The effect of homogenization practice and alloy Mn content on the dispersoid density and high temperature constitutive behaviour of AA3xxx aluminum alloys has been studied. Experimental work was conducted on three as-cast alloys with different Mn compositions:​ AA3102 (0.26 wt% Mn), an intermediate Mn alloy (0.75 wt% Mn), and AA3003 (1.27 wt% Mn). Homogenization treatments were conducted at soak temperatures from 500 to 630°C and times of 1 to 24 hours.

The evolution of microstructure during homogenization (at 600°C over a soak time of 24 hours) was characterized using electrical conductivity measurements and optical microscopy. Electrical conductivity measurements were used to estimate the variation of Mn in solid solution during homogenization. Qualitative observations of constituent particle morphology and dispersoid precipitation/dissolution were made. Compression tests were conducted using a Gleeble 3500 thermomechanical simulator at strain rates (0.1 to 10s⁻¹) and deformation temperatures (300 to 600°C) experienced during the industrial extrusion of AA3xxx alloys. Yield stress, flow stress, and work hardening results were obtained from the compression tests and a physically-based constitutive model was employed to describe the results. The model was used to quantify the effect of homogenization practice and alloy Mn content on constitutive behaviour. Homogenized microstructure observations were combined with model results to determine the effect of dispersoid density on constitutive behaviour.

Extrusion trials were performed on Rio Tinto Alcan’s state-of-the-art research extrusion press located at the Alcan Research and Development Center in Jonquiere, Quebec. AA3102 and AA3003 alloys were extruded in as-cast and homogenized onditions at temperatures of 400 and 500°C. Extrusion pressure results were used to develop a relationship between extrusion pressure and flow stress