采用 5 k W连续 CO2 激光器对经等离子喷涂的 Ni Co Cr Al Y结合层和 Zr O2 陶瓷层进行二次重熔处理 ,并利用金相显微镜、扫描电镜和电子探针对激光熔敷涂层进行了显微结构和元素分布观察与测试。结果表明 :激光熔敷涂层中基体对 Ni Co ...采用 5 k W连续 CO2 激光器对经等离子喷涂的 Ni Co Cr Al Y结合层和 Zr O2 陶瓷层进行二次重熔处理 ,并利用金相显微镜、扫描电镜和电子探针对激光熔敷涂层进行了显微结构和元素分布观察与测试。结果表明 :激光熔敷涂层中基体对 Ni Co Cr Al Y合金层产生稀释 ,形成成分和组织偏析。加入了 Ti O2 - Al- Ti添加剂的 Zr O2 陶瓷层激光重熔后得到了无裂纹的定向生长柱状晶 ,并且呈现一次枝晶平均间距为 2 .3μm的表层和平均间距为 3.展开更多
A self-invented atomization process, in which molten metal is atomized into powder by a high-velocity gas stream carrying solid particles as the atomization medium, was introduced. The characteristics of powders prepa...A self-invented atomization process, in which molten metal is atomized into powder by a high-velocity gas stream carrying solid particles as the atomization medium, was introduced. The characteristics of powders prepared by common gas atomization and dual-phase flow atomization under similar conditions were compared. The experimental results show that the dual-phase flow-atomized powders have average particle sizes that are one-half that of the common gas-atomized particles;additionally, they possess a finer microstructure and higher cooling rate under the same atomization gas pressure and the same gas flow. The Weber number in the crash criteria of liquid atomization is adopted to measure the crash ability of the atomization media. The Weber number of the dual-phase flow atomization medium is the sum of that of the gas and the solid particles. Furthermore, the critical equation of the crash model in dual-phase flow atomization is established, and the main regularities associated with this process were analyzed.展开更多
Based on volume of fluid(VoF)interface capturing method and shear-stress transport(SST)k-ω turbulence model,numerical simulation was performed to reveal the flow mechanism of metal melts in melt delivery nozzle(MDN)d...Based on volume of fluid(VoF)interface capturing method and shear-stress transport(SST)k-ω turbulence model,numerical simulation was performed to reveal the flow mechanism of metal melts in melt delivery nozzle(MDN)during gas atomization(GA)process.The experimental validation indicated that the numerical models could give a reasonable prediction on the melt flow process in the MDN.With the decrease of the MDN inner-diameter,the melt flow resistance increased for both molten aluminum and iron,especially achieving an order of 10^(2) kPa in the case of the MDN inner-diameter≤1 mm.Based on the conventional GA process,the positive pressure was imposed on the viscous aluminum alloy melt to overcome its flow resistance in the MDN,thus producing powders under different MDN inner-diameters.When the MDN inner-diameter was reduced from 4 to 2 mm,the yield of fine powder(<150μm)soared from 54.7%to 94.2%.The surface quality of powders has also been improved when using a smaller inner-diameter MDN.展开更多
文摘采用 5 k W连续 CO2 激光器对经等离子喷涂的 Ni Co Cr Al Y结合层和 Zr O2 陶瓷层进行二次重熔处理 ,并利用金相显微镜、扫描电镜和电子探针对激光熔敷涂层进行了显微结构和元素分布观察与测试。结果表明 :激光熔敷涂层中基体对 Ni Co Cr Al Y合金层产生稀释 ,形成成分和组织偏析。加入了 Ti O2 - Al- Ti添加剂的 Zr O2 陶瓷层激光重熔后得到了无裂纹的定向生长柱状晶 ,并且呈现一次枝晶平均间距为 2 .3μm的表层和平均间距为 3.
文摘A self-invented atomization process, in which molten metal is atomized into powder by a high-velocity gas stream carrying solid particles as the atomization medium, was introduced. The characteristics of powders prepared by common gas atomization and dual-phase flow atomization under similar conditions were compared. The experimental results show that the dual-phase flow-atomized powders have average particle sizes that are one-half that of the common gas-atomized particles;additionally, they possess a finer microstructure and higher cooling rate under the same atomization gas pressure and the same gas flow. The Weber number in the crash criteria of liquid atomization is adopted to measure the crash ability of the atomization media. The Weber number of the dual-phase flow atomization medium is the sum of that of the gas and the solid particles. Furthermore, the critical equation of the crash model in dual-phase flow atomization is established, and the main regularities associated with this process were analyzed.
基金the National Natural Science Foundation of China(No.52074157)Shenzhen Science and Technology Innovation Com-mission,China(Nos.JSGG20180508152608855,KQTD20170328154443162)Shenzhen Key Laboratory for Additive Manufacturing of High-performance Materials,China(No.ZDSYS201703031748354).
文摘Based on volume of fluid(VoF)interface capturing method and shear-stress transport(SST)k-ω turbulence model,numerical simulation was performed to reveal the flow mechanism of metal melts in melt delivery nozzle(MDN)during gas atomization(GA)process.The experimental validation indicated that the numerical models could give a reasonable prediction on the melt flow process in the MDN.With the decrease of the MDN inner-diameter,the melt flow resistance increased for both molten aluminum and iron,especially achieving an order of 10^(2) kPa in the case of the MDN inner-diameter≤1 mm.Based on the conventional GA process,the positive pressure was imposed on the viscous aluminum alloy melt to overcome its flow resistance in the MDN,thus producing powders under different MDN inner-diameters.When the MDN inner-diameter was reduced from 4 to 2 mm,the yield of fine powder(<150μm)soared from 54.7%to 94.2%.The surface quality of powders has also been improved when using a smaller inner-diameter MDN.
