Analysis of the Liquid State Fabrication Process of Aluminum Alloy Matrix Composites with Al_2O_3 Fiber of Powder

为了研究液态金属基复合材料的制备原理，对熔融金属基复合材料在Al_2O_3纤维预制件中的渗透过程进行了实验和分析研究。研究了Al_2O_3表面形貌、金属涂层和液体运动速度对Al_2O_3与Al_2O_3润湿性的影响。首先，采用座滴法研究了表面形貌和孔隙率对Al_2O_3粉末或纤维基材与熔融Al的润湿性的影响。熔融Al在纤维基材和有光泽粉末基材上的表观接触角(Rheta)与混合润湿性准则Cassie方程计算的结果基本一致，Rheta由光滑透明的Al_2O_3基材上的接触角(Rheta_1)和由基材的体孔率(Fv)计算的表面孔隙率(Fvs)计算得出。另一方面，RETA对无光泽烧结粉末…的影响更多的r底物比由Rheta_1估计的大得多，而从Fv估计的FV则更大。通过图像处理系统测量的表面孔隙率(FVS)准确地估计了无光泽衬底上的Rheta。其次，研究了涂层厚度和温度对熔融Al在Ni离子镀Al_2O_3表面润湿性的影响。在973、1073和1173K下，当delta值分别大于0.1、0.5和0.8um时，镀镍层使浸润角从90-110；；此外，还测量了移动液体在Al_2O_3表面的推进和后退润湿角随液体前沿移动速度的变化。最后，利用流体在多孔介质中流动的D‘Arcy定律，考虑了熔融金属的表面张力和润湿性，分析了熔融金属在Al_2O_3纤维预制体中的渗透过程。对熔融铅和铝的渗透实验研究表明，在假定预制件中不同尺寸的气孔分布的情况下，该分析是有效的。较少

To study the principles of the liquid state fabrication of metal matrix composites, the infiltration process of molten mital into Al_2O_3 fiber perform was investigated both experimentally and analytically. The influences of surface morphorogy of Al_2O_3, metal coating and moving rate of liquid, on the wettability of molten Al to Al_2O_3 was also measured. Firstly, the influences of surface morphology and porosity on the wettability of sintered Al_2O_3 powder or fiber substrates by molten Al was investigated by the sessile drop method. The apparent contact angles (rheta) of molten Al on sintered fiber substrate and lustrous sintered powder substrate were almost equal to those calculated by Cassie's equation, the rule of mixture for wettability ; rheta was calculated from the contact angle (rheta_1) on smooth transparent Al_2O_3 substrate and the surface porosity (fvs) which was evaluated from the bulk porosity (fv) of substrate. On the other hand, rheta on the lusterless sintered powde … More r substrate was much larger than that estimated from rheta_1 and fvs evaluated from fv. rheta on the lusterless substrate was accurately estimated from the surface porosity (fvs) measured by an image processing system. Secondly, the influences of thickness (delta) of coating layer and temperature on the wettability of molten Al on Ni ion plated Al_2O_3 was evaluated. Ni coating reduced the wetting angle from 90-110^<> to less than 10^<> when delta was larger than 0.1, 0.5 and 0.8mum at 973, 1073 and 1173K, respectively. Further, the advancing and receding wetting angle of moving liquid on Al_2O_3 were measured as a function of moving rate of the liquid front. Finally, the infiltration process of molten metal into Al_2O_3 fiber perform was analyzed by using D'Arcy's law on fluid flow in a porous media, with the consideration of surface tension and wettability of the molten metal. The experimental study on the infiltration of molten Pb and Al revealed the validity of the analysis with an assumption of a distribution of different sizes of pores in the perform. Less