The fabrication. microstructure and mechanical properties of ZrO2-Ni functionally gradient materials (FGM ) have been studied. FGM as well as non-FG M of ZrO2-Ni system was developed by powder metallurgical process. X...The fabrication. microstructure and mechanical properties of ZrO2-Ni functionally gradient materials (FGM ) have been studied. FGM as well as non-FG M of ZrO2-Ni system was developed by powder metallurgical process. X-ray diffractometer (XRD ). electron probe microanalyzer (EPMA), scanning electron microscope (SEM ) and optical microscope were employed to investigate the crystalline phases. chemical composition and microstructure Experimental results demonstrate that the composition and microstructure of ZrO2-Ni FGM have the expected gradient distribution. There are no distinct interfaces in the FGM due to the gradient change of components. that is, the constituents are continuous in microstructure everywhere. Moreover, Vickers hardness and flexural strength were measured for the common composites as a function of composition. It is made clear that the mechanical properties of the FGM vary corresponding to the constitutional changes as well展开更多
A thixoforging process of the 9Cr18 steel was conducted in a designed setup, and a kind of multi-diameter component was fabricated. The effects of the forming temperature and the strain rate on the solid-/liquid-phase...A thixoforging process of the 9Cr18 steel was conducted in a designed setup, and a kind of multi-diameter component was fabricated. The effects of the forming temperature and the strain rate on the solid-/liquid-phase flow behavior were discussed. The results showed that functional gradient properties of the 9Cr18 steel could be obtained after thixoforging. Changes of microstructure along radial direction could be obtained. Solid austenite was retained after fast cooling, and the liquid film enriched in alloying elements was extruded outside to form a dendrite skin layer. As temperature increased, more molten liquid formed during thixoforging. A heterogeneous flow phenomenon was activated as free liquid channels were formed. The macro-separation of solid and liquid phases was critical for the formation of functional gradient properties. Above 1300 ℃, full dendrite skin layer could be formed. The strain rate affected the thixotropic property via influencing the deformation time of thixoforging. In the presence of lower strain rates, there was more time for the flow of liquid metal, which was the key to the extension of the thixotropic stage. High temperatures and low strain rates contributed to the formation of full skin layer for the designed specimen. The average thickness of skin layer for current specimen could be over 1000 ktm when thixoforged at 1340 ℃ and under a strain rate of 0.02 s^-1.展开更多
文摘The fabrication. microstructure and mechanical properties of ZrO2-Ni functionally gradient materials (FGM ) have been studied. FGM as well as non-FG M of ZrO2-Ni system was developed by powder metallurgical process. X-ray diffractometer (XRD ). electron probe microanalyzer (EPMA), scanning electron microscope (SEM ) and optical microscope were employed to investigate the crystalline phases. chemical composition and microstructure Experimental results demonstrate that the composition and microstructure of ZrO2-Ni FGM have the expected gradient distribution. There are no distinct interfaces in the FGM due to the gradient change of components. that is, the constituents are continuous in microstructure everywhere. Moreover, Vickers hardness and flexural strength were measured for the common composites as a function of composition. It is made clear that the mechanical properties of the FGM vary corresponding to the constitutional changes as well
基金supported by the National Natural Science Foundation of China(No.51175036)
文摘A thixoforging process of the 9Cr18 steel was conducted in a designed setup, and a kind of multi-diameter component was fabricated. The effects of the forming temperature and the strain rate on the solid-/liquid-phase flow behavior were discussed. The results showed that functional gradient properties of the 9Cr18 steel could be obtained after thixoforging. Changes of microstructure along radial direction could be obtained. Solid austenite was retained after fast cooling, and the liquid film enriched in alloying elements was extruded outside to form a dendrite skin layer. As temperature increased, more molten liquid formed during thixoforging. A heterogeneous flow phenomenon was activated as free liquid channels were formed. The macro-separation of solid and liquid phases was critical for the formation of functional gradient properties. Above 1300 ℃, full dendrite skin layer could be formed. The strain rate affected the thixotropic property via influencing the deformation time of thixoforging. In the presence of lower strain rates, there was more time for the flow of liquid metal, which was the key to the extension of the thixotropic stage. High temperatures and low strain rates contributed to the formation of full skin layer for the designed specimen. The average thickness of skin layer for current specimen could be over 1000 ktm when thixoforged at 1340 ℃ and under a strain rate of 0.02 s^-1.
