The Promise of Nanocrystalline Metals

ARL – Thermo-Kinetic Stabilized Grain and Phase Boundary Stabilized Bulk Nano-Crystalline solids

These alloys were designed utilizing thermo-kinetic stabilization, where thermodynamic and kinetic approaches are combined to achieve synergistic effects and maximize the stability of the nanocrystalline structure. By employing thermodynamic modifications, the driving force for grain growth is reduced, creating a more favorable energy landscape for stabilization. Simultaneously, kinetic barriers are introduced to further impede grain boundary motion, limiting the growth and coarsening of grains.

Thermodynamic stabilization focuses on modifying the material’s composition or microstructure to lower the driving force for grain growth. This can be achieved by incorporating alloying elements or impurities that alter the grain boundary energy. By selecting appropriate compositions and concentrations, the thermodynamic stability of the nanocrystalline structure can be improved. Kinetic stabilization, on the other hand, aims to hinder grain growth by introducing obstacles that impede the movement of atoms and restrict the motion of grain boundaries. This can be accomplished through techniques such as introducing impurity segregation or incorporating ordered phases or precipitates through severe plastic deformation.

The combined effect is an unprecedented level of stability is imparted into the alloys which enables these copper-based alloys to be operated at near melting temperature with an extremely stable microstructure as compared to any other structural materials.  The alloys exhibit mutually exclusive and drastically deviating properties which allows them to manifest near perfect creep resistance, exhibit yield strengths on para with high strength steels, be immune to the damage created during intense radiation, shock loading events and cyclic fatigue all while exhibiting high thermal and electrical conductivity. Such distinctive properties have significant consequences as they will enable highly conductive and convective copper-based alloys to be used in various high-temperature applications such as heat exchangers for next generation power plants and high-temperature inlet guide veins of propulsion systems and many other extreme applications where Cu alloys have never been considered as viable options.