Aluminum-silicon phase diagram

Silicon is soluble in aluminum in the solid state to a maximum of 1.62 wt % at 577°C (2). It is soluble in silver, gold, and 2inc at temperatures above their melting points. Phase diagrams of systems containing silicides are available (2,3). 

Phase diagrams for the systems silver/copper (limited solubility in the solid) and aluminum/silicon (formation of an eutectic mixture)... 

The phase diagram for aluminum/silicon (Fig. 4.5) is a typical example of a system of two components that form neither solid solutions (except for very low concentrations) nor a compound with one another, but are miscible in the liquid state. As a special feature an acute minimum is observed in the diagram, the eutectic point. It marks the melting point of the eutectic mixture, which is the mixture which has a lower melting point than either of the pure components or any other mixture. The eutectic line is the horizontal line that passes through the eutectic point. The area underneath is a region in which both components coexist as solids, i.e. in two phases. 

The melting point of pure aluminum is 660 °C and aluminum and silicon form a eutectic, the eutectic temperature is 577 °C, the eutectic composition is 12% Si, and the maximum solubility of of silicon in solid aluminum is 1.65%. Assume the phase diagram consists of straight lines. If aluminum containing 0.15 wt% Si were solidified, what would be the composition of the first solid to form ... 

Si02 and AIPO4 are isoelectronic and isostructural. They have the same crystalline forms, and transitions between these forms follow the same order and even occur at similar temperatures. Thus, the phase diagrams for both are quite similar. On the periodic table, silicon is bordered by aluminum on the left, and phosphorus on the right. Si4+ in the silica matrix can be replaced by alternating Al3+ and P5+ in the analogous... 

The alloy of the metallic intermediate layer is in many applications based on a composition of silicon (Si) with gold (Au) or aluminum (Al). Furthermore, there are other alloy compositions, which are each associated with a specific melting temperature. In a phase diagram, the melt temperature of the phases as a function of the concentration of alloying elements as well as the concentration ratios is plotted. Figure 1 shows the Au-Si alloy system with the corresponding phase diagram. 

The Al-Si system has a phase diagram of the eutectic type. Aluminum almost does not dissolve in Si, while up to 1.65 at % Si can dissolve in aluminum. The eutectic melts at a temperature of 577°C. A result of such character of the interaction in the system is the dissolution of silicon from the substrate in aluminum at relatively low temperatures i.e., aluminum acts as a solvent of silicon. 

Mon] Mondolfo, L.F., Aluminum-Iron-Silicon , in Metallography of Aluminum Alloys , John Wiley Sons, Inc., New York, 95-97 (1943) (Phase Diagram, Review,, 27)... 

Bar] Barlock, J.G., Mondolfo, L.F., Structure of Some Aluminum-Iron-Magnesium-Silicon Alloys , Z. Metallkd., 66, 605-611 (1975) (Ciys. Structure, Phase Diagram, Experimental,, 7)... 

---