Macro-heterogeneities in microstructures, concentrations, defects and tensile properties of die cast Al–Mg–Si alloys

Abstract

The heterogeneities in tensile properties, microstructure, solute concentrations and defects levels were studied for the castings with different thicknesses made by high pressure die cast Al–Mg–Si alloys. For the local mechanical properties, the casting skin provided the highest, whereas the casting centre provided the lowest yield strength, ultimate tensile strength and elongation. The microstructural heterogeneity was characterised by the segregation of coarse fragmented dendrites, the reduction of solute concentrations of Mg and Si, and the increase of porosity level from the surface to the centre of castings. The growth velocities of eutectic α-Al phase estimated using the Jackson–Hunt model confirm that the growth variation is larger in the thin castings than that in thick castings. This paper is part of a thematic issue on Light Alloys.