Predictions of Phase Equilibria
The TCS Nb-based Alloys Database (TCNB) can be used to calculate phase equilibria, including phase fractions and compositions, to reliably account for phase transformations. All the stable solution phases and intermetallic compounds that exist in the assessed and their extrapolated systems are included in the database. This version of the database (TCNB1) is able to predict the stable phases and phase compositions for a given composition and condition within the recommended composition range of the database.
The table shows the calculated phases and compositions in various Nb alloys compared with experimentally determined ones. The TCS Nb-based Alloys Database (TCNB)is able to predict the phase types at each given alloy composition and heat treatment temperature correctly and able to predict the phase compositions within the experimental errors.
| Comparisons between the measured and the calculated (in parentheses) phase compositions | ||||||
|---|---|---|---|---|---|---|
| Sample | Phase | Nb (at.%) | Al (at.%) | Cr (at.%) | Ti (at.%) | Si (at.%) |
| Nb-5Al-10Si-15Ti 1500 °C [1993Sub] | BCC | 76 (77.7) | 8 (6.0) | 16 (14.6) | 1 (1.7) | |
| Nb5Si3 | 49 (46.2) | 3 (1.8) | 14 (16.3) | 34 (35.7) | ||
| Nb-5Al-24Ti-18Si 1500 °C [2006Zel] | BCC | 62 (62.6) | 7 (8.1) | 29 (26.9) | 0.5 (2.4) | |
| Nb5Si3 | 44 (42.8) | 2 (1.8) | 19 (19.7) | 34 (37.5) | ||
| M3Si (4%) | (41.6) | (33.4) | (25.0) | |||
| Nb-10Cr-15Si-23Ti 1350 °C [2008Yan] | BCC | 58.2 (60.3) | 13.3 (13.9) | 27.4 (24.3) | 1.2 (1.5) | |
| Nb5Si3 | 42.2 (40.9) | 0.6 (0.1) | 21.2 (21.5) | 36.1 (37.5) | ||
| C14 | 29.1 (23.0) | 47.1 (54.2) | 14.7 (11.9) | 9 (10.9) | ||
| Nb-11Cr-13Si-23Ti 1350 °C [2008Yan] | BCC | 59.4 (60.3) | 13.5 (13.9) | 26 (24.3) | 1.2 (1.5) | |
| Nb5Si3 | 43.7 (40.9) | 0.5 (0.1) | 19.5 (21.5) | 36.2 (37.5) | ||
| C14 | 26 (23.0) | 51 (54.2) | 13 (11.8) | 10 (10.9) | ||
| Nb-9Al-14Si-18Ti 1450 °C [2020Sun] | Nb5Si3 | 49 (45.2) | 4 (3.1) | 15 (17.3) | 32 (34.4) | |
| Nb3Al* | 67 (64.2) | 13 (16.1) | 15 (16.4) | 5 (3.3) | ||
| BCC | 69 (68.3) | 8 (11.0) | 23 (19.3) | 0 (1.4) | ||
| Nb-36Al-14Si-12Ti 1450 °C [2020Sun] | Nb5Si3 | 51 (45.2) | 7 (5.9) | 13 (17.3) | 29 (31.6) | |
| W5Si3 | 49 (50.6) | 17 (22.4) | 15 (11.9) | 19 (15.1) | ||
| AlTi_L10 | 28 (28.2) | 55 (55.1) | 17 (16.7) | 0 (0.0) | ||
| Al3Ti_D022 | 27 (23.8) | 68 (72.5) | 5 (3.7) | 0 (0.0) | ||
| * Nb3Al is modeled as Cr3Si_A15 in TCNB1 | ||||||
References
[1993Sub] P. R. Subramanian, M. G. Mendiratta, D. M. Dimiduk, Microstructures and Mechanical Behavior of Nb-Ti Base Beta + Silicide Alloys. MRS Proc. 322, 491 (1993).
[2006Zel] K. Zelenitsas, P. Tsakiropoulos, Study of the role of Ta and Cr additions in the microstructure of Nb–Ti–Si–Al in situ composites. Intermetallics. 14, 639–659 (2006).
[2008Yan] Y. Yang, B. P. Bewlay, S. Chen, M. R. Jackson, Y. A. Chang, Effect of Cr Addition on the Multiphase Equilibria in the Nb-rich Nb-Si-Ti System - Thermodynamic Modeling and Designed Experiments. MRS Proc. 1128, 1128-U05-42 (2008).
[2020Sun] Z. Sun, W. Wu, X. Tian, F. Zhang, C. Ai, X. Zhang, Y. Li, X. Guo, Phase equilibria and multi-element interaction study in the metal-rich side of the Nb–Ti–Si–Al quaternary system. Intermetallics. 120, 106760 (2020).