Extracting information from noisy data: strain mapping during dynamic in situ SEM experiments

Abstract

Micromechanical testing techniques can reveal a variety of characteristics in materials that are otherwise impossible to address. However, unlike to macroscopic testing, these miniaturized experiments are more challenging to realize and analyze, as loading and boundary conditions can often not be controlled to the same extent as in standardized macroscopic tests. Hence, exploiting all possible information from such an experiment seems utmost desirable. In the present work, we utilize dynamic in situ microtensile testing of a nanocrystalline equiatomic CoCrFeMnNi high entropy alloy in conjunction with initial feature tracking to obtain a continuous two-dimensional strain field. This enables an evaluation of true stress–strain data as well as of the Poisson’s ratio and allows to study localization of plastic deformation for the specimen. We demonstrate that the presented image correlation method allows for an additional gain of information in these sophisticated experiments over commercial tools and can serve as a starting point to study deformation states exhibiting more complex strain fields. Graphic abstract

Current trends in nanomechanical testing research

“…This focus issue also witnesses the use of other emerging techniques, such as atom probe tomography (APT), which provides chemical composition mapping with strongly enhanced spatial resolution [29,33]. Regardless of the nanomechanical testing method, post-mortem analyses appear to greatly benefit from the increasing availability of image processing algorithms, such as digital image correlation [11,25,35,36].…”