Prof Andreas Mortensen
Laboratory for Mechanical Metallurgy, Institute of Materials, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
This seminar will be chaired by Prof Upadrasta Ramamurty.
Oxide inclusions are present in nearly all iron-based alloys as a direct consequence of the steelmaking process and are known to affect the mechanical properties of steel products. While the relation between the steelmaking practice and the characteristics of oxide inclusions is currently receiving strong attention, much remains to be learned about the local structure and properties of the oxides themselves and the influence they exert on properties of the steel in which they are contained. In this work, oxide inclusions are produced by melting and deoxidizing high purity iron under a controlled atmosphere. Local inclusion properties are measured by means of instrumented indentation and by in-situ micromechanical testing conducted on individual inclusions. The latter tests are performed by milling, with a focused ion beam (FIB), two sample geometries, namely (i) “C-shaped” test samples, produced from inclusions partially exposed by selective dissolution of the matrix and that measure the particle strength, and (ii) bend beams that are produced parallel to the polished surface and test the strength of the interface between the inclusion and the iron matrix. Coupling data with finite elements simulations, strength values are obtained for both the inclusions and their interface with the matrix. Data reveal that spherical silicon oxide inclusions grown in iron are strongly bonded to the metal and break at stress values that approach the highest measured values for the fracture strength of dry silica.
This work is sponsored by the Swiss National Science Foundation, Grant No. 200021_182557.
Andreas Mortensen earned his engineering diploma in 1980 from the Ecole des Mines de Paris and his Ph.D. from the Massachusetts Institute of Technology (MIT) in 1986. He is currently Professor and director of the Laboratory for Mechanical Metallurgy of the Ecole Polytechnique Fédérale de Lausanne (EPFL). At EPFL he has also served successively as dean of doctoral studies, director of the institute of materials, dean for research, vice-provost and then vice-president for research. Prior to joining EPFL in 1997 he was, from 1986 to 1996, a member of the faculty in the Department of Materials Science and Engineering at MIT, holding the successive titles of ALCOA Assistant Professor, Associate Professor, and Professor. He was also a postdoctoral researcher at Nippon Steel in 1986, and an invited professor at the Ecole des Mines in Paris in 1995-1996.
His research focuses on the processing, microstructural development and mechanical behavior of metal alloys and advanced metallic materials including metal matrix composites and microcellular metals. He has contributed to our understanding of infiltration processing, composite micromechanics, to the probing of in-situ mechanical properties and various aspects of the microstructural development, embrittlement, fracture and plasticity of multiphase metallic materials. He is co-author of two monographs, around 200 refereed scientific publications and 15 patents. He has served industry and government, on committees or as a consultant, and has edited several journals and books. His most recent awards are an ERC and SNSF advanced grant in 2012 and 2022, respectively, and the 2016 Grande Médaille of the Société Française de Métallurgie.