Materials under harsh conditions

Material decay under harsh environmental conditions is known through phenomena such as corrosion, stress-corrosion cracking and hydrogen embrittlement - by far the most severe phenomena limiting the longevity and integrity of metal products, destroying about 3.4 % of the global gross domestic product every year, a value translating to 2.5 trillion Euros.Hence, any progress in corrosion resistance has large effects on the life span and safety of products and is thus also the most eminent single factor in improving the sustainability of industrialized civilizations.
Loss of material and system failure due to oxidation accounts for the vast majority of the economic impact of corrosion and is an essential factor in infrastructure costs worldwide. Oxidation of metallic structures proceeds mostly through galvanic corrosion, which occurs when adjacent microstructural regions or different metals with unlike electrochemical potentials are in conductive contact.
Hydrogen embrittlement is another type of corrosion and poses a serious impediment for carbon-free hydrogen-propelled technologies. Unlike other corrosion products such as oxides and hydroxides, hydrogen is hard to detect and several embrittling effects can occur such as hydrogen-enhanced plasticity, decohesion, superabundant vacancies, hydride formation or nanovoids. The interplay among them makes it difficult to identify a clear cause of failure. Also, hydrogen-related damage can occur suddenly, causing abrupt catastrophic failure of structures. Hydrogen embrittlement can occur in structural alloys, particularly in iron, aluminium, nickel and titanium alloys with strength levels above 650 MPa.
Motivated by this essential context, the MPIE is worldwide one of the leading hubs for corrosion and hydrogen-related research using latest state of the art methodologies, reaching from advanced Kelvin-probe methods to single atom hydrogen detection in cutting edge atom probe tomography.

In this project, we directly image and characterize solute hydrogen and hydride by use of atom probe tomography combined with electron microscopy, with the aim to investigate H interaction with different phases and lattice defects (such as grain boundaries, dislocation, etc.) in a set of specimens of commercially pure Ti, model and commercial Ti-alloys. more
For understanding the underlying hydrogen embrittlement mechanism in transformation-induced plasticity steels, the process of damage evolution in a model austenite/martensite dual-phase microstructure following hydrogenation was investigated through multi-scale electron channelling contrast imaging and in situ optical microscopy. more
Study of hydrogen embrittlement by using multi-scale and spatially <br />resolved hydrogen mapping in a Ni-Nb model alloy and in alloy 718
In this project we investigate the hydrogen distribution and desorption behavior in an electrochemically hydrogen-charged binary Ni-Nb model alloy. The aim is to study the role of the delta phase in hydrogen embrittlement of the Ni-base alloy 718. more
Understanding hydrogen-assisted embrittlement of advanced structural materials is essential for enabling future hydrogen-based energy industries. A crucially important phenomenon in this context is the delayed fracture in high-strength structural materials. Factors affecting the hydrogen embrittlement are the hydrogen content,... more
Hydrogen embrittlement affects high-strength ferrite/martensite dual-phase (DP) steels. The associated micromechanisms which lead to failure have not been fully clarified yet. Here we present a quantitative micromechanical analysis of the microstructural damage phenomena in a model DP steel in the presence of hydrogen. more
Hydrogen embrittlement of austenitic steels is of high interest because of the potential use of these materials in hydrogen-energy related infrastructures. In order to elucidate the associated hydrogen embrittlement mechanisms, the mapping of heterogeneities in strain, damage (crack/void), and hydrogen and their relation to the underlying microstructures is a key assignment in this field. more
This group is concerned with the 3D mapping of hydrogen at near-atomic scale in metallic alloys with the aim to better understand hydrogen storage materials and hydrogen embrittlement. more
Ab initio study of corrosion: Adsorbate phases on surfaces and <br />phase diagrams
The project aims to study corrosion, a detrimental process with an enormous impact on global economy, by combining denstiy-functional theory calculations with thermodynamic concepts. more
The fundamental mechanism behind H2 evolution at anodically polarized <br />Mg surfaces
We apply our novel potentiostat approach to study the chemical reactions that take place during initial corrosion at the water-Mg interface under anodic polarization. Based on the gained insight, we derive an atomistic model that explains the origin of the anodic hydrogen evolution. more
ZnO is a wide band gap semiconductor which is of interest to such diverse areas of application as passivation layers on steel surfaces, catalysis, corrosion, adhesion, gas sensing, and micro- or optoelectronics. Understanding the surface structure and stoichiometry is of high practical interest and essential for any of the mentioned applications. Keeping in mind that the chemical environment interfacing with the surface plays a decisive role in the stabilisation and atomic structure of the surface reconstruction, we combine density functional theory (DFT) calculations with atomistic thermodynamics to investigate and understand the stability of polar Zn-terminated ZnO(0001) surfaces in dry and humid environment. more
Solid-liquid interfaces are at the heart of many problems of practical importance, such as water electrolysis and batteries, photo catalytic water splitting, electro-catalysis, or corrosion. Understanding the structures forming at surfaces of solids immersed in an aqueous electrolyte is, therefore, of particularly high interest. In this project, we investigate the role the liquid environment plays in shaping such structures. We show that solvation effects are highly selective, having little effect on surfaces with metallic character, but largely stabilizing semiconducting structures, particularly those that experience a high electrostatic penalty in vacuum. more
Hydrogen embrittlement is a persistent mode of failure in modern structural materials. The processes related to HE span various time and spatial scales. Thus we are establishing multiscale approaches that are based on the parameters and insights obtained by accurate ab initio calculations in order to simulate HE at the continuum level. more
Understanding hydrogen-assisted embrittlement of advanced high-strength steels is decisive for their application in automotive industry. Ab initio simulations have been employed in studying the hydrogen trapping of Cr/Mn containing iron carbides and the implication for hydrogen embrittlement.   more
Hydrogen induced embrittlement of metals is one of the long standing unresolved problems in Materials Science. A hierarchical multiscale approach is used to investigate the underlying atomistic mechanisms. more
Hydrogen at crack tips can embrittle steels and lead to catastrophic material failure. In this project we develop a continuum model for the formation of hydride zones in the tensile regions of a crack tip. It changes the fracture properties of static and propagating fractures. more
Materials degradation due to wear and corrosion is a major issue that can lead to efficiency loss or even failure. As wear may accelerate corrosion and corrosion may accelerate wear, this interaction is of increasing interest in the wind, hydroelectric, oil and gas energy domains and in the bio-medical field. more
Understanding hydrogen-microstructure interactions in metallic alloys and composites is a key issue in the development of low-carbon-emission energy by e.g. fuel cells, or the prevention of detrimental phenomena such as hydrogen embrittlement. We develop and test infrastructure, through in-situ nanoindentation and related techniques, to study independently hydrogen absorption and further interaction with trap binding sites or defects and its effects on the mechanical behavior of metals. more
With the support of DFG, in this project the interaction of H with mechanical, chemical and electrochemical properties in ferritic Fe-based alloys is investigated by the means of in-situ nanoindentation, which can characterize the mechanical behavior of independent features within a material upon the simultaneous charge of H. more
Hydrogen embrittlement of steels: environment-assisted in-situ <br />micro-mechanical tests
Hydrogen embrittlement (HE) of steel is a great challenge in engineering applications. However, the HE mechanisms are not fully understood. Conventional studies of HE are mostly based on post mortem observations of the microstructure evolution and those results can be misleading due to intermediate H diffusion. Therefore, experiments with a simplified stress states and in-situ mechanical loading are required to better understand HE. more
Oxidation and corrosion of noble metals is a fundamental problem of crucial importance in the advancement of the long-term renewable energy concept strategy. In our group we use state-of-the-art electrochemical scanning flow cell (SFC) coupled with inductively coupled plasma mass spectrometer (ICP-MS) setup to address the problem. more
Microbiologically influenced corrosion (MIC) of iron by marine sulfate reducing bacteria (SRB) is studied electrochemically and surfaces of corroded samples have been investigated in a long-term project. more
Mechanical behavior of additively manufactured alloys under <br />hydrogen environment
Despite the immanent advantages of metals and alloys processed by additive manufacturing (e.g. design freedom for complex geometry) and unexpected merits (e.g. superior mechanical performance) of AM processes, there are several remaining issues that need to be addressed in order to practically apply AM alloys to various industries. One of the most important issues is the mechanical behavior of AM alloys under hydrogen environments, since it is easily encountered in the industrial fields and has generally detrimental effects on metals and alloys. more
In this project, the hydrogen embrittlement mechanisms in several types of high-entropy alloys (HEAs) have been investigated through combined techniques, e.g., low strain rate tensile testing under in-situ hydrogen charging, thermal desorption spectroscopy (TDS),... more
In this project, the electrochemical and corrosion behavior of high entropy alloys (HEAs) have been investigated by combining a micro-electrochemical scanning flow cell (SFC) and an inductively coupled plasma mass spectroscopy (ICP-MS) element analysis. more
Thermo-chemo-mechanical interactions due to thermally activated and/or mechanically induced processes govern the constitutive behaviour of metallic alloys during production and in service. Understanding these mechanisms and their influence on the material behaviour is of very high relevance for designing new alloys and corresponding thermomechanical processing routes. more
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