Microstructure Evolution and Microstructural Characteristics of Al–Mg–Si Aluminum Alloys Fabricated by a Modified Strain-Induced Melting Activation Process

A modified strain-induced melting activation (SIMA) process is shown to improve high-temperature formability. The microstructural characteristics of the spheroidized grains of SIMA-processed alloys affect high-temperature formability. The effects of hot extrusion parameters and chemical composition on the evolution of spheroidized grains were investigated using several 6xxx series aluminum alloys subjected to a modified SIMA process. The results show that 6066 aluminum alloy is the most suitable alloy for the SIMA process, as it contains sufficient Mg, Si, Cu, and Mn. Adequate amounts of Mg, Si, and Cu lead to a high liquid fraction, and a sufficient addition of Mn inhibits grain growth. Proper hot extrusion parameters are essential, because initial fine and uniform recrystallized grains lead to fine and uniform globules. The phases at the global grain boundaries of 6066 aluminum alloy are eutectic phases of Al and Si, Al and Mg2Si, and Al and Al2Cu, as analyzed using transmission electron microscopy.