PD Dr. rer. nat. F. Roters (Max-Planck Institut für Eisenforschung, Düsseldorf)
High-manganese steels offer the unique possibility of influencing the deformation behavior SLIP, TWIP, TRIP and MBIP by means of alloy variation, and thus independently of the strength level. The challenge is to use the available mechanisms individually or in combination in a targeted manner in order to tailor materials for specific requirements such as deformation or crash. Cloud I is dedicated to the following research question:
How can the strengthening mechanisms of high manganese steels be used to achieve an optimal hardening behavior for different applications?
The aim of the work is to provide an optimal setting of the hardening behavior for selected applications by understanding the relationships between chemical composition, microstructure, activated deformation mechanisms and the resulting strengthening properties (Fig. 16). Here the chemical composition controls the strengthening behavior via the stacking fault energy, the solid solution hardening and short-range order phenomena. Along the process chain further microstructural features (element distribution, grain size, texture, etc.) are influenced in order to control the strengthening behavior.
In conventional steels, it is known to explain and quantitatively predict the mechanical properties based on the present material microstructure. By definition, the microstructure of a material is described by shape, size, distribution and orientation of phases and interfaces. In the case of high manganese steels, however, a quantification of the microscopically visible structural constituents is no longer sufficient to derive microstructure-property correlations since the solidification behavior is decisively determined by structures on the nanometer scale. Accordingly, it is necessary to describe high manganese steels, taking into account the structure of the nanoscale, and then to adjust them during the production processes in a targeted manner.
Cloud I deals with
- with the Characterization of microstructures (predominantly on the nano scale) and the strengthening properties of selected high manganese steels
- with the derivation of quantitative physical relationships between the microstructures and the resulting strengthening properties
- with the targeted adjustment of desired strengthening properties by alloy design and modification of the microstructures along the process chain
The aim is to realize as much as possible idealized strengthening properties which are adapted to the application. As an important potential application for high manganese steels, the energy absorption capacity under crash load is to be adjusted in Cloud I first. Due to their exceptional combination of strength and elongation, high-manganese steels have, in principle, a high specific energy absorption capacity. In the SFB, it has already been shown that significantly different material properties result both by varying the alloy composition and by different annealing treatments (Fig. 17). However, it turned out that the high strengthening potential had to be made available by the adaptation of the construction design for the technical use. For the maximization of the energy absorption capacity of a component, it is therefore necessary to adapt the deformation mechanisms to the dynamic buckling and failure behavior of the component structure. This task combines several subprojects from areas A, B and C, which form the start-up configuration of the Cloud I.
Strain_Hardening_Engineering [5.6 M]