The Nb-Ti-Si ternary phase diagram: Determination of solid-state phase equilibria in Nb- and Ti-rich alloys

Ternary Nb-Ti-Si phase equilibria have been investigated for the metal-rich end of the ternary phase diagram using scanning electron microscopy, XRD, and electron beam microprobe analysis. Microstructural and microchemical ob servations have been used to define isothermal sections at temperatures of 1500 and 1340 degrees C. These temperatures delineate regimes defined by li quid-solid reactions. Additional isothermal sections were estimated at 1350 , 1320, and 1150 degrees C using these data. A broad range of Nb and Ti com positions were investigated for Si concentrations up to 35.0%. Alloys conta ining up to four phases, Nb(Ti)(5)Si-3, Ti(Nb)(5)Si-3, (Nb,Ti)(3)Si, and (N b,Ti,Si) were studied. The effect of Ti on the eutectoid reaction, (Nb,Ti)( 3)Si --> (Nb,Ti,Si) + Nb(Ti)(5)Si-3 was investigated, as was the effect of Nb on the peritectoid reaction, Ti(Nb)(5)Si-3 + (Nb,Ti,Si) --> (Nb,Ti)(3)Si .