Neutron Diffraction studies of Austenite-to-Ferrite Transformations in Low-Alloy Steels

V. Davydov^1,2, P. Lukáš¹, O. Muránsky¹, S. Vratislav², P.G. Xu³, Y. Tomota³ and Y. Adachi⁴

¹Nuclear Physics Institute, 250 68 Řež, Czech Republic

²Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, 115 19 Prague, Czech Republic

³Institute of Applied Beam Science, Graduate School of Science and Engineering, Ibaraki University, Hitachi, 316-8511, Japan

⁴Steel Research Center, National Institute for Materials Science, Tsukuba, 305-0047, Japan

Production of construction materials with well balanced strength and toughness is a many years challenge task for material designers. Taking into account also economic aspects, one of the promising ways is a production of the multiphase low-alloyed steel with favorable phase composition and fine grain microstructure yielded by a special concept of thermo-mechanical processing. In the present work, the austenite-to-ferrite phase transformation in low alloy steels was studied by neutron diffraction methods. This method was used in situ during thermo-mechanically controlled processing /TMCP/ to study transformation kinetics and behavior of phase lattice strains. Moreover, the neutron diffraction is also used for monitoring of texture evolution during TMCP. Two types of steels containing different amount of Nb addition were examined. The influence of production parameters such as deformation degree and Nb addition on the steel microstructure and its mechanical properties is reported in particular.