Spark plasma sintering method （SPS） was used to consolidate mixed W-5.6Ni-1.4Fe （mass fraction, %） powders from commercial fine elemental powders, and both the densification behavior and microstructure evolution i...Spark plasma sintering method （SPS） was used to consolidate mixed W-5.6Ni-1.4Fe （mass fraction, %） powders from commercial fine elemental powders, and both the densification behavior and microstructure evolution in sintering were investigated at different heating rates. The results show that the SPS densification process can be divided into three stages. At the initial unshrinking stage, fast heating generates instantaneous discharge and locally inhomogeneous temperature distribution in solid-state powder particles, enhancing later densification; during the intermediate solid state sintering stage, diffusion is more sufficient in the slow-heated SPS process; at the final transient liquid-phase sintering stage, tungsten grains become sphered and coarsen rapidly, but fast heating helps maintain rather small grain sizes.展开更多
WC-6MoxC-0.47Cr3C2-0.28VC binderless carbide was prepared by hot pressing （1700 °C, 20 MPa）. The sample was observed and analyzed by scanning electron microscopy, energy dispersive X–ray spectroscopy and X–ra...WC-6MoxC-0.47Cr3C2-0.28VC binderless carbide was prepared by hot pressing （1700 °C, 20 MPa）. The sample was observed and analyzed by scanning electron microscopy, energy dispersive X–ray spectroscopy and X–ray diffraction. The results show that during the hot pressing process, W atoms dissolve substantially into the MoxC crystal lattices; whilst, the reverse dissolution of Mo atoms into the WC crystal lattices takes place. Consequently, the main phase and binder phase structure are formed. The phase compositions of the main phase and binder phase are a WC-based solid solution containing Mo and a Mo2C-based solid solution containing W, respectively. The isotropic dissolution and precipitation of W and Mo atoms do not result in substantial carbide coarsening. The mechanism for the densification was discussed.展开更多
Discrete media filled thin-walled hollow profiles are frequently used as integer structures for special purpose, e.g., in certain materials processing or architectural components. To understand the deformation of such...Discrete media filled thin-walled hollow profiles are frequently used as integer structures for special purpose, e.g., in certain materials processing or architectural components. To understand the deformation of such composite structures which is a complicate mechanics process, involving coupled elastic-plastic deformation of dense metal, compaction of particle and interaction between the filler and the wall, the forward extrusion of Al 6061 tubes filled with various particles was studied. The analysis regarding internal volume variation of round tubes during forward extrusion indicates that with the diameter reduction the volume of tubes decreases commonly. The cavity shrinkage brings about triaxial pressure on the filler, resulted in compaction and densification of it. Loose powders filling leads to higher extrusion load. Due to dissimilar migration behaviors of the particles, the load?stroke curves of the tubes filled with fine powders and coarse balls are quite different. Small Lankford value of the tube wall material leads to higher hydrostatic pressure of the filler and then more powders are compacted.展开更多
基金Project (2010CB635104) supported by the National Basic Research Program of ChinaProject (2007AA03Z112) supported by the National High-Tech Research and Development Program of China+2 种基金Project (9140A18040709JW1601) supported by the Advanced Research Fund of DOD, ChinaProject (2009ZZ0019) supported by the Fundamental Research Funds for the Central Universities, ChinaProject (NCET-10-0364) supported by the Program for New Century Excellent Talents in University, China
文摘Spark plasma sintering method （SPS） was used to consolidate mixed W-5.6Ni-1.4Fe （mass fraction, %） powders from commercial fine elemental powders, and both the densification behavior and microstructure evolution in sintering were investigated at different heating rates. The results show that the SPS densification process can be divided into three stages. At the initial unshrinking stage, fast heating generates instantaneous discharge and locally inhomogeneous temperature distribution in solid-state powder particles, enhancing later densification; during the intermediate solid state sintering stage, diffusion is more sufficient in the slow-heated SPS process; at the final transient liquid-phase sintering stage, tungsten grains become sphered and coarsen rapidly, but fast heating helps maintain rather small grain sizes.
基金Project (51074189) supported by the National Natural Science Foundation of ChinaProject (20100162110001) supported by Research Fund for the Doctoral Program of Higher Education of ChinaProject (2011BAE09B02) supported by the National Key Technology R&D Program of China
文摘WC-6MoxC-0.47Cr3C2-0.28VC binderless carbide was prepared by hot pressing （1700 °C, 20 MPa）. The sample was observed and analyzed by scanning electron microscopy, energy dispersive X–ray spectroscopy and X–ray diffraction. The results show that during the hot pressing process, W atoms dissolve substantially into the MoxC crystal lattices; whilst, the reverse dissolution of Mo atoms into the WC crystal lattices takes place. Consequently, the main phase and binder phase structure are formed. The phase compositions of the main phase and binder phase are a WC-based solid solution containing Mo and a Mo2C-based solid solution containing W, respectively. The isotropic dissolution and precipitation of W and Mo atoms do not result in substantial carbide coarsening. The mechanism for the densification was discussed.
基金Project(51575066)supported by the National Natural Science Foundation of ChinaProject(2012ZX04010-081)supported by the National Key Technologies R&D Program of China
文摘Discrete media filled thin-walled hollow profiles are frequently used as integer structures for special purpose, e.g., in certain materials processing or architectural components. To understand the deformation of such composite structures which is a complicate mechanics process, involving coupled elastic-plastic deformation of dense metal, compaction of particle and interaction between the filler and the wall, the forward extrusion of Al 6061 tubes filled with various particles was studied. The analysis regarding internal volume variation of round tubes during forward extrusion indicates that with the diameter reduction the volume of tubes decreases commonly. The cavity shrinkage brings about triaxial pressure on the filler, resulted in compaction and densification of it. Loose powders filling leads to higher extrusion load. Due to dissimilar migration behaviors of the particles, the load?stroke curves of the tubes filled with fine powders and coarse balls are quite different. Small Lankford value of the tube wall material leads to higher hydrostatic pressure of the filler and then more powders are compacted.
