Microstructure evolution in surface textured materials under reciprocating tribological loading
Sarah Becker1, Christian Greiner1
1 Karlsruhe Institute of Technology,
Institute for Applied Materials,
Kaiserstrasse 12, 76131 Karlsruhe, Germany
Correlating the microstructure of a material with its properties is one of the most central questions in materials science and engineering. An emerging field in material science is tribology. For sliding interfaces, there is a significant lack of knowledge about the mechanics for the microstructure evolution. As tribological contacts have significant industrial relevance, gaining more knowledge about the materials science governing friction and wear will have wide spread impact . The initial phase in the life of a tribosystem is known as ‘running-in’ , during which a mechanically altered layer grows into the material. This layer has often nanocrystalline character . Experiments have provided that the majority of the plastic deformation during sliding is carried by dislocation movement [1,2]. This leads to an increase in dislocation density and to a decrease in grain size .
An ideal method to understand this evolution is to use samples with a morphological surface texture. We will concentrate on model materials like oxygen-free high-purity copper structured with a membrane-like texture. These copper specimens are in contact with a sapphire disc. The experiment runs in reciprocating motion.
One of these geometry parameters we systematically varied is the aspect ratio.
We will present how, with increasing the aspect ratio, an annealed microstructure is transformed into a nanocrystalline surface layer. We follow this evolution with scanning electron and focused ion beam microscopy. The calculation of the elastic strains will be based on the friction data telling us the static and dynamic friction forces deforming the membranes. Correlating the elastic and plastic behavior with the microstructure evolution depending on size effects, energetic and mechanistic considerations, the goals will be the formulation of a model description in order to understand these changes and their influence on tribological properties.
 Holmberg K, Andersson P, Erdemir A, Tribology International 47, 221-234 (2012).
 Blau P, Journal of Materials Engineering 13(1), 47-53 (1991).
 Dienwiebel M, Scherge M, in Fundamentals of Friction and Wear, Springer, 549-560 (2007).