Relation between local necking and cavitation during high-temperature tensile deformation of polycrystalline pure aluminum

For polycrystalline aluminum with grain size of 170 and 346 μm, tensile deformation was carried out at a true strain rate of 1 × 10−2/s and a temperature of 553 K (=0.59Tm, Tm: melting temperature in K). Onset and progress of local necking during the deformation were investigated by measurements of small-angle X-ray scattering (SAXS) from a viewpoint of cavity formation on grain boundaries. The cavitation was observed in the change of the SAXS intensities as a function of local strain along the gauge part of specimen. The intensities increase rather slowly during the beginning uniform deformation. However, it increases rapidly in the gauge part where the local necking has occurred. The degree of cavitation is found to be more remarkable for a specimen with smaller grain size. Cavity size and size distribution are evaluated from the SAXS profiles. The local necking phenomenon is discussed from a viewpoint of cavitation.