Although sometimes dynamic strain aging is used interchangeably with the Portevin–Le Chatelier effect (or serrated yielding), dynamic strain aging refers specifically to the microscopic mechanism that induces the Portevin–Le Chatelier effect. This strengthening mechanism is related to solid-solution strengthening and has been observed in a variety of fcc and bcc substitutional and interstitial alloys, metalloids like silicon, and ordered intermetallics within specific ranges of temperature and strain rate.
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Description of Mechanism
In materials, the motion of dislocations is a discontinuous process. When dislocation meets obstacles (like forest dislocations) they are temporary arrested for a certain time. During this time solutes (such as interstitial particles) diffuse around the dislocations further strengthening the obstacles held on the dislocations. Eventually these dislocations will overcome these obstacles with sufficient stress and will quickly move to the next obstacle where they are stopped and the process can repeat again. This process's most well-known manifestations are Lüders bands and the Portevin–Le Chatelier effect. Though the mechanism is known to affect materials without these physical observations.
Material Property Effects
Although serrations in the stress-strain curve caused by the Portevin–Le Chatelier effect are the most visible effect of dynamic strain aging, other effects may be present when this effect is not seen. Often when serrated flow is not seen, dynamic strain aging is marked by a lower strain rate sensitivity. That becomes negative in the Portevin–Le Chatelier regime. Dynamic strain aging also causes a plateau in the strength, a peak in flow stress a peak in work hardening, a peak in the Hall–Petch constant, and minimum variation of ductility with temperature. Since dynamic strain aging is a hardening phenomenon it increases the strength of the material.
Material specific example of Dynamic Strain Aging
Dynamic strain aging has been shown to be linked to these specific material problems: