Magnesium based Mg2X (X = Si, Sn) intermetallic compounds are of great interest due to their potential applications in lithium-ion batteries, infrared sensors, solar cell and thermoelectric devices. Mg2X compounds are also important owing to non-toxicity, abundance of raw materials, and relatively inexpensive constituents, as well as having good mechanical and chemical properties and a low density.
Processing of these materials beyond small scales is a challenging task. The major difficulty in this context is the difference in the melting point of Si with T=1440°C and the boiling point of Mg with T=1090°C. Hence, common melt metallurgical methods show problems in controlling the stoichiometric composition due to the volatilization and oxidation of Mg coupled with large differences in vapor pressure of the constituents. For these reasons, we propose an alternative method for manufacturing Mg2X intermetallic compounds. This method is based on a splitting of the common melt metallurgical processing route into several successive steps. Firstly, an open-pore cellular Si structure is fabricated by investment casting. In a further step, the cellular Si structure is infiltrated by a molten Mg alloy, followed by a subsequent thermal and/or mechanical treatment. The attractive aspects in this context are the open-pore structure, which ensures a fluid exchange between the individual cells and, thus, the infiltration with molten metal, and the very large specific surface area, which promotes the diffusion process between the cellular structure and the infiltrated matrix material.
Recently, we have described the formation and dispersion behavior of the intermetallic compound resulting by the infiltration process. Based on these results, we further study the interface formation of Mg2X (X = Si, Sn) resulting by annealing experiments and we identify the degradation temperature of the compound. SEM is used for observing the microstructure of the composites and EDX to determine the phase compositions.