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[charlie T colton]

Manufacturing: Pushing boundaries (at Oak Ridge National Laboratory)

Manufacturing – Pushing boundaries - March 2, 2017

March 2, 2017 – Advanced manufacturing will benefit from additive manufacturing techniques as demonstrated by a team led by Michael Kirka of Oak Ridge National Laboratory. The method uses electron beam melting to precisely control the microstructure of additive manufactured materials, determining the mechanical properties at different locations within a part. “This research will change the way we design components in the future where engineers can use variations in microstructure to enhance performance and not just geometry and bulk properties as we do today,” Kirka said. The work is detailed in a paper titled “Strategy for Texture Management in Metals Additive Manufacturing,” published in Journal of Materials Science - First Online: 31 January 2017.


From the referenced paper:

Conclusions

In this work, an alternative point heat source fill was demonstrated for controlling the texture of the Ni-base superalloy Inconel 718 in the EBM process on a bulk scale. Through changes in key parameters in the point source fill, it was shown that materials with both columnar- and equiaxed-grained structures could be obtained in the as-fabricated state. The determination of whether columnar or equiax grains form in the point heat source fill is determined by the imparted energy in the series of points, and the ability for the melt pool to merge with neighboring melt pools on successive rows. In the case of the standard raster scan, the melt pool remains localized and the columnar grains aligned with the build direction result.

Upon post-processing the material, the texture was found to remain consistent with the as-fabricated material, while grain growth was experienced due to the lack of carbides to pin the grain boundaries as in the columnar-grained material fabricated through the standard raster scan. Monotonically, the equiaxed material formed using the point heat source fill resulted in isotropic tensile properties that fell between those of the columnar-grained material when tested both parallel to the building direction and transverse to it.