Ultrasound-velocity measurement of strain in metallic polycrystals

Abstract 

During extension tests of metallic polycrystals, in situ measurement of ultrasound velocity (USV, V _US ) was carried out for the plastically deforming metallic polycrystalline specimens. USV has been found to depend on the plastic strain or acting stress of plastic flow. The complicated form of these dependencies is discussed in the context of the concept of evolution of lattice defects. V _US is shown to be associated with the multistage nature of the plastic flow curve. This allows plastic flow stages to be recognised with a higher degree of certainty. Thus the linear stage of work hardening has been separated for Al polycrystals by the procedure of USV measurement and certain peculiarities of plastic strains localisation as associated with USV variation have been investigated.