Abstract
The homogenization practice for EN AW 6005A was investigated. It requires an 8-hour soaking at 853 K (580 °C) to even out the Mg and Si distribution in the aluminum matrix and to fully transform the monoclinic β-Al5FeSi plates into relatively small round αc-Al12(Fe,Mn)3Si particles with a “necklace” type configuration. It is predominantly the equilibrium β-Mg2Si phase that precipitates during subsequent cooling at 1000 K h−1 while orthogonal β′-Mg2Si platelets are also noted starting at 500 K h−1. The hardness decreases with decreasing cooling rate from 41.1 ± 1 HV to 35.8 ± 0.8 HV, by 15 pct, over the range investigated. The precipitation capacity retained in homogenized samples cooled to room temperature at less than 250 K h−1 is reduced substantially. The solvus temperatures of these samples are below 773 K (500 °C) ensuring full solutionizing of the Mg2Si precipitates below the press exit temperatures typically employed by extruders. An 8-hour soaking at 853 K (580 °C) followed by cooling at 250 K h−1 is identified to be the optimum homogenization treatment as it gives a homogeneous structure with predominantly spherical-shaped αc-Al12(Fe,Mn)3Si particles and sufficiently low hardness for improved extrudability and a solvus temperature below 773 K (500 °C) to ensure adequate age-hardening capacity.
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The author is pleased to thank Mr. F. Alageyik for his help with the experimental work.
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Manuscript submitted March 8, 2012.
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Birol, Y. Homogenization of EN AW 6005A Alloy for Improved Extrudability. Metall Mater Trans A 44, 504–511 (2013). https://doi.org/10.1007/s11661-012-1379-y
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DOI: https://doi.org/10.1007/s11661-012-1379-y