Understanding the mechanisms of amorphous creep through molecular simulation

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Metallic glasses exhibit complex creep behavior under stress.
• Understanding atomic-level deformation mechanisms is crucial for material design.

Purpose of the Study:

• To simulate and elucidate molecular creep processes in metallic glass thin films.
• To explain the stress-dependent creep rate and map deformation regimes.

Main Methods:

• Metadynamics-based atomistic simulations at experimental timescales.
• Analysis of atomic strains and nonaffine displacements.
• Nanoscale spatial and sub-second temporal resolution.

Main Results:

• Mechanistic explanation for the variation of creep rate with stress.
• Construction of a deformation map distinguishing diffusional and deformational creep.
• Identification of nonlinear coupling between diffusion and shear deformation via dynamic heterogeneity.

Conclusions:

• Validated two models of amorphous plasticity: free volume diffusion and stress-induced shear.
• Demonstrated the interplay of atomic diffusion and shear deformation in metallic glass creep.
• Highlighted the role of dynamically heterogeneous fluctuations in out-of-equilibrium systems.