Superplastic Behavior and Microstructural Features of the VT6 Titanium Alloy with an Ultrafine-Grained Structure...

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Superplasticity in titanium alloys is crucial for advanced manufacturing.
• Ultrafine-grained (UFG) structures enhance mechanical properties.
• Equal-channel angular pressing (ECAP) is a key technique for UFG material production.

Purpose of the Study:

• To investigate the superplastic behavior of VT6 titanium alloy with an UFG structure.
• To determine the influence of temperature and strain rate on superplasticity.
• To analyze microstructural evolution and phase formation during deformation.

Main Methods:

• Deformation via upsetting at temperatures of 650-750 °C and strain rates of 1 × 10^-4-5 × 10^-1 s^-1.
• Calculation of apparent activation energy to understand deformation mechanisms.
• Microstructural analysis using electron microscopy to observe grain structure and phase evolution.

Main Results:

• Observed increased strain-rate sensitivity (m) under specific deformation conditions.
• Calculated apparent activation energy for superplastic flow between 160-200 kJ/mol.
• Identified preservation of UFG structure at 650-700 °C, with recrystallization and grain growth at higher temperatures or lower strain rates.
• Observed diffusion-controlled formation of α₂-phase plates within a specific temperature and strain-rate range.

Conclusions:

• Superplastic behavior in UFG VT6 alloy is dependent on temperature and strain rate, influencing relaxation processes.
• A transition from grain-boundary sliding to bulk diffusion mechanisms occurs when superplasticity is impeded.
• The formation of α₂-phase plates affects the alloy's mechanical properties, warranting further investigation.