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SFB 761:  Steel - Ab Initio. Quantum Mechanics Guided Design of New Fe-based Materials

Subject Area Materials Science and Engineering
Chemistry
Mechanical and Industrial Engineering
Physics
Term from 2007 to 2019
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 29898171
 
Final Report Year 2019

Final Report Abstract

In the Collaborative Research Centre 761 "Steel ab initio - quantum mechanics guided design of new Fe based materials", scientists and engineers from RWTH Aachen University and the Max Planck Institute for Iron Research have conducted research on mechanism-controlled material development with the particular example of high manganese alloyed steels. From 2007 to 2019, a total of 55 part projects and 4 transfer projects with industrial participation (some running until 2021) have dealt with material and process design as well as material characterization. The idea of the Collaborative Research Centre was to develop a methodologically new approach for the design of structural materials. Since the mid-1990s, considerable progress had been achieved in modelling and measurement technology, so that a systematic knowledge-based development of the particularly demanding new material group of high manganese alloyed steels could be tackled. With these high Mn steels (up to 30 wt.% Mn) extraordinary phenomena in plastic deformation are observed and on this basis, exeptional property combinations can be realized. As a central scientific working hypothesis, it was assumed that the stacking fault energy in particular controls the deformation mechanisms. The stacking fault energy thus served as a parameter for the development of processes and materials, as it is experimentally accessible and can also be calculated with modern ab initio methods. The challenge was therefore to combine scientific theories based solely on physical and chemical parameters with established engineering concepts in materials engineering. The participating researchers from various engineering disciplines, from physics and from chemistry have developed and applied models and methods from the atomistic to the macroscopic scale. The scientific and technical interest in high Mn steels has grown significantly in recent years. Current considerations involve transferring the deformation mechanisms observed in a fully austenitic high Mn steels (SLIP: dislocation slip, TRIP: Transformation Induced Plasticity, TWIP: TWinning Induced Plasticity, MBIP: MicroBand Induced Plasticity) to the multiphase austenitic/martensitic microstructure in medium Mn steels. In addition to lower alloying costs due to lower manganese contents, this promises easier integration of these materials into the current industrial infrastructure. At the same time, the property profile can be adapted to a wide range of component requirements. Common to all new steel concepts of the so-called "Advanced High Strength Steels" (AHSS 1st, 2nd, 3rd generation) is a controlled microstructure adjustment on the nanometer scale. Important results of the Collaborative Research Center are that with sophisticated simulation methods, e.g. based on ab initio calculations, a basic understanding of the occurrence of the various deformation mechanisms and the resulting material properties can be achieved. With newly developed characterization methods, e.g. by combining SEM, TEM and APT investigations, the project has enabled new insights into the nanostructuring of microstructures and local segregation phenomena of alloying and accompanying elements. Experimental evaluation of different process chains up to the presentation of a demonstrator component was possible and potentials for the application of the new steel groups could be shown. Looking back on twelve years of intensive cooperation, it can be stated that it has been possible to use modelling approaches on different scales up to ab initio methods for the development of a new class of metallic structural materials. From today's perspective, these approaches as well as the further development of characterization methods are necessary for the design of materials structured on the nanometer scale and for the understanding of the metallurgical phenomena occurring here. A great potential for the future development of new iron-based materials is seen.

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