- Dr. Jinming Guo, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Austria
The usually immiscible composites in thermodynamic equilibrium condition can be forced into a metastable supersaturated state through deformation, which has received enormous scientific attention in recent decades. Severe plastic deformation processing has unique advantages, inducing dissolution of second phases and considerable grain refinement down to the nanometer range. The as-generated materials have various processing-induced nanostructural features such as deformation twins, nonequilibrium grain boundaries, dislocation substructures, vacancy agglomerates, solute segregation, and clusters. By specifically designing and controlling these features, many nanocrystalline materials show extraordinary mechanical and electrical properties compared with their coarse-grained counterparts.
To understand these phenomena in nanocrystalline alloys, two cases of copper-chromium and copper-iron systems were produced and investigated. The results revealed the related deformation-induced phenomena and mechanisms at the atomic scale through use of advanced transmission electron microscopy, and insights were gained into the oxygen behaviors in severely deformed nanocrystalline alloys. The findings provided direct observations of oxide formation and offered a pathway for the design of nanocrystalline materials strengthened by oxide dispersions.