Multiple precipitation pathways in an Al-7Si-0.6Mg alloy fabricated by selective laser melting

The ageing responses of selective laser melted Al-7Si-0.6Mg alloy with different solid solution treatment times are investigated in this work. Silicon particles with random crystallographic orientations are the dominant precipitates at the direct aged condition. With 1 or 8 h solid solution treatment, the precipitation sequence resembles that of cast/wrought Al-Si-Mg alloys. However, the main precipitates at the peak-aged condition are different and are premature B′ (1 h) and β″ (8 h), respectively. These unusual precipitation pathways are attributed to the uniaxial strains in the Al matrix, suggesting new heat treatment procedures required for selective laser melted alloys.