Anisotropic behaviour law for sheets used in stamping: A comparative study of steel and aluminium

For a car manufacturer, reducing the weight of vehicles is an obvious aim. Replacing steel by aluminium moves towards that goal. Unfortunately, aluminium's stamping numerical simulation results are not yet as reliable as those of steel. Punch-strength and spring-back phenomena are not correctly described. This study on aluminium validates the behaviour law Hill 48 quadratic yield criterion with both isotropic and kinematic hardening. It is based on the yield surface and on associated experimental tests (uniaxial test, plane tensile test, plane compression and tensile shearing)

High temperature oxidation of IN 718 manufactured by laser beam melting and electron beam melting: Effect of surface topography

The oxidation behaviour of IN 718 alloys produced by laser beam melting and electron beam melting was compared to that of the wrought alloy at 850 °C in laboratory air. Oxide scales of all alloys were similar in nature and morphology with small differences due to powder particles sintered on the surface of additive manufacturing parts. Nevertheless, major differences in surface topography were noticed, these could affect surface area estimations and consequentlymass gain estimations. A quantitative correlation was determined between apparent parabolic rate constant and surface area

Oxydation à haute température d’échantillons en Inconel 718 réalisés par fabrication additive : influence de l’état de surface et de la microstructure

Les matériaux issus de la fabrication additive sont-ils aussi performants que leurs homo-logues forgés ou coulés, en termes de résistance à l’oxydation ? Le comportement d’échan-tillons en IN 718 produits par fusion laser et faisceau d’électrons, est comparé à celui d’un alliage de référence forgé-traité

Intergranular oxidation of Ni-base alloy 718 with a focus on additive manufacturing

The intergranular oxidation in air at 850 °C of alloy 718 produced by laser beam melting and electron beam melting was compared to that of the wrought alloy. Quantitative analyses revealed that the amount of grain boundary oxidation was similar for these alloys. However, the additively manufactured ones presented deeper and thicker oxides at grain boundaries, due to grain size heterogeneity and to a smaller number of special boundaries. Results show that intergranular oxidation kinetics follows Wagner’s theory on internal oxidation considering not only O diffusion at the intergranular oxide/metal interfaces but also Al and Ti diffusion in the bulk

A new localized inverse identification method for high temperature testing under resistive heating: Application to the elastic‐viscoplastic behaviour of L‐PBF processed In718

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Oxydation à haute température d’échantillons en Inconel 718 réalisés par fabrication additive : influence de l’état de surface et de la microstructure

International audienceLes matériaux issus de la fabrication additive sont-ils aussi performants que leurs homo-logues forgés ou coulés, en termes de résistance à l’oxydation ? Le comportement d’échan-tillons en IN 718 produits par fusion laser et faisceau d’électrons, est comparé à celui d’un alliage de référence forgé-traité

Fused filament fabrication process window for good interlayer bonding: Application to highly filled polymers in metallic powder

Extending the fused filament fabrication process to highly filled thermoplastics in metallic powder used in metal injection molding is a promising method to produce small series. However, the lack of adhesion between deposited filaments can cause ruptures during the fabrication or debinding process. We designed a simple device to measure the shear strength required to tear off a filament deposited on a substrate. This device makes it possible to quickly determine the processing window for a good welding of filaments. We developed a 2D thermal simulation using the finite difference method while integrating the enthalpy of fusion and crystallization kinetics of the material. We then fitted it to the thermal measurements at depths of 0.45 and 0.75 mm under the substrate surface using small-diameter thermocouples. Simulation results highlight the key role of the thermal contact resistance between the filament and the substrate in the evolution of the interface temperature. This provides essential information to explain the process window that can be determined experimentally. The characteristic time of macromolecule diffusion was determined by rheological measurements and was found to be too small to play a role in filament bonding for the simulated cooling rates for the studied material. The methodology introduced in this work was used to improve highly filled polymers interlayer adhesion, but it can be used to improve other filled or unfilled polymer

Cyclic oxidation of alloy 718 produced by additive manufacturing compared to a wrought-718 alloy

The cyclic oxidation resistance at 900 °C of the alloy 718 produced by laser beam melting and electron beam melting was compared to that of the wrought-718 alloy. Results showed large differences regarding the rate of oxide layer spallation. The wrought alloy presents much more adherent oxide scale. Moreover, the standard heat treatment and the surface grinding slightly delay the catastrophic spallation. The role of sulfur and manganese on the adhesion of the oxide scale is quantitatively discussed using thermodynamic modelling. This result may force restrictions on the chemical composition of the alloy 718 powder used for additive manufacturing