GammaPrint (R)-700(1) is a recently developed high gamma ' (similar to 70% volume fraction) CoNi-based superalloy designed to combine high-temperature mechanical performance with laser powder bed fusion processability. Room-temperature yield strength ranged from 610 to 658 MPa and increased to 661 MPa (longitudinal) and 730 MPa (transverse) at 760 degrees C. The creep behavior compared favorably to high-gamma ' Ni-based superalloys manufactured via laser powder bed fusion such as Incoloy (R) 939 and Inconel (R) 738LC.(2) In-situ neutron diffraction data measured during creep revealed that plastic deformation was largely localized to the gamma phase at 760 degrees C, allowing the gamma' phase to elastically compensate and maintain creep strain resistance. However, at 900 degrees C, this load sharing behavior was weakened, contributing to accelerated creep rate and rupture.

Refractory multi-principal element alloys (RMPEAs) promise to significantly enhance gas turbine engine efficiency, but their poor oxidation performance inhibits their implementation. Alumina-forming bond coat alloys can provide oxidation protection, but discovering suitable chemistries remains a challenge. We employed a design methodology that screens for alumina-formation capability using Al activity and phase constitution predictions from CalPhaD (Thermo-Calc). Alloy down-selection from approximately 7,800 alloys in the Nb-Si-TiAl-Hf system was conducted via analysis of calculated thermodynamic properties with number-density topology style maps. This approach is validated by creating and testing the composition Nb12Si23Ti24Al36Hf5, which forms protective alumina scales up to 1400 C-degrees and resists pesting at 800 C-degrees. Further, the alloy has an average coefficient of thermal expansion of similar to 10.1 ppm/K, making it well matched to Nb-based refractory alloys. The methodology will be useful for the design of coatings for RMPEAs, enabling their implementation and significant efficiency benefits sooner.

Accurate quantification of the energy distribution of backscattered electrons (BSEs) contributing to electron backscatter diffraction (EBSD) patterns remains as an active challenge. This study introduces an energy-resolved EBSD methodology based on a monolithic active pixel sensor direct electron detector and an electron-counting algorithm to enable the energy quantification of individual BSEs, providing direct measurements of electron energy spectra within diffraction patterns. Following detector calibration of the detector signal as a function of primary beam energy, measurements using a 12 keV primary beam on Si(100) reveal a broad BSE energy distribution across the diffraction pattern, extending down to 3 keV. Furthermore, an angular dependence in the weighted average BSE energy is observed, closely matching predictions from Monte Carlo simulations. Pixel-resolved energy maps reveal subtle modulations at Kikuchi band edges, offering insights into the backscattering process. By applying energy filtering within spectral windows as narrow as 2 keV centered on the primary beam energy, significant enhancement in pattern clarity and high-frequency detail is observed. Notably, BSEs in the 9-10 keV range dominate Kikuchi pattern formation, while BSEs in the 2-8 keV range, despite having undergone substantial energy loss, still produce Kikuchi patterns. By enabling energy determination at the single-electron level, this approach introduces a versatile tool-set for expanding the quantitative capabilities of EBSD, thereby offering the potential to deepen the understanding of diffraction contrast mechanisms and to advance the precision of crystallographic measurements.

Slip localization formation is the chief mechanism underlying the deformation of nearly all metals, from pure elements to high-performance superalloys. The intensity of individual slip localizations is often related to the ultimate strain level for failure but not to the strength of the metal. Here we show that across 15 distinct metals, the intensity of slip in individual slip localizations and slip localization spacings are strongly related to material yield strength. Using a three-dimensional crystal plasticity-based micromechanical model that explicitly simulates the growth of discrete slip localizations, we reveal that the stronger the metal, the faster and earlier slip localizations intensify. The relationship is attributed to the formation of a zone that surrounds the slip localization where the driving force for slip is absent. We find that the zone size is controlled by the strength of the neighboring crystal. Consequently, as strength increases, slip becomes increasingly preferred within the slip localization itself and formation of other slip localizations becomes more likely further away.

Electron backscatter diffraction (EBSD) is a powerful tool for determining the orientations of near-surface grains in engineering materials. However, many ceramics present challenges for routine EBSD data collection and indexing due to small grain sizes, high crack densities, beam and charge sensitivities, low crystal symmetries, and pseudo-symmetric pattern variants. Micro-cracked monoclinic hafnia, tetragonal hafnon, and hafnia/hafnon composites exhibit all such features, and are used in the present work to show the efficacy of a novel workflow based on a direct detecting EBSD sensor and a state-of-the-art pattern indexing approach. At 5 and 10 keV primary beam energies (where beam-induced damage and surface charge accumulation are minimal), the direct electron detector produces superior diffraction patterns with 10x lower doses compared to a phosphor-coupled indirect detector. Further, pseudo-symmetric variant-related indexing errors from a Hough-based approach (which account for at least 4%-14% of map areas) are easily resolved by dictionary indexing. In short, the workflow unlocks fundamentally new opportunities to characterize materials historically unsuited for EBSD.

Refractory metals and more complex refractory alloys are of interest for high temperature propulsion systems. While materials are subject to cyclic loading in these environments, there is relatively limited knowledge of the typical fatigue behavior of refractory BCC metals and alloys. Ultrasonic fatigue has been employed to study properties of annealed Nb-10%Hf C103 alloy in the very-high cycle fatigue (VHCF) regime. The fatigue strength is observed to be close to the yield strength, as is common for single phase BCC materials, when accounting for inherent strain rate sensitivity. No fatigue limit was observed for testing to 109 cycles. Fractures consistently initiated at a single site on sample surfaces, with the crack propagating perpendicular to the loading direction. Electron backscatter diffraction (EBSD) maps collected pre-and post-fatigue reveal inhomogeneous straining during cyclic loading. The fatigue behavior of C103 is discussed in comparison to other refractory BCC metals.

Ru-based B2 phases have shown promise as strengthening precipitates in refractory alloys due to their (>= 1600 degrees C) solvus temperatures. Of the Ru-based B2 phases, the HfRu-B2 phase is the most thermally stable a solution and ageable BCC + HfRu-B2 alloy has yet to be reported. Three HfRu-containing refractory alloys arc-melted and their phase equilibria investigated from 1300-1900 degrees C: Ta30Mo28Nb22Hf11Ru9, 30 Mo 28 Nb 22 Hf 11 Ru 9 , Nb52Mo28Hf11Ru9, 52 Mo 28 Hf and Nb52V28Hf11Ru9 52 V 28 Hf 11 Ru 9 (at%). Scanning electron microscopy was used to characterize the microstructures annealing. In all alloys, a HfRu-B2 phase was present as precipitates embedded in a disordered BCC phase. HfRu-B2 phase was stable up to 1750 degrees C and additional Hf- and V-rich phases were stable at 1300 degrees C. After cooling, the HfRu-B2 precipitates in Nb52V28Hf11Ru9 52 V 28 Hf 11 Ru 9 evolved in morphology from spheres to cubes to cuboidal arrays with increasing aging time, characteristic of a low misfit between the HfRu-B2 and BCC phases.

Laser heating during additive manufacturing (AM) induces extreme and transient thermal conditions which critically influence the microstructure evolution and mechanical properties of the resulting component. However, accurately resolving these conditions with sufficient spatiotemporal accuracy remains a central challenge. We demonstrate a unique approach that couples high-speed infrared imaging, during selective laser melting of MAR-M247, with a transient three-dimensional (3D) multiphysics simulation to reconstruct the dynamic sub-surface temperature distribution of the melt pool. This integrated framework enables the estimation of experimentally-validated, 3D solidification conditions-including solidification velocities and cooling rates-at the solid-liquid interface while also significantly lowering computational cost. By quantifying solidification conditions, we predict variations in microstructure size and orientation driven by laser processing parameters and validate them with ex situ scanning electron microscopy and electron backscatter diffraction maps. Our findings substantiate that an integrated experimental-computational approach is crucial to realize in situ prediction and optimization of microstructures in commercial AM.

High heat flux environments, such as those encountered in atmospheric re-entry and nuclear fusion, impose severe thermal gradients and high local temperatures on structural components. Scalable heat transfer methods need to be integrated with structural designs to manage these extreme heat loads. Transpiration cooling is a potential approach for managing localized heating and maintaining structural durability in these environments. Capillary-driven transpiration cooling shows potential to adapt to dynamic heat flux conditions, but has not yet been investigated under high heat flux conditions. In this investigation, a porous structure was tested with active transpiration cooling under multiple heat flux conditions. Additive manufacturing was employed to produce a specimen with a tailored porous geometry using a refractory niobium-based alloy (C103). Water was selected as the coolant due to the high magnitude of energy absorbed during vaporization. To generate high heat flux environments for testing, an experimental apparatus that employs a high powered laser and corresponding characterization equipment has been designed. Coolant flow through the structure was driven by capillary forces, which enabled rapid adaptation to changes in heat flux from 132–330 W/cm2. Stable coolant flow rates and temperatures were observed under a range of constant high heat flux conditions. The C103 porous sample maintained average surface temperatures below 170 °C while subject to heat fluxes up to 330 W/cm2, indicating the transpiration cooling of the printed structure provided effective heat dissipation in these conditions.

Refractory multi-principal element alloys (RMPEAs) could provide next-generation high temperature alloys, but their ductility and high temperature strength need significant improvement. Emulating superalloy gamma-gamma' micro-structures, RMPEAs combining a ductile BCC matrix with embedded B2 precipitates for strengthening could meet this goal. Two-phase BCC-B2 RMPEAs have recently been demonstrated, but the B2 phase typically exhibits insufficient thermodynamic stability for operating temperatures >= 1300 degrees C. Using high-throughput CALPHAD predictions, we screen across 3,500 potential BCC-B2 systems. Promising compositions are predicted for alloys combining Ru-based B2s with refractory BCC elements. A total of 20 such compositions were arc-melted to characterize their as-cast and heat-treated microstructures. In these alloys, the RuHf B2 exhibits exceptional stability beyond 1900 degrees C but cannot be solutionized. By contrast, RuTi does sol-utionize and reprecipitate between 1300 and 1900 degrees C, providing a robust thermal processing pathway. RuAl can be solutionized but also tends to form competing intermetallic phases. Altogether, Ru-B2 RMPEAs offer great design flexibility and surpass the stability and thermal processability of previously studied BCC-B2 refractory alloys.

Emulating the Ni-base superalloy γ + γ ^' microstructure in BCC–B2 refractory alloys is a promising design strategy to achieve high temperature strength and ductility. Ru-base B2 precipitates have shown exceptional thermal stability but can be difficult to solutionize, making high cooling rate solidification pathways like additive manufacturing (AM) a promising approach for synthesis of more homogeneous microstructures. Using single track laser experiments on aged bulk substrates, five representative refractory alloys with varying Ru-base B2 precipitates (AlRu, HfRu, TiRu) and matrix constituents (Mo, Nb) were investigated for their solidification behavior and defect susceptibility under laser melting conditions. Susceptibility to solidification cracking, solid-state cracking, and keyhole formation was found to be highly dependent on the matrix composition. Characterization of the melt pools by scanning and transmission electron microscopy shows evidence for disordered BCC upon solidification, enabling tailoring of the B2 precipitates that are thermodynamically stable above 1300 °C. The B2 precipitate morphologies in the melt tracks after aging treatments are influenced by the partitioning behavior of Ru from laser melting. Results from these single track experiments provide guidance toward design strategies for fabricable refractory BCC–B2 alloys.

Refractory alloys can be difficult to fabricate by laser-based manufacturing methods due to their high melting temperatures, high interstitial solubility, and propensity for low temperature brittleness. Laser-based processes, such as welding and additive manufacturing (AM), yield similar populations of defects, including microsegregation and solidification and solid-state cracking. Given the extreme challenges and cost associated with the production of refractory powders, this research aimed to develop a rapid screening methodology that combines predictive defect formation metrics with single track melting experiments. A flexible single laser track melting platform was designed to perform screening experiments on conventional and multi-principal element refractory alloys across a wide range of laser energy inputs. The platform was employed to investigate laser melting on solid substrates, or on a substrate with a single layer of powder feedstock, and is demonstrated with the highly fabricable Nb-base alloy C103. Preliminary investigations are performed on refractory multi-principal element alloys in the Hf-Mo-Nb-Ta-Ti family, and significant differences in cracking resistance and solidification morphology are observed. Implications for future alloy design and processing strategies for defect-resistant refractory alloys for AM are discussed.

Hypersonic vehicles must withstand extreme conditions during flights that exceed five times the speed of sound. These systems have the potential to facilitate rapid access to space, bolster defense capabilities, and create a new paradigm for transcontinental earth-to-earth travel. However, extreme aerothermal environments create significant challenges for vehicle materials and structures. This work addresses the critical need to develop resilient refractory alloys, composites, and ceramics. We will highlight key design principles for critical vehicle areas such as primary structures, thermal protection, and propulsion systems; the role of theory and computation; and strategies for advancing laboratory-scale materials to manufacturable flight-ready components. Hypersonic vehicles experience extreme temperatures, high heat fluxes, and aggressive oxidizing environments. Here, the authors highlight key materials design principles for critical vehicle areas and strategies for advancing laboratory-scale materials to flight-ready components.

Additive manufacturingAdditive manufacturing enables the fabrication of complex part geometries, and is attractive for advanced aerospace components. Laser powder bed fusion (LPBF)Laser Powder Bed Fusion (LPBF), specifically, is being assessed for manufacturing structural components of gas-turbine engines made from high- ^' volume fraction superalloys. However, the formation of crack defects during LPBFLaser Powder Bed Fusion (LPBF) of nearly all superalloys within this class has undercut their mechanical performance greatly. This study builds on prior work examining the cracking susceptibility of high- ^' volume fraction superalloys during LPBF by simplifying the LPBF process down to single track laser meltingLaser melting scans. The CoNi-base alloy GammaPrint-700 is utilized in this study, as the cracking resistance of the alloy can be controlled through the boronBoron content. A means of improving the cracking resistance of the alloy through homogenization treatments prior to laser meltingLaser melting was identified. Characterization of the single tracks reveals a possible mechanism of crack initiationCrack initiation via liquation cracking of grain boundariesGrain boundary in the substrate material, and propagation via solidification crackingSolidification cracking along grain boundariesGrain boundary in the melt pool. Additionally, a protocol for assessing the cracking resistance while developing new high- ^' volume fraction superalloys for additive manufacturingAdditive manufacturing is discussed.

We explore the ability of GPT-4 to perform ad-hoc schema based information extraction from scientific literature. We assess specifically whether it can, with a basic prompting approach, replicate two existing material science datasets, given the manuscripts from which they were originally manually extracted. We employ materials scientists to perform a detailed manual error analysis to assess where the model struggles to faithfully extract the desired information, and draw on their insights to suggest research directions to address this broadly important task.

The dynamics of laser spot melting and metallic alloy solidification are investigated through synchrotron x-ray radiography, 3D electron backscatter diffraction data, and computational fluid dynamics (CFD) simulations on a model NiMoAl alloy. Solidification velocities are measured from in-situ images to validate a CFD model of the spot melt. TriBeam tomography is used to reconstruct the melt pool in 3D, characterize the microstructure, and validate the CFD model melt pool dimensions. 3D geometrically necessary dislocation (GND) density calculations reveal extensive deformation at the sample surface. GND calculations integrated with the CFD model reveal that the halo of small, equiaxed grains adjacent to the fusion line is a result of recrystallization that occurred in the heat affected zone. By combining in-situ and ex-situ data modalities across a variety of temporal and spatial length scales, the microstructure formation mechanisms and their relationship to melt pool solidification are quantified.

Ru-based B2 phases present an opportunity to design two-phase BCC + B2 refractory multi-principal element alloys (RMPEAs) with higher temperature stability compared to B2 phases observed in RMPEAs. In this investigation, seven equiatomic Ru-containing RMPEAs were characterized in the as-cast and annealed conditions. Of the two Hf-free alloys, Mo _25 Nb _25 Ta _25 Ru _25 was determined to be a single-phase B2 alloy and Mo _20 Nb _20 Ta _20 W _20 Ru _20 was single-phase BCC. Within all five Hf-containing alloys, phases formed during solidification included HfRu–B2, disordered BCC, and HfO _2 phases. The Hf-containing alloys also precipitated B2 nanoparticles within the BCC phases after further cooling in the solid. All phases were still present after annealing at 1500 ^∘ C to 1600 ^∘ C. The HfRu–B2 nanoparticles in as-cast Hf _20 Mo _20 Nb _20 Ta _20 Ru _20 were characterized by transmission electron microscopy (TEM), and a lattice misfit of < 1 pct between the BCC phase and B2 nanoparticles was calculated. Room-temperature micropillar compression tests were performed on BCC + B2 nanoparticle regions in annealed Hf _20 Mo _20 Nb _20 Ta _20 Ru _20 . Post-mortem TEM analysis revealed precipitate shearing by dislocations, resulting in paired dislocations, along with bowing of dislocations around precipitates. Utilizing the insights from this investigation, compositions for RMPEAs with solutionable B2 precipitates stable above 1200 ^∘ C are suggested.

This study investigates the role of geometrically necessary dislocations (GNDs) and microstructure on void nucleation and growth in wrought and additively manufactured (AM) tantalum subjected to high-strain rate loading. Multi-modal 3D data was collected using TriBeam tomography to calculate GND densities and their spatial relationship to voids. A microstructural comparison between the wrought and AM samples identified distinct void shapes and locations, with intragranular voids and more spherical voids frequently observed in the AM dataset. Results indicate that voids preferentially form at both high-angle grain boundaries and low-angle subgrain boundaries, the latter of which are frequently observed in the AM material. Through a radial distribution analysis of all voids in the datasets, significant GND localization to near-void-surface regions was observed in both samples. 3D crystal plasticity simulations were employed to extend the experimental observations, revealing higher void growth rates in [111] oriented grains when compared to [001] grains. The simulations also suggest that GNDs can be generated as part of the void growth process, with more GND accumulation for growth in a [111] grain than a [001] grain. These findings provide valuable insights into the links between nanoscale void nucleation, mesoscale void growth, and microstructural effects in dynamically loaded tantalum.

Multiphase bcc/B2-based alloy systems have recently received considerable attention because their microstructures are often remarkably similar to the gamma /gamma' microstructure of Ni-based superalloys. The underlying plastic deformation mechanisms of bcc-based intermetallics, however, are not well understood across the composition space where they are thermodynamically stable. Within this contribution, we analyze deformation of B2 intermetallics to develop a reliable platform for efficiently predicting antiphase boundary energies and the associated fault widths as a function of elemental substitution on a particular lattice site of the intermetallic. To achieve this we extend the diffuse multilayer fault model to predict close packed structures that recreate the bonding environment within the layers adjacent to the 12 (111){110} antiphase boundary of the B2 intermetallic. Specifically, the impact of elemental substitution on both antiphase boundary energy and fault width is presented for Hf1_xTixRu and Hf1_xAlxRu and the implications of our findings are discussed. We also highlight a simple bonding model for transition metal -based B2 intermetallics that explains their chemical stability and large antiphase boundary energies. The results presented here offer insight into both the nature of plastic deformation within the B2 intermetallic and the important underlying chemical concepts that can potentially be leveraged to aid in the design of bcc-based alloy systems that rival Ni-based gamma /gamma' microstructures.