Characterization of Multiscale Interfaces of Hierarchical High-Entropy Alloys by Advanced Microscopy and Microanalysis

Informazioni relative al progetto

MultiScaleDesign

ID dell’accordo di sovvenzione: 897407

DOI

10.3030/897407

Progetto chiuso

Data della firma CE 10 Aprile 2020

Data di avvio 1 Agosto 2022

Data di completamento 31 Luglio 2024

Finanziato da

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Costo totale

€ 184 820,16

Contributo UE

€ 184 820,16

Coordinato da

MONTANUNIVERSITAET LEOBEN
Austria

Periodic Reporting for period 2 - MultiScaleDesign (Characterization of Multiscale Interfaces of Hierarchical High-Entropy Alloys by Advanced Microscopy and Microanalysis)

Periodo di rendicontazione: 2023-08-01 al 2024-07-31

Sintesi del contesto e degli obiettivi generali del progetto

This project aims to develop methods for studying a new class of technologically important hierarchical materials with multiscale interfaces synthesized by advanced bottom-up approaches. The research focuses on understanding how the microstructure of structurally and compositionally complex metallic/alloy materials relates to their properties to design novel advanced materials that balance strength and toughness and thus overcome limitations of traditional materials.

The focus lies on the correlation of the grain size/grain orientation distribution and composition, twin density variations, multilayer architecture and structure and composition of the primary phase in multi-principle element alloys with their mechanical properties and thermal stability.

The new material design concepts rely on advanced methods for characterization of materials microstructure and mechanical properties at multiple length scales, including multiscale multimodal transmission electron microscopy and atomistic characterization by atom probe microscopy. Their development together with the host institution (The University of Sydney) and integration into the research at the beneficiary (Montanuniversität Leoben) will contribute to the fundamental understanding of the process-structure-property relations of hierarchical materials and identifying the role of multiscale interfaces on their mechanical properties and thermal stability.

As microstructural design has a great application potential for various materials, it is relevant for a majority of applications in which reliability, in terms of structural and mechanical stability, is a key property. Besides safety-critical applications, the knowledge gained in this project can be applied also in tooling applications, in microelectronics, sensor and display technology and materials for energy storage and conversion. The general design rules established in the course of the project are expected to have interdisciplinary overlap, contributing to the improvement of quality of a variety of products, and thus attracting attention of researchers across academia and industry.

Lavoro eseguito dall’inizio del progetto fino alla fine del periodo coperto dalla relazione e principali risultati finora ottenuti

In the first part of the project, research activities comprised of comprehensive hands-on trainings on (scanning) transmission electron microscopy, electron diffraction analysis, 4D STEM and atom probe tomography. The experimental work was supported by a dedicated methods for sample preparation by laser ablation, focused ion beam milling and plasma polishing, post-processing of diffraction data by Python scripts collaboratively developed in the project. In order to correctly conduct the experiments and evaluate experimental data, knowledge has been gained through a series of seminars, workshops and discussion forums dedicated to characterization and analytical methods used in the project.

The methodologies have been applied for a variety of metallic and multi-principle element alloy materials with microstructures spanning from amorphous, nanostructured with amorphous matrix, nanocrystalline and polycrystalline microstructures to investigate various approaches necessary to get reasonable results at the highest possible resolution across multiple length scales.

An important part of the conductions, hands-on trainings and seminars was focused on the methodology development and improvement of skills to characterize the metals and alloys at the atomistic level. Dedicated microscopes, double corrected STEM Themis Z microscope equipped with a fast EDS detector and high-resolution EELS spectrometer and dual-beam deep UV pulse laser Cameca 6000 Invizo APT microscope have been employed.

As next, interfaces of layered metallic Ti/Ta multilayers have been studied by HR STEM/EDS techniques with a focus on establishing methods for structural characterization of interfaces at the atomic level. These methods have been further validated for epitaxially grown TiN/VN multilayers to optimize the experimental setup for high-resolution imaging and nanoanalysis. The knowledge has been applied for CrMnFeCoNi multilayers with a specific focus on segregation of elements towards interfaces formed between individual layers.

Apart of the utilization of the state-of-the-art equipment for the specimen preparation, Python-based procedures for automated FIB milling were tested and strategies for implementation at the beneficiary have been developed.

Furthermore, in-situ SEM and TEM micromechanical testing of the CrCoNi-based alloys was performed and deformation zones correlated with the experimental stress-strain curves by using conventional and high-resolution microscopy to study interaction of dislocations with interfaces. The same concept has been applied also for brittle high-entropy refractory MoNbTaWV alloy with embedded ductile Cu nanoparticles.

The experimental results have been summarized and a research plan for the second period of the project developed to apply the most promising approaches of the microstructural design in synthesis of hard, tough and thermally stable novel metallic and alloy materials. The concepts will be demonstrated for a variety of materials which application is compromised by a lack of specific sets of properties. The characterization methodology will be transferred to beneficiary, results published in high-ranking journals and further development conducted through a collaborative work with the host institution.

Progressi oltre lo stato dell’arte e potenziale impatto previsto (incluso l’impatto socioeconomico e le implicazioni sociali più ampie del progetto fino ad ora)

The uniqueness of the thermodynamic non-equilibrium sputtering processes used for the synthesis of the multi-principal element alloys and metallic films in this project allowed for the fabrication of compositions and microstructures, which are not accessible by thermal treatment, commonly used to control phase composition of bulk alloys. This allowed to study phenomena in the materials science, which are expected to enhance properties of alloys and metals, but could be studied in bulk materials only in specific cases of highly deformed materials, by e.g. high pressure torsion technique or additive manufacturing processes. Although the first approach is capable to produce nanostructured alloys, there are usually very defective, exhibiting high residual stresses. The latter approach, on the other hand, still does not produce materials with grains in the nanometre range.

Designing the multi-principal element alloys with complex microstructures, varying in the grain size, exhibiting twins with specific distributions and separation distances, with decorated grain boundaries and with varying amount and composition of precipitates formed during the controlled decomposition of the primary phase, goes beyond the state-of-the-art material design.

The combination of the conventional methods with multimodal complementary advanced characterization methods and new characterization approaches, including the unique 4D STEM technique utilizing pixel array detectors and dual-beam deep UV laser pulse APT with a new counter electrode concept, makes this project exceptional, significantly contributing to the understanding of fundamental material science phenomena.

By deriving novel design concepts of interface-rich hierarchical structures, the project has ambitions to develop novel durable structurally and compositionally complex metallic materials and alloys, which may solve some non-trivial material science questions (such as strength-ductility trade-off) and contribute to the replacement of some traditional materials with insufficient properties.

Research questions

Precipitation phenomena in metallic and alloy materials

Activities at host institution

Project name

TEM equipment 2

Research strategy

TEM equipment 1

Thermal stability of multicomponent alloys

Biomimetic microstructural design of metals and alloys

Sustainable by design

Study of twin and grain boundaries of polycrystalline alloys

Atomistic study of interfaces in metallic multilayer thin film systems

Local Electrode Atom Probe

Study of interphases in polycrystalline alloys