Portevin-Le Chatelier effect in Al-Zn-Mg-Cu-Zr aluminum alloy

Portevin-Le Chatelier (PLC) effect in a severely cold-rolled Al-Zn-Mg-Cu-Zr aluminum alloy (AA7055 type) plate before and after annealing was investigated. The results show that the sample annealed at 300 degrees C undergoes PLC effect, whereas the PLC effect is not observed in the deformed sample or the samples annealed at 110 degrees C or 200 degrees C. The main precipitates in the sample annealed at 300 degrees C are the coarsened eta phases, while a mixture of small eta' phases and eta phases dominates in the sample annealed at 200 degrees C. In the deformed sample and sample annealed at 110 degrees C, GP zone are the main precipitates. The different flow behaviors are ascribed to the type of precipitates as well as the dislocation density differences.