Prof. Jeongho Han Ph.D. (2015), Yonsei University, Korea Assistant Professor, Chungnam National University Ph.D. (2015), Yonsei University, Korea Thesis: Advanced high strength steels (Mn steels) 2015.09 – 2016.02 Postdoctoral Researcher, Research Institute for Iron and Steel Technology, Yonsei University 2016.04 – 2016.08 Humbolt research Fellowship for Postdoctoral Researchers, Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany • Manganese steels (Medium Mn, High Mn) • Thermo-mechanical process • Hydrogen embrittlement • Advanced alloy design (Ti alloy, High entropy alloy)

Research stream of medium Mn steels With an increasing demand for cost efficient advanced high strength steels in modern industry, medium Mn transformation-induced plasticity (TRIP) steels have received significant attention since both their reasonable materials cost and excellent mechanical properties. Medium Mn TRIP steels are defined as the steel with Mn concentration ranging from ~3 wt.% to ~12 wt.% and C concentration less than ~0.4 wt.%, and sometimes they contain a low concentration of additional alloying elements. The steels generally exhibit an α′ martensite microstructure after hot rolling and cold rolling and a dual phase microstructure of α ferrite and retained γ austenite (γR) with ultrafine grain size after intercritical annealing. The volume fraction of γR ranges between ~0.2 and 0.5 and it is controlled by intercritical annealing conditions such as temperature and time. Both the ultrafine grain size and active TRIP phenomenon from the large fraction of γR result in a remarkable tensile properties of yield strength up to ~1000 MPa, tensile strength up to ~1400 MPa and elongation up to ~32%. The present review summarises the important results of previous studies, such as effects of intercritical annealing condition, alloying elements and initial martensite morphology on the final microstructure and mechanical properties of medium Mn steels. Time: Mar. 9th 4:30~5:45pm Location: GIFT Auditorium #101 Speaker: Prof. Jeongho Han (Chungnam Nat’l University) Host: Prof. Jee-Hyun Kang