A study of AlSi5Cu3Mg alloy produced by laser powder bed fusion: porosity assessment, microstructure, mechanical properties

Abstract

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.