Heterogeneous lattice strain strengthening in severely distorted crystalline solids

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Multi-principal element alloys (MPEAs) show exceptional mechanical properties due to severe lattice distortion, differing from traditional alloys.
• The mesoscopic physics governing dislocation activities for strength-ductility synergy in MPEAs remains poorly understood.
• Eshelby mean-field theories are inadequate for analyzing yielding and plasticity in highly distorted crystalline solids.

Purpose of the Study:

• To investigate the strengthening mechanisms responsible for the strength-ductility synergy in MPEAs at the mesoscopic scale.
• To explore the role of heterogeneous strain fields in influencing dislocation behavior and mechanical properties.
• To develop a simulation approach that accounts for experimentally measured lattice strain.

Main Methods:

• Developed a three-dimensional discrete dislocation dynamics (DDD) simulation approach.
• Incorporated experimentally measured lattice strain fields from a model FeCoCrNiMn MPEA.
• Analyzed dislocation behaviors, including kinks, jogs, and cross-slips, under heterogeneous strain conditions.

Main Results:

• Identified unusual dislocation behaviors such as multiple kinks/jogs and bidirectional cross slips.
• Demonstrated that heterogeneous lattice strain is a key factor in MPEA strengthening.
• Revealed the underlying mechanisms for the observed strength-ductility synergy in MPEAs.

Conclusions:

• Heterogeneous lattice strain in MPEAs induces unique dislocation dynamics that enhance both strength and ductility.
• The developed DDD approach provides critical insights into designing robust and ductile crystalline materials.
• Findings are applicable to high-entropy alloys and ceramics, guiding future materials design.