Gradient Microstructure Induced by Surface Mechanical Attrition Treatment in Grade 2 Titanium Studied Using Positron...

Area of Science:

• Materials Science
• Metallurgy
• Surface Engineering

Background:

• Grade 2 titanium is widely used in various industrial applications.
• Surface properties significantly influence material performance, especially in corrosive environments.
• Surface mechanical attrition treatment (SMAT) is a method for modifying surface microstructure.

Purpose of the Study:

• To investigate the microstructural alterations in grade 2 titanium induced by SMAT.
• To characterize the types and distribution of lattice defects introduced by SMAT.
• To evaluate the impact of SMAT on the corrosion resistance of titanium in a saline environment.

Main Methods:

• Positron annihilation lifetime spectroscopy (PALS) was employed to detect and quantify lattice defects.
• Complementary methods, including microhardness testing, were used for characterization.
• Electrochemical impedance spectroscopy (EIS) assessed corrosion resistance in a saline solution.

Main Results:

• SMAT introduced significant lattice defects, evidenced by an increased mean positron lifetime.
• PALS revealed the presence of vacancy clusters (approximately 3-4 vacancies) and dislocations.
• Dislocation density decreased with depth, while vacancy cluster concentration increased, correlating with microhardness changes.
• SMAT improved the corrosion resistance of titanium, even after the removal of the as-formed oxide layer.

Conclusions:

• SMAT effectively modifies the microstructure of grade 2 titanium by introducing vacancy clusters and dislocations.
• The defect structure induced by SMAT enhances the corrosion resistance of titanium in saline environments.
• The findings suggest SMAT is a promising surface treatment for improving the durability of titanium components.