Predicting the Microstructural Evolution of Electron Beam Melting of Alloy 718 with Phase-Field Modeling
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RECENTLY, powder bed additive manufacturing (AM) has attracted great interest from the manufacturing industries and research community because of its capacity to produce near net shape structures with complex geometries, which cannot be manufactured CHAMARA KUMARA and PER NYLE´N are with the Division of Subtractive and Additive Manufacturing Processes, Department of Engineering Science, University West, 461 86 Trollha¨ttan, Sweden. Contact e-mail: [email protected] DUNYONG DENG is with the Division of Engineering Materials, Department of Management and Engineering, Linko¨ping University, 58183 Linko¨ping, Sweden. FABIAN HANNING is wiht the Department of Industrial and Materials Science, Chalmers University of Technology, 412 96 Go¨teborg, Sweden. MORTEN RAANES is with the Department of Materials Science and Engineering, IMA, NTNU, Alfred Getz vei 2,7491 Trondheim, Norway. JOHAN MOVERARE is with the Division of Subtractive and Additive Manufacturing Processes, Department of Engineering Science, University West and also with the Division of Engineering Materials, Department of Management and Engineering, Linko¨ping University. Manuscript submitted November 21, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
with traditional methods. Among the powder bed manufacturing processes, electron beam melting (EBM) process has attracted more attention because if its relatively higher productivity due to the high beam speed and high beam power density. In addition, the EBM operation occurs at a high temperature in a vacuum environment, which creates less residual stress and less oxidation in the component obtained.[1] These features are beneficial for the manufacture of the critical components used in aerospace applications and gas turbine engines. Nickel-based superalloys are among the most important alloys used in aerospace applications and gas turbine engines because of their high-temperature strength, high resistance to creep deformation, and corrosion resistance.[2,3] Among these superalloys, Alloy 718 is one of the most widely used nickel-iron-based superalloys and it is suitable for AM processes because of its good weldability due to the sluggish precipitation of the main strengthening phase c¢¢.[4] The microstructure of Alloy 718 is dominated by an austenitic c fcc matrix. Precipitates such as Laves, c¢/c¢¢, and d phases, and various metallic carbides and nitrides can be found within the matrix. The formation of the Laves phase is
usually observed in the interdendritic region due to the segregation of the elements. The complete microstructure, including the phases present as well as their distribution, morphology, and orientation, is mainly related to the primary manufacturing technology employed and the subsequent post-processing conditions. Heat treatments are commonly used to tailor the microstructure of Alloy 718 to obtain the desired properties required for the application. Due to the inherent features of the layer-by-layer manufacturing approach, the microstructure of Alloy 718 after the EBM process exhi
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