Serrated plastic flow |
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Authors: | P Rodriguez |
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Affiliation: | (1) Metallurgy Programme, Reactor Research Centre, 603 102 Kalpakkam, India |
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Abstract: | This paper attempts an assessment of the current understanding of the phenomenon of “serrated plastic flow”, which manifests
itself as serrations, load drops, jerkiness or other discontinuities in the stress-strain curves obtained in constant extension
rate tensile tests, and as sudden bursts of strain in constant loading rate tests and in constant load (stress) creep tests
(the so called staircase creep). Though one can identify at least seven physical processes that can cause serrations, the
discussion here is restricted mainly to serrated yielding in tension tests originating from dynamic strain ageing (dsa). The characteristics of the five types of serrations that have been identified so far and the experimental conditions under
which they occur are discussed. The various models of serrated flow that have been put forward are reviewed critically. Some
recent results on 316 stainless steel are presented to illustrate the effects of grain size, temperature and strain rate on
serrated flow. Manifestations ofdsa other than serrations such as a negative strain rate sensitivity, positive temperature dependence for flow stress and work
hardening, and the ductility minimum are also discussed. Finally the various issues to be resolved are enumerated. |
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Keywords: | Serrated flow dynamic strain ageing continual mechanical twinning flow stress work hardening peaks ductility minimum |
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