Physicochemical interaction at the contact of higher manganese silicide with chromium

Diffusion processes taking place at the contact of higher manganese silicide MnSi1.71-1.75 with chromium at elevated temperatures are considered. The microstructures of cast and annealed samples show a diffusion region that evolves at the HMS/Cr interface during the HMS melt crystallization on chromium flakes. As the temperature and time of annealing of HMS/Cr samples increase, the diffusion region grows thicker and new phases appear. It is shown that the diffusion is of reaction character. The diffusion coefficients of magnesium, chromium, and silicon in the solid solution based on manganese and chromium monosilicides and in the solid solution based on the Cr3Si compound are calculated. It is also shown that, when the temperature of the HMS used as a thermoelement positive leg is optimal, the depletion time of a 10-mum-thick chromium layer exceeds 15 000 h. Intermetallic phases forming in the diffusion region between the HMS and Cr are of metallic conduction and exhibit a high thermal conductivity, which minimizes energy losses in the contact layers of thermoelements. (C) 2002 MAIK "Nauka/Interperiodica".