2014

Premature failure of dies is a critical problem of manufacturers in hot-working processes, e.g. metal die casting, hot extrusion and/or thixoextrusion of aluminium/magnesium or steel. Typically, die material has to be resistant to heat cycling or corrosion environment, to plastic deformation and wear, especially when exposed to high temperature during continuous working cycle. The resistance of dies could be increased by the modification of their surfaces, i.e. by the application of an adequate coating. An improvement of the resistance of H11 steel substrate will be presented and discussed.

In this paper evolution from hot forging to thixoforging process is proposed and talked over. A realcase study is presented, namely a steel-made steering piston produced by thixoforging technique is considered and some parameter has been numerically analyzed. The transition between the traditional forging process and the new one involves several transformations and presents difficulties mainly due to the high working temperature.

The primary objective of the present research was to provide a fundamental understanding of the processing science necessary to fabricate the Aluminum Nitride (AIN) reinforced Aluminum-Magnesium (AIMg) composites via Reactive Gas (N2) Injection in the AIMg alloy melt. Aluminum nitride (AlN) matrix composites were prepared by a novel approach. It was possible to produce a considerable amount of AIN particles in the AI alloy matrix at a reaction temperature as low as 900 °C utilizing the in-situ nitration reaction process developed in the present study.

Selective laser melting (SLM) process allows fabricating strong, lightweight and complex metallic structures. To successfully produce metallic parts by SLM, additional structures are needed to support overhanging surfaces in order to dissipate process heat and to minimize geometrical distortions induced by internal stresses. However, these structures are often massive and require additional post-processing for their removal. A minimization of support structures would therefore significantly reduce manufacturing and finishing efforts and costs.

Casting process simulation is nowadays established as a strategic tool in process optimisation to improve product quality. However, sometimes the required three-dimensional mathematical model of the casting is not available, because the original drawings are not-up-to date and parts are subjected to design changes. In these cases, reverse engineering (RE) is the most suitable method to reconstruct the geometrical model of the casting. In this paper, a RE-based procedure is proposed to obtain the three-dimensional CAD model of a casting from its physical equipment.

We report on a simple, fast and low-cost synthesis procedure for the complete covering of zinc oxide (ZnO) 1D nanostructures with a protective shell of titania (TiO2) nanoparticles. ZnO nanowires (NWs) were grown on transparent F-doped Tin Oxide (FTO) conductive layer on glass by seed layer-assisted hydrothermal route in aqueous media, while the titania shell was deposited on the ZnO NWs through an in situ non-acid sol-gel synthesis. The nanowires impregnation time in the titania sol was varied from 3 to 10 min.

Metal nanoparticles (NPs) have recognized a growing importance in chemistry, electronics, optics, physics, and biology in the last decades. The possibility of tuning their unique properties varying dimension and morphology widely extends the range of possible applications. Several innovative chemical routes have been investigated to design shape-controlled synthesis to combine high-yield production with controllable and repeatable morphology.

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.

Experimental evidences are reported on the potential of direct metal laser sintering (DMLS) in manufacturing flat and finned heat sinks with a remarkably enhanced convective heat transfer coefficient, taking advantage of artificial roughness in fully turbulent regime. To the best of our knowledge, this is the first study where artificial roughness by DMLS is investigated in terms of such thermal performances. On rough flat surfaces, we experience a peak of 73 % for the convective heat transfer enhancement (63 % on average) compared to smooth surfaces.

Silver particles with spiky nanostructured morphologies have been obtained by two different wet-synthesis approaches. A detailed investigation was carried out into the synthesis parameters to tune the shape of the sample into desert-rose- and succulent-like particles. The first synthetic route was based on the reduction of silver nitrate by iron sulfate in the presence of maleic acid as anisotropic agent, whereas in the second method ascorbic acid was used as the reducing agent and citric acid as the anisotropic agent.