A Nanomechanical Testing Framework Yielding Front&Rear-Sided, High-Resolution, Microstructure-Correlated SEM-DIC Strain Fields

• Published in: Experimental mechanics Vol. 62; no. 9; pp. 1625 - 1646
• Main Authors: Vermeij, T., Verstijnen, J.A.C., Ramirez y Cantador, T.J.J., Blaysat, B., Neggers, J., Hoefnagels, J.P.M.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.11.2022; Springer Nature B.V; Society for Experimental Mechanics
• Subjects: Alignment; Biomedical Engineering and Bioengineering; Characterization and Evaluation of Materials; Control; Deformation; Deformation mechanisms; Dual phase steels; Dynamical Systems; Engineering; Engineering Sciences; High resolution; Lasers; Mapping; Martensite; Mechanical properties; Microstructure; Multiphase; Optical Devices; Optics; Optimization; Photonics; Research Paper; Solid Mechanics; Spatial resolution; Speckle patterns; Strain localization; Tensile tests; Vibration; Microstructure strain alignment; Interface mechanics; Nano tensile testing; Nano SEM-DIC
• ISSN: 0014-4851; 1741-2765
• DOI: 10.1007/s11340-022-00884-0

Background 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. Objective We propose a nanomechanical testing framework that has been carefully designed to integrate several state-of-the-art testing and characterization methods. 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. Results 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. Conclusions The proposed testing and alignment framework yields front&rear-sided aligned microstructure and strain fields providing 3D interpretation of the deformations and opening new opportunities for unprecedented validation of advanced multiphase simulations.