Abstract: The effects of Cr and Cr/Mn combined additions on the semi-solid microstructure of wrought Al-Mg-Si alloys are investigated. In the Cr-added alloy, the Al7Cr compound is formed with homogeneously distributed in the α-Al matrix after homogenization. Both of the Al7Cr and α-Al12Mn3Si2 dispersiod particles are found in the homogenized microstructure of the Cr/Mn-added alloy. In the semi-solid microstructures, the smallest α-Al grains are obtained in the 60% cold-rolled alloys. After prolonged holding time, the α-Al grain size of the Cr/Mn-added alloy is smaller than that of the Cr-added alloy. Heavy deformation by cold-rolling accelerates spheroidization of the α-Al grains. The D-SSF process is found to be useful to modify the microstructures of both the Cr-added and Cr/Mn-added Al-Mg-Si alloys.

Key words: D-SSF process, Semi-solid processing, Thixoforming, Al-Mg-Si alloy