  The continuous development of new multiphase alloys with improved mechanical
properties requires quantitative microstructure-resolved observation of the
nanoscale deformation mechanisms at, e.g., multiphase interfaces. This calls
for a combinatory approach beyond advanced testing methods such as microscale
strain mapping on bulk material and micrometer sized deformation tests of
single grains. We propose a nanomechanical testing framework that has been
carefully designed to integrate several state-of-the-art testing and
characterization methods: (i) well-defined nano-tensile testing of carefully
selected and isolated multiphase specimens, (ii) front&rear-sided SEM-EBSD
microstructural characterization combined with front&rear-sided in-situ SEM-DIC
testing at very high resolution enabled by a recently developed InSn nano-DIC
speckle pattern, (iii) optimized DIC strain mapping aided by application of SEM
scanning artefact correction and DIC deconvolution for improved spatial
resolution, (iv) a novel microstructure-to-strain alignment framework to
deliver front&rear-sided, nanoscale, microstructure-resolved strain fields, and
(v) direct comparison of microstructure, strain and SEM-BSE damage maps in the
deformed configuration. Demonstration on a micrometer-sized dual-phase steel
specimen, containing an incompatible ferrite-martensite interface, shows how
the nanoscale deformation mechanisms can be unraveled. Discrete
lath-boundary-aligned martensite strain localizations transit over the
interface into diffuse ferrite plasticity, revealed by the nanoscale
front&rear-sided microstructure-to-strain alignment and optimization of DIC
correlations. The proposed framework yields front&rear-sided aligned
microstructure and strain fields providing 3D interpretation of the deformation
and opening new opportunities for unprecedented validation of advanced
multiphase simulations.
