Integrated Control of Melt Pool Geometry and Microstructure in Laser Powder Bed Fusion of AlSi10Mg

Abstract

Solidification microstructure control via melt pool geometry control is investigated in detail for the AlSi10Mg alloy in a laser melting process. Relationships between cell spacing and melting process parameters—beam power and velocity, are investigated. Single beads and multi-layer pad experiments are performed and analyzed for melt pool geometry and microstructure. Information from these experiments is used to achieve location-specific control of cell spacing in a single part using an EOS laser powder bed fusion machine. Along with experiments, thermal modeling is used to map the effect of melting parameters on solidification conditions. Optical microscopy and scanning electron microscopy are used to determine the melt pool dimensions and cell spacing, respectively. Results from the model and experiments show that cell spacing can be varied by controlling the cooling rate of the melt pool via beam power and travel speed for both single bead and multi-layer pad experiments. In addition, the relationship between melt pool area and cooling rate is used to demonstrate integrated melt pool geometry and microstructure control. This is also critical for process qualification using simple observable metrics such as melt pool size. This relationship is then used to demonstrate location-specific control of cell spacing in a single component.

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Acknowledgments

The authors wish to acknowledge Robert Speer, Martin Marinack, and John Siemon at the Arconic Technical Center for performing single bead experiments on their EOS M280 machine. The authors would like to thank Professor Anthony Rollett and Suraj Rao for providing particle size distribution information for AlSi10Mg powder. The authors would also like to convey their gratitude to William Pingitore for helping with sample preparation and Dr. Tom Nuhfer for helping with the SEM. This research was supported by the Research for Additive Manufacturing in Pennsylvania (RAMP) program, Prime Award Number FA8650-12-2-7230, Subaward Number 543105-78001, National Science Foundation under Award CMMI 1335298, and generous funding by a Carnegie Mellon Alumnus, Mr. Richard Fieler.

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Correspondence to Sneha P. Narra.

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Manuscript submitted January 31, 2018.

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Narra, S.P., Scime, L. & Beuth, J. Integrated Control of Melt Pool Geometry and Microstructure in Laser Powder Bed Fusion of AlSi10Mg. Metall Mater Trans A 49, 5097–5106 (2018). https://doi.org/10.1007/s11661-018-4804-z

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