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2 µm - eTheses Repository - University of Birmingham

2 µm - eTheses Repository - University of Birmingham

Si alloy

Si alloy of the type EN AC-AlSi12Fe. In the following discussions this alloy is designated as IS. The other was an Al-Mg alloy of the type EN AC-AlMg9, designated as IM. Both alloys were purchased from VAW Imco, Germany. As shown in Table 3.2, the atomic fractions of the main alloying elements, silicon and magnesium, were 10.77% and 10.25% respectively. Table 3.2 Chemical compositions of the alloys used for sessile drop tests and MMC fabrication in accordance to the suppliers certificates. Alloy Code Si Fe Cu Mn Mg Ti Sr Na Be Al weight-% EN AC-Al Si12(Fe) IS 11.10 0.76 0.05 0.20 0.01 0.044

using a AVT-Horn (Aalen, Germany) macro-zoom objective was connected to a Nikon Coolpix 990 digital camera. The resolution of the image of the droplet was measured to be 0.01 mm/pixel. Vacuum chamber Vacuum + resistance resistancechamber heater coil PID control Control panel Rotary pump Diffusion pump Gas control Rotary pump control 66 Observation Oberservation hole TCout to PID hole Observation hole hole to PID to PID OT Water cooling system Ar Detail: Observation hole Ti-sponges substrate Heater Figure 3.1 Sketch of the vacuum furnace unit and detail view through the observation window: holder with thermocouples (TC) close to the substrate. Radial TiAl6V4 - shielding droplet Prior to the test, the substrates were cleaned using high purity ethanol. Cubes of the Al alloy with an edge length of 4 mm were ground and cleaned with ethanol. The first measurements were performed by contact heating of the alloy sample directly on the substrate as shown schematically in Figure 3.2 a). To enable cleaning of the liquid metal surface prior to the sessile drop test, a more refined set-up was adapted. The cube of the Al alloy was clamped in an Al2O3 tube, which was fixed to the substrate holder at an elevated position. At the lower end of the tube a sharp-edged Al2O3 sheet material was introduced into the interior of the tube. The sheet covered about 25% of the internal cross-sectional area. At 750°C the liquid metal in the tube was forced towards the substrate by an mechanical impulse applied to the holder as shown schematically in Figure 3.2 b).

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