【摘要】 混合元素法激光立体成形(LSF)过程中元素粉末的输送性对沉积试样的化学成分有重要影响,为实现混合元素法激光立体成形过程中各元素粉末的输送一致性,进而保证沉积试样的化学成分与目标成分一致,对混合元素法激光立体成形过程中的粉术输送性展开研究。结合喷嘴管道内外气-粉两相流分析,建立粉末颗粒在喷嘴管道内外的运动微分方程,揭示元素粉末特性对粉术输送性的影响规律。结果表明,送粉工艺一定的条件下,元素粉末的出口速度和加速度均随粉术密度和粒度的减小而增大。各元素粉末的输送一致性条件为在送粉工艺一定的情况下,各元素粉末流具有相同的出口速度。基于以上的粉末输送一致性条件,获得混合元素法激光立体成形过程中各元素粉末特性的匹配关系,进而保证了激光直接沉积试样的成分与预混合元素粉末成分的一致。更多还原

【Abstract】 The delivery behavior of the elemental powder has important influence on the composition of as-deposited sample during laser solid forming (LSF) from blended elemental powders. In order to ensure the consistency of the elemental powders delivery processes, and further to realize the composition control, the delivery behavior of the elemental powder during LSF is investigated. Based on the analysis of gas-powder two-phase flow, a mathematical model is established to describe the motion of the powder particles inside and outside the nozzle, and the influence of the powder characteristics on the powder delivery behavior is investigated. It is found that both the powder particle exit velocity and the motion acceleration increase with the decrease of the powder particle size and density. The consistency condition for different elemental powders delivery process is obtained, which is the identity of the exit velocity of the elemental powders. Based on the consistency condition, the match relation among the elemental powder characteristics (including the particle size and density) can be obtained, which ensures the consistency in composition between the laser deposits and the premixed elemental powders during LSF from blended elemental powders.更多还原