Application of Friction Stir W T. Nagira 1 1 Research Center for Structural Materials, National Institute for Materials Science (NIMS) The Fe-15Mn-10Cr-8Ni-4Si (FMS) alloy was recently developed to utilize as a seismic steel damper owing to its excellent plastic fatigue life. However, the alloy is highly susceptible to solidification cracking. In this study, friction stir welding (FSW), which is one of the promising solid-state joining techniques, was applied to the 10 mm thick plate for the FMS alloy using a polycrystalline cubic born nitride (pcBN) tool. Because it has several advantages over the conventional fusion welding. For example, FSW enable us to suppress the solidification cracking and improve the mechanical properties including the strength and toughness induced by the grain refinement of weld zone. The sound FSW joint was obtained without the macro-defects. However, many small pores with diameters of 1-5 μm were formed throughout the stir zone under the high heat input condition. EDS analysis showed that the formation of pores was caused by the drop-off the BN particles induced by the wear of the pcBN tool. The decrease in the heat input remarkably suppressed the tool wear. The grain refinement occurred in the stir zone owing to the sever deformation during FSW specimen under the low heat input condition showed the higher tensile strength of 759 MPa due to the grain refinement and the relatively high elongation of 50% compared to the base metal. In addition, the FSW specimen showed the excellent fatigue life of 9723 cycles. Elevated Temperature Exploration of MGlass through Nanoindentation Testing S. Pomes 1,2, N. Adachi 3, M. 1 Research Center for Structural Materials, National Institute for Materials Science (NIMS) 2 Department of Materials Science and Engineering, Kyushu University 3 Department of Mechanical Engineering, Toyohashi University of Technology Metallic glasses offer significant potential as structural materials, enabling the development of lightweight, durable, and energy-efficient transportation and infrastructure systems. Their utilization aligns with several sustainable development goals, including affordable and clean energy, sustainable infrastructure, and responsible consumption and production. However, their structural state and deformation behavior are significantly influenced by environmental temperature, particularly in the range of glass transition temperatures, further complicating their application in structural scenarios. In our study, we investigate the mechanical response of a Zr-based bulk metallic glass in two distinct structural states: as-cast and as-relaxed. We employ elevated-temperature nanoindentation testing, conducting experiments at room temperature and both above and below the glass transition temperature, spanning a range of 100°C to 500°C with 100°C increments. Our extensive experimental dataset is analyzed to assess mechanical properties and explore potential creep deformation dynamics as a function of temperature. This analysis provides valuable insights into the material's response to applied stress under varying temperature conditions, shedding light on its deformation mechanisms. Wakeda 1 and T. Ohmura 1,2 Poster Presentation ｜NIMS Award Symposium 2023 elding for Fe-Mn P2 ｜ Characterization-Si Alloy echanical Behavior in Zr-based Bulk MW. The FSPP22--0077 PP22--0088 etallic 47
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