Microstructure and Texture Evolution during Superplastic Deformation of SP700 Titanium Alloy

Area of Science:

• Materials Science
• Metallurgy
• Physical Metallurgy

Background:

• Superplasticity in titanium alloys is crucial for advanced manufacturing.
• Understanding deformation mechanisms is key to optimizing alloy performance.
• SP700 (Ti-4.5Al-3V-2Mo-2Fe) is a titanium alloy with potential for superplastic applications.

Purpose of the Study:

• To investigate the superplastic tensile deformation mechanism of SP700 titanium alloy at 760 °C.
• To correlate microstructure evolution with deformation behavior.
• To determine the primary deformation mechanism responsible for superplasticity.

Main Methods:

• Superplastic tensile testing of SP700 alloy at 760 °C using the maximum m value method.
• Microstructural characterization using electron microscopy and crystallographic analysis.
• Analysis of elemental diffusion and dislocation accumulation during deformation.

Main Results:

• SP700 alloy demonstrated exceptional superplasticity with a fracture elongation of 3000% and a fine grain size of ~1.3 μm.
• Increased strain led to grain growth, increased β phase fraction, and diffusion of β-stabilizing elements (Mo, Fe, V) into the β phase.
• Dislocation accumulation resulted in a 15% increase in low-angle grain boundaries, accompanied by grain rotation and texture changes.

Conclusions:

• Phase boundary (α/β) sliding, accommodated by dislocation slip, is the predominant mechanism for superplastic deformation in SP700 alloy.
• Microstructural evolution, including grain growth and phase transformation, plays a significant role in achieving high superplasticity.
• The study provides insights into the deformation mechanisms governing superplasticity in advanced titanium alloys.