Stress Relaxation of AA 5182 During Hot Deformation
Bange, Michael Edward
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Permalink
https://hdl.handle.net/2142/83800
Description
Title
Stress Relaxation of AA 5182 During Hot Deformation
Author(s)
Bange, Michael Edward
Issue Date
2003
Doctoral Committee Chair(s)
Beaudoin, A.
Kurath, P.
Department of Study
Mechanical Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
The goal of the current work is to model the recovery in the aluminum alloy, AA 5182, at temperatures above one half the melting point. The project is motivated by the recovery of AA 5182 during the industrial process of hot tandem rolling. The rolling operations typically take place at temperatures between 300°C and 500°C and strain rates on the order of 10 s-1 to 100 s-1. While the material is in transit between rolling operations, interstand tension continues the deformation process under relatively low stress and a much lower strain rate. For AA 5182 deforming at these temperatures and strain rates, there are two distinct deformation mechanisms. The first is a high temperature and low strain rate diffusion regime termed solute drag (SD) which is modeled with an equation posed by Mukherjee and fit to AA 5182 by Chen. The second regime is active at high temperatures and increased strain rates. This regime is referred to in the present work as hardening with concurrent recovery of dislocations (HR) and is characterized using the Mechanical Threshold Strength (MTS) model. In order to capture the correct yield behavior, a short term transient stress (most likely associated with dislocation solute interactions) is accounted for in the current formulation of the MTS model. The two constitutive relations (for SD and HR) are used to predict the stress-strain behavior of the material while deforming in these separate regimes. In addition, while the material is deforming in interstand tension, significant recovery may occur. The amount of recovery undergone by the metal is quantified using load-displacement data acquired from strain rate change tests. A modified form of the model posed by Sellars is used to account for the recovery process. Since the Sellars model is phenomenological, comparisons are also made to a recovery model derived completely from the Mechanical Threshold Strength model accounting for reverse jumps of dislocations.
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