Transforming Grain-Boundary Brittle Precipitates to Ductility Pathways in Complex Concentrated Alloy

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Hard precipitates at grain boundaries (GBs) traditionally embrittle structural alloys, acting as crack initiation sites.
• Overcoming grain boundary embrittlement is crucial for developing advanced high-strength, high-ductility materials.

Purpose of the Study:

• To overturn the conventional understanding of grain boundary precipitates and their role in alloy embrittlement.
• To engineer interfaces at the atomic scale to transform brittle phases into pathways for ductility.
• To develop a generalizable materials design strategy for precipitation-strengthened alloys.

Main Methods:

• Utilized machine learning to identify a model complex concentrated alloy.
• Employed atomic-scale interfacial engineering and tailored thermomechanical processing.
• Fabricated compositionally and structurally graded interfaces (GIs).

Main Results:

• Successfully transformed intrinsically brittle GB phases into ductility pathways.
• Achieved sequential plasticity activation and coordinated deformation across GBs.
• Developed a ductile multi-phase alloy with a yield strength of ~1.2 GPa and ~20% total elongation.

Conclusions:

• Interfacial architecture enables a significant strength-ductility synergy, challenging the paradigm of GB embrittlement.
• The developed interfacial plasticity programming offers a generalizable strategy for designing advanced alloys.
• This approach provides a new pathway to overcome persistent challenges in precipitation-strengthened alloys.