Plastic flow and fracture behavior of an Al-Ti-Cu nanocomposite

Semiatin, S. L.; Jata, Kumar V.; Uchic, Michael D.; Berbon, Patrick B.; Matejczyk, D. E.; Bampton, C.C.

doi:10.1016/s1359-6462(00)00612-6

Cited by 29 publications

(22 citation statements)

References 4 publications

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“…However, an unusual aspect of the response was the elastic-perfectly plastic behavior, as evidenced by the relatively flat stress plateaus after yielding. This observation is consistent with findings in other cryomilled nanostructured Al alloys [11,[14][15][16] and results from other nanostructured or ultrafine-grained materials. [17,18,19] This behavior is observed in various finegrained materials and is attributed primarily to the fine-grained microstructure, as opposed to other metallurgical factors, such as the stacking fault energy.…”

Section: A Compressive Behaviorsupporting

confidence: 93%

“…One possibility is the occurrence of dynamic recovery during plastic deformation. The activation energy for dynamic recovery is expected to be reduced by the presence of residual stress around nanosized dispersoids [11,[14][15][16]20] and an abundance of structural defects present in the alloys. These structural defects might also absorb dislocations generated during plastic deformation.…”

Section: A Compressive Behaviormentioning

confidence: 99%

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Deformation behavior of bimodal nanostructured 5083 Al alloys

Han

Lee

Witkin

et al. 2005

Metall Mater Trans A

240

120

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Cryomilled 5083 Al alloys blended with volume fractions of 15, 30, and 50 pct unmilled 5083 Al were produced by consolidation of a mixture of cryomilled 5083 Al and unmilled 5083 Al powders. A bimodal grain size was achieved in the as-extruded alloys in which nanostructured regions had a grain size of 200 nm and coarse-grained regions had a grain size of 1 m. Compression loading in the longitudinal direction resulted in elastic-perfectly plastic deformation behavior. An enhanced tensile elongation associated with the occurrence of a Lüders band was observed in the bimodal alloys. As the volume fraction of coarse grains was increased, tensile ductility increased and strength decreased. Enhanced tensile ductility was attributed to the occurrence of crack bridging as well as delamination between nanostructured and coarse-grained regions during plastic deformation.

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Section: A Compressive Behaviorsupporting

confidence: 93%

Section: A Compressive Behaviormentioning

confidence: 99%

Deformation behavior of bimodal nanostructured 5083 Al alloys

Han

Lee

Witkin

et al. 2005

Metall Mater Trans A

240

120

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“…[3,4] Early studies by Tellkamp et al [5] on the behavior of nanostructured Al alloys fabricated via a cryomilling (e.g., milling in liquid nitrogen) and consolidation approach suggested that the presence of submicron grains in the nanostructured regions might contribute to ductility via increased plasticity. [6,7,8] These early observations were subsequently confirmed by other investigators' work on copper. [9] In this study, an ultrafine-grained (UFG) copper processed by rolling to a high value of percentage cold work (93 pct) at liquid nitrogen temperature exhibited high strength but poor elongation.…”

Section: Introductionsupporting

confidence: 58%

Simulation of deformation and failure process in bimodal Al alloys

Han

Lavernia

2005

Metall Mater Trans A

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Recent scientific interest in nanostructured materials stems from reports of attractive physical and mechanical properties. It has been proposed that the presence of multiple-length scales in a "nanostructured" matrix can alleviate the problem of low ductility by facilitating dislocation activity. One example of the concept of multiple-length scales is illustrated by a "bimodal" microstructure, e.g., containing a mixture of nanostructured and submicron grains. The present work reports on a numerical study of the tensile deformation and fracture of a nanostructured Al alloy with a bimodal microstructure. In the theoretical framework used in the present study, the elastic-plastic behavior, deformation, and fracture processes are approximated by the Ramberg-Osgood formula and finite-element method, respectively. The numerical results are found to be in reasonable agreement with the experimental behavior.

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“…It is obvious that strain hardening is not a necessary requirement for dynamic strain aging. [14] We note that the near-perfect plastic deformation of the nanostructured 5083 alloy is also observed in other nanostructured metals and alloys, [9,[24][25][26][27][28][29][30] which indicates that there was no dislocation accumulation during the near-perfect plastic deformation and the dislocation density stays at a saturation density. [30,31] The lack of dislocation accumulation in the nanostructured 5083 Al ally could be caused by both dynamic recovery and dislocation annihilation on grain boundaries.…”

mentioning

confidence: 65%

“…[9][10][11][12] While a positive strain rate sensitivity of flow stress at room temperature was observed in the compression deformation of nanocomposite Al-Ti-Cu alloy, [9] a small negative strain rate sensitivity was noticed in the tensile deformation of UFG Al-Mg alloy [12] in a strain rate range of 10 -4 to 10 -2 s -1 . Since the negative strain rate sensitivity observed in coarse-grained Al-Mg alloys is a consequence of dynamic strain aging, [13][14][15][16] it would be of interest to know whether the dynamic strain aging also plays a role in the plastic deformation of nanostructured or UFG Al alloys.…”

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confidence: 97%

Negative Strain‐rate Sensitivity in a Nanostructured Aluminum Alloy

et al. 2006

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Since grain boundaries and triple junctions occupy a considerable volume fraction in nanostructured materials, grainboundary mediated deformation mechanisms, for instance, Coble diffusion creep or grain boundary sliding, are expected to play a significant role in the deformation of nanostructured materials, even at room temperature. The grain-boundary mediated deformation mechanisms, may lead to a large value of strain rate sensitivity in nanostructured materials. Recently, the strain rate sensitivity of several nanostructured/ ultrafine-grained (UFG) materials has been investigated at room temperature to understand the deformation mechanisms. [1][2][3][4][5][6][7][8] Indeed, nanostructured Cu or Ni are found to have much higher strain rate sensitivity than coarse-grain Cu or Ni at room temperature. [1,3,4,[6][7][8] However, although nanostructured/UFG fcc materials have elevated strain rate sensitivity compared to their coarse-grained counterparts, [5] nanostructured/UFG bcc Fe and Ta were found to have lower strainrate sensitivity than coarse-grained Fe and Ta. [5] The reasons for these observations are not fully understood. These observations, however, indicate that the nanostructures have an effect on the strain rate sensitivity, and thus on their mechanical properties, especially their ductility. Therefore, it is of interest to study the strain rate sensitivity of nanostructured materials.The mechanical properties of nanostructured or UFG face centered cubic (fcc) Al alloys have been investigated recently. [9][10][11][12] While a positive strain rate sensitivity of flow stress at room temperature was observed in the compression deformation of nanocomposite Al-Ti-Cu alloy, [9] a small negative strain rate sensitivity was noticed in the tensile deformation of UFG Al-Mg alloy [12] in a strain rate range of 10 -4 to 10 -2 s -1 . Since the negative strain rate sensitivity observed in coarse-grained Al-Mg alloys is a consequence of dynamic strain aging, [13][14][15][16] it would be of interest to know whether the dynamic strain aging also plays a role in the plastic deformation of nanostructured or UFG Al alloys. The purpose of the present study is twofold: (a) to investigate the influence of strain rate on the deformation behavior of a nanostructured 5083 Al alloy processed by cryomilling and hot extrusion, and (b) to provide insight into the underlying deformation mechanisms of nanostructured or UFG Al alloys.The microstructure, taken from a section parallel to the extrusion direction, of the as-extruded cryomilled 5083 Al alloy, is shown in Figure 1(a). Although the ultrafine grains of 100-200 nm are slightly elongated along the extrusion direction, the selected-area electron diffraction pattern does not reveal preferred crystallographic orientation. In a recent investiga- COMMUNICATIONSADVANCED ENGINEERING MATERIALS 2006, 8, No. 10Fig. 1. Microstructure of the as-extruded cryomilled 5083 Al alloy in a section (a) parallel to and (b) normal to the extrusion direction.

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Plastic flow and fracture behavior of an Al-Ti-Cu nanocomposite

Cited by 29 publications

References 4 publications

Deformation behavior of bimodal nanostructured 5083 Al alloys

Deformation behavior of bimodal nanostructured 5083 Al alloys

Simulation of deformation and failure process in bimodal Al alloys

Negative Strain‐rate Sensitivity in a Nanostructured Aluminum Alloy

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