Electron microscopy study on a new phase in beta-titanium alloys aged at a high temperature

Area of Science:

• Materials Science
• Metallurgy
• Titanium Alloys

Background:

• Titanium-molybdenum (Ti-Mo) alloys are crucial in various industrial applications.
• Understanding phase transformations in these alloys is essential for optimizing their properties.
• Previous studies have focused on specific aging conditions and resulting microstructures.

Purpose of the Study:

• To investigate the phase evolution in Ti-20mass%Mo alloys under a two-step aging treatment.
• To identify and characterize a newly observed phase during this process.
• To explore the relationship between the new phase and the existing beta-phase structure.

Main Methods:

• Two-step aging of Ti-20mass%Mo alloys at 623K and 823K.
• Dark-field imaging for phase observation.
• Compositional analysis of the newly discovered phase.
• High-resolution electron microscopy (HREM) for atomic structure determination.

Main Results:

• A novel phase was observed in Ti-20mass%Mo alloys after two-step aging.
• The new phase replaced the previously formed beta-phase crystals during the second aging step.
• The formation of the new phase is intrinsically linked to the beta-phase structure.
• Similar new phases were identified in other titanium alloy types under high-temperature aging.

Conclusions:

• A new phase forms in Ti-20mass%Mo alloys, replacing the beta-phase during specific aging protocols.
• The study provides insights into the complex phase transformations occurring in titanium alloys.
• Further investigation using HREM is needed to fully elucidate the atomic structure of this new phase.