Effect of homogenization treatment and silicon content on the microstructure and hot workability of dilute Al-Fe-Si alloys

The effect of the homogenization treatment on the microstructure and hot workability of two dilute Al-Fe-Si alloys was investigated using optical microscopy, SEM, EBSD, electrical conductivity measurements and hot compression testing. Homogenization promoted the phase transformation from the metastable AlmFe or alpha-AlFeSi phase to the Al3Fe equilibrium phase and induced a significant change in solute levels in the solid solution. The Al3Fe dissolved and transformed completely at 550 degrees C in both alloys. The a-AlFeSi was transformed at 590 degrees C in the low Si alloy (Al-03Fe-0.1Si), whereas it began to decompose and transform to Al3Fe at 630 degrees C in the high Si alloy (Al-0.3Fe-0.25Si). The flow stress behavior of dilute Al-Fe-Si alloys was primarily controlled by the amount of Fe and Si in the solid solution. Homogenization at 550 degrees C significantly reduced the solid solution levels due to the elimination of the supersaturation originating from the cast ingot and produced the lowest flow stress under all of the deformation conditions studied. An increase in the homogenization temperature from 550 to 630 degrees C increased the flow stress by 10-23% and 15-45% for the low Si alloy and the high Si alloy, respectively, over the range of deformation conditions examined. An increase in the silicon level from 0.10% to 0.25% raised the overall flow stresses by 4-11% due to increased solute levels for given homogenization conditions. (C) 2014 Elsevier B.V. All rights reserved.