Mapping Shear Bands in Metallic Glasses: From Atomic Structure to Bulk Dynamics.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Understanding shear banding mechanisms is crucial for enhancing metallic glass mechanical properties.
• Previous atomistic simulations indicated the importance of nanoscale stresses and strains, but experimental evidence was limited.
• Advanced characterization techniques are needed to validate simulation findings.

Purpose of the Study:

• To quantitatively map the atomic density and strain distribution within individual shear bands at high resolution.
• To provide experimental proof for nanoscale phenomena influencing shear banding.
• To establish a comprehensive understanding of shear band formation and propagation in metallic glasses.

Main Methods:

• Utilizing precession nanodiffraction mapping in a transmission electron microscope.
• Achieving a spatial resolution of 2 nm for atomic density and strain mapping.
• Integrating experimental findings with molecular dynamic simulations.

Main Results:

• Demonstrated density alternation within shear bands from atomic to submicron scales.
• Revealed complex strain fields leading to shear band segmentation and deflection.
• Identified autocatalytic generation of shear transformation zones at the atomic scale.
• Observed density alternation at the submicron scale due to shear band propagation, creating strained regions in the surrounding matrix.

Conclusions:

• The study provides a complete picture of shear band formation and propagation by combining experimental and simulation data.
• Atomic-scale density alternation explains shear transformation zone generation.
• Submicron-scale density variations elucidate shear band propagation and interaction with the matrix.
• The findings are fundamental for improving the mechanical performance of metallic glasses.