Permanent magnets without rare earth (RE) elements, such as alnico, will improve supply stability and potentially decrease permanent magnet cost, especially for traction drive motors and other increased temperature applications. Commercial alnico magnets with the highest energy product are produced by directional solidification (DS) to achieve a columnar grain orientation followed by significant final machining, adding to the high cost. Additive manufacturing (AM) is an effective method to process near net-shape parts with minimal final machining of complex geometries. AM also, has potential for texture/grain orientation control and compositionally graded structures. This report describes fabrication of alnico magnets by AM using both laser engineered net shaping (LENS)/directed energy deposition (DED) and electron beam melting powder bed fusion (EBM/PBF). High pressure gas atomized (HPGA) pre-alloyed alnico powders, with high purity and sphericity, were built into cylindrical and rectangular samples, followed by magnetic annealing (MA) and a full heat treatment (FHT). The magnetic properties of these AM processed specimens were different from their cast and sintered counterparts of the same composition and show a great sensitivity to heat treatment. The AM process parameters used in this developmental study did not yet result in any preferred texture within the alnico AM builds. These findings demonstrate feasibility for near net-shape processing of alnico permanent magnets for use in next generation traction drive motors and other applications requiring increased operating temperatures and/or complex engineered part geometries, especially with further AM process development for texture control.

The fabrication of high purity copper using additive manufacturing has proven difficult because of oxidation of the powder feedstock. Here, we present work on the hydrogen heat treatment of copper powders for electron beam powder bed fusion (EB-PBF), in order to enable the fabrication of high purity copper components for applications such as accelerator components and vacuum electronic devices. Copper powder with varying initial oxygen contents were hydrogen heat-treated and characterized for their chemistry, morphology, and microstructure. Higher initial oxygen content powders were found to not only reduce surface oxides, but also reduce oxides along the grain boundaries and form trapped H₂O vapor inside the particles. The trapped H₂O vapor was verified by thermogravimetric analysis (TGA) and residual gas analysis (RGA) while melting. The mechanism of the H₂O vapor escaping the particles was determined by in-situ SEM heated stage experiments, where the particles were observed to crack along the grain boundaries. To determine the effect of the EB-PBF processing on the H₂O vapor, the thermal simulation and the validation of single melt track width wafers were conducted along with melting single layer discs for chemistry analysis. A high speed video of the EB-PBF melting was performed in order to determine the effect of the trapped H₂O vapor on the melt pool. Finally, solid samples were fabricated from hydrogen-treated copper powder, where the final oxygen content measured ~50 wt. ppm, with a minimal residue hydrogen content, indicating the complete removal of trapped H₂O vapor from the solid parts.

Niobium-based tungsten alloys are desirable for high-temperature structural applications yet are restricted in practice by limited room-temperature ductility and fabricability. Powder bed fusion additive manufacturing is one technology that could be leveraged to process alloys with limited ductility, without the need for pre-alloying. A custom electron beam powder bed fusion machine was used to demonstrate the processability of blended Nb-1Zr, Nb-10W-1Zr-0.1C, and Nb-20W-1Zr-0.1C powders, with resulting solid optical densities of 99+%. Ultimately, post-processing heat treatments were required to increase tungsten diffusion in niobium, as well as to attain satisfactory mechanical properties.

Mechanical properties of powder bed fusion processed unalloyed copper are reported majorly in the as-fabricated condition, and the effect of post-processes, common to additive manufacturing, is not well documented. In this study, mechanical properties of unalloyed copper processed by electron beam powder bed fusion are characterized via room temperature quasi-static uniaxial tensile test and Vickers microhardness. Tensile samples were extracted both perpendicular and parallel to the build direction and assigned to three different conditions: as-fabricated, hot isostatic pressing (HIP), and vacuum annealing. In the as-fabricated condition, the highest UTS and lowest elongation were obtained in the samples oriented perpendicular to the build direction. These were observed to have clear trends between sample orientation caused primarily by the interdependencies between the epitaxial columnar grain morphology and dislocation movement during the tensile test. Texture was insignificant in the as-fabricated condition, and its effect on the mechanical properties was outweighed by the orientation anisotropy. The fractographs revealed a ductile mode of failure with varying dimple sizes where more shallow and finely spaced dimples were observed in the samples oriented perpendicular to the build direction. EDS maps reveal that grain boundary oxides coalesce and grow in HIP and vacuum-annealed specimens which are seen inside the ductile dimples and contribute to their increased ductility. Overall, for the post-process parameters chosen in this study, HIP was observed to slightly increase the sample’s density while vacuum annealing reduced the oxygen content in the specimens.

High-entropy alloys (HEAs) offer a pathway for designing microstructures suited to extreme conditions. Eutectic HEA’s leverage a combination of phase ordering, interfacial strengthening, secondary phase strengthening, and heterodeformation induced (HDI) strengthening to achieve high strength and ductility at elevated temperatures. Maintaining these properties past 700 °C has proved challenging due to limitations in phase stability and breakdown of work hardening mechanisms. This paper set out to produce a dual-phase HEA with enhanced high-temperature stability and work hardenability by leveraging the enhanced HDI strengthening. We have designed a dual-phase hierarchical AlCoCrFeNi(CuTiZr) HEA comprised lamellar composite regions containing FCC(L1 ₂ ) lamella in a continuous BCC(B2) matrix which is surrounded by coarse FCC(L1 ₂ ) grains. A Cr-rich fine scale spinodal phase forms within the BCC regions, in addition to slow forming coarse FeCr-type σ phases in the lamellar FCC and minor NiZr intermetallic phase at the coarse FCC-BCC boundaries. Annealing of the cast samples at 1100 °C for 50 h and quenching breaks down the cast lamellar structure, disorders the FCC, and dissolves the coarse σ phases, while preserving the near equal ratio of FCC to BCC and the Cr-rich spinodal phase. Under compression at 800 °C (1/s strain rate), both the as-cast and high-temperature annealed structures display high strength and work hardening. With increasing temperature, a higher degree of strain partitioning is observed in the annealed structure than the as-cast, resulting in an increase in the peak flow and sustained work hardenability at 900 °C and early onset of strain softening in the annealed structure at 1000 °C due to localized activation of dynamic recrystallization. The persistence of this strain partitioning in the annealed samples corresponds to the enhanced thermal stability of the spinodal Cr phase strengthening the BCC(B2) regions. Above 800 °C, this spinodal phase is consumed in the as-cast structure to fuel the growth of coarser σ and α-Cr phases. The absence of these coarser phases in the annealed condition results in the growth of the spinodal phase and enhanced high-temperature strength of the BCC(B2) regions and enhanced heterodeformation at elevated temperatures. These findings deepen understanding of high-temperature deformation in dual-phase HEAs, offering pathways for optimizing alloy design in extreme environments.

High-entropy alloys (HEAs) offer a platform for designing microstructures suited to extreme conditions. Dual-phase HEAs show promising strength-ductility combinations at high temperatures, but maintaining phase stability above 800°C remains challenging. This study introduces a novel dual-phase HEA (FCC + BCC) with microstructural evolution driven by spinodal decomposition and intermetallic stabilization. The alloy transitions from initial FCC to mixed FCC-BCC laths, with spinodal nanophases in the BCC matrix. Coarse σ (FeCr-type) and NiZr-rich intermetallics form at phase boundaries, enhancing stability. Post-solidification analysis shows σ phase consuming spinodal BCC at high temperatures, while retained nanoscale BCC spinodal contributes to strain incompatibility and HDI hardening. This interplay balances phase stability and mechanical performance. Compressive tests at 800-1000°C (strain rate 1/s) reveal phase stability and deformation mechanisms. Behavior is governed by lamellar morphology and σ/α-Cr ↔ B2 interactions. Retained GNDs and enhanced twinning sustain work hardening up to 900°C. At 1000°C, FCC-dominated strain localization triggers rapid softening via dynamic recrystallization. These findings deepen understanding of high-temperature deformation in dual-phase HEAs, offering pathways for optimizing alloy design in extreme environments.