Texture control of Inconel 718 superalloy in laser additive manufacturing by an external magnetic field
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Texture control is a major challenge in laser-assisted additive manufacturing of metal part due to the focused heat source and rapid cooling. In this study, a novel magnetic-field-assisted laser additive manufacturing method is proposed to obtain highly oriented texture. Inconel 718 samples are deposited under a transverse magnetic field of various intensities and different levels of laser power. The elemental distribution, grain morphology, and texture of as-built material are carefully analyzed using various material characterization techniques, including, SEM, EDS, and EBSD. The results indicate that the magnetic field changes the interdendritic microsegregation pattern from a continuous chain to discrete morphology. The <110> direction of deposited material tends to align with the transverse magnetic field. The orientation of stray crystals is more strictly constrained by both vertical heat flux and transverse magnetic field, resulting in a highly oriented <100> texture on horizontal cross-section and <110> texture on the vertical cross-section. It is also observed that by applying the transverse magnetic field, the average grain boundary misorientation angle significantly decreases from 32° to 19°, and the maximum multiple of uniform density increases from 3.0 to 5.3. The effects of laser power as well as magnetic field strength are investigated, and the underlying orientation effect is discussed.
The authors wish to acknowledge the funding support from the National Science Foundation (Award number CMMI# 1746147).
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