[16P-T6-03] Microstructure and Mechanical Properties of Alloy 718 Deposited by Directed Energy Deposition
キーワード：Additive Manufacturing, Alloy718, Directed Energy Deposition, High Temperature Material , Microstructure
Direct Energy Deposition (DED) is expected to be an innovative manufacturing technology that enables flexible shape control by 5-axis control. However, its additive-manufacturing mechanism has not been fully elucidated. In this study, two type distribution of Alloy718 powder was used to build the DED blocks, and their microstructure and strength properties were investigated. After the process, coarse columnar grains were observed, tensile strengths, ductility, and hardness were similar in the lower and middle parts. However, in the upper part, ductility was higher and tensile strength and hardness were lower than those. The lower strength in the upper part would be due to the shorter time spent in the precipitation temperature range, resulting in less precipitation-strengthening phase. It was also found that the standoff distance (SOD) between the nozzle which feed the alloy powder and the molten pool surface could not be kept constant and increased, resulting in a lower ductility.