Influence of Static Magnetic Field on the Microstructure of Nickel-Based Superalloy by Laser-Directed Energy Deposition
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position (DED) processes have lower production rates when compared to those of other additive manufacturing (AM) processes, such as selective laser melting (SLM) and selective electron beam melting (S-EBM). DED processes are capable of producing components with complex geometries and are particularly well suited for repairing or fabricating high value parts at low production volumes.[1–3] Hence, it is not surprising to find numerous published studies on the influence of laser energy density,[4–6] laser source type,[7] scan strategy[8,9] and build direction[10,11] on the
DAFAN DU is with the Shanghai Key Lab of Advanced Hightemperature Materials and Precision Forming, Shanghai Jiao Tong University, Shanghai 200240, P.R. China and also with the Department of Materials Science and Engineering, University of California, Irvine, CA 92697. ANPING DONG, DA SHU, DONGHONG WANG, GUOLIANG ZHU, and BAODESUN are with the Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming, Shanghai Jiao Tong University. Contact e-mail: [email protected]. ENRIQUE J. LAVERNIA is with the Department of Materials Science and Engineering, University of California. Contact e-mail: [email protected] Manuscript submitted December 17, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
microstructure of AM parts by DED. Inspection of the published literature reveals some research on the solidification behavior of the melt pool during DED[12–14]; however many questions remain unanswered. For example, Lee et al.[12] investigated the influence of fluid convection on dendrite arm spacing during solidification and reported an inverse relationship between temperature gradient G and growth speed R. Moreover, the relationship of simulated weld pool convection patterns to predict solidification boundary shape, cooling rate distribution, and dendrite arm spacing (DAS) was also examined. Wei et al.[13] numerically studied heat transfer and liquid metal flow calculations in an effort to provide insight into the evolution of solidification morphology and texture during multi-layer AM processes. Further, O. Nenadl et al.[14] studied the role of solid/liquid interface on the grain orientation structure and texture based on both experimental findings and theoretical analyses. The above discussion underscores the critical influence that solidification mechanisms in the melt pool exert on the final microstructure during DED. Inspired by results from the casting literature,[15–18] researchers have proposed the idea of using a magnetic field to effect melt convection during directional solidification. For example, studies on the influence of a weak static magnetic field (in the order of 0.1 T) on the liquid melt during directional solidification suggest that a static magnetic field promotes thermoelectric magnetic convection (TEMC), and thereby ultimately influences the thermal and solute fields.[15–18] Other related studies reveal that the imposition of a 0.12 T magnetic field on AlSi10Mg during SLM leads to a decrease in pore density and reduced columnar grain morphology
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