Quantitative In-Situ TEM Nanoindentation Instrument

75333S Nanoindentation is the primary technique for assessing the nanomechanical behavior of small volumes of materials. With this technique, the force required to produce a given displacement into a sample by a sharp diamond tip is measured, and the hardness of the material being tested is determined analyzing the force-displacement curve. However, the microstructural origins of the measured mechanical response often are not readily understood. This project will develop a quantitative nanoidentation instrument capable of operating inside a transmission electron microscope. This capability would enable the real-time correlation between the evolving force-displacement curve and images of the evolving microstructure. Insights gained from such experiments would substantially improve the ability to engineer the mechanical behavior of materials. In Phase I, the following three components were developed and assembled into a working quantitative nanoindetation system: a miniature transducer capable of electrostatic actuation and capacitive displacement sensing, an in situ transmission-electron-microscopy holder equipped with a three-axis piezoelectric positioner and a three-axis course positioner, and a force-feedback controller. Tests in a transmission electron microscope showed the feasibility of the concept. Phase II will: (1) develop a prototype, ready-to-commercialize, quantitative nanoindentation instrument that is compatible with the transmission electron microscope; and (2) conduct applications research having industrial relevance using the quantitative nanoindentation system. Commercial Applications and Other Benefits as described by the awardee: The ability to apply quantitative nanoindentation in transmission electron microscopes should provide a crucial understanding of structure-mechanical property correlations at nanoscale, leading to improvements in surface engineering and thin-film technology, and facilitating the design of useful shape-memory alloys and other smart materials.