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Additive manufacturing technologies have several well-known advantages; however, the surface quality of the printed parts is poor, compromising the corrosion and mechanical properties. Thus, surface finishing treatments are necessary. The most post-processing treatments proposed in the literature are mechanical or chemical. The formers are contact techniques and cannot be suitable for complex geometry, while the latter use strong and dangerous reagents. This paper is aimed to investigate the effect of the electropolishing treatment, a contactless technique, using an eco-friendly electrolytic solution in reducing the roughness and improving the fatigue properties of Ti6Al4V specimens produced by electron beam melting technology. Several parameters affecting the effectiveness of the electropolishing treatment have been investigated, as interelectrode distance, stirring rate and duration time. An optimal combination of them allowed a uniform surface treatment and a significant roughness reduction (64% of Sa reduction for cylindrical specimens). Under sinusoidal loading conditions with a maximum stress of 378 MPa and a stress ratio equal to R = 0.1, the mean fatigue life of electropolished dog-bone specimens was 250% longer than that of as-built specimens.

Additive manufacturing (AM), applied to metal industry, is a family of processes that allows complex shape components to be realized from raw materials in the form of powders. Electron beam melting (EBM) is a relatively new additive manufacturing (AM) technology. Similar to electron-beam welding, EBM utilizes a high-energy electron beam as a moving heat source to melt metal powder, and 3D parts are produced in a layer-building fashion by rapid self-cooling. By EBM, it is possible to realize metallic complex shape components, e.g. fine network structures, internal cavities and channels, which are difficult to make by conventional manufacturing means. This feature is of particular interest in titanium industry in which numerous efforts are done to develop near net shape processes. In the field of mechanical engineering and, in particular, in the aerospace industry, it is crucial for quality certification purpose that components are produced through qualified and robust manufacturing processes ensuring high product repeatability. The contribution of the present work is to experimentally identify the EBM job parameters (sample orientation, location of the sample in the layer and height in the build chamber) that influence the dimensional accuracy and the surface roughness of the manufactured parts in Ti6Al4V. The repeatability of EBM is investigated too.

Additive layer manufacturing (ALM) is increasingly attracting the research and industry community interest due to the several benefits provided by the layer-by-layer production approach. With respect to the surface finish, process parameters influence significantly the surface roughness. According to the State of the Art, it is found out that the roughness level may affect the structural performance of ALM products by both quasi-static and fatigue points of view. In this paper, an experimental investigation is proposed, showing that the roughness level plays a more influent role for thin components, with respect to the quasi-static response. The investigated ALM process concerns the electron beam melting technology.

The Electron Beam Melting (EBM) is an Additive Layer Manufacturing (ALM) technique used to directly manufacture 3D functional parts from metal powder, selectively melted, layer by layer, by an electron beam according to a geometry defined by a CAD model. The EBM technology allows benefitting from countless advantages: material waste reduction, easy manufacturing of complex shapes, lead time reduction, etc; on the other hand the EBM process is typically associated with lower resolutions and higher surface roughness (Ra = 25–30 μm) compared to similar laser based powder bed metal processes. Therefore the surface morphology may be a critical issue for the structural integrity of components made in EBM and used in-service in their “as built” condition, i.e. with the characteristic surface released by the process. This study evaluates surface morphology and tensile properties of Ti6Al4V specimens of varying nominal thickness (1–5.0 mm), made by using EBM process with a layer thickness of 50 μm. The aim is therefore to investigate how the surface morphology and the tensile properties are affected by the nominal thickness of the component.

Additive manufacturing of titanium alloy Ti-6Al-4?V has significantly increased over the past few years, primarily due to its broad application over the conventional manufacturing process for complex and near net shape production. However, difficulties arise while printing complex and huge structures and therefore, the components need a suitable joining process. We study the feasibility of friction stir welding of Ti-6Al-4?V plates made by electron beam melting, performing both microstructural and mechanical analysis. Microstructures for all the welds reveal lamellar (??+??) phase and very fine equiaxed ? grain with the prior ? phase at grain boundaries in the stirred zone. Microhardness at different depths of the joint is measured and the strength of the joint is determined using a tensile test. The results obtained prove the feasibility of the process and provide the necessary processing conditions., by Amit Kumar Singha, Bhoopendra Kumara, Kaushal Jha, Astarita Antonello, Squillace Antonino, Stefania Franchitti and Amit Arora

Additive Layer Manufacturing is one of the most promising and investigated manufacturing system due to its advantages to produces near net shape components, also with a very complex shape, in a single shot. Among the different techniques now available, the Electron Beam Melting (EBM) is of particular interest in the production of metal components. Particularly the application of this technique to titanium alloys allows to produces components with a very low buy to fly ratio. In the present paper the microstructure attained is accurately described and mini tensile tests performed allowed to understand the fracture behavior of specimen with the specific microstructure realized under static load. © 2016 Author(s).

The forming limit diagram of superplastic PbSn60 alloy was investigated in this paper. The superplastic sheet was bulged using dies with aspect ratios of 1:1, 15:11, 5:3 and 5:2, at the constant gas pressure and at the temperature of 293 K. Square sheets of dimensions 80 × 80 mm were machined and printed with grid circles of 3 mm diameter. In the test, the specimen is fixed on an elliptical shape die by the action of a blank holder; the sheet is stressed mechanically by a pressure gas, inducing on the pole a biaxial strain state. It was found that the forming limit diagram is not sensitive to die aspect ratio and it is different from a typical cold forming limit diagram.