Phase Equilibria of the Ti-Al-Nb System at 1000, 1100 and 1150 °C

Abstract

1000, 1100 and 1150°C isothermal sections of the Ti-Al-Nb system were studied using x-ray diffraction, scanning electron microscopy and electron probe microanalysis. A small island-like region of single b 0 is present at 1000, but absent at 1100 and 1150°C. c 1 is not a stable phase at 1000 and 1150°C. Three three-phase fields (a 2 ? b 0 ? r, b 0 ? r ? c and a 2 ? b 0 ? c) are identified in the 1000°C isothermal section (30-60 at.% Ti content). The 1100°C isothermal section is firstly studied completely. It includes six three-phase and thirteen two-phase fields. Two three-phase fields b ? a 2 ? c and b ? r ? c are identified in the isothermal section (30-60 at.% Ti content) at 1150°C. These data are helpful to the fabrication of the TiAl and Ti 2 AlNb intermetallics. Keywords intermetallics Á microstructure Á phase diagram Á TiAl alloy Dedicate to the celebration of Prof. Zhanpeng Jin's 80th birthday. This invited article is part of a special issue of the Journal of Phase Equilibria and Diffusion in honor of Prof. Zhanpeng Jin's 80th birthday. The special issue was organized by Prof. Ji-Cheng (JC) Zhao,

The Polythermal Section of Ti-22Al-xNb (30-78at.%Ti) in Ti–Al–Nb System

“…Based on the above experimental results, the polythermal section in the Ti-Al-Nb ternary system covering the composition range of 30-78 at.% Ti was established and is illustrated in Figure 7. The experimental data in this work are highlighted in red and compared with some reported ones from the literature [17,21,22]…”

“…Due to the lack of thermodynamics data and phase equilibria, their results are questionable. In 1995, Miracle Metals 2020, 10, 871 2 of 15 et al [20] obtained a partial polythermal section of Ti-22Al, but the Ti-Al boundary and the O phase region of the polythermal section are quite different from those reported later [21,22]. For example, Muraleedharan et al [23] found that the upper temperature limit for the stability of the O phase is about 1000 • C. Above 1000 • C, the O phase disappears.…”

“…Raghavan [25] summarized the recent results again in 2010. In 2018, Li et al [21] updated the isothermal sections at 1000 • C and 1150 • C again, and studied the phase relationship at 1100 • C completely. They verified that the O phase was only stable below 1000 • C and the β 0 phase was found to be stable at 1000 • C. However, the γ 1 phase reported by Ding et al [26] and Chen et al [12] was not confirmed at 1000 • C. Table 1 lists the accepted phase names and crystal structures of the Ti-A1-Nb ternary system [18].…”

Experimental Phase Equilibria and Isopleth Section of 8Nb-TiAl Alloys

“…Phase diagrams of the three constituent binary systems in the Ti-Al-Nb system-Ti-Al [24], Al-Nb [25], and Ti-Nb [26]-have been sufficiently delineated. The isothermal sections at 1000 • C [27][28][29][30], 1100 • C [30,31], 1150 • C [28][29][30], 1200 • C [27,32], 1300 • C [33], and 1400 • C [28,29,34,35] from experimental data are available in the literature. In addition, isopleth sections show the development of phase equilibria, such as the Ti 72.5 Al 27.5 -Nb [36], Ti 78 Al 22 -Nb [37], TiAl-TiNb [37,38], 45Al [25], 47Al [25], 8Nb [25,39], and 10Nb sections [39].…”

Experimental Phase Equilibria and Isopleth Section of 8Nb-TiAl Alloys

“…Phase diagrams of the three constituent binary systems in the Ti-Al-Nb system-Ti-Al [24], Al-Nb [25] and Ti-Nb [26]-have been sufficiently delineated. The isothermal sections at 1000 °C [27][28][29][30], 1100 °C [30,31], 1150 °C [28][29][30], 1200 °C [27,32], 1300 °C [33], and 1400 °C [28,29,34,35], from experimental data, are available in the literature. In addition, isopleth sections show the development of phase equilibria, such as the Ti72.5Al27.5-Nb [36], Ti78Al22-Nb [37], TiAl-TiNb [37,38], 45Al [25], 47Al [25], 8Nb [25,39], and 10Nb sections [39].…”