Comparative study on twinning characteristics during two post-weld compression paths and their effects on joint...

Area of Science:

• Materials Science
• Metallurgy
• Welding Engineering

Background:

• Friction stir welding (FSW) is a key joining technology for magnesium (Mg) alloys.
• Complex texture distribution in the stir zone (SZ) of FSWed Mg alloys often compromises joint performance.
• Tailoring texture is crucial for improving the mechanical properties of Mg alloy joints.

Purpose of the Study:

• To investigate the effect of post-weld compression along different directions on texture evolution in the SZ of FSWed AZ31 Mg alloy.
• To analyze the twinning behavior and its impact on the joint performance.
• To understand the underlying mechanisms of texture modification and strengthening.

Main Methods:

• Friction stir welding of AZ31 Mg alloy plates.
• Post-weld compression deformation along the normal direction (ND) and welding direction (WD).
• Electron back scatter diffraction (EBSD) for texture and twinning analysis.
• Schmid factor (SF) analysis for basal slip and extension twinning.

Main Results:

• Post-weld compression along ND induced profuse extension twins throughout the SZ.
• Compression along WD resulted in extension twins primarily on the SZ-side.
• Twin bands/chains formed, with orientations related to twin variant habit planes.
• ND compression demonstrated superior strengthening effects compared to WD compression.

Conclusions:

• Post-weld compression is an effective method for tailoring SZ texture in FSWed Mg alloys.
• ND compression promotes more uniform and beneficial twin formation, leading to enhanced joint properties.
• Understanding twinning behavior and its relation to applied stress is key to optimizing FSW joint performance in Mg alloys.