Periodic Reporting for period 4 - TOUGHIT (Tough Interface Tailored Nanostructured Metals)
Reporting period: 2022-11-01 to 2024-04-30
In a global picture, a growing population in combination with a limited amount of resources requires mankind to utilize them as efficiently as possible. Translating this into materials science challenges material scientists to create novel materials that are light-weight and simultaneously possibly strong in order to maximize load-bearing capacity while minimizing weight and material usage. At the same time, structures or components must be failure-tolerant to avoid human harm in case of unexpected overload situations. This poses a severe challenge to the field, as it has been established over decades that maximizing strength and ductility are exclusive targets. Extremely strong materials commonly lack ductility, and without local ductility, it becomes tremendously challenging to stop a crack from propagation, thus catastrophic failure becomes a risk. Furthermore, increased ductility enhances the fatigue strength and leads to an extended lifetime of products. Satisfying all these contrary demands indeed requires a better material property balance in the use of essential and limited resources.
It was the overall objective of this project to overcome this trade-off between strength and ductility by tailoring novel metallic nanomaterials and nanocomposites that uniquely unite high strength and high ductility, and at the same time avoid brittle fracture. We were successful in creating such materials by employing dedicated grain boundary engineering strategies in conjunction with powder-based synthesis routes. The excellent properties were analyzed by a suite of micro- and nanoscale in-situ experiments to unravel the underlying deformation and fracture mechanisms and develop more generalized material design concepts.
In conclusion, the project was successful in creating novel materials offering previously unseen combinations of desired material properties, as well as laying the foundation for the generalization of the employed concepts for other material classes.
It was the overall objective of this project to overcome this trade-off between strength and ductility by tailoring novel metallic nanomaterials and nanocomposites that uniquely unite high strength and high ductility, and at the same time avoid brittle fracture. We were successful in creating such materials by employing dedicated grain boundary engineering strategies in conjunction with powder-based synthesis routes. The excellent properties were analyzed by a suite of micro- and nanoscale in-situ experiments to unravel the underlying deformation and fracture mechanisms and develop more generalized material design concepts.
In conclusion, the project was successful in creating novel materials offering previously unseen combinations of desired material properties, as well as laying the foundation for the generalization of the employed concepts for other material classes.
Within this project, we managed to synthesize metallic nanomaterials as well as nanocomposites starting from input powders, thereby establishing a very versatile additive material synthesis approach. Furthermore, this powder-based material synthesis also enables us to deliberately add doping elements for grain boundary strengthening, which would be impossible utilizing standard processing strategies. Focusing on tungsten as the hard and brittle composite phase, we followed up theoretical predictions to enhance grain boundary cohesion and demonstrate increased ductility with no loss in strength for the grain boundary doped material. The same holds for nanocomposites, where the addition of ductile copper to the nanostructured tungsten reduced the overall strength compared to pure tungsten, but the ductility could be markedly improved. By alloying the softer Cu phase with Zn, we could further strengthen the composite without compromising its fracture toughness. Another strategy to further advance the properties of the softer composite phase copper was to create amorphous grain boundary layers. The powder based synthesis was again successfully completed, and the nanocrystalline copper with amorphous grain boundary films documented very high hardness.
To understand the fundamental mechanisms governing the excellent material behavior, we established detailed micro- and nanomechanical deformation and fracture examinations to unravel the fundamental deformation and fracture processes. Besides employing advanced nanoindentation techniques, we developed elastic-plastic fracture mechanical testing strategies for micro- and nanoscale specimens in the scanning and transmission electron microscope, respectively. Here it is particularly worth mentioning that we possess the unique capability to map the strain field at a crack tip with nanometer resolution and have the capability to conduct these analyses even during in-situ testing in the transmission electron microscope. Accompanying analysis tools were also developed for a better understanding of local strain distribution. Concerning the in-situ experiments on micron-sized specimens conducted in the scanning electron microscope, novel digital vision analysis was designed to aid the continuous identification of the crack advancement process, tremendously aiding the analysis of the respective data. Furthermore, we also implemented micromechanical spectroscopy techniques for sampling grain boundary processes, as well as a transmission microscopy mechanical testing setup in the scanning electron microscope to connect the scanning and transmission worlds in terms of their respective beneficial capabilities. Moreover, we also expanded towards nanoporous but still nanocrystalline tungsten as another promising material to unite high levels of strength, ductility and toughness. We were successful in deriving a novel synthesis technique, establishing a fundamental understanding of the formation process of the nanoporous topology, and could demonstrate that the received material provides again a very attractive combination of materials properties.
Furthermore, we could demonstrate that our novel materials, including nanocrystalline, nanocomposite and nanoporous materials, exhibit excellent performance in harsh conditions, such as elevated temperatures or radiative environments. This renders them as potential go-to materials for the design of new fusion reactor concepts.
Lastly, to broaden the impact of the action we expanded the use of our concepts to microelectronic materials, biological nanocomposites and bio-inspired composites.
These achievements were disseminated in more than 70 peer reviewed publications, including high impact journals such as Nature Communications, Materials Today, Science Advances, as well as numerous works in highly regarded materials science journals such as Acta Materialia or Materials & Design. Furthermore, almost 100 oral contributions were delivered at international workshops and conferences, including two plenary and 36 invited contributions, as well as several outlets to the general public via web pages, newsletters, newspapers, etc.
To understand the fundamental mechanisms governing the excellent material behavior, we established detailed micro- and nanomechanical deformation and fracture examinations to unravel the fundamental deformation and fracture processes. Besides employing advanced nanoindentation techniques, we developed elastic-plastic fracture mechanical testing strategies for micro- and nanoscale specimens in the scanning and transmission electron microscope, respectively. Here it is particularly worth mentioning that we possess the unique capability to map the strain field at a crack tip with nanometer resolution and have the capability to conduct these analyses even during in-situ testing in the transmission electron microscope. Accompanying analysis tools were also developed for a better understanding of local strain distribution. Concerning the in-situ experiments on micron-sized specimens conducted in the scanning electron microscope, novel digital vision analysis was designed to aid the continuous identification of the crack advancement process, tremendously aiding the analysis of the respective data. Furthermore, we also implemented micromechanical spectroscopy techniques for sampling grain boundary processes, as well as a transmission microscopy mechanical testing setup in the scanning electron microscope to connect the scanning and transmission worlds in terms of their respective beneficial capabilities. Moreover, we also expanded towards nanoporous but still nanocrystalline tungsten as another promising material to unite high levels of strength, ductility and toughness. We were successful in deriving a novel synthesis technique, establishing a fundamental understanding of the formation process of the nanoporous topology, and could demonstrate that the received material provides again a very attractive combination of materials properties.
Furthermore, we could demonstrate that our novel materials, including nanocrystalline, nanocomposite and nanoporous materials, exhibit excellent performance in harsh conditions, such as elevated temperatures or radiative environments. This renders them as potential go-to materials for the design of new fusion reactor concepts.
Lastly, to broaden the impact of the action we expanded the use of our concepts to microelectronic materials, biological nanocomposites and bio-inspired composites.
These achievements were disseminated in more than 70 peer reviewed publications, including high impact journals such as Nature Communications, Materials Today, Science Advances, as well as numerous works in highly regarded materials science journals such as Acta Materialia or Materials & Design. Furthermore, almost 100 oral contributions were delivered at international workshops and conferences, including two plenary and 36 invited contributions, as well as several outlets to the general public via web pages, newsletters, newspapers, etc.
We were able to confirm our main hypothesis, successfully synthesized materials that outperform what is currently available on the market, and still see significant potential for further improvement of our achievements, which we will pursue in the recently started PoC BulkNanoWe2.
We are capable of executing and analyzing micro-/nanomechanical tests to address local deformation and fracture processes at a worldwide leading level, thereby providing unseen insights into the fundamental processes governing deformation and failure of the investigated materials. This enabled us to derive design guidelines for creating such outstanding materials properties also in other material systems.
The powder-based severe plastic deformation synthesis route as well as experimental micro /nanomechanical in-situ investigations are generally applicable and suited to a wide interdisciplinary palette of materials issues. We also demonstrated a positive impact of our work in other fields of materials science, such as microelectronics, biomaterials and bioinspired structures.
We are capable of executing and analyzing micro-/nanomechanical tests to address local deformation and fracture processes at a worldwide leading level, thereby providing unseen insights into the fundamental processes governing deformation and failure of the investigated materials. This enabled us to derive design guidelines for creating such outstanding materials properties also in other material systems.
The powder-based severe plastic deformation synthesis route as well as experimental micro /nanomechanical in-situ investigations are generally applicable and suited to a wide interdisciplinary palette of materials issues. We also demonstrated a positive impact of our work in other fields of materials science, such as microelectronics, biomaterials and bioinspired structures.