Phase stabilities and equilibria of the Ti-Al-Nb ternary system at intermediate temperatures II. The 980 degrees C isothermal section and reactions

This paper is a continuation of our recent publication [S. Xu, et al. Journal of Alloys and Compounds 900 (2022) 163399-163407]. We systematically characterized the diffusion multiples using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), electron backscatter diffraction (EBSD), trans-mission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM) and constructed the whole composition range of the 980 degrees C isothermal sections. The constructed range includes nine stable phases, twenty two-phase regions and ten three-phase regions at 980 degrees C. Six phase reactions occurring between 900 degrees C and 980 degrees C were determined. The omega o phase was formed by the beta o+ gamma ->omega o reaction at a temperature just below 980 degrees C. The beta o phase vanished through the beta o ->alpha 2 +omega o+O reaction at a temperature just above 900 degrees C. These experimental results will bridge the existing research gap by providing the missing ther-modynamic data. We believe that accurate predictions of phase diagrams and reactions occurring at in-termediate temperatures using the obtained data are now feasible and the recomputations will resolve previous inconsistences and disputes. (c) 2023 Elsevier B.V. All rights reserved.