The present study focuses on advancing one of the most popular AM techniques, namely, laser powder bed fusion (LPBF) technology, which has the ability to produce complex geometry parts with minimum material waste but continues to face challenges in minimizing the surface roughness. For this purpose, a novel hybrid manufacturing technology, which applies in a single setup (in-envelope) both LPBF technology and high-speed machining, was examined in this research for the fabrication of tensile specimens with three different surface finish conditions: as-built, hybrid (in-envelope machining) and post-machining (out-of-envelope) on Inconel^® alloy 718, hereafter referred to as IN718. As the application of the IN718 alloy in service is typically specified in the precipitation-hardened condition, three different heat treatments were applied to the tensile specimens based on the most promising thermal cycles identified previously for room-temperature tensile properties by the authors. The as-built (AB) specimens had the highest average surface roughness (R_a) of 5.1 μm ± 1.6 μm, which was a significant improvement (five-fold) on the hybrid (1.0 μm ± 0.2 μm) and post-machined (0.8 μm ± 0.5 μm) surfaces. The influence of this surface roughness on the mechanical properties was studied both at ambient temperature and at 650 °C, which is close to the maximum service temperature of this alloy. Regardless of the surface conditions, the room-temperature mechanical properties of the as-fabricated IN718 specimens were within the range of properties reported for standard wrought IN718 in the annealed condition. Nonetheless, detailed examination of the strain localization behavior during tensile testing using digital image correlation showed that the IN718 specimens with AB surfaces exhibited lower ductility (global and local) relative to the hybrid and post-machined ones, most likely due to the higher surface roughness and near-surface porosity in the former. At 650 °C, even though the mechanical properties of all the heat-treated IN718 specimens surpassed the minimum specifications for the wrought precipitation-hardened IN718, the AB surface condition showed up to 4% lower strength and 33–50% lower ductility compared with the hybrid and PM surface conditions. Microfocus X-ray computed tomography (µXCT) of the fractured specimens revealed the presence of numerous open cracks on the AB surface and a predisposition for the near-surface pores to accelerate rupture, leading to premature failure at lower strains.

The magnetic performance of NdFeB permanent magnets rapidly decreases as their operation temperature increases. This limits the power output of electric motors as their internal temperature quickly increases with the power demand. This is particularly problematic for applications where high peak power is required for a short period of time, for example during automobile highway acceleration or during an airplane lift-off. With the advances in additive manufacturing, one can envision to fabricate more complex motor geometries and magnetic structures, without additional costs, allowing for enhanced functionalities such as better thermal management. In this context, this paper investigates the feasibility of using phase changing materials (PCMs) to mitigate the temperature rise in permanent magnets (PMs) fabricated by additive manufacturing. The potential of PCM and its relevance was validated by modeling the thermal response of an electric motor during a representative electric vehicle driving scenario. It was found that segmented magnets with embedded phase changing materials would allow to efficiently control temperature rise. To validate the simulation results, PM test pieces with and without embedded PCMs were fabricated using cold spray additive manufacturing and tested using a custom laser thermal cycling setup.

Characterizing powder feedstock is crucial for ensuring the quality and reliability of parts produced through metal additive manufacturing (AM). The morphology of particles impacts the flowability, packing density, and spreadability of powders, affecting productivity and part quality. A new methodology has been developed to classify particle morphological features in AM powder feedstocks, such as spherical or elongated shapes, and the presence of satellites and facets. This approach uses multiple descriptors for quantitative evaluation. The results from shape descriptors can vary based on image resolution, gray/color thresholding, and software algorithms. There are various commercial systems available for characterizing particle shape, some of which use images taken of static particles, while others use images of particles in motion. This diversity can lead to differences in powder characterization across laboratories with different equipment and methods. This paper compares results from a particle classification approach using two software programs that work with metallographic images with those from an automated static particle analyzer. While traditional methods offer higher resolution and precision, this study shows that automated systems can achieve similar particle shape classification using different shape descriptors and thresholds.

This study investigated the effect of supersolidus liquid-phase sintering conditions on the powder particle bonding and the AlN-phase formation of an AlSi10Mg alloy. Sintering was conducted at temperatures between 550 and 579 °C, with a holding duration of 2 h under a nitrogen atmosphere. The sintering cycles included four heating segments, performed at rates ranging from 0.2 to 5 °C/min for a total of between 5 and 15 h, and a cooling segment performed at two different cooling rates, 0.15 and 5 °C/min, resulting in durations of 12 and 70 h, respectively. Three powder batches exhibiting different particle size distributions were tested. An X-ray diffractometer, optical microscopy, and scanning electron microscopy were used to characterize phase formation and particle bonding. The results show that higher sintering temperatures and faster heating/cooling rates led to a lower fraction of AlN. In contrast, lower sintering temperatures or slow heating promoted the development of a thicker AlN shell around powder particles, inhibiting the bonding of the AlSi10Mg powder and preventing densification via the sintering process. These findings suggest that sintering at temperatures between 570 and 575 °C, with heating and cooling rates of at least 2 °C/min, constitutes a more favorable window for the densification of AlSi10Mg under a nitrogen atmosphere.

Characterizing powder feedstock is crucial for ensuring the quality and reliability of parts produced through metal additive manufacturing (AM). The morphology of particles impacts flowability, packing density, and spreadability of powders, affecting productivity and part quality. A new methodology has been developed to classify particle morphological features in AM powder feedstocks, such as spherical or elongated shapes, and the presence of satellites and facets. This approach uses multiple descriptors for quantitative evaluation. The results from shape descriptors can vary based on image resolution, grey/colour thresholding, and software algorithms. There are various commercial systems available for characterizing particle shape, some of which use images taken of static particles, while others use images of particles in motion. This diversity can lead to differences in powder characterization across laboratories with different equipment and methods. This paper compares results from a particle classification approach using two software programs that work with metallographic images with those from an automated static particle analyzer. While traditional methods offer higher resolution and precision, the study shows that automated systems can achieve similar particle shape classification using different shape descriptors and thresholds.

This study investigates the correlation between sintering temperature, microstructure, and mechanical properties in AlSi10Mg alloy produced by supersolidus liquid phase sintering and subsequent artificial aging. Sintering was performed at 571, 575, and 579 °C using different heating rates for a total duration of approximately 5 h, followed by a 2 h dwell at the sintering temperature. At low sintering temperature, the alloy exhibits relatively fine α-Al grains with uniformly distributed Si precipitates, whereas intermediate temperature promotes Si coarsening. At higher temperature, excessive liquid formation leads to coarse α-Al grains and the development of partially interconnected Si networks. β-Al₅FeSi progressively coarsen with increasing sintering temperature. In the as-sintered state, the modest mechanical properties result from coarse α-Al grain size and subgrain structure, as well as from the size, morphology, and distribution of the Si phase. After aging (at 160 °C for 6 h following solution treatment at 530 °C for 30 min), the hardness and UTS were almost double (going from 44 ± 1 to 103 ± 2 HV and from 121 ± 1 to 273 ± 40 MPa). Meanwhile, α-Al grain size and Si morphology remained unchanged and Fe-rich intermetallics partially transformed into the more stable γ-Al₃FeSi₂ phase.