Experimental phase diagram study of the TiAl-rich part of the Ti–Al–Ni ternary system

• Published in: Calphad Vol. 80; p. 102521
• Main Authors: Nakashima, Hirotoyo, Yu, Jianhui, Takeyama, Masao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-03-2023
• Subjects: Isothermal sections; Phase equilibria; Ti–Al–Ni; Phase equilibria; Isothermal sections; Ti–Al–Ni
• ISSN: 0364-5916; 1873-2984
• DOI: 10.1016/j.calphad.2022.102521

Phase equilibria of the TiAl-rich part of the Ti–Al–Ni ternary system have been studied experimentally by scanning electron microscopy and electron probe micro-analysis of heat-treated alloys. Partial isothermal sections involving the liquid, β-Ti, α-Ti, α2-Ti3Al, γ-TiAl and τ3-Al3NiTi2 phases were constructed between 1623 and 1273 K. Eight three-phase regions of the L + β + α, L + α + γ, L + β + γ, β + α + γ, L + β + τ3, β + γ + τ3, β + α2 + τ3 and α2 + γ + τ3 were derived. Extrapolations of these tie-triangles indicate the occurrence of three transition-type reactions; L + α = β + γ at around 1593 K, L + γ = β + τ3 at around 1553 K, and β + γ = α + τ3 at around 1393 K. The Ni solid solubility in the α and α2 phase is extremely low, less than 1 at.% in all studied temperature ranges.
•Partial isothermal sections of the TiAl-rich part were experimentally determined at 1623, 1598, 1573, 1473, 1373, and 1273 K.•Three invariant reactions were deduced from the temperature change in the phase relations.•The α and α2 phases exhibit considerably small Ni solubility, less than 1 at.% in the studied temperature range.