open access

https://hdl.handle.net/2115/75138

Effect of Niobium or Vanadium Addition on the Microstructure and Hardness of MoSi2-Mo5Si3 Eutectic Alloys

日本語

micro-hardness

1999-05-01

日本金属学会

Journal of the Japan Institute of Metals

63(5)

613-616

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.

学術雑誌論文

Version of Record

0021-4876

1880-6880

AN00062446