On the origin and universality of dislocation creation and void nucleation in FCC ductile metals

TL;DR

This study uses molecular dynamics and theoretical analysis to elucidate the universal mechanisms of dislocation creation and void nucleation in FCC ductile metals during tensile deformation.

Contribution

It reveals the detailed three-stage process of dislocation formation and the two-stage void nucleation mechanism, demonstrating their universality across FCC metals with low stacking fault energy.

Findings

Dislocations form via activation of FOSs, stacking of defect clusters, and slip-induced fault creation.

Void nucleation involves vacancy string formation and transformation into voids.

The mechanisms are universal for FCC ductile metals with low stacking fault energy.

Abstract

We clarify via molecular dynamic simulations and theoretical analysis the origin of dislocation creation and void nucleation during uniaxial tensile process in face-centered-cubic (FCC) ductile metals. We show that the dislocations are created through three distinguished stages: (i) Flattened octahedral structures (FOSs) are randomly activated by thermal fluctuations; (ii) The double-layer defect clusters are formed by self-organized stacking of FOSs on the close-packed plane; (iii) The stacking faults surrounded by the Shockley partial dislocations are created from the double-layer defect cluster due to the relative slip of internal atoms. Whereas, the void nucleation is shown to follow a two-stages description: (i) The vacancy strings are first formed by intersection of different stacking faults; (ii) Then the vacancy strings transform into the voids by emitting dislocations. We demonstrate that our findings on the origin of dislocation creation and void nucleation is universal for a variety of FCC ductile metals with low stacking fault energy.