Structure and size of the plastic zone formed during nanoindentation of a metallic glass

TL;DR

This study uses molecular dynamics simulations to analyze the size and structure of the plastic zone during nanoindentation of a metallic glass, revealing it is smaller and more homogeneous than in crystalline materials.

Contribution

It provides detailed insights into the plastic zone characteristics in metallic glasses, highlighting differences from crystalline substrates and introducing the plastic-zone size factor.

Findings

Plastic zone in metallic glasses is significantly smaller than in crystals.

The plastic-zone size factor in metallic glasses is around 1.

Homogeneous deformation causes the small plastic zone in metallic glasses.

Abstract

Using molecular dynamics simulation, we study the plastic zone created during nanoindentation of a large CuZr glass system. The plastic zone consists of a core region, in which virtually every atom undergoes plastic rearrangement, and a tail, where the density distribution of the plastically active atoms decays to zero. Compared to crystalline substrates, the plastic zone in metallic glasses is significantly smaller than in crystals. The so-called plastic-zone size factor, which relates the radius of the plastic zone to the contact radius of the indenter with the substrate, assumes values around 1, while in crystals -- depending on the crystal structure -- values of 2--3 are common. The small plastic zone in metallic glasses is caused by the essentially homogeneous deformation in the amorphous matrix, while in crystals heterogeneous dislocations prevail, whose growth leads to a marked extension of the plastic zone.