Self-Supporting Structures Produced through Laser Powder Bed Fusion of AlSi10Mg Alloy: Surface Quality and Hole Circularity Tolerance Assessment

In the context of the Design for Additive Manufacturing (DfAM), the elimination and/or reduction of support structures for the parts is a key issue for process optimization in terms of sustainability and surface quality. In this work, the assessment of the surface quality of overhanging thin walls and unsupported holes with different diameters (4, 6, 8 mm) was carried out through confocal microscopy, SEM-EDS analysis and CMM measurements. To this aim, two different types of AlSi10Mg alloy parts were produced with the L-PBF technology, having self-supporting features such as thin walls and holes with different overhang angles. The results showed that (i) unsupported, down-facing surfaces can be printed consecutively without supports up to a 30◦ overhang angle and with a surface roughness (Sa) ranging from 3 to 40 μm; (ii) unsupported holes can be produced as well, having a mean circularity tolerance ranging from 0.03 to 0.55 mm, regardless of the diameter value; (iii) density and microstructure analysis both revealed that the parts’ integrity was not affected by the design choices

Mechanical response of 2024-7075 aluminium alloys joined by Friction Stir Welding

none3Codice Scopus: 2-s2.0-23744450678P. Cavaliere;E. Cerri;A. SquillaceCavaliere, Pasquale Daniele; E., Cerri; A., Squillac

Selective electrochemical machining of the steel molds in hot isostatic pressing of Ti6Al4V powder

Anodic dissolution is proven to be an effective method to remove stainless steel molds from Ti6Al4V compacts obtained from powder by hot isostatic pressing. Two different working solutions were studied: 2 M NaCl and 2 M NaCl + 0.05 M Na2EDTA. While both were capable of removing the steel mold, the latter was also capable of removing the diffusional layer made by the intermetallic phases generated between titanium and steel during the compaction process

Friction-Stir Welding of AA 2198 Butt Joints: Mechanical Characterization of the Process and of the Welds Through DOE Analysis

In this study, rolled plates of AA 2198 T3 aluminium alloy are friction-stir welded in butt configuration varying two fundamental process parameters: rotational and welding speeds. Two sets of empirical models based on regression analysis are developed. The first one predicts the stationary values of the in-plane and downwards forging welding forces in dependence of the process parameters under investigation. The second one predicts the mechanical strength, in particular yield and tensile strength, of the friction-stir welded joints as function of the same parameters. For the development of the empirical models, two 32 full factorial designs are used: one having the stationary values of the welding forces and the other having the yield and tensile strength as observed responses, respectively. Statistical tools such as analysis of variance, F tests, Mallows’ CP, coefficient of determination etc. are used to build and to validate the developed models. By using the desirability function approach, the optimum process parameters to simultaneously obtain maximum possible yield and tensile strength are found within the investigated range. The developed models can be effectively used to predict the stationary forces and the mechanical proprieties of the joints at 95% confidence level

Effect of fibre laser marking on surface properties and corrosion resistance of a Fe-Ni-Cr alloy

Fiber laser techniques are increasing their use in many applications, including modification of material surface properties. In particular they are often used for materials' marking as a non-contact processing. In spite of this, the impact of the laser beam on the surface causes metallurgical and morphological changes. The developments during the laser-material interaction can also affect other surface properties, especially corrosion properties which are crucial in the case of Iron-Nickel alloys. Effect of laser marking on a Fe-Cr-Ni alloy using a Tm-fibre laser (IPG Photonics TRL1904; maximum power: 50W, wavelength: 1904 nm), is described in this paper. In order to evaluate the effect of the laser on corrosion properties a specific ageing test in salt spray has been performed. Moreover, superficial morphology analyses have been performed on samples before and after corrosion tests. Possibilities and limitations of laser marking on these alloys have been discussed, in particular from the point of view of the marked surface corrosion resistance preservation

Development of an innovative method to predict and to characterize the performances of Ti-6Al-4V LBW joints

Every manufacturing process leaves on the surface of the piece a typical "technology signature". In particular, the laser welding leaves a feature at the edge of the weld bead called "undercut". In this work an experimental campaign has been conducted on Ti6Al4V butt joints. In particular a Central Composite Design (CCD) with the central point repeated three times has been investigated. In the CCD there are two factors (power and speed of the fiber laser) and five levels for each factor. This paper deals with the investigation about the correlation between the severity of the undercut and the process parameters of the laser welding. In particular, through the confocal microscopy, the original geometry of the joint was accurately acquired and rebuilt in order to make a FEM model and simulate the mechanical behavior using Ansys14.5. Moreover, response surfaces and level curves were carried out to understand and predict the depth and the width of the undercut starting from the power and the speed of the laser. At last a mathematic and geometry regression was performed in order to find a unique conical curve that interpolates all the different undercuts and that varies its parameters according to the process parameters. It is established that the process with higher speed minimizes and optimizes the undercut in the joints

Friction stir welding of AlSi10Mg plates produced by selective laser melting

A preliminary research work is carried out to demonstrate the feasibility of friction stir welding AlSi10Mg plates produced by selective laser melting. The metallurgical evolutions occurring have been studied and discussed on the basis of detailed microstructure observations. The FSW process enhances the structure of the parent material so that the weld presents an overall refinement of the microstructure and a decrease in microporosity in all its zones. Using the friction stir welding technology, sound welds harder than the parent material can be obtained

Metallization of Fiber Reinforced Composite by Surface Functionalization and Cold Spray Deposition

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Form and Dimensional Accuracy of Surfaces Generated by Longitudinal Turning

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Rotation-assisted Abrasive Fluidised Bed Machining of AlSi10Mg parts made through Selective Laser Melting Technology

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