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 the recent development of AM has clearly demonstrated its potential as a new paradigm for advanced manufacturing, significant 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 levels 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 challenging 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 the National Institute of Standards and Technology. It seeks to understand AM alloys' structure and microstructure evolution 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 pathways, 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.
 Zhang F, Levine LE, Allen AJ, Stoudt MR, Lindwall G, Lass EA, Williams ME, Idell Y, Campbell CE. Effect of heat treatment on the microstructural evolution of a nickel-based superalloy additive-manufactured by laser powder bed fusion. Acta Materialia. 2018 Jun 15;152:200-14.
 Chou CY, Pettersson NH, Durga A, Zhang F, Oikonomou C, Borgenstam A, Odqvist J, Lindwall G. Influence of solidification structure on austenite to martensite transformation in additively manufactured hot-work tool steels. Acta Materialia. 2021 Aug 15;215:117044.
 Jia Q, Zhang F, Rometsch P, Li J, Mata J, Weyland M, Bourgeois L, Sui M, Wu X. Precipitation kinetics, microstructure evolution and mechanical behavior of a developed Al–Mn–Sc alloy fabricated by selective laser melting. Acta Materialia. 2020 Jul 1;193:239-51.
 König HH, Pettersson NH, Durga A, Van Petegem S, Grolimund D, Chuang AC, Guo Q, Chen L, Oikonomou C, Zhang F, Lindwall G. Solidification modes during additive manufacturing of steel revealed by high-speed X-ray diffraction. Acta Materialia. 2023 Jan 19:118713.
additive manufacturing; synchrotron; X-ray scattering; X-ray diffraction; advanced materials; materials characterization; precipitation; phase transformation;