EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Precipitation hardening is the key of the mechanical properties for 6xxx series Aluminium alloys. The precipitation sequence is complex and dependent of the alloy composition, particularly on the Mg/Si ratio. A compositionally-graded alloy is obtained with high-temperature compaction using Spark Plasma Sintering on Al-Si and Al-Mg model alloys atomised powders. The different stages of the fabrication process include a sequence of interdiffusion heat treatment, homogenisation, and quenching. Energy dispersive X-ray spectroscopy (EDX) and wavelength dispersive X-ray spectroscopy (WDS) ensure a well-controlled gradient in a single direction. Small pores are formed during the interdiffusion treatment with a volume fraction below 1.5%. After ageing, the composition-dependent precipitation is evaluated by microhardness profiles and multiple differential scanning calorimetry (DSC) measurements, supported by transmission electron microscopy observations. Mechanical behaviour is also inspected through tensile tests on both homogeneous and graded specimens. In parallel, simulations of precipitation kinetics within the graded material are performed and optimised in order to match with the experimental results.