Microstructures and Cast Alloy S. Takamori, F. Yoshinaka and T. Sawaguchi Research Center for Structural Materials, National Institute for Materials Science (NIMS) A seismic damper alloy with the composition of Fe–15Mn–10Cr–8Ni–4Si that exhibits excellent plastic fatigue properties has been developed. This material was designed for thermo-mechanical processing, and its properties as a casting material have not been investigated. In this study, sand castings and permanent mold castings were made from this alloy to investigate the microstructures and material properties. The cast alloy was heat-treated at 1000°C for up to 24 hours, and the changes in microstructure and tensile and fatigue properties were examined. The results showed that both sand castings and permanent mold castings exhibited good tensile properties. Permanent mold castings showed good plastic fatigue properties at heat treatment times of 2 to 8 hours, and the number of failure cycles exceeded 10,000 cycles with a strain amplitude of ±1%. Transformation from γ-austenite to ε-martensite was observed during plastic deformation, suggesting that this transformation contributed to the good plastic fatigue properties. In the cast microstructure, Mn, Ni, and Si were observed to segregate clearly in the interdendritic region, suggesting that the remaining segregation also contributes to the good fatigue properties. Evaluation of Laser Absorptivity of Titanium Powder by Using Ray Tracing H. Honda and M. WatanabeResearch Center for Structural Materials, National Institute for Materials Science (NIMS) Additive manufacturing is expected to be new production methods due to its capability to make complex shaped products rapidly. In laser metal-based powder-bed fusion additive manufacturing, metal powder is spread in a sheet and melted by laser, and the solidified parts are piled up. Laser absorptivity is one of the parameters influencing the additive manufacturing process, and it is necessary to evaluate laser absorptivity of metal powder in order to understand the process. In this study, the laser absorptivity of titanium powder was evaluated by using a ray-tracing simulation program assuming the powder consists of spheres of a single size. Mechanical Properties ofPoster Presentation ｜NIMS Award Symposium 2023 Fe–15 P1 ｜ ProcessMn–10Cr–8Ni–4Si Seismic Damper PP11--0099 PP11--1100 39
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