Anomalous size effect on yield strength enabled by compositional heterogeneity in high-entropy alloy nanoparticles

Area of Science:

• Materials Science
• Metallurgy
• Nanotechnology

Background:

• High-entropy alloys (HEAs) are typically considered random solid solutions.
• Recent findings reveal nanoscale compositional heterogeneity in HEAs.
• This heterogeneity can significantly influence material properties.

Purpose of the Study:

• To investigate the impact of compositional heterogeneity in HEAs on their mechanical properties.
• To explore the size-dependent mechanical behavior of HEAs.
• To understand the underlying mechanisms of observed size effects.

Main Methods:

• In situ compression testing within a transmission electron microscope (TEM).
• Molecular dynamics (MD) simulations at the atomic scale.
• Analysis of compositional variations and deformation mechanisms.

Main Results:

• An anomalous size effect on yield strength was observed in HEAs.
• HEAs initially show a
• smaller-is-stronger
• size effect, typical of conventional materials.
• Below a critical size (~180 nm), a
• smaller-is-weaker
• effect emerges due to nanoscale compositional fluctuations.
• Deformation transitions from homogeneous to heterogeneous planar slip.

Conclusions:

• Nanoscale compositional heterogeneity is a key factor in HEA mechanical behavior.
• Controlling local compositional variations can tune HEA properties.
• The study reveals a transition in size effect governed by material heterogeneity.