Phase stabilities and equilibria of the Ti-Al-Nb ternary system at intermediate temperatures II. The 980 °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.

Automated summary

This paper continues our previous publication and systematically characterizes diffusion multiples using various techniques. The constructed isothermal sections include stable phases and phase regions at 980 degrees C. The experimental results provide missing thermodynamic data and enable accurate predictions of phase diagrams and reactions at intermediate temperatures.