Phase Formation and Solidification Routes Near Mo-Mo5SiB2 Eutectic Point in Mo-Si-B System

The phase formation behaviour during solidification in the Mo Si-B system was experimentally examined around the triple junction point (Gamma) of the Mo solid solution (Mo-55) Mo5SiB2 (T-2) and Mo2B primary phases in the Mo Si B liquidus projection suggested by Yang and Chang through thermodynamic calculations and the solidification routes of the Mo-Si-B alloys were reconsidered trisect on the obtained results Alloys of four different compositions ground the T point were produced by arc-melting The primary phases observed in these alloys were in excellent agreement with the liquidus projection proposed by Yang and Chang The solidification routes were basically Mo-55 (primary) -> Mo-55 + Mo2B -> Mo-55 + T-2 eutectic -> Mo-55 + T-2 + Mo3Si (A15) T-2 (primary) -> Mo-55 + T-2 eutectic -> Mo-55 + T-2 + A15 or Mo2B (primary) -> Mo-55 + T-2 eutectic -> Mo-55 + T-2 + A15 depending on the composition However a quantitative EPMA analysis indicated the compositions of the Mo-55-T-2 eutectic and Mo-55 + T-2 A15 phases differed from the reported liquidus projection This is clue to the difficulties interpreting the unusual solidification routes in the Mo-Si-B system and their as cast microstructures [doi 10 2320/matertrans M2010153]