Phase relations and crystal structure of τ6-Ti2(Ti(0.16)Ni(0.43)Al(0.41))3

Area of Science:

• Materials Science
• Crystallography
• Metallurgy

Background:

• The Ti-Ni-Al system is of interest for its complex phase behavior.
• Understanding novel intermetallic compounds is crucial for materials development.
• The τ(6) phase represents a new compound in the Ti-rich region of this system.

Purpose of the Study:

• To characterize the crystal structure of the novel τ(6) phase.
• To determine the phase equilibria and reaction temperatures for τ(6).
• To elucidate the formation and decomposition mechanisms of τ(6).

Main Methods:

• X-ray single crystal and neutron powder diffraction were used for structural analysis.
• Electron Probe Microanalysis (EPMA) and X-ray powder diffraction determined phase equilibria.
• Annealing and quenching experiments at controlled temperatures were performed.

Main Results:

• The crystal structure of τ(6)-Ti(2)(Ti,Ni,Al)(3) was solved (space group C2/m).
• τ(6) forms via a peritectoid reaction at 980 °C and decomposes eutectoidally at 870 °C.
• Phase equilibria involving τ(6) were established across various temperatures and summarized in a Schultz-Scheil diagram.

Conclusions:

• The novel τ(6) phase has been successfully identified and structurally characterized.
• Precise reaction temperatures for τ(6) formation and decomposition were determined.
• The established phase diagram provides a foundation for further research in the Ti-Ni-Al system.