Portevin-Le Chatelier characterization of annealed Al-Mg alloy sheets with different Mg contents

The stress-strain flow curves of solid solution treated and annealed Al-(2.86-9.41)Mg aluminum alloy sheets were investigated during tensile process at room temperature at a strain rate of 1 x 10(-3) s(-1), in order to reveal the effect of solute Mg atoms and beta-phase nanoparticles in the alpha-Al matrix on their Portevin-Le Chatelier (PLC) characteristics. The results show that with the increase of Mg contents of alloys, the concentration of solute Mg atoms and the volume fraction of beta-phase nanoparticles in the alpha-Al matrix of the annealed alloy sheets increase. The beta-phase nanoparticles promote the PLC effect during the tensile process, causing the increase of stress drop amplitude Delta sigma of the tensile curves of the alloy sheets. However, the beta-phase nanoparticles have little influence on the strain period Delta epsilon(max)(T) of rectangular waves. The flow strain difference Delta epsilon c-sigma between the yield point and the beginning of PLC effect decreases monotonically from 5.4 x 10(-4) to 5 x 10(-5) as the Mg contents of alloy sheets increase from 2.86 wt.% to 9.41 wt.%. The strain period Delta epsilon(max)(T) of the rectangular waves corresponding to the high flow stress and stress drop amplitude Delta sigma obtained for the serrated stress-strain curves of the alloy sheets gradually increase with the increasing Mg contents of alloy sheets.