Molecular dynamics study of nano-indentation deformation behavior of Al/AlSm nanolaminate.

CONTEXT

Molecular dynamics-based investigation has been carried out to simulate the nano-indentation loading in crystalline Al-amorphous AlSm metallic glass (MG) with an aim to investigate the effect orientation of crystalline-amorphous (C/A) interface orientation on the nano-indentation behavior of the C/A Al-AlSm nanolaminate for varying indenter speeds. Post-analysis techniques like adaptive-common neighbor analysis (a-CNA), atomic strain, dislocation extraction algorithm (DXA), and Voronoi polyhedral analysis (VP) have been employed to capture the structural evolution during simulated nano-indentation loading. C/A Al-AlSm nanolaminate with C/A interface orientated perpendicular to the indenter exhibits the presence of elastic regime followed by plastic curve, whereas load versus depth curve behaves plastically since the beginning in case of C/A Al-AlSm nanolaminate with C/A interface orientated parallel to the indenter. The dislocation density growth is slower in case of C/A Al-AlSm nanolaminate with C/A interface orientated perpendicular to the indenter attributed to the sinking of dislocations into MG counterpart of the nanolaminate, thereby triggering shear transformation zone activation. Whereas, the dislocation generation is delayed in case of C/A Al-AlSm nanolaminate with C/A interface orientated parallel to the indenter by virtue of amorphous AlSm MG coating on crystalline Al but is extensive and rapid. The disintegration of ICO-like structures and mixed clusters and growth of crystal-like clusters is discernible in C/A Al-AlSm nanolaminate with C/A interface orientated perpendicular to the indenter. On the other hand, the VP population exhibits cyclic variation in C/A Al-AlSm nanolaminate with C/A interface orientated parallel to the indenter. A transformation pathway of VPs has been mapped out for C/A Al-AlSm nanolaminate under nano-indentation loading.

METHODS

The simulations have been carried out by employing Molecular Dynamics using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) platform. Post-analysis techniques like adaptive-common neighbor analysis (a-CNA), atomic strain, dislocation extraction algorithm (DXA), and Voronoi polyhedral analysis (VP) have been employed to capture the structural evolution during simulated nano-indentation loading.