Amorphous intergranular films as toughening structural features

Abstract

The ability of amorphous intergranular films to mitigate damage formation at grain boundaries is studied with molecular dynamics simulations. We find that such films can alter both crack nucleation and crack growth rates by efficiently absorbing dislocations, with thicker films being more effective sinks. Local plastic strain brought by incoming dislocations is diffused into a triangular region within the amorphous film and is accommodated by a flow of boundary atoms which resembles a vortex shape; this vortex grows inside of the amorphous intergranular film as more dislocations are absorbed until it reaches the opposite amorphous-crystalline interface, after which cracks can finally be nucleated. Even after nucleation, these cracks grow more sluggishly in an amorphous intergranular film than they do along a clean grain boundary, since the driving force for crack growth is lower in the amorphous film. The results presented here suggest that amorphous intergranular films can act as toughening features within a microstructure, and thus are promising for designing nanostructured materials with better ductility and fracture toughness.

Molecular dynamics study of deformation behavior of crystalline Cu/amorphous Cu 50 Zr 50 nanolaminates

“…The reason for choosing the orientation is here that the resolved shear stress is highest on the slip plane and dislocations can be driven towards the interface[33]. Tensile deformation of the nanolaminates with various layer thicknesses ranging from 1 nm to 10 nm is simulated to investigate size effects.…”

Effect of grain boundary character on segregation-induced structural transitions

“…On the other hand, disordered intergranular films may potentially improve the ductility of nanocrystalline materials by facilitating grain boundary sliding [13,14] and by efficiently suppressing crack nucleation and growth induced due to repeated dislocation adsorption at grain boundaries [15,16]. Since complexions offer interesting opportunities for materials design and optimization, the thermodynamics associated with complexion transitions are of great interest.…”

High-Temperature Stability and Grain Boundary Complexion Formation in a Nanocrystalline Cu-Zr Alloy

“…42 However, complexions are not always deleterious to mechanical properties. Molecular dynamic simulations by Pan and Rupert 43,44 on…”