Design And Application Of Wetting Angle Measuring Device

Wetting angle is an angle which is located in the contacting region among the gas, liquid and solid phases. It is usually characterized by measuring the tangents of the liquid-solid interface and the liquid-gas interface. It is the most available method to assess the wetting between the molten metal and the solid interface which has a great influence on the preparation of materials science, materials machining, metallurgy, especially in the area of the welding and metal matrix composite. The fabrication and the utility of the materials are largely decided on the wetting between the heterogeneous materials.Among the methods for measuring the wetting angles, the sessile drop method is most widely used for the easy operation and detection. In this paper, an apparatus was fabricated based on the sessile drop method. By referring to the mechanism of this method, the main systems (heat preservation, heating and vacuum system) and supplementary systems (water cooling system, image capture and materials transmission system) were designed, calculated and confirmed. The assembly and debugging of the apparatus were also conducted. The operating procedures were determined in detail. A succession of experiments was performed for measuring the wetting angles between silicon carbide (SiC) ceramic based plate and pure Al or Al-Si alloy (AlSi3,AlSi6, AlSi9 and AISi12) by the apparatus. The obtained results are showed as below:(1) The apparatus was efficient to be used for the measurement of the Al-based matrix materials. The vacuum electric resistance furnace was used as main component of the equipment. The maximum working temperature was 1000? and the vacuum could be reached to 1×10-3Pa.(2) According to the wetting ability of the pure Al or Al alloy with the SiC ceramic based plate obtained by conventional sessile drop method, the wetting and spreading process was mainly composed of three stages, namely the rupture of oxide film in the initial stage; the rapidly spreading in the middle stage and the final stage corresponding with gradually stabilizing. When the temperature was 740?, the wetting angle was between 135°?140°firstly and decreased to 90°?95°.(3) Based on the results obtained by the improved sessile drop method, the process of wetting and spreading was mainly composed of two stages, namely the rapid spreading stage at first and the gradually stabilizing in the later stage. The wetting angle was measured between 120°?130°. It was commonly 10° less than the angle which was obtained by the conventional sessile drop method.(4) Based on the measurement data, the wetting angle is decreased gradually with the increase of the Si content. Then in the following spreading process, the spreading rate slower in the Al alloy with high content of Si than in the Al alloy with low Si content.(5) The wetting angles were similar between the Al-Si alloy and the SiC-based plate which was subjected to oxidation treatment or not. But in the further spreading process, the spreading rate was increased by the oxidation treated SiC plate due to the increment of the SiO2.