Samples of AlSi10Mg alloy were first constructed, selecting the manufacturing parameters through a parametric method based on an experimental design; with the same technique, samples of a metallic matrix composite (AlSi10Mg matrix base and particles of SiC reinforcements) were also made. The evolution of the density with the introduction of reinforcements into the AlSi10Mg alloy was studied. This showed an increase in the porosity level with the reinforcement volume fraction. The material hardness and electrical conductivity were then evaluated, along with conventional mechanical characteristics, and microstructural changes with respect to heat treatments on both the AlSi10Mg alloy material and AlSi10Mg matrix composite. Doing so allows correlating material hardness and electrical conductivity (as observed for conventionally produced alloys: casting or wrought). The tensile strength, yield strength and Young's modulus were measured. A significant increase in the conventional mechanical characteristics compared with casting was shown, due to hardening by structure refinement. Evidence is given to relate the yield strength value to the reduction in the dendrite arm spacing (DAS) by application of the Hall-Petch law. We discuss the understanding of the thermal process involved (temperature distribution and fast cooling rate). In addition, observations and analysis of the microstructural changes are presented: building tracks, the disturbed zone, and structural variations linked to heat treatment.
Various selective laser melting (SLM) configurations (8 in all) were tested on aluminum alloy AlSi7Mg0.6 by making single tracks on parallelepipeds specimens. We used an energy balance as a means of connecting the machine parameters (power, speed, etc.) of the 8 configurations to the morphology (geometry) of the single tracks. On this basis, we correlated the width, depth and especially the section area of the melt pool (single track) to the linear energy density. We were also able to assess the absorption coefficient of the aluminum alloy AlSi7Mg0.6 as a function of the temperature. The study was then focused on the microstructure and the possible impacts on the material properties including on the mechanical characteristics and the anisotropy observed in literature based on the build direction. Evidence suggests that the Hall-Petch relation can be used to explain this anisotropy. The thermal analysis highlighted two laser operating modes: the keyhole mode and the conduction mode. These modes have also been described via the morphology of the single tracks. Finally, a comparison between Rosenthal’s theoretical model (in the case of the conduction mode) and actual conditions was proposed by the obtained geometry of the single tracks as well as the cooling speeds calculated and measured using the dendrite arm spacing (DAS). The maximum temperatures achieved were also assessed by Rosenthal’s theoretical model which made it possible to explain the evaporation of some chemical elements during the manufacturing of the aluminum alloy through SLM.
Selective Laser Sintering (SLS) is a manufacturing method which has existed since the 1990s. It was initially limited to manufacturing prototypes as it does not require any other tooling than the laser sintering machine to manufacture the part. For several years now, the use of this process has extended to manufacturing of real parts. This article presents an analysis carried out to better understand the advantages and drawbacks of SLS for Rapid Manufacturing. The influence of the various parameters linked with the manufacturing process on the final quality of parts was assessed. We then assisted industrial partners in using this manufacturing method for their own production. The aspects studied are: product design, its qualification and finally support in industrialisation.
After having determined the LPBF additive manufacturing parameters for the AlSi5Cu3Mg alloy by means of a design of experiment method, three tempers are studied on the manufactured test pieces: as built, direct aging and T6. The study reviews the impact of these three tempers on porosity assessment, microstructure and mechanical properties. It appears that the microstructures in the as built and direct aging tempers are often comparable to those of the AlSi7Mg0.6 and AlSi10Mg alloys which are used as references. However, a significant difference appears with the T6 temper, which does not show any change in porosity for the AlSi5Cu3Mg alloy, unlike the two other alloys. Moreover, due to a high density of type θʺ and/or θ′ fine precipitates, the T6 temper features a high yield strength but also an almost isotropic behaviour with good elongation. The analysis of the mechanical behaviour of the AlSi5Cu3Mg alloy in the three tempers is completed with an analysis of the strain hardening rate which is put into perspective with an EBSD analysis of the dislocation density, thus highlighting a close relationship between the microstructures (especially fine dendritic structures) and a high dislocation density. Lastly, a technical and ergonomic study is presented which compares the AlSi5Cu3Mg and AlSi7Mg0.6 alloys. Finally, we explain the interest of the T6 temper for the AlSi5Cu3Mg alloy after LPBF additive manufacturing.
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