Simultaneously enhancing the ductility and strength of cryorolled Zr via tailoring dislocation configurations

Guo, Defeng; Li, Ming; Shi, Yindong; Zhang, Zhibo; Ma, Tengyun; Zhang, Haitian; Zhang, Xiangyi

doi:10.1016/j.msea.2012.08.061

Cited by 33 publications

(11 citation statements)

References 19 publications

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“…The tensile strength and ductility of RTR alloy were less by 6.0% and 47.0%, respectively, as compared to RTCR alloy in the present work. The increase in ductility may be due to multimodal grain structure and movement of preexisting dislocation at higher stress [12,33,34]. Annealing at 673 K for 30 min results in nucleation and grain growth in deformed zircaloy-2, thus forming ultrafine and nanocrystalline grains.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Texture Evolution and Ultrafine Grain Formation in Cross-Cryo-Rolled Zircaloy-2

Goel

Jayaganthan

Singh

et al. 2015

Acta Metall. Sin. (Engl. Lett.)

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The texture and mechanical properties of cross-rolled zircaloy-2 at 77 and 300 K were investigated. Crossrolling at 77 K was performed to impart different thickness reductions of 25% and 50%, while at 300 K with 25%, 50%, 75% and 85% reductions to the sample. EBSD analysis of deformed sample showed that near-basal orientation is not deformed completely after 50% rolling reduction. The activation of prismatic silp, f11 " 22g contraction twin and f10 " 12g extension twin were evident from the deformed microstructure at 77 K. The propensity for activation of basal slip \a[ at 77 K was also observed. The deformation of the sample at 300 K occurs by prismatic, basal \a[ and pyramidal \c ? a[ slips, which were predicted by pole figures. After annealing, the tensile strengths (735 and 710 MPa) are almost the same for 50% cryo-cross-rolled and room-temperature cross-rolled zircaloy-2 with almost 2.7% difference in their ductility. KAM analysis of the deformed samples was made to estimate the stored strain energy and dislocation density. Annealing of deformed sample at 673 K for 30 min results in recrystallization, which leads to the formation of ultrafine grains.

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Section: Mechanical Propertiesmentioning

confidence: 99%

Texture Evolution and Ultrafine Grain Formation in Cross-Cryo-Rolled Zircaloy-2

Goel

Jayaganthan

Singh

et al. 2015

Acta Metall. Sin. (Engl. Lett.)

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“…[5,6] More recently, our studies demonstrate strain rate has a significant effect on the dislocation configurations of cryorolled Zr, and the dislocations in lamella configurations are movable under high stress and contribute to plastic deformation. [7] Moreover, dislocation dynamics simulations show that in hcp Zr no dislocation junction forms between intersecting screw dislocations at low temperature, which results in a weak forest hardening. [8] These studies hint a work toughening behavior, not hardening behavior, may be observed in the hcp Zr if appropriate dislocation configurations, in which dislocations are moveable under high stress, are yielded through cryogenic deformation.…”

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confidence: 99%

Extraordinary Toughening by Cryorolling in Zr

Shi

Guo

et al. 2013

Adv Eng Mater

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High strength and good ductility are essential for the applications of structural materials. However, the strength and ductility of materials are often mutually exclusive. For example, deformed materials always exhibit a hardening behavior, i.e. enhanced strength accompanied with reduced ductility. [1] This is attributed to the mutual entanglement and blockage of high-density dislocations induced by plastic deformation, which greatly inhibit the motion of dislocations. [2] Thermal annealing is indispensable for enhancing the ductility of deformed materials at the expense of their strength.Recently, studies show that dislocations in some special configurations are movable, which prevents localized shear deformation and contributes to the ductility of deformed materials. [3] To tailor dislocation configurations in deformed materials, high-density dislocations induced by plastic deformation are indispensable. This can be achieved by suppressing the dynamical recovery of deformed materials using cryogenic deformation that has been successfully employed to study lowtemperature properties of materials, [4] tailor their microstructures and mechanical properties. [5,6] More recently, our studies demonstrate strain rate has a significant effect on the dislocation configurations of cryorolled Zr, and the dislocations in lamella configurations are movable under high stress and contribute to plastic deformation. [7] Moreover, dislocation dynamics simulations show that in hcp Zr no dislocation junction forms between intersecting screw dislocations at low temperature, which results in a weak forest hardening. [8] These studies hint a work toughening behavior, not hardening behavior, may be observed in the hcp Zr if appropriate dislocation configurations, in which dislocations are moveable under high stress, are yielded through cryogenic deformation. To unambiguously confirm this supposition through experimentally procedure, both room temperature (RT) and cryogenic deformation experiments of metal Zr with increased strain were designed and performed in this study, and an extraordinary work toughening behavior is observed in the cryogenically deformed Zr, in contrast to the work hardening behavior of RT-cryorolled Zr. ExperimentalHigh-purity Zr (99.95%) sheets with a fully recrystallized microstructure (average grain size $30 mm) were rolled at RT and liquid nitrogen (LN) temperature at a strain rate of 2.63 s À1 with various strains e ¼ 0.5-2.95, respectively. The cryorolling was performed by immersing the samples into liquid nitrogen for 10 min before and after each rolling pass. The rolling temperature was determined to be À90 to À160°C by using both a Pt100 resistance thermometer and an adiabatic calorimeter. Cryorolled Zr sheets were annealed from 100 to 150°C for 1 h, and the annealed specimens were air-cooled to RT after annealing. The microstructure of cryorolled Zr in the RD-TD plane was characterized using a transmission electron microscope (TEM) and an X-ray diffractometer (XRD) with Cu Ka radiation. Dislocation densi...

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“…Annealing of deformed alloy at 400°C for 30 min proves to be helpful in removing internal strains and rearrangement of dislocations (Ref [33][34][35]. Due to plastic deformation, internal lattice strains are developed locally.…”

Section: Tem Resultsmentioning

confidence: 99%

Development of Ultrafine Grained Zircaloy-2 by Room Temperature Cross Rolling

Goel

Keskar

Jayaganthan

et al. 2014

J. of Materi Eng and Perform

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Effect of change in strain path by cross rolling up to a true strain of 1.89 has been studied in the present work. The Zircaloy-2 was subjected to solutionising heat treatment at 800°C in argon environment for 2 h and subsequently quenched in mercury prior to cross rolling at room temperature. The fragmentation of near basal grains due to change in strain path is evident from the EBSD micrographs. The dislocation density in the crossrolled alloy increases with true strain as calculated from the XRD and EBSD data and it is found to be 2.806453 3 10 16 /m 2 . 10 " 12 f gextension twins are observed initially up to 25% reduction, with the further reduction in thickness, near basal grains are oriented toward the normal direction. These basal grains undergone fragmentation due to changes in strain path upon cross-rolling as observed from KAM and EBSD images. TEM results of the cross-rolled sample confirm the formation of ultrafine and nanograins in the alloy due to orientation of incidental dislocation boundaries in the direction of macroscopic plastic flow and post-annealing treatment of the deformed alloy. A tensile strength of 991 MPa with 7.5% ductility is observed in the 85% cross-rolled alloy. The cross-rolled alloy upon annealing at 400°C for 30 min improves ductility to 11%.

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Simultaneously enhancing the ductility and strength of cryorolled Zr via tailoring dislocation configurations

Cited by 33 publications

References 19 publications

Texture Evolution and Ultrafine Grain Formation in Cross-Cryo-Rolled Zircaloy-2

Texture Evolution and Ultrafine Grain Formation in Cross-Cryo-Rolled Zircaloy-2

Extraordinary Toughening by Cryorolling in Zr

Development of Ultrafine Grained Zircaloy-2 by Room Temperature Cross Rolling

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