Deformation mechanisms and cavity formation in superplastic AA5083

The deformation mechanisms and failure modes of superplasticity are reviewed. Mechanical property data in the form of strain rate versus modulus-compensated stress for uniaxial tension tests on AA5083 material at T = 450degreesC exhibits a transition from grain boundary sliding (GBS) to dislocation creep control of deformation. An initially random texture is retained and grain growth occurs during GBS while a fiber texture comprising <111> and <100> components develops during dislocation creep controlled deformation. The grain-to-grain disorientation distribution has a random component and a low-angle (0degrees-5degrees) peak reflecting grain elongation and substructure formation during dislocation creep deformation. Biaxial deformation under dislocation creep control of deformation results in a <100> + <110> two-component fiber texture (<uvw> is the direction parallel to the sheet normal). Disorientation distributions across cavities are consistent with GBS leading to grain boundary separation even for material deformed under dislocation creep conditions.