In the present paper, in order to better understand the third type “dynamic strain
aging” occurring during the plastic flow of metals, the uniaxial compressive experimental
data ever obtained in University of California, San Diego using an Instron servo-hydraulic
testing machine and the Hopkinson technique are systematically analysed. These experimental
data cover the plastic flow stress of several fcc, hcp, bcc polycrystalline materials and several
alloys at a broad range of temperatures (77K – 1,100K) and strain rates (0.001/s – 10,000/s).
In analysis, the appearing region of the “dynamic strain aging ” under different temperatures
and strain rates are respectively plotted by the curves of stress vs temperature, and stress vs
strain for fcc, hcp and bcc metals. The results show that: (1) this third type “dynamic strain
aging ” occurs in all hcp, bcc and fcc polycrystalline or alloy materials, and there are different
profiles of stress-strain curve; (2) the “dynamic strain aging ”occurs in a matching
coincidence of the temperature and strain rate, its temperature region will shift to higher
region with increasing strain rates; (3) bcc materials do not have an initial pre-straining strain
as the onset of work-hardness rate change for the “dynamic strain aging ”; and (4) based on
the explanations of dynamic strain aging with serration curves (Portevin-Lechatelier effect)
and other explaining mechanisms of references, The mechanism of third DSA is thought as
the rapid/continuous formation of the solute atmospheres at the mobile dislocation core by the
pipe diffusion along vast collective forest dislocations to result in a continuous rise curve of
flow stress. Finally, several conclusions are also presented.
Elasto-thermoviscoplastic finite element analyses of cold upsetting and forging processes of S25C steel with dynamic strain aging considered