The effect of serrated yielding on the determination of r-values in aluminium alloys and yield locus calibration

W Kilpatrick, D Brown, R McMurray, AG Leacock

Research output: Contribution to journalArticle

Abstract

This study investigates the effect serrated yielding (Portevin-Le Châtelier effect) has on the determination of the plastic strain ratio (r-value) for the 2024 aluminium alloy. The aluminium alloy specimens were initially in the fully annealed O-condition. The specimens experienced a softening mechanism through a solution heat treatment (SHT) process, followed by an oil quench. The specimens were permitted to recover for periods ranging between 0.5 and 12 h by room temperature (RT) natural ageing before undergoinga uniaxial tensile test along the longitudinal axis to determine the r-value as a function of natural ageing time. The current study reveals the irregular variation in the transverse strain affects the gradient of the longitudinal–transverse strain plot and consequently the r-value. It is demonstrated that the serrated yielding directly influences the Hill 1948 yield locus when calibrated using two r-values and one yield strength for the 2024 aluminium alloy. Serrated yielding results in an underestimation of the plane stress (rolling) of 0.5≤plane stress rolling (MPa)≤5.6, plane stress (transverse) of 1.0≤plane stress transverse (MPa)≤9.2, and biaxial stress of 1.4≤biaxial stress (MPa)≤7.4. It is also shown that serrated yielding occurs after a critical strain of 0.07≤plastic strain≤0.13 and is reduced by natural age hardening. © 2010 Elsevier B.V. All rights reserved.
LanguageEnglish
Pages7557
JournalMaterials Science and Engineering: A
Volume527
Issue number29-30
DOIs
Publication statusPublished - 2010

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plane stress
loci
aluminum alloys
Aluminum alloys
Calibration
plastics
Portevin-le Chatelier effect
precipitation hardening
Plastic deformation
yield strength
tensile tests
Aging of materials
softening
heat treatment
Age hardening
oils
plots
gradients
Yield stress
Oils

Cite this

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title = "The effect of serrated yielding on the determination of r-values in aluminium alloys and yield locus calibration",
abstract = "This study investigates the effect serrated yielding (Portevin-Le Ch{\^a}telier effect) has on the determination of the plastic strain ratio (r-value) for the 2024 aluminium alloy. The aluminium alloy specimens were initially in the fully annealed O-condition. The specimens experienced a softening mechanism through a solution heat treatment (SHT) process, followed by an oil quench. The specimens were permitted to recover for periods ranging between 0.5 and 12 h by room temperature (RT) natural ageing before undergoinga uniaxial tensile test along the longitudinal axis to determine the r-value as a function of natural ageing time. The current study reveals the irregular variation in the transverse strain affects the gradient of the longitudinal–transverse strain plot and consequently the r-value. It is demonstrated that the serrated yielding directly influences the Hill 1948 yield locus when calibrated using two r-values and one yield strength for the 2024 aluminium alloy. Serrated yielding results in an underestimation of the plane stress (rolling) of 0.5≤plane stress rolling (MPa)≤5.6, plane stress (transverse) of 1.0≤plane stress transverse (MPa)≤9.2, and biaxial stress of 1.4≤biaxial stress (MPa)≤7.4. It is also shown that serrated yielding occurs after a critical strain of 0.07≤plastic strain≤0.13 and is reduced by natural age hardening. {\circledC} 2010 Elsevier B.V. All rights reserved.",
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The effect of serrated yielding on the determination of r-values in aluminium alloys and yield locus calibration. / Kilpatrick, W; Brown, D; McMurray, R; Leacock, AG.

In: Materials Science and Engineering: A, Vol. 527, No. 29-30, 2010, p. 7557.

Research output: Contribution to journalArticle

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AB - This study investigates the effect serrated yielding (Portevin-Le Châtelier effect) has on the determination of the plastic strain ratio (r-value) for the 2024 aluminium alloy. The aluminium alloy specimens were initially in the fully annealed O-condition. The specimens experienced a softening mechanism through a solution heat treatment (SHT) process, followed by an oil quench. The specimens were permitted to recover for periods ranging between 0.5 and 12 h by room temperature (RT) natural ageing before undergoinga uniaxial tensile test along the longitudinal axis to determine the r-value as a function of natural ageing time. The current study reveals the irregular variation in the transverse strain affects the gradient of the longitudinal–transverse strain plot and consequently the r-value. It is demonstrated that the serrated yielding directly influences the Hill 1948 yield locus when calibrated using two r-values and one yield strength for the 2024 aluminium alloy. Serrated yielding results in an underestimation of the plane stress (rolling) of 0.5≤plane stress rolling (MPa)≤5.6, plane stress (transverse) of 1.0≤plane stress transverse (MPa)≤9.2, and biaxial stress of 1.4≤biaxial stress (MPa)≤7.4. It is also shown that serrated yielding occurs after a critical strain of 0.07≤plastic strain≤0.13 and is reduced by natural age hardening. © 2010 Elsevier B.V. All rights reserved.

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