Plasticity in brittle intermetallics enabled by framework of amorphous interfaces and preexisting dislocations.

Abstract

Intermetallics are highly attractive for their exceptional strength and high melting points, offering significant potential as advanced structural materials. However, their inherent brittleness at room temperature severely limits practical applications. In this work, we introduce a structure of framework of amorphous interfaces (FAIs) and preexisting dislocations into nanocrystalline (NC) CoAl intermetallics to synergistically enhance both strength and plasticity. Micropillar compression tests reveal a high yield strength exceeding 6 gigapascals, a sustained work hardening to approximately 8.5 gigapascals, and a compressive plastic strain exceeding 15%. The FAIs accommodate the plastic deformation of NC CoAl grains, preventing intergranular fracture while promoting dislocation emission and propagation into CoAl through deformation-induced crystallization. Molecular dynamics (MD) simulations confirm that dislocations are emitted from crystalized regions (BCC-like local motifs) and reveal that preexisting dislocations impede dislocation motion via interactions and multiplication, promoting dislocation storage. Together, these mechanisms enable enhanced work hardening and large plasticity. This strategy offers an approach to achieving room temperature plasticity in brittle materials, which often show limited dislocation activity.