Strain-amplitude-dependent mechanical loss at intermediate temperatures in a Ni₃(Al, Ta) single crystal

Abstract

Dislocation dynamics in a Ni₃(Al, Ta) single-crystal alloy have been studied by means of mechanical spectroscopy at intermediate temperatures, that is 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 temperature, predeformation level and heating rate. Thermal cycling (heating-cooling) and ageing experiments were also performed, which provided additional 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 simultaneously occurring as the temperature is increased from 300 to about 500 K: exhaustion of the mobile dislocation parts (superkinks) and pinning of the screw dislocation segments via cross-slip from the (111) onto the (010) planes.