MoSi2-Mo5Si3共晶材の組織および硬さに及ぼすNb, Vの影響

福井 俊彦, 上野 俊吉, 田中 良平, 三浦 誠司, 三島 良直

doi:10.2320/jinstmet1952.63.5_613

Effects of Nb or V additions on microstructure and hardness of MoSi₂/Mo₅Si₃ eutectic alloys are investigated for the improvement of room temperature toughness of multi-phase intermetallic alloys based on MoSi₂. Alloys prepared by the argon arc melting process have compositions of 4-23 mol%Nb or 10-19 mol%V which substitutes Mo in MoSi₂ and Mo₅Si₃ phases. Examinations are made on microstructural observation by back scattered electron image, X-ray diffraction for phase identification, the concentration of Nb or V in the constituent phases by EPMA, and Vickers hardness of the multi-phase alloys in both macro- and microscopic scales. The phase constitution changes from the two-phase, MoSi₂(C11b) and (Mo, Nb)₃Si₅, to the three-phase, MoSi₂(C11b)/(Mo, Nb)Si₂(C40)/(Mo, Nb)₅Si₃, with increasing Nb additions. In the series of alloys with V additions, a similar shift from the two- to the three-phase is accompanied with increasing V addition. Macroscopic hardness of the multi-phase alloys with Nb addition exhibits a complex concentration dependence, in which with increasing Nb content, the hardness first decreases, exhibits a minimum and then increases back. The reason could be attributed to the fact that the hardnesses of the C40 and C11b phase have individual dependence on Nb concentration as revealed by micro-scale hardness measurement. For the improvement in toughness, Nb additions to the eutectic alloys may be preferred because the MoSi₂/Mo₅Si₃ eutectic microstructure is fine as compared with that obtained by the V addition.

MoSi<SUB>2</SUB>-Mo<SUB>5</SUB>Si<SUB>3</SUB>共晶材の組織および硬さに及ぼすNb, Vの影響

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