@article {1406,
	title = {Solidification-driven orientation gradients in additively manufactured stainless steel},
	journal = {Acta Materialia},
	volume = {183},
	year = {2020},
	pages = {249{\textendash}260},
	abstract = {<p>
	A sample of 304L stainless steel manufactured by Laser Engineered Net Shaping (LENS) was characterized in 3D using TriBeam tomography. The crystallographic, structural, and chemical properties of the as-deposited microstructure have been studied in detail. 3D characterization reveals complex grain morphologies and large orientation gradients, in excess of 10o, that are not easily interpreted from 2D cross-sections alone. Misorientations were calculated via a methodology that locates the initial location and orientation of grains that grow during the build process. For larger grains, misorientation increased along the direction of solidification. For grains with complex morphologies, K-means clustering in orientation space is demonstrated as a useful approach for determining the initial growth orientation. The gradients in misorientation directly tracked with gradients in chemistry predicted by a Scheil analysis. The accumulation of misorientation is linked to the solutal and thermal solidification path, offering potential design pathways for novel alloys more suited for additive manufacturing.
</p>
},
	keywords = {Additive manufacturing, Microstructure, Solidification, Tomography, Tribeam},
	issn = {13596454},
	doi = {10.1016/j.actamat.2019.10.047},
	author = {Polonsky, Andrew T. and Lenthe, William C. and Echlin, Mclean P. and Livescu, Veronica and Gray, George T. and Pollock, Tresa M.}
}
@article {1326,
	title = {Defects and 3D structural inhomogeneity in electron beam additively manufactured Inconel 718},
	journal = {Materials Characterization},
	volume = {143},
	year = {2018},
	pages = {171{\textendash}181},
	abstract = {<p>
	Material structure and defects created during additive manufacturing contribute to the variability in mechanical properties of these parts, limiting their use for critical applications. Three-dimensional crystallographic, structural, and chemical information in electron beam melted Inconel 718 was collected from the sub-micron to the millimeter scale using the TriBeam tomography system. The relationship of defects to the surrounding microstructure has been studied in detail. Lack of fusion defects created sharp discontinuities in the grain morphology that extended several build layers beyond the layer where the defect originated. Nitrides and carbides in the size range of 1.25 \&mu;m to 10 \&mu;m were observed throughout the volume, with pronounced nitride clustering. The similarities between solidification in additive manufacturing and traditional manufacturing processes are demonstrated by the comparable size and distribution of carbides measured for industrial-scale samples of 718. Defects created during additive manufacturing cannot be easily remedied via standard post-processing techniques, and will likely diminish the mechanical performance of additively manufactured parts.
</p>
},
	keywords = {Additive manufacturing, Electron beam melting, Lack of fusion, Microstructure, Tomography},
	issn = {10445803},
	doi = {10.1016/j.matchar.2018.02.020},
	author = {Polonsky, Andrew T. and Echlin, Mclean P. and Lenthe, William C. and Dehoff, Ryan R. and Kirka, Michael M. and Pollock, Tresa M.}
}
