Optimization of homogenization for a low alloyed AlMgSi alloy

The homogenization practice for EN AW 6060 was investigated. It takes an 8-hour soak at 580 degrees C to level out the Mg and Si distribution in the matrix and to transform the monoclinic beta-Al5FeSi plates into relatively small alpha-AlFeSi particles. The solute Si and Mg are largely retained in solution during subsequent cooling at >500 degrees C h(-1). Mg2Si precipitation is considerable, however, during cooling at <250 degrees C h(-1), producing a hardness decrease from 39.5 +/- 1.4 HV to 34.4 +/- 0.2 HV, by 15%, over the range investigated. The solvus temperatures of the homogenized samples are below 500 degrees C regardless of the cooling rate, ensuring full solutionizing of the Mg2Si precipitates below the typical industrial press exit temperatures. An 8 hour soak at 580 degrees C followed by cooling at 250 degrees C h(-1) is identified to be the optimum homogenization treatment as it gives a homogeneous structure with predominantly round alpha(c)-Al-12(Fe,Mn)(3)Si particles and sufficiently low hardness for improved extrudability and a solvus temperature below 500 degrees C to ensure adequate age hardening capacity. (C) 2013 Elsevier Inc. All rights reserved.