Capture Deformation Twinning in Mg during Shock Compression with Ultrafast Synchrotron X-Ray Diffraction

Area of Science:

• Materials Science
• Mechanics of Materials
• Crystallography

Background:

• Deformation twinning is crucial for plastic deformation in hexagonal-close-packed (hcp) metals.
• Mechanisms of twinning under high strain rate shock compression remain poorly understood.

Purpose of the Study:

• To investigate the mechanisms of deformation twinning in shock-compressed magnesium (Mg), a representative hcp metal.
• To elucidate the role of shock compression and release on twinning behavior in Mg.

Main Methods:

• In situ, ultrafast synchrotron X-ray diffraction was employed to observe deformation twinning.
• Magnesium (Mg) was subjected to high strain rate shock compression.

Main Results:

• Extension twinning was observed along specific crystallographic directions (⟨112[over ¯]0⟩ and ⟨101[over ¯]0⟩) during shock compression.
• Twinning occurred only upon release for loading along the ⟨0001⟩ direction.
• The observed deformation mechanisms are attributed to the polarity of deformation twinning, influenced by resolved shear stress.

Conclusions:

• Deformation twinning in Mg under shock compression exhibits polarity dependent on loading direction and stress magnitude.
• These findings provide critical insights into the plastic deformation mechanisms of hcp metals at high strain rates.
• The identified mechanisms may be applicable to magnesium and its alloys across various strain rates.