ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Regular Article
Predicting the Critical Stress for Initiation of Dynamic Recrystallization
Abbas NajafizadehJohn J. Jonas
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2006 Volume 46 Issue 11 Pages 1679-1684

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Abstract

The critical stress for initiation of dynamic recrystallization (DRX) can be identified from the inflection point on the strain hardening rate (θ=dσ/dε) versus flow stress (σ) curve. This kind of curve can be described by an equation that fits the experimental θ–σ data from zero to the peak stress. Such a curve must have an inflection point and the simplest relation that has such properties is a third order equation.
Hot compression tests were carried out on a 304 H stainless steel over the temperature range 900–1 100°C and strain rate range 0.01–1 s−1 to a strain of 1. An appropriate third order equation was fitted to the strain hardening data. The results show that the critical stress at initiation σc=−B/3A where A and B are coefficients of the third order equation. It is evident that this value depends on the deformation conditions. The stress–strain curve was then normalized with respect to the peak stress, leading to a normalized value of the critical stress (uc) equal to uccp=−B′/3A′. Here A′ and B′ are coefficients of the normalized third order equation. This value is constant and independent of the deformation conditions.

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© 2006 by The Iron and Steel Institute of Japan
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