A Revised Criterion for the Portevin–Le Châtelier Effect Based on the Strain-Rate Sensitivity of the Work-Hardening RateReport as inadecuate




A Revised Criterion for the Portevin–Le Châtelier Effect Based on the Strain-Rate Sensitivity of the Work-Hardening Rate - Download this document for free, or read online. Document in PDF available to download.

Metallurgical and Materials Transactions A

, Volume 42, Issue 13, pp 4008–4014

First Online: 13 October 2011

Abstract

An improved analysis is presented of the stability of plastic deformation under conditions where dynamic strain aging DSA occurs, which leads to instabilities known as the Portevin–Le Châtelier PLC effect. It is shown that PLC instabilities can occur for conditions that are not covered by the currently prevailing criterion presented by Estrin and Kubin 1991, which focuses on a negative strain rate sensitivity of the flow stress, caused by interactions of solutes with thermally activated glide of mobile dislocations. The current analysis recognizes that the strain-rate sensitivity of the flow stress consists of two contributions, one associated with glide of mobile dislocations and the second with work hardening, related to storage of immobile dislocations. In this paper, an instability criterion is proposed that takes into account the possibility of a negative strain-rate sensitivity of the work-hardening rate, which is caused by diffusion of solutes to immobile dislocations. The latter contribution leads to an extended instability criterion. This criterion also provides an explanation for the existence of a critical strain above which instabilities occur. In this article, previously published tensile test data are used to show that a negative strain-rate sensitivity of the work-hardening rate, which influences significantly the occurrence of the PLC effect, can indeed occur under DSA conditions.

Manuscript submitted June 2, 2010.

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Author: Peter Van Liempt - Jilt Sietsma

Source: https://link.springer.com/







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