Strain-amplitude-dependent mechanical loss at intermediate temperatures ina Ni-3(Al, Ta) single crystal

Dislocation dynamics in a Ni-3(Al, Ta) single-crystal alloy have been studi ed by means of mechanical spectroscopy at intermediate temperatures, that i s in the temperature range of the flow stress anomaly. The mechanical loss of specimens predeformed at 300 K was found to be strongly dependent on tem perature, pre-deformation level and heating rate. Thermal cycling (heating- cooling) and ageing experiments were also performed, which provided additio nal information about the annealing time dependence of the mechanical loss, elastic modulus of the material and plastic deformation of the specimens. The obtained results can be explained by a combination of two phenomena sim ultaneously occurring as the temperature is increased from 300 to about 500 K exhaustion of the mobile dislocation parts (superkinks) and pinning of t he screw dislocation segments via cross-slip from the (111) onto the (010) planes.