The Effect of Mn on Microstructure Evolution during Homogenization of Al-Mg-Si-Mn Alloys

A study was conducted on the evolution of microstructure during homogenization for two Al-Mg-Si alloys with different Mn levels, i.e. 0 and 0.5wt%. The homogenization treatment was conducted over a wide range of temperatures above the Mg 2 Si solvus. The holding time at the peak temperature ranged from 2 hour to one week. Microstructure evolution of the constituent particles and Mn dispersoids were characterized by means of optical microscopy and FEG-SEM. The Mn content in and out of solution was estimated using the Thermo-calc (TTAl6 database) and resistivity measurements. The micro-segregation and distribution of the main alloying elements before and after homogenization were systematically studied by electron probe micro analysis (EPMA). It was found that the Mn content together with the homogenization practice had a significant influence on the microstructure evolution. By combining all the measurements, a comprehensive quantitative dataset describing microstructure evolution during homogenization was developed.