Effect of TM-Addition on the Aging Behaviour of Al-Mg-Si Alloys

Abstract

Microstructure and aging hardness variation of Al-Mg-Si-TM alloys (TM = Mn, Cr, Fe, Y, and Gd) were investigated to reveal the effect of TMs on the age-hardening behavior of Al-Mg-Si-TM alloys. The peak hardness of Cr- and Fe-added alloys is similar to the base alloy, while the peak hardness of Mn-, Gd-, and Y-added alloys is much lower than the base alloy. It was found different TMs formed the dispersoids with different ratio of TM/Si calculated from the EDS result of the dispersoid. The Si expensed for the formation of the dispersoid is the most for Y-added alloy and the least for Fe-added alloy among the five TM-added alloys. It is thought that this will result in the difference of Si in the matrix for the formation of the precipitate.