Metal additive manufacturing processes often use gas-atomized powder as feedstock, but these processes use different methods for consolidation. Depending on the consolidation temperature, secondary phases may be retained during processing, making it important to understand powder microstructure prior to consolidation. Commercial alloy compositions are typically used for these powders because they have been widely studied and qualified; however, the microstructure of the powder form of these compositions has not been studied. This paper aims to understand the commercial Al 6061 powder: how the internal microstructure of the powder differs from wrought both in the as-manufactured and thermally-treated conditions. A specific focus is put on the Mg-rich phases and their morphologies. This was accomplished through transmission electron microscopy, scanning transmission electron microscopy, and energy dispersive x-ray spectroscopy. Both the size and morphology of the phases in the powder differ greatly from those in the wrought form.

Cold gas-dynamic spray is a solid-state materials consolidation technology that has experienced successful adoption within the coatings, remanufacturing and repair sectors of the advanced manufacturing community. As of late, cold spray has also emerged as a high deposition rate metal additive manufacturing method for structural and nonstructural applications. As cold spray enjoys wider recognition and adoption, the demand for versatile, high-throughput and significant methods of particulate feedstock as well consolidated materials characterization has also become more notable. In order to address the interest for such an instrument, nanoindentation is presented herein as a viable means of achieving the desired mechanical characterization abilities. In this work, conventionally static nanoindentation testing using both Berkovich and spherical indenter tips, as well as nanoindentation using the continuous stiffness measurement mode of testing, will be applied to a range of powder-based feedstocks and cold sprayed materials.

In this literature review, the antipathogenic properties and contact-mediated antibacterial and antiviral performance of copper cold spray surfaces are assessed and compared with alternative antimicrobial materials that are able to kill and/or inactivate infectious agents via direct contact. Discussion is also provided concerning the suitability of copper cold spray material consolidations as biocidal and viricidal surfaces that retain long-term functionality as a preventative measure against fomite transmission of pathogenic agents and hospital-acquired infections from contaminated high-touch surfaces. Numerable alternative antimicrobial coatings and surfaces that do not rely upon the oligodynamic action of copper are detailed. Given the ongoing need for recognition of said alternative antimicrobial materials by authoritative agencies, such as the U.S. Environmental Protection Agency, the relevant literature on non-copper-based antipathogenic coatings and surfaces are then described. Furthermore, a wide-ranging take on antipathogenic copper cold spray coatings are provided and consideration is given to the distinctive grain-boundary mediated copper ion diffusion pathways found in optimizable, highly deformed, copper cold spray material consolidations that enable pathogen inactivation on surfaces from direct contact. To conclude this literature review, analysis of how copper cold spray coatings can be employed as a preventative measure against COVID-19 was also presented in light of on-going debates surrounding SARS-CoV-2’s non-primary, but non-negligible, secondary transmission pathway, and also presented in conjunction with the inevitability that future pathogens, which will be responsible for forthcoming global pandemics, may spread even more readily via fomite pathways too.

Developments in polymer 3D printing (3DP) technologies have expanded their scope beyond the rapid prototyping space into other high-value markets, including the consumer sector. Processes such as fused filament fabrication (FFF) are capable of quickly producing complex, low-cost components using a wide variety of material types, such as polylactic acid (PLA). However, FFF has seen limited scalability in functional part production partly due to the difficulty of process optimization with its complex parameter space, including material type, filament characteristics, printer conditions, and “slicer” software settings. Therefore, the aim of this study is to establish a multi-step process optimization methodology—from printer calibration to “slicer” setting adjustments to post-processing—to make FFF more accessible across material types, using PLA as a case study. The results showed filament-specific deviations in optimal print conditions, where part dimensions and tensile properties varied depending on the combination of nozzle temperature, print bed conditions, infill settings, and annealing condition. By implementing the filament-specific optimization framework established in this study beyond the scope of PLA, more efficient processing of new materials will be possible for enhanced applicability of FFF in the 3DP field.