Spatial and Temporal Characteristics of Propagating Deformation Bands in AA5182 Alloy at Room Temperature

The spatial and temporal characteristics of propagating deformation bands in the Al-Mg alloy AA5182 in O temper were studied experimentally at room temperature. Tensile tests were carried out on flat specimens at strain rates in the range from 10(-5) to 10(-1) s(-1). Digital image correlation (DIC) and digital infrared thermography (DIT) were applied to monitor the propagating bands. It was found that the material exhibits a sharp yield point, and Luders bands were seen at all the strain rates. Jerky flow took place all along the Luders plateau. It thus seems that the Portevin-Le Chatelier (PLC) effect starts at incipient yielding and that there is no critical strain. At the end of the Luders plateau, PLC bands immediately started to propagate back and forth along the gage section of the specimen. The work hardening of the material decreased consistently with increasing strain rate, while the flow stress on the Luders plateau was rather unaffected by the strain rate. This indicates that the dynamic strain aging (DSA) mainly affects the strength of the interaction between mobile and forest dislocations. The strain to necking was found to decrease gradually with strain rate for this alloy, which is consistent with the lower work-hardening rate at the higher strain rates.