contrast analysis technique. The results show that the observed dislocation networks consist of three
基金supported by National Advanced Materials Committee of China。
文摘The dislocation structures of arc-melted,near-equiatomic TiAl alloys containing 1.5-2.0 wt.-%manga-nese were analysed and compared with those of binary TiAl alloy processed in a similar fashion.It was found that the pinning effect of a/6[112]partial dislocations was eliminated by Mn addition,as a result,the movement of a[101]and a/2[112]superdislocations and twinning and played an important role in the plastic deformation and increased the ductility of TiAl alloys.In addition,the workability of the Mn-ductilized TiAl alloy was evaluated with hot extrusion and forging.
基金Founded by the National Natural Science Foundation of China(No.91216302)the National Program on Key Basic Research Project of the People's Republic of China(No.2015CB655200)
文摘ZrC coatings were deposited on graphite substrates by low pressure chemical vapor deposition（LPCVD） with the Br2-Zr-C3H6-H2-Ar system. The effects of deposition time on the microstructures and growth behavior of ZrC coatings were investigated. ZrC coating grew in an island-layer mode. The formation of coating was dominated by the nucleation of ZrC in the initial 20 minutes, and the rapid nucleation generated a fine-grained structure of ZrC coating. When the deposition time was over 30 min, the growth of coating was dominated by that of crystals, giving a column-arranged structure. Energy dispersive X-ray spectroscopy showed that the molar ratio of carbon to zirconium was near 1：1 in ZrC coating, and X-ray photoelectron spectroscopy showed that ZrC was the main phase in coatings, accompanied by about 2.5mol% ZrO2 minor phase.
基金Supported by the National Natural Science Foundation of China (Grant No. 50774005)the Program for New Century Excellent Talents in University (Grant No. NCET-06-0081)
文摘The continuing miniaturization of electronic devices in microelectronics and semiconductors drives the development of new packaging materials with enhanced thermal conductivity to dissipate the heat generated in electronic packages. In recent years, several promising composite materials with high thermal conductivity have been developed successfully for high performance electronic equipment to replace the traditional Kovar and Cu/W or Cu/Mo alloys, such as SiCp/Al, SICp/Cu, diamond/Al and diamond/Cu. However, these materials with high content of reinforcements have not been widely used in packaging field because they are hard to be machined into complex-shaped parts due to their greater hardness and brittleness. So, it is necessary to explore a near-net shape forming technology for these composites. In this paper, a novel technology of powder injection molding-infiltration is introduced to realize the near-net shaped preparation of the composite packages with high thermal conductivity.
基金National Basic Research Program of China (Grant No. 2004CB719802)Hi-Tech Research and Development Program of China (Grant No. 2006AA03Z113)
文摘Micro powder injection molding (μPIM),a miniaturized variant of powder injection molding,has advantages of shape complexity,applicability to many materials and good mechanical properties. Co-injection molding has been realized between met-als and ceramics on micro components,which become the first breakthrough within the PIM field. Combined with the prominent characteristics of high features/cost ratio,micro powder injection molding becomes a potential technique for large scale production of intricate and three-dimensional micro components or micro-structured components in microsystems technology (MST) field.
