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

Project Information

FunBlocks

Grant agreement ID: 852096

DOI

10.3030/852096

Project closed

EC signature date 25 September 2019

Start date 1 June 2020

End date 30 November 2025

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 499 719,00

EU contribution

€ 1 499 719,00

Coordinated by

RHEINISCH-WESTFAELISCHE TECHNISCHE HOCHSCHULE AACHEN
Germany

Periodic Reporting for period 4 - FunBlocks (Fundamental Building Blocks – Understanding plasticity in complex crystals based on their simplest, intergrown units)

Reporting period: 2024-12-01 to 2025-11-30

Summary of the context and overall objectives of the project

The transition to sustainable energy conversion, transport, and industrial technologies requires structural materials that combine high strength with reliable deformability at elevated temperatures. While many intermetallic compounds offer exceptional strength and thermal stability, their limited or poorly understood plasticity has long restricted their practical use. The central challenge addressed by FUNBLOCKS was therefore to understand how plastic deformation operates in complex intermetallic crystals and how this knowledge can be used to identify materials that are both strong and safe in application.

While plasticity in metals is well understood, this knowledge does not readily transfer to intermetallics with large and complex unit cells, which are therefore often dismissed as brittle without a mechanistic basis. FUNBLOCKS addressed this gap by introducing a reductionist strategy: instead of tackling complex crystal structures directly, the project focused on their fundamental structural building blocks. These building blocks recur across many intermetallic phases and thus provide a transferable basis for understanding deformation.

The overall objective of FUNBLOCKS was to establish the fundamental relationships between crystal structure and plasticity beyond simple metals by systematically studying these basic building blocks. This approach aimed to resolve deformation mechanisms at the atomic scale in representative systems, transfer this understanding to more complex intermetallic phases, and enable informed exploration of the largely unexplored intermetallic phase space.

To achieve this, FUNBLOCKS combined state-of-the-art micromechanical testing with advanced modelling and atomic-scale characterisation. Controlled compositional variations were used to test the central hypothesis that plasticity in complex crystals is governed by the properties and interactions of their fundamental building blocks.

By the end of the project, FUNBLOCKS had demonstrated that dislocation-mediated plasticity is more widespread and more diverse in intermetallics than previously assumed and that key deformation mechanisms can be traced back to recurring structural motifs. These insights provide a mechanistic foundation for identifying and designing high-performance structural materials supporting sustainable energy and advanced engineering.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the first phase of FUNBLOCKS, the experimental and computational foundations of the project were established. Experimentally, reliable synthesis routes were developed for the targeted Ta–Fe–Al and Sm–Co intermetallic systems, achieving well-controlled microstructures, which were comprehensively characterised by scanning electron microscopy prior to micromechanical testing. Conventional and high-resolution transmission electron microscopy were additionally employed to study dislocations and planar defects at the atomic scale.

Building on this groundwork, state-of-the-art nanomechanical testing was applied to identify active slip systems and deformation behaviour at room temperature. This included detailed studies of Sm–Co phases and Fe–Ta Laves and µ-phases, complemented by nanoindentation-based screening across additional Ta–Fe–Al compositions.

In parallel, extensive computational work was carried out on the same material systems. Elastic constants and stacking fault energies were calculated for key intermetallic phases in the Ta–Fe–Al and Sm–Co systems, providing quantitative input for interpreting experimental observations. Fundamental mechanisms of dislocation motion were explored in Laves phases isostructural to the experimentally synthesised materials, as well as in SmCo₅, enabling direct comparison between simulations and experiments. Order was identified as a key factor in intermetallic elasticity and plasticity, including both magnetic order and sub-lattice occupancy, the latter offering a promising route for property tailoring.

Beyond the direct scientific results, FUNBLOCKS delivered methodological advances with broader impact. Tools for experimental slip-trace analysis were developed to facilitate the identification of active slip systems in complex crystals. On the computational side, analysis and visualisation tools were created to identify crystal building blocks and defects in atomistic simulation data, particularly for Laves and TCP phases. These tools support data-driven exploration of complex intermetallic structures beyond the specific systems studied.

The project also fostered collaborations extending beyond classical intermetallic systems. Insights and methods developed within FUNBLOCKS were applied in studies on metallic alloys where ordered structures emerge locally at defects and interfaces, exhibiting strong structural analogies to intermetallic building blocks and demonstrating the transferability of the FUNBLOCKS concepts.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

FUNBLOCKS advanced the state of the art by providing the first systematic, mechanism-based understanding of plasticity in key structural building blocks of complex intermetallic crystals. A central outcome was the demonstration that deformation in several classes of intermetallic phases, including Laves phases and µ-phases, is governed by dislocation-mediated plasticity. This included SmCo₅, previously thought to deform primarily by amorphous shear band formation. Active slip systems and their critical stresses were identified and consistently rationalised through a direct combination of micromechanical experiments and atomistic simulations.

Beyond identifying individual mechanisms, the project established clear links between local crystal structure, chemical occupancy, and deformation behaviour. Small changes in composition and site occupancy within fundamental crystal building blocks were shown to induce pronounced changes in active slip systems, critical stresses, and deformation anisotropy, highlighting the decisive role of local bonding environments and sub-lattice configurations.

A further advance was the extension of these concepts from isolated building blocks to composite and structurally related phases. While elastic properties could often be understood in terms of the constituent building blocks, plastic deformation mechanisms were shown to deviate when changes in bonding character or stacking regularity occurred. This clarified the limits and applicability of building-block-based transferability in complex crystals.

By the end of the project, FUNBLOCKS had delivered experimentally validated descriptors for plasticity in selected intermetallic systems, including active Burgers vectors, preferred slip planes, and structure–chemistry indicators governing their activation. More broadly, the project established a transferable methodology linking atomic-scale structure and chemistry to mechanical behaviour beyond simple metals, opening new pathways for the rational design of high-performance structural and functional materials.

Visual summary of FunBlocks project