Additive manufacturing (AM) of metals represents a suite of emerging technologies that manufactures three-dimensional objects directly from digital models through an additive process. AM allows rapid manufacturing of complex objects with few constraints, little lead time and assembly, which makes it an attractive option for fabrications of customized, high value-added parts in industries ranging from aerospace, oil and gas, healthcare, and defense.
While recent development of AM has clearly demonstrated its potential as a new paradigm for advanced manufacturing, major technical challenges still exist. Many of these challenges are rooted in the extreme material processing conditions during the AM build process, where repeated rapid heating and cooling (with rates up to 10^6 K/s) leads to materials with high level of residual stress, heterogeneous metastable microstructures, and nonequilibrium elemental compositions or phase distributions. The microstructure evolutions during the build process and the post-build heat treatment are often poorly understood, making it difficult to construct the critical structure-process-performance relationship of the industrially important AM alloys.
To overcome these measurement challenges, this NRC postdoctoral research opportunity extends ongoing efforts at the Materials Measurement Science Division of National Institute of Standards and Technology and seeks to understand the structure and microstructure evolution of AM alloys through rigorous in situ and ex situ high-energy synchrotron X-ray scattering, diffraction, and imaging experiments. Essential to this opportunity is the design and execution of experiments to optimize processing pathway, validate predictive modeling, and enable further development of AM technologies, with emphasis on AM materials structures. This research is expected to be conducted through internal and external collaboration, which provides access to a full range of materials characterization and modeling capabilities.
 F. Zhang, L.E. Levine, A.J. Allen, M.R. Stoudt, G. Lindwall, E.A. Lass, M.E. Williams, Y. Idell, C.E. Campbell, Effect of heat treatment on the microstructural evolution of a nickel-based superalloy additive-manufactured by laser powder bed fusion, Acta Materialia 152 (2018) 200-214.
 J. Ilavsky, F. Zhang, R.N. Andrews, I. Kuzmenko, P.R. Jemian, L.E. Levine, A.J. Allen, Development of combined microstructure and structure characterization facility for in situ and operando studies at the advanced photon source, Journal of Applied Crystallography 51(3) (2018) 867-882.
 F. Zhang, L.E. Levine, A.J. Allen, C.E. Campbell, E.A. Lass, S. Cheruvathur, M.R. Stoudt, M.E. Williams, Y. Idell, Homogenization kinetics of a nickel-based superalloy produced by powder bed fusion laser sintering, Scripta materialia 131 (2017) 98-102.
additive manufacturing; synchrotron; X-ray scattering; X-ray diffraction; advanced materials; materials characterization; precipitation; phase transformation;