SFB 1394:  Structural and Chemical Atomic Complexity: From Defect Phase Diagrams to Material Properties

New metallic materials are essential for realising future key technologies, from efficient energy conversion over lightweight transport to safe medical devices. Two approaches have proven immensely successful for the design of new metallic materials. Firstly, thermodynamic models of crystal phases have enabled alloy tailoring and processing to obtain desired microscale structures. Secondly, understanding and manipulation of crystal defects, which govern strength, formability and corrosion resistance, has led to alloying and processing concepts that resulted in some of the most advanced high-performance alloys in operation today. However, these two approaches are essentially decoupled, employed by scientists and developers from different communities. This separation is deeply engrained in materials science and most textbooks discuss phases and defects separately. On the other hand, it seems blatantly obvious that phases and defects are not independent factors for the properties of a material. It is the vision of this CRC to join and integrate the two approaches into a new, unified framework that will consider defects and phases in a holistic, all-encompassing manner. This will enable new materials design concepts that originate from the atomic scale and jointly consider the local crystalline structure at defects (structural complexity), the distribution of chemical elements in phases and defects (chemical complexity) and the prevalent defects for given external conditions, such as chemical potentials, temperature, applied stress or electrode potential. The CRC will not only investigate and clarify the interrelation between structural complexity, chemical complexity and defect phases, but further support the development of novel materials design concepts by providing new quantitative descriptors of the local structure and chemistry of defect phases which govern a materials' bulk properties. Here a defect phase is defined as a structurally and chemically distinct atomic-scale defect configuration with properties that are smooth functions of intensive external variables. Defect phase diagrams display the observed defects for given external conditions and show the transition between and the coexistence of defect phases. In the first funding period, the CRC has successfully identified and described several defect phases in theory and experiment. Examples include planar defect phases that do not grow to form precipitates and chemically induced structural transitions of grain boundary defect phases in Mg, as well as mechanism transition of dislocation defect phases in the Ca(Mg,Al)2 Laves phases. Structural and chemical complexity at the atomic scale is ubiquitous in materials. We believe that by studying defect phases, we will lead a paradigm change in the physical description of metallic materials and provide a powerful toolbox for future design of engineering materials with tailored properties regarding both, mechanical and corrosion performance.

DFG Programme Collaborative Research Centres

• A01 - Solid solution effects on the formation of defect phases in Ni-X solid solutions (Project Heads Raabe, Dierk ;  Sandlöbes-Haut, Stefanie )
• A02 - High-throughput simulations of dislocation and grain boundary defect phases (Project Heads Bitzek, Erik ;  Guénolé, Ph.D., Julien ;  Neugebauer, Jörg )
• A03 - Correlative structural, chemical and bonding characterisation of 1D and 2D defect phases (Project Heads Mayer, Joachim ;  Schwedt, Alexander )
• A04 - Prior knowledge-based analysis of atomic-resolution image data (Project Head Berkels, Benjamin )
• A05 - Generalised deformation mechanism maps and interaction of dislocation defect phases with vacancies in Laves phases (Project Heads Korte-Kerzel, Ph.D., Sandra ;  Xie, Zhuocheng )
• A06 - Efficient and highly accurate interatomic potentials for defect phase simulation (Project Heads Drautz, Ralf ;  Huber, Liam ;  Neugebauer, Jörg )
• A07 - Machine learning for defect phases (Project Head Kerzel, Ulrich )
• B01 - Atomic structure and composition of defect phases in Mg- and Ni-based systems (Project Head Scheu, Christina )
• B02 - Combinatorial synthesis of Ni-Nb-Cu-Al-Au model layer systems (Project Head Schneider, Ph.D., Jochen M. )
• B03 - Local chemical composition of defects (Project Head Hans, Marcus )
• B04 - Formation of defect phases on surfaces of Ni(+X) alloys in corrosive environments (Project Head Todorova, Mira )
• B05 - Corrosion mechanisms and properties of Ni-Cu solid solutions (Project Head Zander, Daniela )
• B06 - Grain boundary phases in Ni, Ni-Cu and Ni-Au solid solution films (Project Heads Dehm, Gerhard ;  Ramachandramoorthy, Ph.D., Rajaprakash )
• B08 - Formation of defect phases via hydrogen exposure in nickel alloys (Project Heads Hans, Marcus ;  Raabe, Dierk )
• C02 - Chemical ordering and dislocation defect phases in ternary intermetallic phases (Project Head Korte-Kerzel, Ph.D., Sandra )
• C03 - Cathodic hydrogen uptake and permeation in passivated Ni-Nb intermetallic phases (Project Head Zander, Daniela )
• C04 - Combinatorial microstructure design (Project Head Springer, Hauke )
• C05 - Ab initio thermodynamics of defect phases (Project Heads Hickel, Tilmann ;  Janssen, Jan )
• MGK - Integrated Research Training Group (Project Head Berkels, Benjamin )
• S - Targeted generation of solid solution materials and intermetallic phases (Project Head Springer, Hauke )
• T01 - From experimental and atomistic simulation data to Calphad assessments (Project Heads Hickel, Tilmann ;  Kerzel, Ulrich )
• Z - Central task (Project Head Korte-Kerzel, Ph.D., Sandra )

• C01 - Multiphysics description of Mg composites at the grain scale (Project Heads Roters, Franz ;  Sandlöbes-Haut, Stefanie )
• C06 - Thermodynamic modelling of Mg-Al-Ca and its defect phases (Project Head Hallstedt, Bengt )

Applicant Institution Rheinisch-Westfälische Technische Hochschule Aachen

Participating Institution Bundesanstalt für Materialforschung und -prüfung (BAM); Max-Planck-Institut für Nachhaltige Materialien GmbH (MPI SusMat)

Participating University Ruhr-Universität Bochum
Interdisciplinary Centre for Advanced Materials Simulations (ICAMS)

Spokesperson Professorin Dr. Sandra Korte-Kerzel, Ph.D.