© Wiley-VCH Verlag GmbH & Co. KGaA

Research Projects

The phase-field method is particularly well-suited to model coupled mechanical-thermal-chemical microstructure evolution and structure-property relations.
It has been successfully applied to model multiple thermo-chemo-mechanical processes including solidification, precipitation, fracture and dislocation motion. more
One purpose of metallurgical and materials science is the theory-guided tailoring of materials, including elasto-plastic mechanical response, chemical composition and microstructure, in order to obtain improved properties for a sustainable technological development. more
To reach highest quality of microstructure and mechanical properties, adjustment of downstream processing parameters are often required along the process chain, dependent on exact chemical composition of the batch and the preceding casting, deformation and annealing processing steps. more
By using the DAMASK simulation package we developed a new approach to predict the evolution of anisotropic yield functions by coupling large scale forming simulations directly with crystal plasticity-spectral based virtual experiments, realizing a multi-scale model for metal forming. more
New product development in the steel industry nowadays requires faster development of the new alloys with increased complexity. Moreover, for these complex new steel grades, it is more challenging to control their properties during the process chain. This leads to more experimental testing, more plant trials and also higher rejections due to unmatched requirements. Therefore, the steel companies wish to have a sophisticated offline through process model to capture the microstructure and engineering property evolution during manufacturing. more
Crystal Plasticity (CP) modeling [1] is a powerful and well established computational materials science tool to investigate mechanical structure–property relations in crystalline materials. It has been successfully applied to study diverse micromechanical phenomena ranging from strain hardening in single crystals to texture evolution in polycrystalline aggregates. more
<strong>Basics of constitutive formulations, crystal kinematics, homogenization, multiple scales, and multiphysics approaches in crystal plasticity finite element modeling: theory, experiments, applications</strong>

F. Rotersa,*, P. Eisenlohra, L. Hantcherlia, D. D. Tjahjantoa, T. R. Bielerb , D. Raabea

aMax-Planck-Institut für Eisenforschung, Düsseldorf, Germany
bChemical Engineering and Materials Science, Michigan State University, East Lansing MI, USA

Abstract

This article reviews continuum-based variational formulations for describing the elastic–plastic deformation of anisotropic heterogeneous crystalline matter. These approaches, commonly referred to as crystal plasticity finite element models, are important both for basic microstructure-based mechanical predictions as well as for engineering design and performance simulations involving anisotropic media. Besides the discussion of the constitutive laws, kinematics, homogenization schemes, and multiscale approaches behind these methods we also present some examples including in particular comparisons of the predictions with experiments. The applications stem from such diverse fields as orientation stability, microbeam bending, single-and bicrystal deformation, nanoindentation, recrystallization, multiphase steel (TRIP) deformation, and damage prediction for the microscopic and mesoscopic scales and multiscale predictions of rolling textures, cup drawing, Lankfort (r) values, and stamping simulations for the macroscopic scale.

more
<div style="text-align: justify;"><strong>Influence of dislocation climb on the creep rates in γ'-strengthened Ni base superalloy single crystals: A discrete dislocation dynamics study</strong></div>
Creep of single crystal superalloys is governed by dislocation glide, climb, reactions, and annihilation. We use discrete 3D dislocation dynamics (DDD) simulations to study the evolution of the dislocation substructure in a γ/γ’ microstructure of a single crystal superalloy for different climb rates and loading conditions. A hybrid mobility law for glide and climb is used to map the interactions of dislocations with γ’ cubes.
more
<p style="text-align: justify;"><strong>Orientation dependence of shear banding in fcc single crystals</strong></p>
We present crystal plasticity finite element simulations of plane strain compression of α-brass single crystals with different initial orientations. The aim is to study the fundamentals of mesoscale structure and texture development in fcc metals with low stacking fault energy (SFE). Shear banding depends on the initial orientation of the crystals. In Copper and Brass-R oriented crystals which show the largest tendency to form shear bands, an inhomogeneous texture distribution induced by shear banding is observed. To also understand the influence of the micromechanical boundary conditions on shear band formation, simulations on Copper oriented single crystals with varying sample geometry and loading conditions are performed. We find that shear banding can be understood in terms of a mesoscopic softening mechanism. The predicted local textures and the shear banding patterns agree well with experimental observations in low SFE fcc crystals. Keywords: fcc material; shear band; texture; crystal plasticity finite element analysis
more
This progress report discusses how physically based material models can contribute to the development and optimization of new materials. Using in addition enhanced simulation techniques such as density functional theory a true multi scale material development can be established. more
Dual-phase (DP) steel is the flagship of advanced high-strength steels, which were the first among various candidate alloy systems to find application in weight-reduced automotive components. On the one hand, this is a metallurgical success story: more
Single crystalline copper beams with thicknesses between 0.7 and 5 μm are manufactured with a focused ion beam technique and bent in a nanoindenter. The yield strengths of the beams show a mechanical size effect (smaller-is-stronger). more
In this project we pursue an approach for the computationally efficient and quantitatively accurate prediction of solid-solution strengthening. It combines the 2-D Peierls–Nabarro model and a recently developed solid-solution strengthening model. Solid-solution strengthening is examined with Al–Mg and Al–Li as representative alloy systems... more
In this project we identify and analyze general trends governing solid solution strengthening in binary alloys containing solutes across the Periodic table using quantum-mechanical calculations. Here we present calculations for the model system of Al binary solid solutions. more
In this project we study a new strategy for the theory-guided bottom up design of beta-Ti alloys for biomedical applications using a quantum mechanical approach in conjunction with experiments. Parameter-free density functional theory calculations are used to provide theoretical guidance in selecting and optimizing Ti-based alloys... more
Ab initio calculations are becoming increasingly useful to engineers interested in designing new alloys because these calculations are able to accurately predict basic material properties only knowing the atomic composition of the material.  In this project, single crystal elastic constants of 11 bcc Mg-Li alloys are calculated using density-functional theory (DFT) and compared with available experimental data. 
Bcc Mg-Li-based alloys are a promising light-weight structural material. In order to tailor the Mg-Li composition with respect to specific industrial requirements, systematic materialsdesign concepts need to be developed and applied. Quantum-mechanical calculations are increasingly employed when designing new alloys as they accurately predict basic thermodynamic, structural, and functional properties using only the atomic composition as input. more
Go to Editor View