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

Abstract

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 × 10−3 s−1, in order to reveal the effect of solute Mg atoms and β-phase nanoparticles in the α-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 β-phase nanoparticles in the α-Al matrix of the annealed alloy sheets increase. The β-phase nanoparticles promote the PLC effect during the tensile process, causing the increase of stress drop amplitude Δσ of the tensile curves of the alloy sheets. However, the β-phase nanoparticles have little influence on the strain period ΔεTmax of rectangular waves. The flow strain difference Δεc−σ between the yield point and the beginning of PLC effect decreases monotonically from 5.4 × 10−4 to 5 × 10−5 as the Mg contents of alloy sheets increase from 2.86 wt.% to 9.41 wt.%. The strain period ΔεTmax of the rectangular waves corresponding to the high flow stress and stress drop amplitude Δσ obtained for the serrated stress-strain curves of the alloy sheets gradually increase with the increasing Mg contents of alloy sheets.