This project deals with the phase quantification by nanoindentation and electron back scattered diffraction (EBSD), as well as a detailed analysis of the micromechanical compression behaviour, to understand deformation processes within an industrial produced complex bainitic microstructure.
The combination of high strength and ductility is vital for industrial products like line pipe or structural steels. Increasingly, such products are made of bainitic steels with complex microstructures [1-3]. Since such complex microstructures often consist of granular bainite and polygonal ferrite, and both phases are very difficult to distinguish under the light optical microscope, two different approaches have been applied [4-5].
As a first approach, nanoindentation tests and extreme property mapping (XPM) were used, which were additionally analysed using k-means clustering. In addition, an automatised MATLABMTEX tool was created to determine the misorientation angle within each grain, which enables the differentiation between both phases [5-7]. Furthermore, micropillar compression tests were applied on both constituents to understand the deformation process by mechanism-based models. The critical resolved shear stress (CRSS) and the corresponding activated slip systems will be used as a decisive criterion.
Subsequently, the relevant parameters to describe the representative behaviour of real microstructures can be used as an input for a computational material model to be implemented in the crystal plasticity simulation tool DAMASK [8].
This project is in cooperation and supported by Dillinger (AG der Dillinger Hüttenwerke).
Fig. 1: The granular bainite has been separated by the kernel average misorientation threshold. a) the detected granular bainite grains (the low angle grain boundaries are displayed as red lines) show also a higher kernel average misorientation compared to polygonal ferrite grains in b).
Fig. 1: The granular bainite has been separated by the kernel average misorientation threshold. a) the detected granular bainite grains (the low angle grain boundaries are displayed as red lines) show also a higher kernel average misorientation compared to polygonal ferrite grains in b).
Fig. 2: According to the crystallographic orientation of the tested grain, the slip planes are predicted for all three slip families which can be active due to the highest Schmid factor a). In comparison with a) the {112} slip plane was activated in b) during this microcompression test.
Fig. 2: According to the crystallographic orientation of the tested grain, the slip planes are predicted for all three slip families which can be active due to the highest Schmid factor a). In comparison with a) the {112} slip plane was activated in b) during this microcompression test.
Y. W. Chen et al., “Phase quantification in low carbon Nb-Mo bearing steel by electron backscatter diffraction technique coupled with kernel average misorientation
Mater. Charact., vol. 139, no. September 2017, pp. 49–58, 2018
Franz Roters, Martin Diehl, Pratheek Shanthraj, Philip Eisenlohr, Jan Christoph Reuber, Su Leen Wong, Tias Maiti, Alireza Ebrahimi, Thomas Hochrainer, Helge-Otto Fabritius, Svetoslav D. Nikolov, Martin Friák, Noriki Fujita, Nicolò Grilli, Koenraad G.F. Janssens, Nan Jia, Piet Kok, Duancheng Ma, Felix Meier, Ewald Werner, Markus Stricker, Daniel M. Weygand, and Dierk Raabe, "DAMASK – The Düsseldorf Advanced Material Simulation Kit for modeling multi-physics crystal plasticity, thermal, and damage phenomena from the single crystal up to the component scale," Computational Materials Science 158, 420-478 (2019).
International researcher team presents a novel microstructure design strategy for lean medium-manganese steels with optimized properties in the journal Science
Oxides find broad applications as catalysts or in electronic components, however are generally brittle materials where dislocations are difficult to activate in the covalent rigid lattice. Here, the link between plasticity and fracture is critical for wide-scale application of functional oxide materials.
The fracture toughness of AuXSnY intermetallic compounds is measured as it is crucial for the reliability of electronic chips in industrial applications.
Within this project we investigate chemical fluctuations at the nanometre scale in polycrystalline Cu(In,Ga)Se2 and CuInS2 thin-flims used as absorber material in solar cells.
This project aims to investigate the dynamic hardness of B2-iron aluminides at high strain rates using an in situ nanomechanical tester capable of indentation up to constant strain rates of up to 100000 s−1 and study the microstructure evolution across strain rate range.
