Low-energy, Mobile Grain Boundaries in Magnesium

Area of Science:

• Materials Science
• Crystallography
• Computational Materials Science

Background:

• Magnesium alloys commonly develop strong basal texture during rolling and annealing.
• Understanding the atomic structure of grain boundaries (GBs) is crucial for explaining this texture.

Purpose of the Study:

• To investigate the atomic-level dislocation structures of <0001> tilt and twist grain boundaries in magnesium.
• To elucidate the role of these GBs in the formation of basal texture during magnesium alloy processing.

Main Methods:

• Analysis of symmetrical tilt and twist GBs across a range of rotation angles (0°-60°).
• Application of grain boundary dislocation models.
• Molecular dynamics simulations to explore GB mobility.

Main Results:

• Ordered atomic structures were identified for both tilt and twist GBs.
• 30° tilt and twist GBs correspond to energy minima.
• 30° tilt GBs feature Shockley partial dislocations; 30° twist GBs exhibit stacking faults.
• Molecular dynamics revealed high mobility of 30° GBs due to collective Shockley partial dislocation glide.

Conclusions:

• The observed ordered atomic structures and high mobility of 30° tilt and twist GBs are key factors in the development of strong basal texture in magnesium alloys.
• These findings provide atomic-level insights into grain growth mechanisms in Mg alloys.