石墨/铜基复合材料真空液相浸渗过程动力学研究

On Exploring Infiltration Kinetics of Copper Melt in Graphite Porous Preform under Vacuum Suction Infiltration Pressure

用真空浸渗法制备石墨 /铜基复合材料 ,从多孔介质的渗流物理理论出发 ,分析了颗粒堆积多孔体的孔隙结构 ,研究了在 0 .0 985 MPa的压力作用下 ,铜液浸渗石墨颗粒堆积多孔体的浸渗动力学过程 ,分析认为铜液对多孔体的浸渗以紊流方式进行。文中还同时探讨了浸渗过程中浸渗速度的变化 ,润湿角对浸渗的影响。比较了铜液分别浸渗未涂层处理石墨颗粒、碳化物涂层石墨颗粒后的组织。结果表明 ,涂层能有效促进浸渗并改善浸渗缺陷 ,在真空负压压力下 ,铜液可以浸透由涂层石墨颗粒组成的多孔体。

Graphite/Cu matrix composite is an advanced electronic packaging material. The material has been fabricated by powder metallurgy method or squeeze infiltration method. However, due to the poor wettability between graphite and copper, there exist the problems of high fabrication pressure (7~150 MPa) [5,6] , complex fabrication process, high fabrication cost. In this paper, We present a vacuum suction infiltration method for manufacturing graphite/Cu matrix composite. Its specific process is that copper melt infiltrates a graphite-particle porous preform with carbide coating under about 0.1MPa vacuum suction pressure and then solidifies. Fabricating graphite/Cu matrix composite in this way is not reported in the open literature. In the vacuum suction infiltration method, such problems as infiltration kinetics and effect of interface wettability on infiltration need further exploration. Subsection 2.1 analyzes in detail the pore structure of the graphite porous preform according to vadose physics theory of porous media; it also derives eq.(9) for describing the relationship between pore size and the average size of graphite particles. Subsection 2.2 deals with the nature of flow of the copper fluid in the graphite porous preform. Subsection 2.2 uses eq.(10) to calculate the Reynolds number Re of molten copper fluid in the graphite porous preform to be 16.55~30.06. Re=16.55~30.06 is higher than the critical Re of 5~10 as calculated in Ref.11.So subsection 2.2, different from the viewpoint of past researchers, deems that this molten copper fluid is a turbulent flow and that Darcy law and its diffusion formulas are no longer valid. Subsection 2.2 then uses the turbulent flow equation to derive eq.(15) for calculating the threshold pressure of the molten copper fluid infiltrating the graphite porous preform. Fig.3 in subsection 2.2 shows the variation of infiltration speed with infiltration length of copper melt. Figs.4 and 5 show respectively the microstructure of the graphite/Cu matrix composite without coating and that of graphite/Cu matrix composite with carbide coating. Subsection 2.3 indicates that the carbide coating can obviously change the wettability between graphite and copper and effectively promote infiltration. This paper finally concludes that graphite/Cu matrix composite can be fabricated under only 0.0985 MPa vacuum suction infiltration pressure.