Microstructure Physics and Metal Forming

HomeMUMicrostructure Physics and Metal Forming

Professor Dierk Raabe

 

Microstructure and Mechanical Properties

The department conducts basic research on the mechanical properties of crystalline materials. These are determined by the thermodynamic constitution of the material on the one hand and the kinetics of microstructure evolution on the other hand. Microstructure evolves in crystalline matter primarily through elasto-plastic deformation, phase transformations (typically non-equilibrium), recrystallization, and grain growth so that studies on the underlying mechanisms of these processes form the basis of our work.

In the case of engineering materials such as steel, titanium, magnesium, and nickel-base alloys microstructures evolve under complex thermomechanical history and boundary conditions. This means that the effect of processing on the microstructure and hence on the final behavior of the materials is taken into consideration in our projects.

In order to elucidate which specific mechanisms lead to certain microstructures we use a combination of advanced characterization, well defined model experiments, and theoretical models of microstructure evolution and microstructure-property relationships at different length scales, Fig. 1. A close integration of theory and experiment is, hence, a common feature of our approach [1-8]. Most of the microstructure models that are developed in our group are formulated as continuum–based rate formulations of lattice defect kinetics and corresponding kinetic equations of state describing the resulting properties. The underlying differential equations are typically solved using variational methods [9-16]. Corresponding simulations are then conducted under boundary conditions that are of interest with respect to a certain processing step or model experiment. Typical examples of such models are dislocation-density based crystal plasticity formulations that are solved by using standard finite element solvers [4-16].

We use simulations not only for studying the fundamentals of microstructure evolution and the resulting properties: Owing to the increasing complexity of modern mechanical experimental and characterization results, particularly at nanoscaopic scales, it is often difficult to interpret experimental observations without the use of accompanying simulations. Often microstructure observations can be highly sensitive with respect both to the boundary conditions imposed during an experiment and also to the underlying mechanisms that take place before or during an experiment [1-3,5]. In such cases simulations help us to critically interrogate the true relationships between microstructure mechanisms and boundary conditions imposed during an experiment. In other words, the inverse use of simulations can help us to identify what the true boundary conditions of an experiment or process have been, Figs. 1a,b [1].

Overview

For pursuing the aims outlined above six main competence groups are currently operative. They form the cornerstones of the department.

Theory and Simulation (F. Roters)

 Diffraction and Microscopy (S. Zaefferer)

 Thermomechanical Processing (D. Ponge)

 Biological Materials (H. Fabritius)

 MPG-FhG-Group on Computational Mechanics of Polycrystals (P. Eisenlohr)

 MMM-Group on the Theory and Simulation of Complex Fluids (F. Varnik)

 Atom probe tomography (P. Choi)

The latter two initiatives are temporary groups. The project of P. Eisenlohr on the Computational Mechanics of Polycrystals is jointly funded after two subsequent evaluation workshops (2005, 2008) by the Max-Planck-Society and the Fraunhofer-Society for 3+3 years, 2005-2011. The project of F. Varnik on the Theory and Simulation of Complex Fluids is funded by the Max-Planck-Multiscale Modeling Initiative for 4 years, 2005-2009.

Many projects in our department are jointly pursued by members of different groups including also other departments. The most important interdisciplinary research fields of the department during the past two years are given in the list below. Fig. 2 presents the connection between these research areas and gives examples of corresponding projects.

• Structure and properties of high strength steels

• Multiphase tomographic 3D EBSD nano- and microtexture analysis

• Nano- and microscale mechanics of crystals

• Multiscale modeling starting from ab-initio predictions

• Structure and properties of biological nanocomposites

• Multigrain and multiphase homogenization theory in crystal plasticity

The projects are conducted using a number of highly specialized laboratories. The main laboratory facilities of the department are

• Mechanical testing laboratory

• High resolution scanning orientation electron microscopy

• 3D electron microscopy: Joint focused ion beam microscopy and 3D nanotexture laboratory

• Transmission electron microscopy laboratory

• X-ray diffraction laboratory

• Strain mapping digital image correlation (photogrammetry) laboratory

• Surface confocal topography laboratory

• Nanomechanical testing and atomic force microscopy laboratory

• Laboratory for deformation dilatometry

• Computational materials science laboratory

• Large scale thermomechanical treatment laboratory

• Hot and cold rolling laboratory

• Heat treatment laboratory

• Laboratory for mechanical testing

• Micromechanical testing laboratory

• Optical metallography laboratory

In the following sections we present the scientific directions of the different groups and give examples of their projects and interdisciplinary cooperations.

Projects within our group and also among the departments are pursued in an interdisciplinary and team-oriented spirit. Scientists in our department come from such different backgrounds as physics, materials science, metallurgy, biology, informatics, chemistry, and mechanics. Projects are conducted in an atmosphere of mutual inspiration, discussion, and cooperation. Paramount to the success of our work is the close exchange among theorists and experimentalists.

The working atmosphere in our group was during the past 2 years dominated by an international flair bringing together young scientists and visiting scholars from Algeria, Australia, Belgium, Brazil, Bulgaria, China, Egypt, France, Germany, India, Indonesia, Israel, Iran, Japan, Jordan, Korea, Nigeria, Russia, Sweden, Spain, Thailand, Turkey, UK, USA, and Venezuela, (Fig. 3). Our international orientation is also reflected by our extramural cooperation partners, namely, Prof. Bleck and Prof. Gottstein (RWTH Aachen, Germany), Prof. Rollett (Carnegie Mellon University, USA), Prof. Radovitzky (MIT, USA), Prof. Mao (University of Science and Technology Beijing, China), Prof. Sandim (University of Lorena, Brazil), Prof. Bieler and Prof. Crimp (Michigan State University, USA), Prof. Mason (Albion College, USA), Prof. Hono and Prof. Adachi (National Institute for Materials Science, Japan).

The international visibility of the department is reflected by more than 15 plenary and keynote lectures at international conferences in the past 2 years, numerous memberships of scientists from the department in international editorial, conference, and advisory boards, and a number of awards with which the department was honoured in the last 2 years. For instance M. Calcagnotto was awarded with a grant from the Japan Society for Promotion of Science (JSPC); F. Varnik received the Best Talk Award at the Nano- and Microfluidics Conference in Bad Honnef; F. Weber provided the figure for the front cover of Advanced Engineering Materials Vol. 10, No. 8, August 2008; L. Raue received the Outstanding Student Researcher Award at the 15th International Conference on Textures of Materials (ICOTOM 15) in Pittsburgh, USA; C. Zambaldi was awarded with the 1st prize in the Poster Competition of the RMS Electron Backscatter Diffraction Meeting in Sheffield, UK; T. Gronau was honored by the Max-Planck-Society with the Outstanding Apprentice Award; D. Raabe was elected as a member of the Nordrhein-Westfälische Academy of Sciences; D. Raabe received the Lee Hsun Lecture Award of the Institute of Metal Research of the Chinese Academy of Sciences in Shenyang, China; K. Verbeken and D. Raabe received the Best-Poster-Award for their contribution “Identification of  martensite in Fe-based shape memory alloys by means of EBSD” at the E-MRS 2007 conference in Warsaw, Poland; D. Raabe was elected as a Member of the Board of Governers of Acta Mater. Inc. , USA; D. Raabe was elected as a member into the Selection Committee of the Alexander von Humboldt Foundation, Germany; C. Zambaldi, F. Roters, T. R. Bieler and D. Raabe were awarded by the 11th World Conference on Titanium (JIMIC5) with the Best Poster Award in Kyoto, Japan; C. Zambaldi was awarded with a grant research fellowship from the Japan Society for Promotion of Science (JSPC) to the "National Institute for Materials Science (NIMS)"; M. Frommert, D. Dorner, L. Lahn, D. Raabe, and S. Zaefferer received the “Best Poster Award” for their contribution “3D Investigation of Early Stages of Recrystalllization in Deformed Goss-Oriented Fe3%Si Single Crystals” at the “Third International conference on Recrystallization and Grain Growth, ReX & GG III in Korea; P. Eisenlohr was elected as an AICES "Young Researcher"; P. Romano was awarded a grant research residency from the Japan Society for Promotion of Science (JSPC) to the "National Institute for Materials Science (NIMS)"; C. Sachs was awarded with a Max-Planck Minerva Short-Term Research Grant; C. Sachs was awarded with the best paper award by TMS for the paper “Homogeneous Steel Infiltration”; B. Stieger was honored by the Max-Planck-Society with the Outstanding Apprentice Award; A. Brahme received the Annual Student Award from Acta Mater. for his contribution “3D reconstruction of microstructure in a commercial purity aluminum” Scripta Materialia 55, 2006, 75-80, September 2007 at the MS&T Conference, Detroit, USA; and H. Faul received the honorary needle in silver for his 10 years of commitment in professional training by the Industrie- und Handelskammer, Stuttgart. All these honours were received during the years 2007 and 2008.

Besides these awards two habilitation procedures out of the Department for Microstructure Physics and Metal Forming were initiated during the past 2 years (F. Varnik, S. Zaefferer).

A number of senior scientists received professorship positions during the past 2 years: Dr. Y. Cao became a Professor for Soft Matter Mechanics at Tsinghua University in China; Dr. S. Hild became Professor for Polymer Science at Linz University in Austria; Dr. N. Zaafarani became Professor for Materials Mechanics at Tanta University in Cairo; Dr. S. Nikolov will become Professor at the Bulgarian Academy of Science in Sofia; and Dr. Z. Huang became Professor for Metallurgical Modeling at Shanghai Jiao Tong University in China.

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This page is maintained by Gabriele Geelen. Last update: 25.08.2009