Berlin 2012 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 55: Topical Session Modern Atom Probe Tomography V - Steels, Alloys and Structural Materials

MM 55.1: Talk

Thursday, March 29, 2012, 15:45–16:00, H 0107

Characterisation by Atom Probe Tomography of a Precipitation Hardened Lean Maraging-TRIP Steel — •Julio Millán, Dirk Ponge, Pyuck-Pa Choi, and Dierk Raabe — Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, 40237 Düsseldorf, Germany

Nano-scaled microstructural changes generated in two as-quenched multicomponent alloy systems Fe-xMn-2Ni-1Mo-1Ti-0.15Al-0.01C (x=9 and 12, mass%) during aging at 450°C for 48 hours were evaluated by atom probe tomography. After the solution treatment and subsequent quenching, an initial microstructure consisting of a fully martensite matrix or a mixture of retained austenite and martensite were obtained in the 9%Mn and 12%Mn alloy, respectively. Upon aging, precipitation of nano-sized particles and simultaneous formation of reverted austenite occurred in both materials. No differences in the chemistry of the particles core were found when the nominal Mn content in the alloy was increased from 9 to 12%. However, a difference in formation and growth of the reverted austenite was observed depending on the presence of retained austenite in the quenched state. In absence of retained austenite (9%Mn alloy), the accumulation of Mn together with other alloying elements was detected at the internal interfaces of the martensite matrix, suggesting the formation of a metastable thin-film of reverted austenite. In contrast, the 12% Mn alloy exhibited an accelerated formation of reverted austenite occurring not only at the martensite-martensite interfaces but also around the retained austenite.