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Materials 2017, 10(11), 1260; https://doi.org/10.3390/ma10111260

Grain Structure Control of Additively Manufactured Metallic Materials

1
Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60201, USA
2
Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261, USA
3
Quad City Manufacturing Laboratory-Western Illinois University, Rock Island, IL 61201, USA
*
Authors to whom correspondence should be addressed.
Received: 1 October 2017 / Revised: 24 October 2017 / Accepted: 24 October 2017 / Published: 2 November 2017
(This article belongs to the Special Issue NextGen Materials for 3D Printing)
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Abstract

Grain structure control is challenging for metal additive manufacturing (AM). Grain structure optimization requires the control of grain morphology with grain size refinement, which can improve the mechanical properties of additive manufactured components. This work summarizes methods to promote fine equiaxed grains in both the additive manufacturing process and subsequent heat treatment. Influences of temperature gradient, solidification velocity and alloy composition on grain morphology are discussed. Equiaxed solidification is greatly promoted by introducing a high density of heterogeneous nucleation sites via powder rate control in the direct energy deposition (DED) technique or powder surface treatment for powder-bed techniques. Grain growth/coarsening during post-processing heat treatment can be restricted by presence of nano-scale oxide particles formed in-situ during AM. Grain refinement of martensitic steels can also be achieved by cyclic austenitizing in post-processing heat treatment. Evidently, new alloy powder design is another sustainable method enhancing the capability of AM for high-performance components with desirable microstructures. View Full-Text
Keywords: metal additive manufacturing; grain morphology; grain size; post-processing heat treatment metal additive manufacturing; grain morphology; grain size; post-processing heat treatment
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Yan, F.; Xiong, W.; Faierson, E.J. Grain Structure Control of Additively Manufactured Metallic Materials. Materials 2017, 10, 1260.

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