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Fundamental Building Blocks – Understanding plasticity in complex crystals based on their simplest, intergrown units

Periodic Reporting for period 1 - FunBlocks (Fundamental Building Blocks – Understanding plasticity in complex crystals based on their simplest, intergrown units)

Reporting period: 2020-06-01 to 2021-11-30

New structural materials with higher strength and temperature capabilities are the key enablers of sustainable energy conversion and transport technology of the future.

The question is: How do we find those central high-performers combining high strength and the essential deformability giving safety in application?

It is the aim of FUNBLOCKS to provide the first systematic studies of plasticity mechanisms in the most fundamental building blocks of complex crystals. These will allow us to deduce the missing basic mechanisms and signatures of plasticity. FUNBLOCKS will take a new approach by studying the much simpler sub-units that form the multitude of more complex crystals with large unit cells amongst the intermetallics. This has three major implications: i) the reduction to fundamental units allows suffi-cient time to unravel the major deformation mechanisms to the atomic level, ii) the recurrent nature of the few fundamental building blocks will allow a transfer of this knowledge to a large number of complex phases and iii) together, this will enable data mining from the vast and largely unexplored phase space of intermetallics.

The key aspect of FUNBLOCKS is therefore to close the existing gap in knowledge and allow us to find promising new phases by elucidating the fundamental relationships between crystal structure and plasticity beyond what we know in simple metals. To identify and quantify the intrinsic mechanical properties of each sub-unit, state-of-the-art micromechanical testing techniques will be used. Transfer of data and verification of the central hypothesis, that fundamental units govern plasticity in complex crystals, will be achieved via additional alloyed crystals forming ternary variants of the binary structures.

Ultimately, FUNBLOCKS will answer fundamental questions in plasticity, most prominently the interplay of deformation and structure in complex crystals, and thereby support the development of new high performance materials.
Experimental work
- synthesis of Fe-Ta phases by small scale casting processes and heat treatments
- synthesis of Sm-Co phases by small scale casting processes nd heat treatments
- poly/single crystal phase analysis (SEM, EDX, EBSD) in the Sm-Co and Fe-Ta
- nanomechanical testing (indentation and pillar compression) with slip trace analysis of Sm5Co single crystals and polycrystalline samples at room temperature
- nanomechanical testing (indentation and pillar compression) with slip trace analysis of Fe6Ta7 µ-phase samples at room temperature

Computational work
- Calculation of elastic constants of Sm-Co and Fe-Ta phases
- Calculation of stacking fault energies of Sm5Co
- Calculation of stacking fault energies of Al2Cu
- Calculation of stacking fault energies of Mg2Ca
- Fundamental investigations of basal slip in Laves phases and mechanisms of motion of synchroshear partial dislocations
- Fundamental investigations of thermal activation in the motion of synchroshear partial dislocations


Tools developed for use by others
- Laves Crystal Analysis (LaCA) for analysis of atomic environments allowing the visualisation and analysis of Laves Phase crystal structures and their defects from atomistic simulations
- Slip trace analysis toolbox - Collection of tools with an associated open access tutorial for slip plane identification based on several experimental methods, such as slip traces after bulk deformation, local indentation and micropillar compression
- Experimental characterisation of single crystal plasticity of the investigated intermetallic phases
- Computational investigations of the mechanisms of motion of synchroshear dislocations
Visual summary of FunBlocks project