Abstract
Nanocrystalline (NC) materials are considered the next frontier for lightweighting from a metallurgical standpoint, because reducing crystal size to the nanoscale increases material strength and, in turn, potentially reduces material thickness and weight requirements for structural components. However, NC materials coarsen even at low homologous temperatures, leading to a loss of mechanical and functional properties and limiting their suitability for structural applications. Using a mechanical alloying process to develop NC-microparticles (MPs), we establish a thermodynamic strategy that addresses this thermal instability by doping a host NC multicomponent alloy solvent with a solute that prefers to decorate grain boundaries (GBs) rather than remain in the grain interior—a process that effectively offsets the excess energy at GBs that drives coarsening. The careful selection of this solute involves breaking an age-long, well-established rule in the field of metallurgy. To enhance splatting, flattening, and bonding of NCMPs during solid-state cold-spray additive manufacturing, another scaling law is intentionally broken. This is followed by heat treatment of the consolidated parts to develop bulk-stable, GB-decorated multicomponent alloys beyond the electrodeposition thickness limit to which the field is accustomed. This approach ensures that the stable nanocrystalline structure of NC multicomponent alloys is retained after consolidation. Taken together, this work represents a significant advance in tailoring NC multicomponent alloys for structural applications.