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FeCrAl alloys are under development as possible candidate materials of accident-tolerant fuel cladding in light water reactors. In this study, the cracking resistance of FeCrAl alloys was evaluated using half-size Charpy impact tests at temperatures ranging from room temperature to 600 °C. Ingot-metallurgy wrought FeCrAl alloys with base alloy compositions of Fe-(10–13)Cr-6Al-2Mo, in weight percent, and commercial powder-metallurgy FeCrAl alloys (Kanthal APMT) were investigated. All studied alloys showed almost zero absorbed impact energy at room temperature with brittle fracture behavior. The as-received APMT alloys exhibited poor impact toughness even at 600 °C. The ductile-brittle transition temperatures of the wrought FeCrAl alloys varied from 119 to 318 °C. The possible effects of microstructures, residual strain, materials preparation methods, process conditions, and chemical composition on the impact toughness of FeCrAl alloys were investigated by examining the Charpy impact data in combination with microstructural details of the alloys. [ABSTRACT FROM AUTHOR]

The processability of a Mo-containing FeCrAl alloy (Fe-13Cr-5.2Al-2Mo base, in wt%), developed for accident-tolerant nuclear fuel claddings, was evaluated through a stepwise rolling process at 400 °C under two different inter-pass annealing conditions (i.e., 650 °C for 1 h and at 870 °C for 30 min). The inter-pass annealing at 870 °C easily softened the FeCrAl alloy; however, it led to the formation of coarse grains of ~200 µm. On the other hand, the FeCrAl alloy maintained elongated, deformed grains with the inter-pass annealing at 650 °C, but the annealed samples showed relatively high deformation resistance and strong texture. Important aspects concerning the processability and microstructural control of FeCrAl alloys, such as deformation inhomogeneity, texture development, and grain coarsening, were discussed. Optimized processing conditions were recommended, based on the results, to achieve desirable microstructures with balanced processability and mechanical properties. [ABSTRACT FROM AUTHOR]

A widespread implementation of large scale additive manufacturing (AM) processes, such as wire arc-directed energy deposition (WA-DED) AM can transform the current manufacturing supply chain networks. Naturally, such implementation requires control of the microstructural attributes, such as texture and phase evolution in the processed alloys. Currently, the texture evolution in fusion-based AM (F-BAM) processes is majorly rationalized by the phenomena occurring only during solidification. However, such rationalization is insufficient for understanding the evolution of primary and secondary crystallographic orientations, and consequently, fails to offer a comprehensive understanding and control of overall texture in F-BAM processed alloys. To this end, we report a single crystal (SX)-like texture in WA-DED processed SS316L for the first time. Furthermore, we assess the physical phenomena that may lead to such unique microstructural evolution during WA-DED AM. Subsequently, using microstructural characterization spanning the build height and thermomechanical simulations we investigate the effect of competitive growth and epitaxial growth occurring during solidification and thermally induced plastic deformation occurring post solidification on the overall texture of WA-DED processed SS316L. A spatial variation in solidification pathway is also established and correlated with variation in undercoolings across the build. Tensile tests revealed a strong orientation dependence of deformation mechanisms with over 110% elongation to failure of specimens deformed along <011>. Such anisotropy is rationalized using Schmid's analysis of dislocation slip and deformation twinning. Overall, the mechanisms outlined in this work will facilitate an enhanced understanding and subsequent control of texture evolution, solidification behavior and mechanical behavior of WA-DED processed steels. [Display omitted] • A SX-like texture is reported in a directed energy deposition processed SS316L. • Phenomena occurring during and post solidification affect texture in DED. • Tip temperatures of γ and δ phases and solidification modes vary with build height. • Stray-grain formation is rationalized using spatially varying thermokinetics. • Orientation dependent behavior of leading/trailing partials leads to anisotropy. [ABSTRACT FROM AUTHOR]

Abstract: Foil and sheet forms of the nickel-based superalloy 625 have been examined in an ‘as-processed’ condition and following creep-rupture testing in air at 750°C and 100MPa. Both scanning and transmission electron microscopies were employed to correlate microstructures with creep behavior, and indicate the additional processing required to achieve foil form reduces creep life compared to thicker-section wrought product forms. Prior to creep testing, the microstructure consists of γ phase with M6C precipitates. This microstructure changes during creep into one consisting of orthorhombic δ phase extending across the γ grains, and grain boundaries dominated by the presence of rhombohedral μ phase, δ phase, and a Si-rich variant of diamond-cubic M6C (η phase). Thermodynamic modeling was also used to calculate the stable temperature ranges and compositions of equilibrium phases. The phases predicted by modeling and their compositions generally agree with those observed within alloy 625 after creep testing. [Copyright &y& Elsevier]