NON-EQUILIBRIUM PROCESSING ROUTES FOR ULTRAFINE GRAINED OR NANOSTRUCTURED MATERIALS

摘要

The sequential combination of different processing routes that drive a material to a different extent -, with different rates - and by different means from thermodynamic equilibrium present new and attractive processing opportunities to obtain bulk nanocrystalline or massive ultrafine grained materials that are widely unexplored. More specifically, processing routes based on rapid quenching or plastic deformation have been combined such that the initial state is continuously energized and successively driven farer away from thermodynamic equilibrium. Here, different deformation methods with largely different strain and pressure levels have been applied on rapidly quenched metallic glasses, but also on elemental sheet samples. Both processing routes result in a nanocrystalline microstructure with remarkable properties, especially with respect to strength and hardness. The basic underlying mechanisms that lead to ultrafine grained or nanocrystalline microstructures are discussed and the current state of nanostructure control is highlighted by selected examples.