TY - JOUR A1 - Schneider, J. A1 - Farris, L. A1 - Nolze, Gert A1 - Reinsch, Stefan A1 - Cios, G. A1 - Tokarski, T. A1 - Thompson, S. T1 - Microstructure evolution in Inconel 718 produced by powder bed fusion additive manufacturing JF - Journal of manufacturing and materials processing N2 - Inconel 718 is a precipitation strengthened, nickel-based super alloy of interest for the Additive Manufacturing (AM) of low volume, complex parts to reduce production time and cost compared to conventional subtractive processes. The AM process involves repeated rapid melting, solidification and reheating, which exposes the material to non-equilibrium conditions that affect elemental segregation and the subsequent formation of solidification phases, either beneficial or detrimental. These variations are difficult to characterize due to the small length scale within the micron sized melt pool. To understand how the non-equilibrium conditions affect the initial solidification phases and their critical temperatures, a multi-length scale, multi modal approach has been taken to evaluate various methods for identifying the initial phases formed in the as-built Inconel 718 produced by laser-powder bed fusion (L-PBF) additive manufacturing (AM). Using a range of characterization tools from the bulk differential thermal analysis (DTA) and x-ray diffraction (XRD) to spatially resolved images using a variety of electron microscopy tools, a better understanding is obtained of how these minor phases can be properly identified regarding the amount and size, morphology and distribution. Using the most promising characterization techniques for investigation of the as-built specimens, those techniques were used to evaluate the specimens after various heat treatments. During the sequence of heat treatments, the initial as-built dendritic structures recrystallized into well-defined grains whose size was dependent on the temperature. Although the resulting strength was similar in all heat treated specimens, the elongation increased as the grain size was refined due to differences in the precipitated phase distribution and morphology. KW - Metal additive manufacturing KW - Inconel 718 KW - Heat treatment KW - Grain boundary precipitates KW - Laves phase PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-542758 DO - https://doi.org/10.3390/jmmp6010020 SN - 2504-4494 VL - 6 IS - 1 SP - 1 EP - 20 PB - MDPI CY - Basel AN - OPUS4-54275 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schneider, J. A1 - Terrell, J. A1 - Ferris, L. A1 - Tucker, D. A1 - Leonhardt, T. A1 - Goldbeck, Hennig T1 - Low-Cost Fabrication of Tungsten-Rhenium Alloys for Friction Stir Welding Applications JF - Metallurgical and Materials Transactions B N2 - Friction stir welding (FSW) of high-melting temperature alloys, such as steel and Inconel, requires tooling that can survive under the applied loads at the elevated temperatures. Tungsten-Rhenium (W-Re) alloys are a suitable candidate for this application; however, the costs typically associated with achieving the required densities and grain structure for the tooling are high due to the lengthy traditional processing required. Further costs are incurred in machining the starting bar stock to the final FSW tooling configuration. An alternate processing method is used in this study to shorten the fabrication time using direct current sintering which rapidly consolidates the starting powders at lower temperatures than used in traditional powder metallurgy. Although this process enables retention of the fine grain size, the sintering time is too short to form the desired single, solid phase. Therefore, the specimens were subjected to a post-consolidation heat treatment to fully solutionize the W matrix. Once the desired density and solid solution phase was verified in coupons, the final processing parameters were used to consolidate a net shape tool for FSW. KW - Tungsten-Rhenium KW - Friction Stir Welding KW - Fabrication PY - 2019 DO - https://doi.org/10.1007/s11663-019-01726-6 VL - 51 IS - 1 SP - 35 EP - 44 PB - Springer AN - OPUS4-50027 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -