October 4-9, 2015
It is well known that the grain boundaries (GBs) act as a barrier for dislocation motion (Clark 1992), leading to the well-known strength increase with reduced grain size, as explained by the Hall-Petch relation. Unfortunately the strength increase often leads to a reduction of ductility, except one example: Nano-twinned microstructures. The twin-boundary (TB) dislocation interaction is still not thoroughly understood (Imrich 2014, Gumbsch 2006).
Recent developments in deforming micron sized samples on synchrotron beamlines allow to study the interplay of the single dislocation with a specific grain boundary. In present work we conduct in situ compression on micron-sized copper specimens with differently oriented coherent Σ3 twin boundaries. The samples were grown by the Bridgman method and subsequently fabricated using FIB milling. The in situ Laue microdiffraction experiments (µLaue) were performed on BM32 at the ESRF synchrotron light source. The experiments allow a clear insight into the stress state, and the density and type of geometrically necessary dislocations stored inside the material during compression. The complementary in situ scanning electron microscope (SEM) experiments further allow to analyze slip transfer by slip step analysis.
The discussion will concentrate on the dislocation transmission mechanism through the TB and the necessity to store dislocations in some specific loading directions as against others.
Clarck W.A.T., Wagoner, R.H., Shen, Z.Y. (1992): On the criteria for slip transmission across interfaces in polycrystals – In: Scripta Metallurgica et Materialia, 26, 203-206. Imrich P.J, Motz C.,Dehm G., Kirchlechner C. (2014): Differences in deformation behavior of bicrystalline Cu micropillars containing a twin boundary or a large-angle grain boundary – In: Acta Materialia, 73, 240-250. Jin Z.-H.,Gumbsch P., Ma E., Albe K., Lu K., Hahn H., Gleiter H.(2006): The interaction mechanism of screw dislocations with coherent twin boundaries in different face-centered cubic metals – In: Scripta Materialia, 54, 1163-1168.