时 间：2018年6月22日（星期五） 下午14：30（开始时间）
地 点： 友谊校区 公字楼334学术报告会议厅
主 题： Intermetallic Titanium Aluminides – Status of Research and Application
内容简介： Intermetallic TiAl alloys based on the γ-TiAl phase are already used as engineering lightweight high-temperature materials in aircraft and automotive engines. Thereby, they partly substitute the twice as heavy Ni-base superalloys. Present applications are, for example, blades in the low-pressure turbine of advanced aero-engines, turbine wheels for turbocharger systems of car diesel engines and engine parts used in racing cars.
Advanced TiAl alloys are complex multi-phase alloys which can be processed by ingot or powder metallurgy as well as precision casting methods. Each process leads to specific microstructures which can be altered and optimized by thermo-mechanical processing and/or subsequent heat-treatments. The background of all these heat-treatments is at least twofold, i.e. concurrent increase of ductility at room temperature and creep strength at elevated temperature. In order to achieve this goal, the knowledge of the occurring solidification processes and the following phase transformation sequences are essential. Therefore, thermodynamic calculations were conducted to predict the phase diagram of engineering TiAl alloys. After verification with experimental methods, e.g. short and long-term heat-treatments, differential scanning calorimetry and X-ray diffraction analysis, these phase diagrams provided the base for the development of smart heat-treatments. To account the influence of deformation and kinetic aspects sophisticated ex- and in-situ methods have been employed to investigate the evolution of the microstructure during thermo-mechanical processing and subsequent multiple heat-treatments. For example, in-situ high-energy X-ray diffraction was conducted to study dynamic recovery and recrystallization processes during hot-deformation tests. Due to the peculiar scattering behaviour of TiAl alloys neutron diffraction was also used for the investigation of order/disorder reactions. Summarizing all results a consistent picture regarding microstructure formation and its impact on mechanical properties in advanced TiAl alloys can be given. Finally, the development status and perspectives of these alloys as innovative automotive and aircraft engine materials are presented in the framework of this lecture.
Helmut Clemens is a distinguished professor of physical metallurgy at the University of Leoben (Montanuniversität Leoben) in Austria. Born in 1957, Helmut Clemens studied Materials Science at the University of Leoben, receiving his doctorate in 1987. He joined Plansee AG, Austria, as head of the Advanced Materials R&D group in 1990, gaining his lecturing qualification in 1997. From 1998 to 2000 he was professor for Metallic Materials at the Institute for Physical Metallurgy, University of Stuttgart, Germany, before moving to the Institute for Materials Research, Helmholtz-Zentrum Geesthacht, Germany, in a joint appointment as Professor at the Christian-Albrechts University Kiel, Germany. Since July 2003 he is head of the Chair of Physical Metallurgy and Metallic Materials at the University of Leoben.
Professor Helmut is a well-known expert on the field of titanium aluminides, with special focus on alloy and process development as well as microstructure-property relationship. Furthermore, he is organizer/co-organizer of many scientific conferences and workshops on intermetallic materials. He has received several national and international awards, including the prestigious Honda Prize in 2014. Professor Helmut has published over 410 journal papers and more than 170 conference papers. In addition, he has been invited to be as Keynote Speaker or Plenary Speaker over 35 times all over the world.