Mechanical Size-Effects of Materials: Processing, Characterization and Modeling
May 12, 2008 — May 16, 2008
Coordinators:
- Christian Mitterer (University of Leoben, Leoben, Austria)
- Gerhard Dehm (Montanuniversitaet Leoben, Leoben, Austria)
Properties of materials are to a large extent determined by size-effects, resulting from the interaction of two length scales, i.e. the dimension characteristic of the physical phenomenon involved and the microstructural dimension of the material itself. Their interaction gives rise to various classic mechanisms well-known in materials science, e.g. Hall-Petch grain refinement, Taylor hardening or Orowan mechanism. Recent advances in micro- and nano-technology enabled the fabrication of miniaturized materials and components, e.g. in the form of thin films, multilayers and superlattices, nanocomposites, and nanowires, giving rise to the application of miniaturized components, micro- and nano-electromechanical systems, and superhard coatings. This ongoing miniaturization leads to dimensional constraints, which often superimpose the one of the microstructure, demanding a fundamental understanding of the effects involved.
The course “Mechanical Size-Effects of Materials: Processing, Characterization and Modeling” reviews the current understanding of plasticity, fracture, and fatigue of materials with small microstructural and / or geometrical dimensions. We cover materials from thin films, hard coatings to bulk micro- and nanocrystalline metals and composites and elucidate the origin of mechanical size-effects by bringing the different communities together. The course will first explain the different processing routes to obtain nanostructured / nanocrystalline materials and thin films. The origin of internal stresses and the process related microstructural evolution of the materials are discussed.
A central topic are the different methods to obtain mechanical data of the materials. Nanoindentation as well as novel synchrotron techniques and the benefit of in-situ straining / bending tests using electron microscopy are explained and compared to ex-situ tests.
Finally, the underlying deformation mechanisms are addressed in detail by modeling the mechanical response and by combining theoretical and experimental insights on dislocation plasticity and interface related deformation mechanisms (sliding, diffusion, …). Especially, the mechanism causing size-effects on the flow stress, fracture stress and strain, and on the fatigue lifetime will be taught.
The course is addressed to PhD students, researchers and industrial engineers, involved in material science, thin films (e.g. microelectronic, MEMS) or hard coatings, and mechanical engineering, interested in recent developments in mechanical size-effects.