In situ TEM has provided great insight into the deformation mechanisms in various material systems. The combination of well-defined sample geometries with advanced deformation holders has enabled to obtain stress-strain curves during in situ deformation. Still, the local transient strain field during deformation remains unknown.
In this presentation we show that local strain mapping can be carried out during in situ deformation in a TEM at the nanometer scale. This is achieved by scanning the electron beam over the sample and recording a full diffraction pattern for every probe position using a fast electron detector. The method is demonstrated for two different material systems, one being amorphous and the other one crystalline. In the first study, a CuZr-based metallic glass sample is deformed under tension. The ellipticity of the amorphous ring pattern can be used to map the local strain. In the second study an in situ tensile test of Al is shown. Here, cross correlation is used to detect the positions of the diffracted peaks, allowing to obtain time-resolved strain maps [1]. The time resolved strain maps acquired during deformation show that the elastic strain varies considerably at the nanoscale, demonstrating the importance of local in situ strain measurements in the TEM.
1. C. Gammer et al., Appl. Phys. Lett. 109 (2016) 081906
