Stacking fault energy in concentrated alloys

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Stacking fault energy (SFE) is a critical parameter in pure metals but complex in concentrated alloys.
• Traditional models assume a unique SFE and equilibrium dislocation dissociation, often conflicting with experimental data and simulations.
• The local atomic environment in alloys creates a distribution of SFE values.

Purpose of the Study:

• To investigate the meaning of SFE and dislocation dissociation assumptions in concentrated alloys.
• To explore the influence of local atomic environments and solute-dislocation interactions on dislocation behavior.
• To evaluate the reliability of conventional SFE measurement techniques in concentrated alloys.

Main Methods:

• Atomistic simulations were employed on a model NiCo alloy across various compositions.
• Dislocation dissociation processes were studied at low temperatures for positive, zero, and negative average SFE.
• Decorrelation stress was computed to analyze the balance of forces on partial dislocations, considering local SFE effects.

Main Results:

• A stable, finite dislocation splitting distance was observed in all simulated cases, regardless of average SFE.
• The force balance on partial dislocations could not be explained by SFE distribution alone in some instances.
• The interaction between dislocations and the local solute environment emerged as a dominant resisting force.

Conclusions:

• In concentrated alloys, SFE is a distribution, not a single value, influenced by local atomic environments.
• Solute-dislocation interactions are a major factor in dislocation behavior, often neglected in traditional analyses.
• Experimental SFE measurements in concentrated alloys are unreliable due to the significant, unmeasured solute-dislocation interaction effects.