Excitements and Challenges in Advanced Materials Research by Non-Equilibrium Processing

Advanced materials such as nanocrystalline materials, bulk metallic glasses have attracted the attention of both academicians and industrialists in recent decades. There are a number of routes for the synthesis of these materials. One of these is high energy ball milling or high kinetic energy processing. This is a non-equilibrium processing route, which can lead to materials that are significantly far from their equilibrium configuration, and thus can have significantly different properties in comparison to conventional materials. In fact, it is possible that in case of nanocrystalline materials, those synthesized by this route can have different properties from those prepared from other routes, though their grain size is the same, due to the differences in the nature and density of defects present. Similarly, amorphous materials and high entropy alloys synthesized by this route could have different structure and hence properties from those developed from other routes. This not only gives opportunities to develop materials with exciting properties by this route but also can take us deeper into the understanding of the behavior of materials far from equilibrium. Rapid solidification processing is another non equilibrium processing route that can lead to nanocrystalline materials either directly from the liquid or by controlled devitrification of the metallic glasses.

Nanocrystalline materials have been successfully synthesized in a number of systems by the above two routes by the group of the speaker. Al based nanocomposites with L1₂-Al₃(Ti,Zr) and Al₃Fe with exceptionally high hardness of 12GPa (equivalent to an yield strength of 4GPa) have been successfully synthesized by MA. Cu based nanocomposites with high strength levels and good conductivity have been synthesized by this route for developing strong conductors. High melting refractory metals such as W can be easily sintered at as low temperatures as 1500°C by converting them into nanocrystalline form by this route. Even functional materials such as hard-soft magnetic nanocomposites and magneto-electric nanocomposites with exceptional properties can be synthesised by this route. The potential of the rapid solidification processing for the development of nanocomposites with excellent mechanical properties in Al, Fe, Mg and Zr based systems with also be discussed. The present talk will deal with the excitements and challenges in this field based on the research being carried out at the laboratory of the speaker.