MSE 2016 - Full Program

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Highlight Lecture

Slip transfer through coherent Sigma 3 (111) twin boundaries loaded in different crystallographic direction: Insights by Laue microdiffraction

Tuesday (27.09.2016)
10:45 - 11:00
Part of:

Grain boundaries (GBs) are among the most relevant internal defects which strengthen polycrystalline materials by acting as an obstacle for the dislocation motion. Apart from this, it has been recognized that GB may absorb [1] and transmit [2] dislocation. The determining factor in all these phenomena is the grain boundary character which plays a crucial role in the mechanical response. For instance, the well-known high strength of nano?twinned bulk materials is accompanied with surprisingly high ductility [3]. Though the origin of this behavior is still not fully understood, several studies tried to unravel the underlying mechanisms in dislocation?twin-boundary (TB) interaction [4]. However, further investigation are required to thoroughly understand the impact of the TB on the mechanical properties.

The aim of present study is to reveal the dislocation Σ3 TB interaction during uniaxial compression along different crystallographic loading directions. Several micro-pillars with a vertically aligned Σ3(111) TB are fabricated by ion beam micromachining (FIB). The loading axes vary from ⟨134⟩ to ⟨112⟩. The samples are tested at BM32 of the ESRF (Grenoble, France) using in situ μLaue diffraction. Mechanical data and post mortem observation show (i) considerable transmission of dislocations through the TB, (ii) little differences between twins and their single crystal counterbodies in terms of yield stress and slip steps and (iii) no measurable differences in dislocation transmission behavior when varying the loading direction.

[1] J. Kacher BPE, B.Cui, I.M. Robertson. Dislocation interactions with grain boundaries. Current opinion in solid state and materials science 2014;18:227-43.

[2] K.Lu LL, S.Suresh. Strengthening Materials by engineering coherent internal boundaries at the nanoscale. Science 2009;324:349-52.

[3] L. Lu YS, X.Chen, L. Qian, K.Lu. Ultrahigh strength and high electrica conductivity in copper. Science 2004;304:422-6.

[4] P.J. Imrich CK, C. Motz, G. Dehm. Differences in deformation behavior of bicrystalline Cu micropillars containing a twin boundary or a large-angle grain boundary. Acta Materialia 2014;73:240-50.

Nataliya Limbach-Malyar
Max-Planck-Institut für Eisenforschung GmbH
Additional Authors:
  • Dr. Jean-Sebastian Micha
    CRG-IF BM32 at ESRF; CEA-Grenoble/ Institut Nanosciences et Cryogénie
  • Prof. Dr. Gerhard Dehm
    Max-Planck-Institut für Eisenforschung GmbH
  • Dr. Christoph Kirchlechner
    Max-Planck-Institut für Eisenforschung GmbH