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Effect of annealing on microstructure and mechanical properties of Al 6061 alloy processed by cryorolling
, Nageswara Rao P., Singh D.
Published in Informa UK Limited
2013
Volume: 29
   
Issue: 1
Pages: 76 - 82
Abstract
An ultrafine grained (UFG) structure developed in precipitation hardenable Al alloys through cryorolling by suppression of dynamic recovery followed by low temperature aging has received great research interest because of its high strength and very good ductility. In the present work, Al 6061 alloy was solution treated and deformed by cryorolling up to an effective true strain of 2?6 and then subjected to annealing at the temperature range from 150 to 350uC to study the effect of annealing on the microstructure and mechanical properties. The evolution of microstructure and precipitates was investigated by employing X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Vickers hardness and tensile testings were performed at room temperature to evaluate the effect of annealing on the mechanical properties. It was observed that the strength and ductility increased upon annealing at 150uC, and further annealing at high temperatures (200-350uC) results in reduction in hardness and strength but increase in ductility. A significant improvement in strength observed at low temperature annealing (150uC) is due to the precipitation of metastable phase b0. It overcompensates the reduction in hardness that occurred due to the softening caused by the recovery effect. It was found that the cryorolled Al 6061 alloy with UFG structure is thermally stable up to temperatures 250uC with slight grain coarsening. At this temperature, the TEM studies revealed that second phase Mg2Si particles are effectively pinning the grain boundaries due to the Zener drag effect. Owing to the presence of heterogeneities in the material, a duplex structure was observed upon annealing at temperatures 150 and 200uC. Abnormal grain growth was observed after annealing at high temperatures (300uC). © 2013 Institute of Materials, Minerals and Mining.
About the journal
JournalMaterials Science and Technology (United Kingdom)
PublisherInforma UK Limited
ISSN02670836
Open AccessNo