ANALYSIS OF STRENGTHENING MECHANISMS IN ALLOYS BY MEANS OF THERMAL-ACTIVATION THEORY

Through a systematic measurement of the strain-rate sensitivity as a function of prestrain. theoretical models of thermally activated flow are used to identify and analyze the dominant strengthening mechanisms in a number of commercial and model alloys. Several examples of the usefulness of the technique as a diagnostic tool are given. At temperatures below the 'plateau' stress, measurements are in good agreement with predictions, even for relatively complex commercial materials, and it was demonstrated that changes in strengthening mechanisms (e.g. during age hardening or thermomechanical processing) can be followed directly even when the scale of the microstructure is too small for convenient observation by transmission electron microscopy. Experiments at high temperature (above the regime of jerky flow) demonstrate that, except at low stress, the material behavior at moderate strain rates is dominated by strain softening mechanisms such as dislocation rearrangement by cross-slip or climb. The major effect of solution hardening at high temperature is to increase the stress at which these processes occur. © 1979.