Effects of ternary additions on the microstructure and thermal stability of directionally-solidified MoSi2/Mo5Si3 eutectic composites

• Various ternary MoSi2/Mo5Si3 eutectic composites were prepared by DS process.
• Fine microstructure of the script lamellar type was obtained for all ternary alloys.
• Ta and W are found to be beneficial to microstructure refinement.
• Fe, Co, Ni, Ir, B and C exhibit a strong tendency to segregate on interfaces.
• The segregation results in microstructure refinement and interface morphology change.

Effects of ternary additions on the microstructure and thermal stability of directionally-solidified MoSi2/Mo5Si3 eutectic composites have been studied for twelve different elements (Ti, V, Cr, Fe, Co, Ni, Nb, Ta, W, Ir, B and C) paying special attention to the variation of lattice misfits and interface segregation behavior with ternary additions. Among six elements (type-1: Ti, V, Cr, Nb, Ta and W) with a relatively high solubility in MoSi2 and Mo5Si3, Ta and W are found to be beneficial to microstructure refinement. All other six ternary elements (type-2: Fe, Co, Ni, Ir, B and C) with a negligibly low solubility in MoSi2 and Mo5Si3 exhibit a strong tendency to segregate on MoSi2/Mo5Si3 interfaces, resulting in both microstructure refinement and the modification of the interface morphology.