Abstract: This study presents a novel method to determine the stress tensor for grain groups with preferred texture orientations and the Critical Resolved Shear Stresses (CRSSs) required to activate slip systems, applied to investigate the elastic-plastic behavior of textured duplex steel [1] and two-phase brass. The approach relies on in situ neutron diffraction measurements of lattice strains in ferritic and austenitic grains for steel, and in α- and β-phase grains for brass, during tensile testing. These measurements enabled direct experimental determination of the evolution of both the stress tensor and the Resolved Shear Stress (RSS) for groups of grains with similar orientations.
For the first time, CRSS values for slip systems in both phases of duplex steel and two-phase brass were directly obtained from experimental data. A key advantage of this methodology is that both grain stress tensors and CRSSs are determined for representative polycrystalline volumes without relying on elastic-plastic models.
Results show that heat treatment significantly hardens the ferritic phase in duplex steel, resulting in a markedly higher CRSS compared to the austenitic phase, strongly influencing the overall yield stress. In contrast, the CRSS values of α- and β-phase grains in two-phase brass are approximately equal, leading to more uniform mechanical behaviour.
Finally, the experimental data were compared with predictions from a multi-scale Elastic-Plastic Self-Consistent (EPSC) model using the experimentally obtained CRSSs as input. Direct determination of CRSS values reduces input parameters in multiscale models and allows verification of theoretical calculations.

Reference: [1] A. Baczmański, et al., International Journal of Mechanical Sciences 283 (2024) 109745.

Keywords: Elastic-plastic deformation, neutron diffraction, crystallographic slip, multiscale model
Acknowledgements: This work was financed by a grant from the National Science Centre, Poland (NCN), No. UMO-2023/49/B/ST11/00774.

Biography: Professor Andrzej Baczmański is a physicist at the Faculty of Physics and Applied Computer Science, AGH University of Krakow, Poland. He received his Ph.D. in Physics of Metals in 1992 and habilitation in Solid State Physics in 2005, both at AGH. In 2014 he was awarded the title of Professor of Physics. His research focuses on diffraction methods in materials science, particularly neutron and X-ray diffraction for studying crystallographic texture, internal stresses, and plastic deformation in polycrystalline and multiphase materials. He has also contributed to the development of self-consistent elasto-plastic models. He has held fellowships and visiting professorships in France, including at ENIM Metz, ENSAM Paris, UTT Troyes, and CEA Saclay, and has conducted experimental work at major European neutron and synchrotron facilities such as ISIS (UK), ESRF (France), DESY and HZB (Germany), and NRI Řež (Czech Republic).