Experimental analysis and thermodynamic calculation of the structural regularities in the fusion diagram of the system of alloys Al-Mg-Si

Sections of the phase diagram Al-Mg-Si with up to 35 at.% magnesium and 35 at.% silicon are constructed. The thermodynamic calculation and experimenta l analysis have shown that the conode of three-phase eutectic equilibrium L double left right arrow alpha -Al + Mg2Si, corresponding to the maximum te mperature of eutectic transformation, does not coincide with the stoichiome tric cross section between Al and Mg,Si in the Al-Mg-Si ternary system, but rather occurs toward the magnesium-rich side of the ternary diagram. A pol ythermal cross section, corresponding to this conode, has been constructed. Concentration-temperature parameters of the univariant eutectic transforma tion L double left right arrow alpha -Al + Mg2Si, as well as the boundaries of the domain of existence of alloys crystallizing with the formation of o nly two phases, namely, alpha -Al and Mg2Si, were determined, Modeling of p hase equilibria involving solid and liquid phases in the ternary system Al- Mg-Si was carried out. The topology of the phase diagram is stable against a wide range variation of the adjustable parameters; the inherent form of t he diagram seems well established. The reasons for this are discussed.