| The oxidation behavior of Ti₃Al+(0, 0.6, 1.1, 1.9at%)Si alloys has been investigated in air at 700, 800, 900℃. The matrix of the plasma jet melted alloys had Ti₃Al with some TiAl. TiAl₃ and Ti_5Si₃. After oxidation, a multi-layered scale was formed on Ti₃Al+Si alloys as was frequently observed on pure Ti₃Al alloys, consisting of an outer TiO₂ layer, an intermediate relatively protective thin Al₂O₃ layer, and an inner TiO₂+Al₂O₃ mixed layer. The major effect of Si on Ti₃Al are considered to be; (1) increment of the oxidation resistance by being oxidized to amorphous SiO₂. (2) refinement of grains or densification of the outer TiO₂ layer by positioning between the TiO₂ grains, though the amount of SiO₂ in this area is extremely small. (3) enhancement of intermediate Al₂O₃ layer formation by decreasing Ti activity, and thereby, increasing Al activity owing to the formation of Ti_5Si₃ inside the matrix. |
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