The effect of strain path on the mechanical behavior and dislocation arrangements in the hot working of copper

Pinheiro, Paula; Monteiro, Waldemar Alfredo; Barbosa, Ricardo Rodrigues; Cetlin, Paulo Roberto

doi:10.1016/j.msea.2003.11.008

Cited by 16 publications

(10 citation statements)

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“…The driver axis slowed down, stopped, reversed straining direction and accelerated back to the required testing strain rate in a time interval of Ϸ0.1 to 0.3 s, as shown elsewhere. 10) As shown in the next section, no significant static softening occurred during the strain reversals. The cyclic torsion tests were performed at the following plastic strain amplitudes: Deϭ0.03, 0.09, 0.20, 0.38, 0.54 and 0.86.…”

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The Mechanical Behaviour and Microstructures of Interstitial Free Steel Strained in Monotonic or Cyclic Torsion at 1223 K

2006

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Fig. 2. Equivalent stress-strain curves for samples deformed in continuous torsion testing at several temperatures and strain rates.maximum time intervals spent in the reversed torsion experiments. It can be seen that softening is negligible and almost nil up to 0.5 s, at the test condition. There is then an increase in the softening fraction to 10 % at times of the order of 1 s. Softening then stops and the curve shows, apparently, a small plateau which is followed by an increase in the fraction of softening up to 30 % at 3 s. The curve was extrapolated using an Avrami type equation to full softening taking about 100 s to completion. It can be concluded that no relevant static softening could have occurred during the time intervals spent in the strain reversals, since they were always smaller than 0.3 s. MetallographySamples were taken from a longitudinal section of the torsion specimens, at a depth of about 150 mm from the surface, for optical and electron scanning microscopy. Preparation of samples for optical microscopy involved grinding down to paper graded 1 000 mesh and polishing with diamond paste sizes 9, 3, 1 and 0.25 mm. Etching was carried out with 6 % nital for a period varying from 20 to 120 s. Results Continuous Torsion Testing Stress-Strain CurvesFigsures 2(a) to 2(d) show the stress-strain curves for samples deformed in continuous torsion testing at several temperatures and strain rates. The stresses increased up to a peak stress, s p , and then decreased until a steady state, s ss , was reached. This shape of the stress-strain curve indicates the occurrence of DRX in all tests. As expected, the values of the peak stress and peak strain increased as the temperature decreased or the strain rate increased. Samples tested at 0.01 s Ϫ1 showed oscillating values of the s ss related to grain size growth during recrystallization whereas all other curves displayed no such oscillations.As already mentioned, the temperature of 1 223 K and the strain rate of 0.1 s Ϫ1 were chosen as the base conditions for all tests in the present research. Figure 4(a) highlights the stress-strain curve obtained under these conditions, whereas Fig. 4(b) shows the work hardening rate (Q) versus stress (s) curve. The value of the peak stress can be measured at the point of the Q-s curve at which the value of Q is nil and, in this case, s p is 102 MPa. The value of the peak strain can then be measured from Fig. 4(a), producing e p ϭ0.6. The values of the critical stress and critical strain at which DRX is initiated can also be determined from the Q-s curve, as seen in Fig. 4(b). The value of the critical stress, e c , is obtained at the first point where the slope of the Q-s curve changes from decreasing to increasing values 18) and then the critical strain, e c , can be determined from the stress-strain curve shown in Fig. 4(a). In the present work, these values were s c ϭ95 MPa and e c ϭ0.38, respectively. In these cases, however, there are straining cycles which tend to be above the value of the monotonic steady state stre...

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“…On the other hand, some results have been reported [10][11][12][13] for a large number of hot cyclic torsions for copper at 673 K and a strain amplitude Deϭ0. 2) for room temperature straining, already discussed in this introduction.…”

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The Mechanical Behaviour and Microstructures of Interstitial Free Steel Strained in Monotonic or Cyclic Torsion at 1223 K

2006

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“…Microstructure evolution in fine or medium-grained copper subjected to plastic deformation has been substantially investigated during recent years [1][2][3][4][5][6][7]. It was found that microstructure evolution leads to the formation of low-energy dislocation structures.…”

Section: Introductionmentioning

confidence: 99%

“…a combination of several simple loading test sequences is an effective way to investigate the dislocation microstructure of sheet metals under such real forming conditions. Several studies connected with dislocation evolution during complex strain paths deal with sequences of two uniaxial tension tests or orthogonal rolling-tension [1][2][3][4]7,8]. The influence of the dislocation microstructure developed during the first strain path on the behaviour after reloading in the second path, was understood in terms of the interaction between the mobile dislocations in the new active slip systems and the dislocation microstructure previously formed during prestraining.…”

Section: Introductionmentioning

confidence: 99%

“…These microbands correspond to regions of the crystal with a misoriented crystal lattice, and have one dimension, which is smaller than the two others. They have also been observed at large strain values during monotonic plastic deformation, in a wide range of metallic materials [3,4,6,9,10]. These microbands can play an important role in the deformation process because of their ability to accumulate large shear strains.…”

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Strain path change effect on dislocation microstructure of multicrystalline copper sheets

Сахарова

Fernandes

2006

Materials Chemistry and Physics

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In this study, coarse-grained copper sheets were subjected to tension-rolling and rolling-tension strain path sequences. In both cases, two different types of strain path change were studied: the tensile and rolling directions were parallel and normal to each other. TEM observations of deformed samples showed the typical dislocation structures for the prestraining paths in tension and rolling. Special microband features, not observed during prestrain, were found during the second strain path, whatever the sequence and type of strain path change. The microstructure observed during reloading is discussed in terms of the sequence and type of strain path change, parallel or normal. The frequency of appearance of microbands is discussed in terms of the activity of new slip systems, i.e. not active during the prestrain path and connected with the number of the active slip systems after reloading. The results from this study, obtained for coarse-grained multicrystalline copper sheets, are compared with previous ones for fine and medium-grained copper.

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Influence of deformation path change on static strain aging of cold rolled steel strip

Koohbor

Serajzadeh

2011

Int J Adv Manuf Technol

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The effect of strain path on the mechanical behavior and dislocation arrangements in the hot working of copper

Cited by 16 publications

References 25 publications

The Mechanical Behaviour and Microstructures of Interstitial Free Steel Strained in Monotonic or Cyclic Torsion at 1223 K

The Mechanical Behaviour and Microstructures of Interstitial Free Steel Strained in Monotonic or Cyclic Torsion at 1223 K

Strain path change effect on dislocation microstructure of multicrystalline copper sheets

Influence of deformation path change on static strain aging of cold rolled steel strip

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