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MM: Fachverband Metall- und Materialphysik

MM 44: Topical Session: Interface-dominated phenomena - Solutes at Interfaces II

MM 44.1: Vortrag

Mittwoch, 18. März 2020, 17:15–17:30, IFW A

Atomic scale analysis on the elemental partitioning across phase boundaries in medium-Mn steels — •Wenwen Song, Yan Ma, and Wolfgang Bleck — Steel Institute (IEHK), RWTH Aachen University

The ultrafine grained medium-Mn steels (3~12 wt.% Mn) emerge as a strong candidate for the 3rd generation of advanced high strength steels, due to its excellent mechanical properties. In the present work, we aim to understand the role of elemental partitioning across the interfaces, in particular the ferrite-austenite phase boundaries, during intercritical annealing and its impact on yielding behaviors. The nanostructured medium-Mn steels were characterized by atom probe tomography (APT), transmission electron microscopy (TEM) and high energy synchrotron x-ray diffraction (SYXRD). The 3D atomic maps show the elements concentration distribution. The elemental partitioning, i.e. C, Mn, Si, as well as the microalloy elements Nb, Mo, across the ferrite-austenite phase boundaries were analyzed. High carbon segregation at the ferrite-austenite phase boundaries were observed after intercritical annealing and air cooling. This segregation resulted in an increase in the yield strength and a pronounced discontinuous yielding phenomenon. The ferrite-austenite interfaces act as preferable nucleation sites for new partial dislocations in austenite and for full dislocations in ferrite. The current study sheds light on novel microstructural design and interface segregation strategies for ultrafine grained multiphase materials through phase-boundary engineering induced strengthening.