Some Slippage Issues in High-Pressure Torsion Using Cu and Ti Samples as an Example

Area of Science:

• Materials Science
• Mechanical Engineering
• Nanotechnology

Background:

• High Pressure Torsion (HPT) is a severe plastic deformation technique.
• Understanding deformation mechanisms, including slippage, is crucial for materials processing.
• Previous studies on HPT of pure Ti and Cu have not fully elucidated the role of slippage on microstructure evolution.

Purpose of the Study:

• To investigate the effect of slippage during High Pressure Torsion (HPT) on pure Ti and Cu.
• To analyze the relationship between slippage, revolutions, and microstructural changes.
• To explain the mechanisms behind strain accumulation despite observed slippage.

Main Methods:

• Utilized the "joint torsion of the disk halves" method to assess slippage.
• Employed Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) for microstructural analysis.
• Performed computer modeling using Deform 3D to simulate HPT conditions.

Main Results:

• Slippage initiates at early stages of HPT and intensifies with increasing revolutions (n).
• No significant torsional deformation was observed beyond n = 5 revolutions due to slippage.
• TEM/XRD revealed nanocrystalline structures in Ti and increased dislocation density from n = 5 to n = 10, despite slippage.
• Computer modeling indicated that anvil inclination leads to significant strain accumulation.

Conclusions:

• Slippage is a significant factor in HPT of pure Ti and Cu, limiting direct torsional deformation at higher revolutions.
• Nanocrystalline structures and increased dislocation density can still form even with substantial slippage.
• Anvil inclination is a plausible mechanism contributing to strain accumulation during HPT, even when surface slippage is dominant.