Recrystallization kinetics of ultrafine-grained Ni studied by dilatometry

Oberdorfer, Bernd; Steyskal, Eva-Maria; Sprengel, Wolfgang; Pippan, Reinhard; Zehetbauer, M.; Puff, Werner; Würschum, Roland

doi:10.1016/j.jallcom.2010.12.130

Cited by 24 publications

(20 citation statements)

References 16 publications

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“…5). For HPT-processed Ni the identical activation energy Q = 1.20 eV is derived as found in our earlier measurements on similarly processed samples [4]. For the route B C 12 of ECAP-processed samples, which exhibits the most pronounced temperature shift with respect to HPT-Ni, also a substantially higher activation energy of 1.42 eV is obtained.…”

Section: Analysis and Discussionsupporting

confidence: 80%

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Structural anisotropy in equal-channel angular extruded nickel revealed by dilatometric study of excess volume

Kotzurek

Sprengel

Krystian

et al. 2017

International Journal of Materials Research

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Structural anisotropy in equal-channel angular extruded nickel revealed by dilatometric study of excess volume Structural anisotropy and excess volume in ultra-fine grained high-purity nickel prepared by equal-channel angular pressing (ECAP) is studied by means of dilatometry and compared with the processing route of high-pressure torsion. Both routes exhibit qualitatively similar three-stage behavior in length change upon defect annealing with a characteristic dependence on the measuring direction related to the deformation axes. Taking into account shape anisotropy of the crystallites, the length change in various directions can be quantitatively analyzed yielding direct access to the concentration of deformation-induced lattice vacancies, the vacancy relaxation, and the grain boundary expansion. The routes A12 and B C 12 of ECAP are compared.Keywords: Dilatometry; Equal-channel angular pressing; High-pressure torsion; Vacancy; Recrystallization IntroductionIn the past few years, difference dilatometry has proven a powerful absolute technique in order to quantify the amount of excess volume in ultrafine grained metals prepared by severe plastic deformation (SPD) [1,2] 1 . In particular, the absolute concentration of deformation-induced lattice vacancies and the grain boundary (GB) expansion as well as issues of structural relaxation, defect kinetics and aggolomeration could be determined focusing on SPD-processed Ni [4 -6] and Cu [7,8]. Studies of these kinds of defects are of pivotal importance since the atomistic processes, which occur during SPD-induced structural refinement and which give rise to the particular mechanical behaviour, are intimately related to structural defects available in these materials in highly abundant concentrations [9,10].Based on systematic dilatometric studies of ultrafine grained metals prepared by high-pressure torsion (HPT) [4 -6, 8, 11], the present work aims at studying free volumes in Ni in detail after an entirely different deformation process, namely equal-channel angular pressing (ECAP). Dilatometric results contributed to an earlier study on ECAP-processed Ni [12]. However, there commercial grade nickel of lower purity (99.6 wt.%) was used, and it is well known that impurities significantly influence the annealing behavior of the different defects. Furthermore, no orientation dependence was measured. Now again, nickel J. A. Kotzurek et al.: Structural anisotropy in equal-channel angular extruded nickel revealed by dilatometric study Int.

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Section: Analysis and Discussionsupporting

confidence: 80%

“…study on HPT-processed Ni [4,5]. According to this study, stage B coincides with the strong crystallite growth and reflects the annealing out of free volume associated with grain boundaries (GB).…”

Section: Resultsmentioning

confidence: 85%

Structural anisotropy in equal-channel angular extruded nickel revealed by dilatometric study of excess volume

Kotzurek

Sprengel

Krystian

et al. 2017

International Journal of Materials Research

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“…Analyzing this shift for the nine dilatometric measuring runs according to Kissinger (for details of the method see Ref. [15]) yields an activation energy Q of crystallite growth of

0.99 \pm 0.11 eV

(see the Kissinger plot, Fig. 4).…”

Section: Resultsmentioning

confidence: 99%

Grain boundary excess volume and defect annealing of copper after high-pressure torsion

et al. 2014

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The release of excess volume upon recrystallization of ultrafine-grained Cu deformed by high-pressure torsion (HPT) was studied by means of the direct technique of high-precision difference dilatometry in combination with differential scanning calorimetry (DSC) and scanning electron microscopy. From the length change associated with the removal of grain boundaries in the wake of crystallite growth, a structural key quantity of grain boundaries, the grain boundary excess volume or expansion eGB=(0.46±0.11)×10-10 m was directly determined. The value is quite similar to that measured by dilatometry for grain boundaries in HPT-deformed Ni. Activation energies for crystallite growth of 0.99±0.11 and 0.96±0.06eV are derived by Kissinger analysis from dilatometry and DSC data, respectively. In contrast to Ni, substantial length change proceeds in Cu at elevated temperatures beyond the regime of dominant crystallite growth. In the light of recent findings from tracer diffusion and permeation experiments, this is associated with the shrinkage of nanovoids at high temperatures.

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“…It is also pertinent to note in this context that the recrystallization effect dominates over the phase transformation effect and the temperature of 850°C can be regarded as the recrystallization stop temperature of the cold-rolled material. Dilatometry is also used to determine the recrystallization stop temperature of materials [22][23][24][25] apart from measuring phase transformation temperatures and kinetics, quantification of phases, etc. [26][27][28].…”

Section: Resultsmentioning

confidence: 99%

“…[26][27][28]. Oberdorfer et al [25] quantified the recrystallization kinetics of an ultrafine-grained high-purity Ni deformed by high-pressure torsion by dilatometry. De Cock et al [22] detected a dilatometric anomaly prior to the ferrite to austenite transformation of a low-carbon steel and concluded that it arises from the recrystallization of ferrite.…”

Section: Resultsmentioning

confidence: 99%

Recrystallization in a low-density low-alloy Fe–Mn–Al–C duplex-phase alloy

Rana

Liu

Ray

2014

Philosophical Magazine Letters

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The recrystallization behaviour of a cold-rolled, low-density, low-alloy duplex-phase alloy (Fe-6.57Al-3.34Mn-0.18C, wt.%) has been studied. Temperature-resolved X-ray diffraction and dilatometry showed that the alloy recrystallizes at 850°C during continuous heating. However, electron back-scattered diffraction investigations using Kernel average misorientation revealed that during annealing ferrite recrystallizes at lower temperatures while austenite remains strained up to 1200°C. This study underlines the complexity of recrystallization of a microstructure comprising of constituents with high and low stacking fault energy.

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Recrystallization kinetics of ultrafine-grained Ni studied by dilatometry

Cited by 24 publications

References 16 publications

Structural anisotropy in equal-channel angular extruded nickel revealed by dilatometric study of excess volume

Structural anisotropy in equal-channel angular extruded nickel revealed by dilatometric study of excess volume

Grain boundary excess volume and defect annealing of copper after high-pressure torsion

Recrystallization in a low-density low-alloy Fe–Mn–Al–C duplex-phase alloy

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