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Urgent environmental challenges and emerging additive manufacturing (AM) technologies push research towards more performant and new materials. In the field of metallurgy, high entropy alloys (HEAs) have recently represented a topic of intense research because of their promising properties, such as high temperature strength and stability. Moreover, this class of multi-principal element alloys (MPEAs) have opened up researcher community to unexplored compositional spaces, making prosper literature of high-throughput methodologies and tools for rapidly screening large number of alloys. However, none of the methods has been aimed to design new MPEAs for AM process known as selective laser melting (SLM) so far. Here we conducted nanoindentation testing on single scan tracks of elemental powder blends and pre-alloyed powders after ball milling of AlTiCuNb and AlTiVNb. Results show that nanoindentation can represent an effective technique to gain information about phase evolution during laser scanning, contributing to accelerate the development of new MPEAs.

The effect of aging treatment on Astroloy fabricated via hot isostatic pressing and subjected to super-, and sub- solvus solutioning has been investigated. The evolution of hardness and microstructural features were followed after each step of the treatment. Since this alloy is commonly subjected to a double aging treatment at two different temperatures, particular attention was given to the effectiveness of the first aging treatment compared to the second one. Coarsening and modification of the γ' reinforcing system together with carbides formation were made the object of research. The cooling rate used after solutioning treatment was also kept into account. Finally, a model to describe secondary and ternary gamma prime coarsening upon aging treatments is presented.

Additive manufacturing technologies have been increasingly applied to the development of radio frequency components in the past few years. Indeed, the free-form capability of these processes allows for the design of novel components, whose actual implementation through conventional machining is rather complex or even not possible. This paper describes a monolithic WR51 component integrating three radio frequency functionalities, namely, bending, twisting, and filtering. Three aluminum prototypes with different bending/twisting radii have been manufactured through the selective laser melting process. They exhibit a measured rejection higher than 60 dB in 17.5 and 21.2 GHz, and a measured return loss better than 20 dB in 12.5 and 15 GHz. Significant mass and envelope reductions (higher than 60% depending on the bending/twisting radius) with respect to the reference subsystem with distinct waveguide components are achieved. These results assess the effectiveness of 3-D metal printing in the miniaturization and integration of waveguide systems.

Laser powder bed fusion (LPBF) process allows to manufacture customized metal porous 3D parts known to have many interesting combinations of physical and mechanical properties. Therefore, the minimum resolution obtainable by this process is of high importance in the design of porous functional parts e.g. thin walls. Knowledge of the relationship between process parameters and material employed is fundamental to obtain these kinds of structures with LPBF. A series of experiments were carried out with a laser-melting system with laser power up to 200 W and a spot of 100 μm to analyze the influence of the manufacturing strategy in the construction of thin walls in AlSi10Mg alloy. The results showed that it is possible to have well defined dense thin walls using appropriate building strategies, providing also useful information for the design rules definition of the LPBF process. The results also showed that the energy density is not able to provide information on the complexity that involves the melt pools formation and propagation. A mathematical model was also developed to build well defined thin walls directly through the process parameters and to reduce the mismatch between as-designed and as-manufactured thin wall structures. The verification of such model was made building thin walls in AlSi10Mg and then comparing them to the as-designed structures.

The influence of solutioning treatment on Astroloy fabricated via Hot Isostatic Pressing has been investigated. Both sub- and super-solvus solutioning treatments were performed, gradually increasing the test temperature from 1115 to 1200 °C in order to cross the ɣ′ solvus. The effects of the solutioning temperature and of the following cooling step were studied in terms of amount of reinforcing precipitate ɣ′, of γ-grain coarsening and of alloy hardness. Grain boundaries morphology was observed to be clearly modified by the solutioning conditions moving from the “smooth” to the “serrated” type. It was also possible to draw a clear correlation between cooling rates and Astroloy hardness.

The paper deals with the corrosion resistance in chloride solutions of an AlSi10Mg alloy obtained by laser powder bed fusion (LPBF) process. The potentiodynamic tests were carried out in solutions having different chloride contents. The results emphasize the role of chloride concentration on localized corrosion. The increase of concentration reduces pitting potential. In addition, the influence of the post-processing heat treatment temperature was recognized. Penetrating attacks occurred either on after low temperatures stress relieving or specimens without any treatment, promoted by selective dissolution of the α-Al phase stimulated by galvanic coupling with noble silicon precipitates at the border of the melt pool. Such penetrating morphology was not observed after heat treatments at high temperature.

The effect of aging treatment on Astroloy fabricated via hot isostatic pressing and subjected to super-, and sub- solvus solutioning has been investigated. The evolution of hardness and microstructural features were followed after each step of the treatment. Since this alloy is commonly subjected to a double aging treatment at two different temperatures, particular attention was given to the effectiveness of the first aging treatment compared to the second one. Coarsening and modification of the &gamma, &prime, reinforcing system together with carbides formation were made the object of research. The cooling rate used after solutioning treatment was also kept into account. Finally, a model to describe secondary and ternary gamma prime coarsening upon aging treatments is presented.

Al Si Ni samples were produced via selective laser melting (SLM) by mixing AlSi10Mg and pure nickel powders. The mixing rate was chosen in order to obtain a chemical composition close to the eutectic and with the aim of exploiting a very narrow solidification temperature range. The building parameters were optimised to reduce the porosity values. Samples produced with the optimised process parameters were then characterized in terms of microstructures and hardness. The results show that even if some Al 3 Ni agglomerates were found, the SLM allows a good dispersion of the nickel within the alloy. The hardness tests revealed that the introduction of nickel strongly increased the hardness of the alloy. This was also demonstrated using nanoindentation measurements.

Stochastic and non-stochastic porous structures, are used in a variety of applications such as biomedical implants, heat exchangers mass and gas separation, water purification, energy conversion and storage due to their interesting combinations of physical and mechanical properties, such as high stiffness in conjunction with very low specific weight or high gas permeability combined with high thermal conductivity. Among the technologies for the production of these porous structures, the additive manufacturing (AM) processes, such as the powder bed based selective laser melting (SLM), are of particular interest. In order to obtain this kind of structures with SLM, it is important to know the relationship between process parameters and material employed. A series of experiments were carried out to analyze the influence of the main SLM process parameters on the width and continuity of manufacture of non-stochastic porous structures and to manufacture stochastic porous structures through the scanning strategy.