Papers by Author: Kai Feng Zhang

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Authors: Kai Feng Zhang, Z.R. Wang, Xiao Ming Lai, G.L. Kan
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Authors: Jun Ting Luo, Qing Zhang, Kai Feng Zhang
Abstract: The Si3N4- Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering(LPS) method. The sintering temperatures ranged from 1500°C to 1700°C. Microstructure and component of the composites were performed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results show that sintered body consists of Si2N2O and β-Si3N4, with an average grain size about 1μm. The maximum value of flexural strength of the material is 680MPa when sintered at 1700°C. Transcrystalline cracking is the main fracture mechanism of the composites.
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Authors: Hui Gai Wang, Fei Wang, Yan Pei Song, Kai Feng Zhang
Abstract: Float polishing is one of the advanced ultra-smooth surface polishing techniques. Mechanical structure and polishing principle of float polishing are introduced. Polishing experiment about polishing ultra-smooth surface of GCr15 rectangular workpiece is performed by the CJY500 ultra-precision polishing machine, experimental results show that float polishing should be achieved metal nanometer level surface without degenerating layer. The application scope of float polishing is extended, the application has significant reference value for polishing ultra-smooth surface of metal workpiece.
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Authors: Xi Feng Li, Kai Feng Zhang, Wen Bo Han, Guo Feng Wang
Abstract: The deformation behavior of gas pressure forming of amorphous Fe78Si9B13 alloy was investigated under equibiaxial tension. The gas pressure forming was carried out in the temperature range of 430°C~530°C below the crystallization temperature Tx and die apertures of 5mm~10mm. The dome height and amorphous ribbon thickness of deformed specimens at the pole was measured. It was found that amorphous Fe78Si9B13 alloy had exhibited good plasticity in the experimental temperature range. The near-semisphere specimens of the radius 5mm and the height 4.5mm were obtained from the gas-pressure forming at 450°C and 530°C for 30min, which is similar to the superplastic forming.
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Authors: Qing Zhang, Jun Ting Luo, Kai Feng Zhang
Abstract: Si3N4- Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the hot press sintering(HPS). The Si2N2O phase was generated by an in-situ reaction 2Si3N4(s)+1.5O2(g)=3Si2N2O(s)+N2(g). The content of Si2N2O phase up to 60% was accepted when the sintering temperature was 1650°C and decreased whether the sintering temperature was increased or not, which indicated that the reaction was reversible. The mass loss, relative density and average grain size increased with raising of sintering temperature. The average grain size was less than 500nm if the sintering temperature was below 1700°C. The sintered body crystaled completely at 1600°C . The microstructure crystaled in 1600°C indicated that most of the grain size was in 150-250nm. The aspect ratio of some grains reached 1.5. The superplastic deep-drawing forming could be undertaken at 1550°C with a forming velocity of 0.2mm/min. The complex-shape gears could be formed by a sinter-forging technology when the sintering temperature was 1600°C and the superplastic forging temperature was 1550°C.
25
Authors: Hui Gai Wang, Yan Pei Song, Fei Wang, Kai Feng Zhang
Abstract: Using ring compression tests, the interfacial friction and flow stress of 3Y-TZP/Al2O3 composite at elevated temperatures were investigated. Theoretical calibration curves of the friction factor and the relative average pressure curves for the ring compression tests of 6:3:2 standard rings were drawn based on a velocity field capable of describing the bulge phenomena. The lubricant was the boron nitride (hexagonal). The tests were adopted at temperature range of 1400°C-1600°C. Results indicate that the interfacial friction factor has the value in the range of 0.34-0.49, so that boron nitride lubricant can be used effectively in present temperatures. As two extremely important parameters, the temperature and strain rate have no significant effect on the fraction factor. It is proved reliable that the ring-compression test at 1400°C and even higher is used to evaluate the performance of boron nitride lubricant.
967
Authors: H.B. Li, Jun Ting Luo, Kai Feng Zhang
Abstract: The amorphous nano-sized silicon nitride powders were sintered by liquid phase sintering method. Si3N4-Si2N2O composites were in-situ fabricated. The Si2N2O phase was generated by an in-situ reaction 2Si3N4(s)+1.5O2(g)=3Si2N2O(s)+N2(g). The content of Si2N2O phase up to 60% was obtained at a sintering temperature of 1650°C and reduced when the sintering temperature increased or decreased, which indicates that the reaction is reversible. The mass loss, relative density and average grain size increase with increasing of sintering temperature. The average grain size is less than 500nm when the sintering temperature is below 1700°C. During the sintering procedure, there is a complex crystallization and phase transition: amorphous Si3N4 → equiaxial α-Si3N4→ equiaxial β-Si3N4 → rod-likeSi2N2O → needle-like β-Si3N4. Small round-shaped β-Si3N4 particles are entrapped in the Si2N2O grains and a high density of staking faults are situated in the middle of Si2N2O grains at a sintering temperature of 1650°C.
1069
Authors: Xiao Ming Lai, Zhe Wang, Yu Liang Zhang, Bo Wang, Kai Feng Zhang, Guo Feng Wang
Abstract: The deep drawing of SiC/2024Al composites using pulse current heating were designed and established in this works. The whole process system mainly include pulse current heating system, electrode lifting system, temperature control system and deep drawing forming system. In addition, the feasibility of thermal deep drawing using pulse current heating was experimentally investigated and the optimal process parameters were explored to ensure defect-free products. The temperature of specimen is up to around 673K at a rate of 13.5K/s under the current density of 21.7A/mm2. The stainless steel inserts make temperature difference reducing by 73.3%. Moreover, the workpiece was successfully deep drawn and exhibited good surface quality. The dimensional accuracy achieved within ±0.2mm.
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