The tortuosity factor is the most critical parameter for the pore characteristic of porous materials. The tortuosity factor for porous FeAl intermetallics was studied based on the Darcy law and Hagen-Poiseuille equati...The tortuosity factor is the most critical parameter for the pore characteristic of porous materials. The tortuosity factor for porous FeAl intermetallics was studied based on the Darcy law and Hagen-Poiseuille equation. Porous stainless steel with the same pore structure parameter as porous FeAl was fabricated by powder metallurgy method for comparison. The results show that the tortuosity factor of porous FeAl intermetallics is smaller than that of porous stainless steel when their pore structure parameters are the same. The average tortuosity factor is 2.26 for the porous FeAl material and 2.92 for the porous stainless steel, calculated by Hagen-Poiseuille equation. The reason of the different tortuosity factors for porous FeAl and porous stainless steel was also explored through studying the pore formation mechanisms of the two types of porous materials.展开更多
Three nanocrystalline alloys, Fe50Al50, Fe42.5Al42.5Ti5B10 and Fe35Al35Ti10B20 (molar fraction, %), were synthesized from elemental powders by high-energy ball milling. The structural evolutions and morphological chan...Three nanocrystalline alloys, Fe50Al50, Fe42.5Al42.5Ti5B10 and Fe35Al35Ti10B20 (molar fraction, %), were synthesized from elemental powders by high-energy ball milling. The structural evolutions and morphological changes of the milled powders were characterized by X-ray diffractometry(XRD), transmission electron microscopy(TEM) and scanning electron microscopy(SEM). The effects of different Ti, B additions on the structure and phase transformation in these alloys were also discussed. It is observed that the diffusion of Al, Ti, B atoms into Fe lattice occurs during milling, leading to the formation of a BCC phase identified as Fe(Al) or Fe(Al, Ti, B) supersaturated solid solution. Fe-based solid solution with nanocrystalline structure is observed to be present as the only phase in all the alloy compositions after milling. Furthermore, the contents of Ti, B affect the formation of mechanical alloying products, changes in the lattice parameter as well as the grain size.展开更多
综合考虑超声的空化作用和声流效应,通过元胞自动机将超声振动作用模型耦合到激光熔覆凝固过程的晶粒形核模型中,研究超声频率对激光熔覆TiC/FeAl凝固组织的影响,并采用直线截点法定量分析凝固组织随超声频率的变化规律,同时采用自行设...综合考虑超声的空化作用和声流效应,通过元胞自动机将超声振动作用模型耦合到激光熔覆凝固过程的晶粒形核模型中,研究超声频率对激光熔覆TiC/FeAl凝固组织的影响,并采用直线截点法定量分析凝固组织随超声频率的变化规律,同时采用自行设计的超声振动工作台制备超声辅助激光熔覆TiC/FeAl复合涂层。结果表明:超声的空化作用及声流效应促使激光熔覆TiC/FeAl凝固组织细化,组织及TiC颗粒分布较为均匀;凝固组织随超声频率的增大先细化后粗化,且振动频率为20 k Hz时晶粒细化效果最佳,达到16.7%。模拟计算结果与试验结果一致。展开更多
基金Project (2009CB623406) supported by the National Basic Research Program of ChinaProjects (50825102, 50721003, 51071178) supported by the National Natural Science Foundation of China+1 种基金Project (11JJ4036) supported by the Natural Science Foundation of Hunan Province, ChinaProject supported by the Central South University Free Exploring Project, China
文摘The tortuosity factor is the most critical parameter for the pore characteristic of porous materials. The tortuosity factor for porous FeAl intermetallics was studied based on the Darcy law and Hagen-Poiseuille equation. Porous stainless steel with the same pore structure parameter as porous FeAl was fabricated by powder metallurgy method for comparison. The results show that the tortuosity factor of porous FeAl intermetallics is smaller than that of porous stainless steel when their pore structure parameters are the same. The average tortuosity factor is 2.26 for the porous FeAl material and 2.92 for the porous stainless steel, calculated by Hagen-Poiseuille equation. The reason of the different tortuosity factors for porous FeAl and porous stainless steel was also explored through studying the pore formation mechanisms of the two types of porous materials.
基金Project(050440704) supported by the Natural Science Foundation of Anhui Province, ChinaProject(103-037016) supported by the Technological Innovation Foundation of Hefei University of Technology, China
文摘Three nanocrystalline alloys, Fe50Al50, Fe42.5Al42.5Ti5B10 and Fe35Al35Ti10B20 (molar fraction, %), were synthesized from elemental powders by high-energy ball milling. The structural evolutions and morphological changes of the milled powders were characterized by X-ray diffractometry(XRD), transmission electron microscopy(TEM) and scanning electron microscopy(SEM). The effects of different Ti, B additions on the structure and phase transformation in these alloys were also discussed. It is observed that the diffusion of Al, Ti, B atoms into Fe lattice occurs during milling, leading to the formation of a BCC phase identified as Fe(Al) or Fe(Al, Ti, B) supersaturated solid solution. Fe-based solid solution with nanocrystalline structure is observed to be present as the only phase in all the alloy compositions after milling. Furthermore, the contents of Ti, B affect the formation of mechanical alloying products, changes in the lattice parameter as well as the grain size.
文摘综合考虑超声的空化作用和声流效应,通过元胞自动机将超声振动作用模型耦合到激光熔覆凝固过程的晶粒形核模型中,研究超声频率对激光熔覆TiC/FeAl凝固组织的影响,并采用直线截点法定量分析凝固组织随超声频率的变化规律,同时采用自行设计的超声振动工作台制备超声辅助激光熔覆TiC/FeAl复合涂层。结果表明:超声的空化作用及声流效应促使激光熔覆TiC/FeAl凝固组织细化,组织及TiC颗粒分布较为均匀;凝固组织随超声频率的增大先细化后粗化,且振动频率为20 k Hz时晶粒细化效果最佳,达到16.7%。模拟计算结果与试验结果一致。
