Elisa Paola Ambrosio

From Powders to Dense Metal Parts: Characterization of a Commercial AlSiMg Alloy Processed through Direct Metal Laser Sintering

In this paper, a characterization of an AlSiMg alloy processed by direct metal laser sintering (DMLS) is presented, from the analysis of the starting powders, in terms of size, morphology and chemical composition, through to the evaluation of mechanical and microstructural properties of specimens built along different orientations parallel and perpendicular to the powder deposition plane. With respect to a similar aluminum alloy as-fabricated, a higher yield strength of about 40% due to the very fine microstructure, closely related to the mechanisms involved in this additive process is observed.

Additive Manufacturing of Al Alloys and Aluminium Matrix Composites (AMCs)

In this chapter a large description of additive manufacturing techniques for obtaining Al alloys and Al matrix composites is given. Results on mechanical properties, roughness and microstructure achievable with such fabrication route on Al alloys are reported

On the Selective Laser Melting (SLM) of the AlSi10Mg Alloy: Process, Microstructure, and Mechanical Properties

The aim of this review is to analyze and to summarize the state of the art of the processing of aluminum alloys, and in particular of the AlSi10Mg alloy, obtained by means of the Additive Manufacturing (AM) technique known as Selective Laser Melting (SLM). This process is gaining interest worldwide, thanks to the possibility of obtaining a freeform fabrication coupled with high mechanical properties related to a very fine microstructure. However, SLM is very complex, from a physical point of view, due to the interaction between a concentrated laser source and metallic powders, and to the extremely rapid melting and the subsequent fast solidification. The effects of the main process variables on the properties of the final parts are analyzed in this review: from the starting powder properties, such as shape and powder size distribution, to the main process parameters, such as laser power and speed, layer thickness, and scanning strategy. Furthermore, a detailed overview on the microstructure of the AlSi10Mg material, with the related tensile and fatigue properties of the final SLM parts, in some cases after different heat treatments, is presented.

Overview on Additive Manufacturing Technologies

This paper provides an overview on the main additive manufacturing/3D printing technologies suitable for many satellite applications and, in particular, radio-frequency components. In fact, nowadays they have become capable of producing complex net-shaped or nearly net-shaped parts in materials that can be directly used as functional parts, including polymers, metals, ceramics, and composites. These technologies represent the solution for low-volume, high-value, and highly complex parts and products.

Tribological Behavior of Aluminum Alloy AlSi10Mg-TiB2 Composites Produced by Direct Metal Laser Sintering (DMLS)

Direct metal laser sintering (DMLS) is an additive manufacturing technique for the production of parts with complex geometry and it is especially appropriate for structural applications in aircraft and automotive industries. Aluminum-based metal matrix composites (MMCs) are promising materials for these applications because they are lightweight, ductile, and have a good strength-to-weight ratio This paper presents an investigation of microstructure, hardness, and tribological properties of AlSi10Mg alloy and AlSi10Mg alloy/TiB2 composites prepared by DMLS. MMCs were realized with two different compositions: 10% wt. of microsize TiB2, 1% wt. of nanosize TiB2. Wear tests were performed using a pin-on-disk apparatus on the prepared samples. Performances of AlSi10Mg samples manufactured by DMLS were also compared with the results obtained on AlSi10Mg alloy samples made by casting. It was found that the composites displayed a lower coefficient of friction (COF), but in the case of microsize TiB2 reinforcement the wear rate was higher than with nanosize reinforcements and aluminum alloy without reinforcement. AlSi10Mg obtained by DMLS showed a higher COF than AlSi10Mg obtained by casting, but the wear rate was higher in the latter case.

On the effect of process parameters on properties of AlSi10Mg parts produced by DMLS

Purpose – The aim of this research is to reach a deep understanding on the effect of the process parameters of Direct Metal Laser Sintering process (DMLS) on macroscopic properties (hardness and density) of AlSi10Mg parts and resulting microstructure. Design/methodology/approach – A full factorial design of experiment (DOE) was applied to determine the most significant process parameter influencing macroscopic properties of AlSi10Mg parts manufactured by DMLS process. The analysis aims to define the optimum process parameters and deduce the process window that provides better macroscopic properties of AlSi10Mg parts. Optical microscopy observations are carried out to link the microstructure to macroscopic properties. Findings – Macroscopic properties of DMLS parts are influenced by the change in process parameters. There is a close correlation between the geometry of scan tracks and macroscopic properties of AlSi10Mg parts manufactured by DMLS process. Originality/value – The knowledge of utilizing optimi...

Enhanced Topology of

A new E-plane filtering structure suitable for very high-power telecom satellite applications is presented. The conceived configuration exploits the design flexibility provided by cascading highly integrated step/stub resonators with pseudoelliptic frequency responses. Several design examples of filters and diplexers in Ku-, K-, and Q-band are reported and supported by experimental tests campaigns. The components have been designed with a full-wave 2-D spectral element method. Prototypes have been realized in aluminum clam-shell technology. Excellent agreement between the models and the experimental results has been achieved. An alternative manufacturing of the proposed architecture based on the selective laser melting technology is also reported. The attractiveness of the structure in view of this emerging additive manufacturing solution is demonstrated. The main advantages of the proposed filter configuration suitable for components operated in heavily loaded multi-carrier environment are: compact design, very low losses, high rejection, and high power-handling capability.

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Additive manufacturing technologies are currently envisaged to boost the development of a next generation of microwave and millimeter-wave devices intended for, among others, satellite telecommunications, navigation, imaging, radio-astronomy, and cosmology. Due to their excellent electromagnetic and mechanical properties, all-metal waveguide components are key building blocks of several radio frequency (RF) systems used in these application domains. This article reports on the prospects originating from the application of all-metal 3D printing to the manufacturing of high-performance microwave waveguide devices. The technology investigated is the selective laser melting process, where a laser beam is used to fuse metal powder particles spread over a building platform. The complete parts are built by overlapping several constant-thickness layers. An overview on process parameters, material properties, and design rules is reported for this technology. The electromagnetic properties of test samples built in Al and Ti alloys have been experimentally characterized. A robust design of Ku/K-band filters aimed at satellite telecommunications has been implemented in several prototypes manufactured in Al. The corresponding measured performance confirm the applicability of the laser selective melting process to the intended applications.

-Plane Resonators for High-Power Satellite Applications

Interest in additive manufacturing (AM) has gained considerable impetus over the past decade. One of the driving factors for AM success is the ability to create unique designs with intrinsic characteristics as, e.g., internal channels used for hydraulic components, cooling channels, and heat exchangers. However, a couple of the main problems in internal channels manufactured by AM technologies are the high surface roughness obtained and the distortion of the channel shape. There is still much to understand in these design aspects. In this study, a cylindrical geometry for internal channels to be built with different angles with respect to the building plane in AlSi10Mg and Ti6Al4V alloys by selective laser melting was considered. The internal surfaces of the channels produced in both materials were analyzed by means of a surface roughness tester and by optical and electron microscopy to evaluate the effects of the material and design choices.

Selective Laser Melting Manufacturing of Microwave Waveguide Devices

Agile and versatile legged robots are expected to become useful machines for applications in unstructured environments where traditional vehicles with wheels and tracks cannot go. Hydraulic actuation has proven to be a suitable actuation technology due to its high power density, robustness against impacts and high stiffness for high bandwidth control. In this paper we demonstrate how additive manufacturing (AM) can produce highly integrated hydraulic components with reduced weight and higher complexity when compared to traditionally manufactured manifolds. To the best knowledge of the authors, this is the first time a successful implementation of direct metal laser sintering (DMLS) of hydraulic manifolds made in aluminium alloy AlSiMg is presented. AlSiMg has several advantages for the construction of hydraulic components when compared to the commonly used Titanium alloys (e.g. Ti64): lower cost, higher thermal conductivity, lower density and easier to post-process. This paper first explains the build process with DMLS of AlSiMg and a pre-study of a pressure-tested hydraulic tube that demonstrated the suitability of AlSiMg for AM hydraulic components. Then, we discuss part orientation and support material during the build process of a highly-integrated hydraulic manifold for the legs of IITs new hydraulic quadruped robot HyQ2Max. A comparison of this manifold with a traditionally manufactured alternative concludes the paper.