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Measuring local strain fields during in situ deformation using STEM diffraction mapping

Tuesday (27.09.2016)
11:30 - 11:45
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In situ deformation in the transmission electron microscope (TEM) has provided great insight into the fundamental mechanisms occurring during deformation. In addition, TEM has demonstrated the ability to measure strain fields around static dislocations. Still, it is of great importance to measure the evolution of the local transient strain around individual defects during plastic deformation to correlate defect structure with material properties.

In the present work we show that strain mapping can be carried out during continuous in situ deformation in a TEM at the nanometer scale. Our method is based on diffraction mapping. During scanning TEM (STEM) imaging, the beam rasters over the sample and on top of the image, a full diffraction pattern is recorded for every probe position. A Gatan K2 IS direct electron detector is used to acquire the diffraction patterns at a rate of 400 frames/s. A strain map is calculated from the diffraction maps by detecting the diffracted beam positions [1]. Using a Hysitron PI-95 picoindenter we will demonstrate the application of diffraction mapping to an in situ tensile test of an Al alloy. The obtained time resolved in situ strain maps allow to measure local and transient strains occurring around moving dislocations.

[1] V.B. Ozdol, C. Gammer, X. Jin, P. Ercius, C. Ophus, J. Ciston and A.M. Minor. Applied Physics Letters, 106 (2015) 253107.

We acknowledge support from the Austrian Science Fund (FWF):[J3397] and the Molecular Foundry, Lawrence Berkeley National Laboratory, which is supported by the U.S. Dept. of Energy under Contract # DE-AC02-05CH11231.

Speaker:
Christoph Gammer
Austrian Academy of Sciences
Additional Authors:
  • Prof. Jürgen Eckert
    Austrian Academy of Sciences
  • Prof. Andrew M. Minor
    Lawrence Berkeley National Laboratory