?School of Mechanical, Materials and Mechatronic Engineering
SEMINAR Materials and Mechanical Engineering Studies using Time-of-Flight Neutron Diffraction at J-PARC, Japan
PRESENTER Dr. Stefanus Harjo WHERE BLD 8-G25 DATE Thursday 7th of July 2016 TIME 12:00-13:00
ABSTRACT In this talk, I will give an introduction about J-PARC (Japan Accelerator Research Complex), neutron scattering facility in there, neutron diffractometer dedicated for materials and mechanical engineering. Some examples related with stress measurement and in situ observation of microstructure during loading, heating/cooling or combination with loading and temperature change will be briefly introduced. TRIP-aided multiphase steels have been widely used in many applications particularly in automotive bodies. TRIP steels contain several tens of percent of metastable retained austenite that transform to martensite during deformation, leading to the improvement of strength and ductility. Deformation induced martensitic transformation behavior and its effect on the strengthening mechanism in two TRIP-aided multiphase steels with different carbon contents were monitored using in situ neutron diffraction experiments during tensile tests to clarifying the effect of TRIP on the improvement of strength. The tensile deformation was conducted in a continuous manner with a constant crosshead speed in plastic regime to suppress the stress relaxation that is often observed in the deformation test with a displacement stepwise manner. The phase stresses were multiplied by the phase fractions to evaluate stress contributions of the constituent phases to the applied stresses. The results suggest that martensite plays an important role in increasing the strength.
ABOUT THE SPEAKER Dr. Stefanus Harjo joined Japan Atomic Energy Agency (JAEA) in 2004. He is currently a Principal Researcher/Instrument Scientist of Engineering Beamline, Neutron Science Section, J-PARC, Japan Atomic Energy Agency. Before joined JAEA, Dr. Harjo worked as a post doctoral fellow on superplasticity of zirconia ceramics at Ibaraki University, where he got his PhD degree in Materials Science and Engineering in 2001.
Dr. Harjo's main research activities involve residual stress analysis and texture measurement using time-of-flight neutron diffraction in superconducting materials, steels, magnesium alloys, concretes, etc. In addition, he has a strong interest in neutron imaging and in-situ neutron diffraction of materials processes such as thermo-mechanical processing. Dr. Harjo has published over 130 peer-reviewed journal papers, and has been often invited to present his research works in international conferences.
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