Elaboration of thin foils in copper and zinc by self-induced ion plating

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

Determination of the Influence of Alloying Elements on Solidification Parameters for the Study of the Thixoformability of a Chromium Steel

peer reviewedThis paper deals with the examination of the influence of alloying elements on the thixoformability of a chromium steel. It focuses on the liquid fraction curves of different chromium steel with and without modification of composition. The liquid fraction versus temperature has been obtained experimentally by differential thermal analysis (DTA), limited to low heating rates. The correlation between liquid fraction and temperature has been studied. The effect of modifications of composition was observed

Tooling materials and solutions for thixoforming steel

The aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during steel thixoforming process in order to determine appropriate tool materials and solutions. This evaluation was realized thanks to experimental trials and to the finite elements simulations. The effect of these loadings on the tool’s failure modes are highlighted and compared to the ones observed in classical forming processes. Beyond this, the failure modes of different tool materials and solutions are presented. The tested materials are hotworking tool steels. Other possibilities and tool coating or surface treatments are discussed as well

Study of complex carbides obtained after solidification and thermal treatment in High Speed Steels

High-speed steels (HSS) rolls are used in front finishing stands of hot strip mills. Good wear resistance and hardness at high temperature are defining characteristics of HSS. Many carbides are present in these alloys, each having different effects upon the final properties of HSS. As a result, the nature, the morphology and the amount of these carbides are factors of important concern. Optical microscopy combined with electron microscopy lead to quicker identification and characterization of HSS carbides

On the Role of Interfacial Reactions, Dissolution and Secondary Precipitation During the Laser Additive Manufacturing of Metal Matrix Composites: A Review

Since current trends in the transportation, energy or mechanical industries impose increasingly demanding service conditions for metallic parts, metal matrix composites (MMCs) are the object of a growing interest. Powder-based laser additive manufacturing, which allows making parts with complex shapes, appears particularly adapted for the production of MMCs. This paper reviews the current state-of-the-art in the production of MMCs by additive processes, with the aim of assessing the potentials and difficulties offered by these techniques. Two main processing routes are envisaged, i.e. (1) the processing of ex situ composites in which the reinforcing phase as a powder—often of ceramic particles—is directly mixed with the powder of the matrix alloy, and both powders are simultaneously processed by the laser. (2) Alternatively, the reinforcing phase can be produced in situ by a chemical reaction during the fabrication of the composite. For both processing routes, a careful control is needed to overcome challenges brought, e.g. by the behaviour of the reinforcement particles in the laser beam, by changes in laser absorptivity or by the dissolution of the reinforcing particles in the molten metal, in order to produce MMCs with enhanced usage properties

Graphitization in chromium cast iron

peer reviewedSome trials with graphite Hi-Cr iron rolls have been done mainly in Japan, for the rolling of stainless steel. This material could lead to good compromise between oxidation, wear and thermal behaviour. By using thermal analysis and resistometry, the conditions for secondary graphite formation have been studied. The amount and volume of free graphite may be strongly increased by a suitable heat treatment, allowing a good thermal conductivity as well as high wear and mechanical properties

Characterisation of thermophysical properties of semi-solid steels for thixoforming

Major challenge for semi-solid processing includes broadening the range of alloys that can be successfully thixoformed and developing alloys specifically for thixoforming. One important parameter is appropriate solidus-liquidus interval. The wider the solidification interval, the wider the processing window. This study is related to the experimental determination of this critical parameter on eight different steel compositions. This parameter was obtained using Differential Scanning Calorimetry. This technique allows to obtain the solid fraction versus temperature. The paper also presents the results of thermophysical properties determination such as thermal diffusivity, heat capacity and thermal conductivity. These properties were measured from room temperature to semi-solid state in one particular steel. The thermal diffusivity was measured using the Laser Flash method and the heat capacity using a DSC calorimeter. The thermal conductivity was obtained by calculation knowing the thermal dilatation measured with a dilatometer. All these measurements were performed for temperatures up to the liquidus. These parameters are difficult to measure but they are important to determine for the conductive heating phase of a semi-solid forming (SSM) process.Peer reviewe

Study of transformations and microstructural modification in Ti-LCB and T-555 alloys using Differential Scanning Calorimetry

peer reviewedThe aerospace industry is the single largest market for titanium products primarily due to the exceptional strength to weight ratio, elevated temperature performance and corrosion resistance. Titanium applications are most significant in jet engine and airframe components that are subject to high temperatures. The studied Ti-LCB and Ti-555 titanium alloys must present good properties to fatigue damage as they are located in a low-pressure compressor. In order to avoid this damage, an optimized alloy microstructure is required. In our case, the optimal microstructure would be a beta matrix in which small alpha particles are uniformly distributed, obtained after a combination of thermomechanical and thermal treatments. The understanding of the mechanisms ruling the microstructure evolution is achieved through the study of phase transformations versus temperature. During heating, the ωath phase is transformed into the ωiso phase, allowing itself the appearance of the α phase. Then this α phase is transformed progressively into the β phase, and the structure becomes totally β when the transus temperature is reached. Therefore, a thermal analysis tool such as DSC (Differential Scanning Calorimetry) was used in order to characterise the phase transformations of the material during imposed controlled temperature programs

Research on durable junction of multimaterials

This collective project aimed to assess the potential of adhesive bonding in various applications in the field of building construction. This evaluation takes into account technical, economical and ecological aspects and provides a methodology that can be easily transferred to other applications.RONDUJU

Rapidly solidified microstructure of 3D parts fabricated by selective laser melting (SLM) - Examples of stainless steel 316L and titanium Ti-6Al-4V

Laser additive manufacturing process capable of producing fully dense metallic parts direct from 3D CAD know a fast development. Major concerns are made to achieve the best accuracy of the final geometry and the reduction of the residual stresses but metallurgical aspects are also essential. The process can be described as a succession of very small welds. A key in the optimization of the mechanical properties is the understanding of the specific solidification mechanisms. Microstructures of two alloys were studied by metallographic examination and EBSD analysis.TIPTOPLA