Isothermal section at 1000 °C of the Nb-Ti-Si system

The isothermal section at 1000 °C of the Nb-Ti-Si system was constructed using a high-efficiency diffusion couple approach, supplemented with 10 alloys, the compositions of which were selected on the basis of the experimental results from the diffusion couple. Both the diffusion couple specimens and the alloys were examined by means of optical microscopy, scanning electron microscopy, and electron probe microanalysis. No ternary compound was found at this isothermal section. Seven three-phase equilibria were observed [1: Ti(Nb)Si2 + Nb(Ti)Si2 + Si, 2: Ti(Nb)Si2 + Ti(Nb)Si + Ti(Nb)5Si4, 3: Ti(Nb)Si2 + Nb(Ti)Si2 + Ti(Nb)5Si4, 4: Ti(Nb)5Si4 + Nb(Ti)Si2 + Nb(Ti)5Si3, 5: Ti(Nb)5Si4 + Ti(Nb)5Si3 + Nb(Ti)5Si3, 6: Ti(Nb)5Si3 + Nb(Ti)5Si3 + (Ti,Nb)3Si and 7: Nb(Ti)5Si3 + (Ti,Nb)3Si + (Nb,Ti,Si)]. The solubilities of Nb in Ti3Si, Ti5Si4 and TiSi2 were determined to be up to 60, 41 and 17.6 at% Nb, respectively. The solubilities of Ti in Nb5Si3 and NbSi2 were measured to be about 31 and 13 at% Ti, respectively.