INVESTIGATION OF THE PORTEVIN-LE CHATELIER SERRATIONS AT TYPE A TO TYPE B TRANSITION REGIME IN Al-2.5Mg ALLOY

摘要

Al-Mg alloys are important technological materials due to their advantageous strength to weight ratio. However, their deformation at room temperature is discontinuous, with strain localizing in narrow bands that produce undesirable surface roughness. This is called Portevin-Le Chatelier phenomenon (PLC) arising from the interactions between solute and dislocations. Three types of deformation bands, namely type A, B and C are observed by varying experimental conditions. To characterize the deformation bands causing undulated surfaces, tensile tests were performed on polycrystalline Al-2.5%Mg samples at different strain rates. With increasing strain rate, the decrease in stress serration represents the change in deformation band character from type B to A. At an intermediate strain rate regime the experimental data reflects the presence of both type A and B bands. Our analysis reveals that in that strain rate regime both types of bands do not appear simultaneously. Rather, the PLC dynamics is governed by a single band which changes in character during deformation.