Kinetics of formation and propagation of type A Portevin-Le Chatelier bands in the presence of a small circular hole

Abstract

Using temperature field measurements performed by infrared thermography, we studied the influence of a small circular hole on the kinetics of formation and propagation of type A Portevin-Le Chatelier (PLC) bands in an Al-3.2%Mg alloy at room temperature. The time dependence of most band characteristics are determined in a single tensile test carried out at the applied strain rate 2 × 10−2 s−1 on a specimen containing a small circular hole at its center. It is shown that the introduced imperfection affects significantly the kinetics of type A bands. The circular hole acts as a source for strain localizations initiation. Bands initiate preferentially around the imperfection and then propagate away. Whenever a band initiates at a sample end, it stops and a new band appears in an area near the hole. The study shows that structural heterogeneities of materials can be privileged locations for the premature initiation of strain localizations. These results are discussed in accordance with dynamic strain aging interpretations.