清華大學材料科學與工程研究院《材料科學論壇》學術報告

報告時間：2024年12月6日上午10:00-11:00

報告人：Alisson Kwiatkowski da Silva (Thermo-Calc Software AB)

報告地點：清華大學逸夫技術科學樓A205會議室

邀請人：闫佳易老師

報告題目：Ultra-high strength Fe18Mn3Ti maraging steel through controlled solute segregation and α-Mn nanoprecipitation

報告簡介：

We designed a compositionally lean Fe18Mn3Ti (wt.%) ultra-high strength steel, susceptible to homogeneous phase decomposition, assisted by segregation. This alloy composition is thermodynamically designed to be unstable against compositional fluctuations at the intended aging temperature, around 450 °C. These fluctuations act as precursors for the nucleation of an unexpected α-Mn nano-precipitate phase, which can decrease the mobility of the dislocations in the matrix, enabling precipitation strengthening of the martensitic matrix. We added 3 wt.% Ti to allow the transformation of austenite to α-martensite during quenching and cold rolling, preventing a high fraction of retained austenite and epsilon martensite (with hexagonal lattice structure), and stabilize the second phase α-Mn precipitates. Such strategy avoids the addition of critical elements such as Co and Mo which enable intermetallic precipitation in conventional ultra-high strength maraging steels. Ni is also completely replaced by Mn which participates both in austenite stabilization and precipitate formation. The importance of Scheil and DICTRA simulations in order to understand and control the microsegregation and associated Laves phase formation during solidification, subsequent hot rolling and homogenization will also be discussed.

報告人簡介：

Alisson Kwiatkowski da Silva was awarded a Doktor Ingenieur (Dr.-Ing.) degree (summa cum laude) in June 2018 under the supervision of Prof. Dr.-Ing. Dierk Raabe at Max-Planck-Institut für Eisenforschung (MPIE). During his PhD studies, he investigated the mechanisms of Mn segregation, austenite reversion and carbide precipitation during intercritical annealing of medium Mn steels. He received twice the best poster award at the Gordon Conference on Physical Metallurgy and the Aaronson Award at the International Conference on Solid-Solid Phase Transformations in Inorganic Materials (PTM) for his contributions to the understanding of Mn segregation and austenite reversion in medium Mn steels. During his postdoctoral investigations, he developed a new Fe18Mn3Ti maraging steel. He now works for Thermo-Calc Software AB developing use cases and models for Computational Materials Engineering and he is also a guest researcher at Max Planck Institute for Sustainable Materials, collaborating and developing research activities related to sustainability, alloy design, phase transformation, corrosion and fundamental aspects of thermodynamics and kinetics of materials.