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An experimental investigation of the phase relations in the titanium (Ti)-aluminum (Al)-silicon (Si) system was undertaken by differential thermal analysis, x-ray diffraction, metallography, and microprobe analysis. The present measurements when combined with those from an earlier investigation at this laboratory provide data for 56 alloy compositions in the Ti-Al-Si system. The combined results allowed the construction of a solidus projection, a melting diagram including both solidus and liquidus, partial isothermal sections at 1270°C and 1250°C, three isopleths with a constant percentage of one or another component, and a reaction scheme. along the Si-Al side of the ternary system was studied by Kamei et al. [1968Kam] andZakharov et al. [1988Zak]. According to Kamei et al. [1968Kam], two invariant equilibria occur in this part of the system: peritectic L + TiAl 3 ↔ TiSi 2 Al + Al; and eutectic L ↔ TiSi 2 Al + Al + Si. The reaction temperatures were not given. Two peritectic equilibria were reported by [1988Zak]: L

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Two boride layers were found to form at the interface of iiron-chromiium alllloys (10 and 25% Cr) or an industrial 13% Cr steel and boron at 850-950 oC and reaction times in the range 1-12 h. In the case of a Fe-10% Cr alloy and the steel, the layers are based on the FeB and Fe2B compounds. With a Fe-25% Cr alloy, the constituent phases are FeB and CrB for the outer layer and Fe2B and Cr2B for the inner layer. Both layers are characterized by a pronounced texture. Diffusional growth kinetics of boride layers are close to parabolic and can alternatively be described by a system of two non-linear differential equations, producing a good fit to the experimental data. The temperature dependence of the layer growth-rate constants obeys a relation of the Arrhenius type.

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