Temperature Dependence of the Dynamics of Portevin-Le Chatelier Effect in Al-2.5%Mg alloy

Tensile tests were carried out by deforming polycrystalline samples of Al-2.5%Mg alloy at four different temperatures in an intermediate strain rate regime of 2x10-4s-1 to 2x10-3s-1. The Portevin-Le Chatelier (PLC) effect was observed throughout the strain rate and temperature region. The mean cumulative stress drop magnitude and the mean reloading time exhibit an increasing trend with temperature which is attributed to the enhanced solute diffusion at higher temperature. The observed stress-time series data were analyzed using the nonlinear dynamical methods. From the analyses, we could establish the presence of deterministic chaos in the PLC effect throughout the temperature regime. The dynamics goes to higher dimension at a sufficiently high temperature of 425K but the complexity of the dynamics is not affected by the temperature.Comment: 18 pages, 8 figures; accepted in Met. Mater. Trans.

On the effects of the Mg content on the critical strain for the jerky flow of Al-Mg alloys

International audienceThe jerky flow of Al-Mg alloys is investigated during tensile tests at imposed strain rate and room temperature. The strain and strain rate dependences of the magnitude of the stress drops, the range of plastic instability and the critical strain for the onset of serrations are studied in connection with the Mg content. In the low strain rate part of the strain rate range of instability, the critical strain decreases with the Mg content. The critical strain rate corresponding to the minimum of the critical strain vs. applied strain rate curve shifts to larger values when the Mg content increases. This behavior leads to an enlargement of the strain rate domain of inverse behavior of the critical strain, at the expense of the domain of normal behavior. In the high strain rate part of the range of instability, the critical strain does not depend on the Mg content. These results are discussed in accordance with dynamic strain aging mechanisms