During homogenization of Al-Mg-Si extrusion ingots, significant changes in the microstructure take place. In the present work, results related to the changes in type, size, and shape of the AlFeSi particles are presented and discussed. Shape- and size-evolution of AlFeSi particles during and after the P-AlFeSi to á-AlFeSi transformation indicates that a significant part of the spheroidization that takes place is not directly related to the ?-AlFeSi to á-AlFeSi transformation reaction. The effect of manganese (Mn) on the ?-AlFeSi to a-AlFeSi transformation rate and on AlFeSi sphericity is measured, and surprisingly it is found that increasing the Mn content appears to give less spheroidized AlFeSi particles after homogenization. A positive effect of Mn addition on extrudability is demonstrated, and this effect appears to be related to a refinement of the Mg_2Si particle distribution in the alloys, rather than to the effect on ?-AlFeSi to á-AJFeSi transformation degree, or to the AlFeSi particle shape.
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