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A new continuum model for metallic glass based on thermodynamics

Xiaoding Wei's picture

My group at Peking University proposed a novel mechano-chemical continuum model based on the framework of thermodynamics that can describe the microstructural evolution in metallic glass, and connect it with the macroscopic plastic deformation. The model successfully simulated the shear band instability and dilatancy effects of metallic glass under uniaxial tension and simple shear. Furthermore, the model discovers that the transition of the creep behavior of metallic glass under low and high-stress levels is associated with two different atomic diffusion mechanisms that driven by thermal energy gradient and strain energy gradient, respectively (Figure 1). At low stresses, the creep is accompanied by atom flows along the concentration gradient, and the material tends to be more uniform; while at high stresses, the creep is accompanied by atom flows along the strain energy gradient, and the structural heterogeneity gradually strengthens until the material becomes unstable. The new continuum constitutive theory helps the understanding of the relationship between the microstructure and macroscopic properties in metallic glass and other amorphous systems. This work has been published in Journal of the Mechanics and Physics of Solids (https://doi.org/10.1016/j.jmps.2020.104216). 

 

Figure 1. Top: different atomic kinetics during the creep of metallic glasses. At low stresses, atoms move from large-free-volume (loose) regions to small-free-volume (dense) regions. At high stresses, however, atoms move from the loose regions to the dense regions. Bottom: Nucleation and formation of a major shear band in metallic glass under uniaxial tension.

 

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