Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 55: Topical Session Modern Atom Probe Tomography V - Steels, Alloys and Structural Materials
MM 55.3: Vortrag
Donnerstag, 29. März 2012, 16:15–16:30, H 0107
Atom probe studies on nano-sized precipitates in lightweight steels — •Jaebok Seol1, Changyung Park2, Pyuckpa Choi1, and Dierk Raabe1 — 1Max-Planck-Insititut für Eisenforschung, Dusseldorf, Germany — 2Dept. of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Republic of Korea
Recently, light-weighted steels containing a low Mn of 3 wt.% and a high Al of 6 wt.% have received considerable attention as a new grade of advanced high strength sheet steels (AHSS) due to their excellent combination of strength and ductility.. The mechanical properties of the steel depend on the precipitation of nano-sized (Fe,Mn)3AlC, κ-carbide particles. However, the decomposition of metastable γ (austenite) into α (ferrite) and κ-carbide as a function of isothermal temperatures has not been studied in detail, in particular at the atomic scale. In this work, phase transformation and elemental redistribution within Fe-Mn-Al-C alloys have been studied by electron back-scatter diffraction (EBSD), X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), and atom probe tomography (APT) in conjunction with thermodynamic descriptions. We observe that as austempering temperature increases, the volume fraction of retained γ decreases with increasing the κ-carbide fraction. In addition, APT results reveal the distribution behaviour of alloying elements in the vicinity of α/carbide interfaces. Based on these observations, we evaluate the correlation between the stability of κ-carbide and isothermal temperature.