Impedance analysis of Portevin-Le Chatelier effect on aluminium alloy

Study of the Portevin-Le Chatelier (PLC) Characteristics of a 5083 Aluminum Alloy Sheet in Two Heat Treatment States

In the present work, the role of Mg atoms in the form of either Mg clusters or β phase on the moving dislocations in 5083 aluminum alloy sheet were investigated by comparing the plastic flow behavior and Portevin-Le Chatelier (PLC) character in annealed and quenched conditions. It is found that the tensile strength of quenched sheets at different strain rates is slightly higher than those under annealed condition while the yield strength at both conditions is similar. In annealed sheets, the yield plateau was clearly observed at all tested strain rates with a strain less than 0.012, and its width increased with the increasing strain rate. However, no yield plateau was observed in quenched sheets. On the other hand, the characters of PLC are greatly varied with applied conditions and strain rate. Generally, annealed sheets have a higher waiting time, but lower critical strain/stress at lower strain rate (~1 × 10⁻⁴ s⁻¹), but they are similar at a higher strain rate (1 × 10⁻² s⁻¹). However, the falling time at both annealed and quenched conditions are almost the same at tested strain rates.

The Portevin-Le Chatelier effect: a review of experimental findings

The Portevin-Le Chatelier (PLC) effect manifests itself as an unstable plastic flow during tensile tests of some dilute alloys under certain regimes of strain rate and temperature. The plastic strain becomes localized in the form of bands which move along a specimen gauge in various ways as the PLC effect occurs. Because the localization of strain causes degradation of the inherent structural properties and surface quality of materials, understanding the effect is crucial for the effective use of alloys. The characteristic behaviors of localized strain bands and techniques commonly used to study the PLC effect are summarized in this review. A brief overview of experimental findings, the effect of material properties and test parameters on the PLC effect, and some discussion on the mechanisms of the effect are included. Tests for predicting the early failure of structural materials due to embrittlement induced by the PLC effect are also discussed.