STRAIN RATE SENSITIVITY AND CAVITATION IN SUPERPLASTIC DEFORMATION OF A COMMERCIAL AL-5083 ALLOY

In this paper the superplastic properties of a commercial 5083 aluminum alloy is studied. The aims are to achieve a proper temperature and strain rate to obtain maximum elongation and to investigate the strain rate sensitivity and cavitation in this alloy. The material is thermomechanically processed to produce fine recrystallized grain size. Then hot tensile test is carried out at various temperatures and strain rates. Velocity jump tests are performed to determine stress-strain rate relation and strain rate sensitivity coefficient (m) at various temperatures and strains. The microstructures are studied by optical and electron microscopy (SEM). The area fraction of cavities is determined by analyzing the micrographs from the surface of tensile specimens at various strains. It is found that maximum elongation about 300% is obtained at 520 degrees C and strain rate of 10(-3) s(-1). Maximum strain rate sensitivity coefficient (m) about 0.6 is achieved at strain 0.5. With increasing strain the peak m value decreases and shifts to lower strain rates. The failure surface is wide and failure occurs by cavitation.