Modeling the Hot Flow Stress of Commercial Purity Coppers with Different Oxygen Levels

García, Vicente Hernández; Cabrera, J.M.; Prado, J. M.

doi:10.4028/www.scientific.net/msf.426-432.3921

Cited by 5 publications

(4 citation statements)

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“…The hot compression tests were performed at eight different temperatures from 600ºC to 950ºC at 50ºC intervals and at six different strain rates, namely 0.3s -1 , 0.1s -1 , 0.03s -1 , 0.01s -1 , 0.003s -1 , and 0.001s -1 . The apparent activation energy, Q app , is 213KJ/mole [7], which is a value close enough to the lattice self-diffusion activation energy, Q sd = 197KJ/mole, of pure copper. The proximity of these activation energy values has allowed use of the self-diffusion activation energy as means of analyzing the stress and strain values in correlation with the Zener-Hollomon parameter [8,9].…”

Section: Methodsmentioning

confidence: 58%

Predicting Multiple Peak Dynamic Recrystallization of Copper

García

Cabrera

Prado³

2004

MSF

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The relationship between the initial grain size and the critical Zener-Hollomon parameter value (D 0 -Z c ) defines the conditions for which a material will dynamically recrystallize with a single or with multiple peaks. The relationship between the stable dynamically recrystallized grain and the Zener-Hollomon parameter (D rex -Z) predicts the conditions for grain refinement or coarsening during dynamic recrystallization. The Relative-Grain-Size model (D 0 -Z c and D rex -Z) adequately predicts the type of hot flow behavior before reaching a stable dynamically recrystallized grain size. However, a model to reliably predict the stress-strain curve is still needed. Several models exist which have been shown to predict the transition from single to multiple peak stresses. Nevertheless few of them report real material parameters and in any case the computational time makes them unviable for any industrial simulation process. The present authors have devised a DRX algorithm to measure the stress due to the diminishing initial grain volume and to measure the correction stress due to recrystallizing grains. One stress contribution is produced as a result of the surrounding or percolating new grains and another stress is due to the response of deforming the initial grain volume. The present authors propose a relatively simple model that in conjunction with existing theories for dynamic recovery can quantitatively predict the transition from single to multiple peak stress behavior during dynamic recrystallization. The predicted stress-strain curves have been correlated to experimental results after compression testing (650ºC-950ºC) commercially 99.9% pure copper.

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Section: Methodsmentioning

confidence: 58%

Predicting Multiple Peak Dynamic Recrystallization of Copper

García

Cabrera

Prado³

2004

MSF

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“…More recently Prasad and Rao [7] have compared different electrolytic tough pitch (ETP) coppers that ranged 100-260 ppm of oxygen and attributed the increase of hot flow stress, or back stress, to increasing volume fractions of Cu 2 O particles in the matrix as the test temperature decreased according to the Cu-O phase diagram. The present authors have also observed an increase of hot flow stress during compression of fire-refined 99.9% pure coppers with increasing oxygen content (26-62ppm) [8], particularly below 850ºC. In this work, a TEM analysis was performed to determine the presence of fine precipitates that could contribute to the hardening the copper matrix.…”

Section: Introductionmentioning

confidence: 64%

Effects of Precipitation during Dynamic Recrystallization of Copper with Different Oxygen Levels

García

Cabrera

Prado³

2007

MSF

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Previous research works assert that the observed increase in hot flow stress of commercially pure copper is attributed to the interactions between solute atoms and dislocations, specifically by interstitial oxygen. This work shows TEM images of the formation of Cu2O precipitates after warm working temperatures that in part help explain the increase of stress during hot compression of 99.9% pure copper. Three commercially pure large-grained coppers with 26, 46 and 62ppm of oxygen were tested at different temperatures (600°C-950°C) and strain rates (0.3s-1- 0.001s-1). At temperatures below 850°C, the stress differences between coppers, tested at same the strain rate, became increasingly higher. A correlation between stress increase and oxygen content was found. Precipitation of nanometric Cu2O did not show any difference in dynamically recrystallized grain size; however hardness tests showed that the final properties were modified. This work discusses the effect precipitation of Cu2O has on the hot flow curve and the final microstructure of hot formed 99.9% pure copper with different oxygen levels.

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“…9) maximum yield stress increment is of 9.7 MPa. However previous analysis [15,29] where the lattice self-diffusion activation energy was used to correlate flow stress led to believe Cu A is not affected by a precipitation caused back stress otherwise an apparent activation energy would be needed [30]. The rest of the arrows only indicate a possible behaviour, because no smaller particles were found during the TEM examination.…”

Section: Theoretical Analysismentioning

confidence: 97%