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Liège, Belgium

Reginster S.,University of Liege | Mertens A.,University of Liege | Paydas H.,University of Liege | Tchuindjang J.,University of Liege | And 4 more authors.
Materials Science Forum | Year: 2013

In this study, samples of alloy Ti-6Al-4V have been processed by different additive manufacturing techniques in order to compare the resulting microstructure. In all three processes, ultrafast cooling gives rise to strongly out-of-equilibrium microstructures. However, the specific of the heat flow in each process lead to significant differences as far as the grains orientation and the resulting microstructural anisotropy are concerned. © (2013) Trans Tech Publications, Switzerland.

Amouzou D.,University of Namur | Fourdrinier L.,CRM Group | Sporken R.,University of Namur
Applied Surface Science | Year: 2015

A study is conducted to investigate the interface between polysilazane (PSZ)coatings and Mo films for understanding adhesion. Two kinds of Mo/PSZ samples are investigated and the chemical environments of their interfaces are compared. Ultra-thin Mo films are deposited on PSZ coatings to probe the interface directly by X-ray photoelectron spectroscopy (XPS) and to avoid long sputtering times in depth profiling of Mo films. The investigations reveal that the sputtered Mo films systematically adhere well to PSZ coatings. The good adhesion arises from a formation of molybdenum oxycarbonitride or molybdenum carbonitride ceramics through covalent bonding between atoms from PSZ and Mo at the interface.

Mertens A.,University of Liege | Reginster S.,University of Liege | Paydas H.,University of Liege | Contrepois Q.,University of Liege | And 3 more authors.
Powder Metallurgy | Year: 2014

Ti-6Al-4V and stainless steel 316L have been processed by selective laser melting under similar conditions, and their microstructures and mechanical behaviours have been compared in details. Under the investigated conditions, Ti-6Al-4V exhibits a more complex behaviour than stainless steel 316L with respect to the occurrence of microstructural and mechanical anisotropy. Moreover, Ti-6Al-4V appears more sensitive to the build-up of internal stresses when compared with stainless steel 316L, whereas stainless steel 316L appears more prone to the formation of 'lack of melting' defects. This correlates nicely with the difference in thermal conductivity between the two materials. Thermal conductivity was shown to increase strongly with increasing temperature and the thermophysical properties appeared to be influenced by variations in the initial metallurgical state. © 2014 Institute of Materials, Minerals and Mining.

Giraud E.,University of Liege | Pace S.,CRM Group | Lecomte-Beckers J.,University of Liege
Medziagotyra | Year: 2014

The aim of this work was to determine the ability to produce thin metallic foils by self-induced ion plating. Foils of pure copper and pure zinc with a thickness of 35 μm have been successfully produced and their characteristics have been compared to foils obtained by conventional techniques (i. e. electroplating and rolling). Results show the following: (i) more or less compact microstructures can be obtained by self-induced ion plating depending on gas pressure and substrate temperature; (ii) microstructures obtained by self-induced ion plating are quite different from those obtained by electroplating and rolling; (iii) Young's modulus depends on foils roughness; (iv) hardness depends on grain size by exhibiting a Hall-Petch behavior in the case of copper foils and an "inverse" Hall-Petch behavior in the case of zinc foils.

Mertens A.,University of Liege | Contrepois Q.,University of Liege | Dormal T.,Sirris Research Center | Lemaire O.,CRM Group | Lecomte-Beckers J.,University of Liege
European Space Agency, (Special Publication) ESA SP | Year: 2012

In this study, samples of alloy Ti-6Al-4V have been processed by Selective Laser Melting (SLM) and by Laser Cladding (LC), two layer-by-layer near-net-shape processes allowing for economic production of complex parts. The resulting microstructures have been characterised in details, so as to allow for a better understanding of the solidification process and of the subsequent phase transformations taking place upon cooling for both techniques. On the one hand, a new "MesoClad" laser with a maximum power of 300 W has been used successfully to produce thin wall samples by LC. On the other hand, the influence of processing parameters on the mechanical properties was investigated by means of uniaxial tensile testing performed on samples produced by SLM with different orientations with respect to the direction of mechanical solicitation. A strong anisotropy in mechanical behaviour was thus interpreted in relations with the microstructures and processing conditions.

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