Materials under harsh environments and their stability of surfaces and interfaces

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.

Advanced Microstructural Characterization of in situ Alloyed Nickel-Based Alloys by Welding

Nickel-based alloys are a particularly interesting class of materials due to their specific properties such as high-temperature strength, low-temperature ductility and toughness, oxidation resistance, hot-corrosion resistance, and weldability, becoming potential candidates for high-performance components that require corrosion resistance and good mechanical properties. This unparalleled combination of properties is achieved by adding alloying elements and changes in microstructure. This research project blended Ni-based metal welds produced by in situ alloying using the tandem GMAW process in a previous research project developed by the Welding Research and Technology Laboratory team at the Federal University of Ceará, in Brazil.

Dynamic mechanical properties of functional ceramic oxides

Within this project, we will investigate the micromechanical properties of STO materials with low and higher content of dislocations at a wide range of strain rates (0.001/s-1000/s). Oxide ceramics have increasing importance as superconductors and their dislocation-based electrical functionalities that will affect these electrical properties. Hence it is fundamental to understand the deformation limits to introduce dislocations for both the fabrication process and in-use performance.

Strain rate, size and defect density interdependence on the deformation of 3D printed microparticles

Statistical significance in materials science is a challenge that has been trying to overcome by miniaturization. However, this process is still limited to 4-5 tests per parameter variance, i.e. Size, orientation, grain size, composition, etc. as the process of fabricating pillars and testing has to be done one by one. With this project, we aim to fabricate arrays of well-defined and located particles that can be tested in an automated manner. With a statistically significant amount of samples tested per parameter variance, we expect to apply more complex statistical models and implement machine learning techniques to analyze this complex problem. more

How hydrogen behaves in aluminium alloys

Researchers of the Max-Planck-Institut für Eisenforschung publish their latest findings in the journal Nature more

Interplay of chemistry and faceting at grain boundaries in a high strength Al alloy

Grain boundaries (GBs) are regions connecting adjacent crystals with different crystallographic orientations. GBs are a type of lattice imperfection, with their own structure and composition, and as such impact a material’s mechanical and functional properties. Structural motifs and phases formed at chemically decorated GBs can be of a transient nature or are local thermodynamic structural-chemical equilibrium states. more

Bidirectional transformation induced plasticity in dual-phase high entropy alloys

Recently developed dual-phase high entropy alloys (HEAs) exhibit both an increase in strength and ductility upon grain refinement, overcoming the strength-ductility trade-off in conventional alloys [1]. Metastability engineering through compositional tuning in non-equimolar Fe-Mn-Co-Cr HEAs enabled the design of a dual-phase alloy composed of metastable face centered cubic (fcc) and hexagonal closed packed (hcp) phases. more

Defect phases –  Thermodynamics and influence on material properties

To design novel alloys with tailored properties and microstructure, two materials science approaches have proven immensely successful: Firstly, thermodynamic and kinetic descriptions for tailoring and processing alloys to achieve a desired microstructure. Secondly, crystal defect manipulation to control strength, formability and corrosion resistance. more

Fundamental Dislocation Processes in Superalloys

Project C3 of the SFB/TR103 investigates high-temperature dislocation-dislocation and dislocation-precipitate interactions in the gamma/gamma-prime microstructure of Ni-base superalloys. more

How will materials fail? Basic simulations on experimental data

New research group on “Microstructure and Mechanics” starts at the MPIE more

Environmental chamber for micromechanical testing under non-ambient conditions

The goal of this project is to develop an environmental chamber for mechanical testing setups, which will enable mechanical metrology of different microarchitectures such as micropillars and microlattices, as a function of temperature, humidity and gaseous environment. more

Additive micromanufacturing of 3-D copper architectures

3D copper microarchitectures will be fabricated using a localized electrodeposition-based microscale additive manufacturing process and mechanically tested under extreme strain rates. Structures to be tested range from simple micropillars to complex microlattices. The suitability of such full-metal architectures towards energy absorption and mechanical band-gap engineering applications will be investigated. more

Laser powder bed fusion based pure copper lattice fabrication and characterization

Within this project, we will use a green laser beam source based selective melting to fabricate full dense copper architectures. The focus will be on identifying the process parameter-microstructure-mechanical property relationships in 3-dimensional copper lattice architectures, under both quasi-static and dynamic loading conditions. more

Instrumentation development for ultra-high strain rate micromechanics

This project will aim at addressing the specific knowledge gap of experimental data on the mechanical behavior of microscale samples at ultra-short-time scales by the development of testing platforms capable of conducting quantitative micromechanical testing under extreme strain rates upto 10000/s and beyond. more

High strain rate and fatigue testing of bulk metallic glass

The goal of this project is the investigation of interplay between the atomic-scale chemistry and the strain rate in affecting the deformation response of Zr-based BMGs. Of special interest are the shear transformation zone nucleation in the elastic regime and the shear band propagation in the plastic regime of BMGs. more

Dynamic thermomechanical testing of dewetted microparticles

Smaller is stronger” is well known in micromechanics, but the properties far from the quasi-static regime and the nominal temperatures remain unexplored. This research will bridge this gap on how materials behave under the extreme conditions of strain rate and temperature, to enhance fundamental understanding of their deformation mechanisms. The mechanical behavior of metals with different crystal topologies, i.e. FCC, BCC and HCP and alloy systems, will be investigated in a statistically relevant manner using dewetted microparticles as the test-beds. more

In situ TEM MEMS based tensile testing of thin films

We plan to investigate the rate-dependent tensile properties of 2D materials such as HCP metal thin films and PbMoO4 (PMO) films by using a combination of a novel plan-view FIB based sample lift out method and a MEMS based in situ tensile testing platform inside a TEM. more

Electrothermomechanical testing of metallic nanowires

We will investigate the electrothermomechanical response of individual metallic nanowires as a function of microstructural interfaces from the growth processes. This will be accomplished using in situ SEM 4-point probe-based electrical resistivity measurements and 2-point probe-based impedance measurements, as a function of mechanical strain and temperature. more

Design of MEMS based testing platforms

This project will aim at developing MEMS based nanoforce sensors with capacitive sensing capabilities. The nanoforce sensors will be further incorporated with in situ SEM and TEM small scale testing systems, for allowing simultaneous visualization of the deformation process during mechanical tests more

Thermo-chemo-mechanical coupling during thermomechanical processing of microalloyed steels (TCMPrecipSteel)

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

Hydrogen-Carbide Interaction

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

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