Effect of refractory metal substitution on the stability of Mo(ss)+T2 two-phase field in the Mo-Si-B system


The influence of refractory metal substitution such as Nb and Cr for Mo in Mo-B-Si alloys on the phase stability has been examined for compositions in the Mo(ss)+T2 two-phase field. The solidification pathways as well as the width of the two-phase field at high temperature are modified by refractory metal substitutions. The characteristically severe solidification segregation found in Mo-B-Si alloys may be significantly reduced if the substitution such as Nb for Mo change the T2-phase lattice constants to facilitate a larger composition exchange between B and Si in the T2 phase. The enhanced B and Si exchange also yield as significant increase in the width of Mo(ss)+T2 two-phase field. This behavior highlights the role of atomic factor in influencing the relative stability of the T2 (D8l) phase.

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International Journal of Refractory Metals and Hard Materials