Effect of symmetric and asymmetric rolling on the mechanical properties of AA5182

Abstract

In this work we study the response of AA5182 to rolling, with emphasis on the effect of severe plastic deformation followed by heat treatment on the strain rate sensitivity of the material. Three rolling techniques are compared namely symmetric rolling, continuous and reversed asymmetric rolling and the subsequent heat treatment is performed at 195 degrees C for times ranging from 30 to 120 mins. The strain rate sensitivity is unaffected by rolling for rolling reductions smaller than 50%. For larger reductions it increases gradually, but remains negative even for reductions as high as 90%. The schedule of the heat treatment makes a difference only for samples with 90% reduction. In these cases the yield stress of symmetrically rolled samples decreases with increasing annealing time, while that of asymmetrically rolled samples increases under the same conditions. Microstructural observations indicate that the grain size decreases continuously, being more pronounced for reductions larger than 50%. Rolling introduces low angle grain boundaries at reductions below 50%, which transform in high angle boundaries at higher reductions. Nanoscale grains are obtained with all rolling methods at 90% reduction. Several mechanisms that may cause the increase of the strain rate sensitivity parameter for reductions larger than 50% are discussed. (C) 2016 Elsevier Ltd. All rights reserved.