选择性激光烧结技术制备的石墨预制体致密度不高, 且内部疏松多孔导热系数也相对较低。本文通过改变选择性激光烧结工艺参数制备了相对密度在18.78%~24.95%的多孔石墨预制体, 并利用瞬态平板热源法测定其在室温下的有效导热系数, 研究了激光能量密度对选择性激光烧结石墨预制体导热性能的影响。结果显示在0.05~0.15 J/mm2之间激光能量密度与导热性能呈正相关的关系, 而在能量密度小于0.136 7 J/mm2时预制体的相对密度随着能量密度的增大而增大, 当能量密度大于0.136 7 J/mm2时预制体相对密度基本不变。通过引入能量密度与导热系数的相关系数, 建立了激光能量密度与多孔石墨预制体导热系数相关的导热理论模型, 并通过实验验证导热模型有效性。结果显示所建导热模型的预测值与多孔SLS石墨预制体实际测量值偏差小于1.5%。

Selective laser sintered graphite part have low relative density, and its thermal conductivity is relatively low. In this paper, porous graphite preforms with densities ranging from 18.78% to 24.95% were prepared by selective laser sintering process with varied process parameters. Effective thermal conductivity of the preforms at room temperature was measured by transient plate heat source method. The effect of laser energy density between 0.05 and 1.5 J/mm2 on the thermal conductivity of the preforms was studied.Results showed that there was a positive correlation between laser energy density and thermal conductivity, and the relative density of preform increased with the increment of energy density when the energy density was less than 1.367 J/mm2, while the relative density of preform remained unchanged when the energy density is greater than 1.367 J/mm2. By introducing correlation coefficient between energy density and thermal conductivity, based on the thermal conductivity data of preforms prepared under different energy densities, a theoretical model of thermal conductivity related to laser energy density and thermal conductivity of porous graphite preforms was established, and the validity of the thermal conductivity model was verified by experiments. Results showed that the deviation between the predicted value of the heat conduction model and the measured value of porous SLS graphite preform is less than 1.5%.