TY - JOUR
T1 - Experimental study of the liquid-solid phase equilibria at the metal-rich region of the Nb-Cr-Si system
AU - Bewlay, B. P.
AU - Yang, Y.
AU - Casey, R. L.
AU - Jackson, M. R.
AU - Chang, Y. A.
PY - 2009/3
Y1 - 2009/3
N2 - There is presently limited information regarding liquid-solid phase equilibria at the metal-rich region of the Nb-Cr-Si system; these data are needed for the development of the Nb-silicide based in situ composites. In the present study a range of metal-rich Nb-Cr-Si alloys with Si concentrations up to 30 at.% was carefully selected using a phase diagram that was calculated from the prior developed thermodynamic description of the Nb-Cr-Si system. The as-cast microstructures were examined using scanning electron microscopy, X-ray diffraction, electron probe microanalysis, and electron backscatter diffraction. A new ternary phase Nb9(Cr,Si)5, isostructural with the Nb9Co3Ge2 phase, was identified in the present study. Four primary solidification regions were identified in these alloys: (Nb), Nb9(Cr,Si)5, Nb5Si3, and Cr2Nb(C14). Microstructural and microchemical evidence suggests six invariant reactions on the liquidus surface of the metal-rich region of the Nb-Cr-Si system. At the Nb-rich side there are four invariant reactions: Liquid + Nb3Si → Nb5Si3 + (Nb), Liquid + Nb5Si3 → Nb9(Cr,Si)5 + (Nb), Liquid + Nb5Si3 → Nb9(Cr,Si)5 + Cr2Nb(C14), and Liquid → Nb9(Cr,Si)5 + (Nb) + Cr2Nb(C14). At the Cr-rich side there are two invariant reactions: Liquid + Nb5Si3 → Cr2Nb(C14) + Cr3Si and Liquid → (Cr) + Cr2Nb(C14) + Cr3Si.
AB - There is presently limited information regarding liquid-solid phase equilibria at the metal-rich region of the Nb-Cr-Si system; these data are needed for the development of the Nb-silicide based in situ composites. In the present study a range of metal-rich Nb-Cr-Si alloys with Si concentrations up to 30 at.% was carefully selected using a phase diagram that was calculated from the prior developed thermodynamic description of the Nb-Cr-Si system. The as-cast microstructures were examined using scanning electron microscopy, X-ray diffraction, electron probe microanalysis, and electron backscatter diffraction. A new ternary phase Nb9(Cr,Si)5, isostructural with the Nb9Co3Ge2 phase, was identified in the present study. Four primary solidification regions were identified in these alloys: (Nb), Nb9(Cr,Si)5, Nb5Si3, and Cr2Nb(C14). Microstructural and microchemical evidence suggests six invariant reactions on the liquidus surface of the metal-rich region of the Nb-Cr-Si system. At the Nb-rich side there are four invariant reactions: Liquid + Nb3Si → Nb5Si3 + (Nb), Liquid + Nb5Si3 → Nb9(Cr,Si)5 + (Nb), Liquid + Nb5Si3 → Nb9(Cr,Si)5 + Cr2Nb(C14), and Liquid → Nb9(Cr,Si)5 + (Nb) + Cr2Nb(C14). At the Cr-rich side there are two invariant reactions: Liquid + Nb5Si3 → Cr2Nb(C14) + Cr3Si and Liquid → (Cr) + Cr2Nb(C14) + Cr3Si.
KW - A. Intermetallics, miscellaneous
KW - A. Silicides, various
KW - B. Phase diagrams
KW - C. Nb-Cr-Si
KW - D. Microstructure
UR - http://www.scopus.com/inward/record.url?scp=58649085892&partnerID=8YFLogxK
U2 - 10.1016/j.intermet.2008.10.005
DO - 10.1016/j.intermet.2008.10.005
M3 - Article
AN - SCOPUS:58649085892
SN - 0966-9795
VL - 17
SP - 120
EP - 127
JO - Intermetallics
JF - Intermetallics
IS - 3
ER -