Direct measurement of vacancy relaxation by dilatometry

Kotzurek, Jaromir Anatol; Steyskal, Eva-Maria; Oberdorfer, Bernd; Hohenwarter, Anton; Pippan, Reinhard; Sprengel, Wolfgang; Würschum, Roland

doi:10.1063/1.4958895

Cited by 19 publications

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References 21 publications

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“…Dilatometric length change DL=L 0 measured for annealing stages A and B of Ni along the various measuring directions, i. e., in normal (N), transverse (T), and extrusion (E) directions of ECAP-samples ( Fig. 1) or in axial (A) and tangential (T) directions of HPT samples [6]. Quoted in each case is the mean value obtained for the various 4 -5 heating rates between 1.5 and 6 K min -1 as well the mean value for the 2 similar heating rates of 2.5 and 3 K min -1 (ECAP) or the mean value of samples for 3 K min -1 (HPT: (A): 2, (T): 4).…”

Section: Resultsmentioning

confidence: 99%

“…4). As discussed recently for HPT-processed Ni, such a characteristic variation with the measuring direction can be attributed to the anisotropic annealing out of relaxed lattice vacancies due to the elongated shape of the crystallites [6]. The simple notion is adopted that vacancies exclusively anneal out at grain boundaries which are enclosing the crystallites along their elongation axis owing to the reduced diffusion length required for reaching the GB sink.…”

Section: Analysis and Discussionmentioning

confidence: 99%

“…in the measuring direction since upon annealing relaxed vacancies are replaced by atoms [6]. The relaxation factor…”

Section: Analysis and Discussionmentioning

confidence: 99%

“…Annealing out of vacancies in measuring direction, i. e., with the elongation axis of the crystallites perpendicular (?) to the measuring direction, yields [6]:…”

Section: Analysis and Discussionmentioning

confidence: 99%

“…The pronounced shape-anisotropy of the crystallites after HPT-deformation is reflected by a substantial variation of the dilatometric length change with measuring direction both in the temperature regime where vacancies anneal out [6] and in the regime where excess volume associated with GBs dissappears during grain growth [5]. This anisotropic annealing behavior even offers the potential for measuring the vacancy relaxation [6]. In ECAP-processing the degree of homogeneity or anisotropy of grain shapes can be controlled by appropriate sample rotations between successive passes [19].…”

Section: Introductionmentioning

confidence: 99%

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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: Resultsmentioning

confidence: 99%

Section: Analysis and Discussionmentioning

confidence: 99%

“…in the measuring direction since upon annealing relaxed vacancies are replaced by atoms [6]. The relaxation factor…”

Section: Analysis and Discussionmentioning

confidence: 99%

“…Annealing out of vacancies in measuring direction, i. e., with the elongation axis of the crystallites perpendicular (?) to the measuring direction, yields [6]:…”

Section: Analysis and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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High‐Precision Dilatometry for the Study of Precipitation Processes and Microalloying Effects in Lightweight Alloys ‐ A Specific Review

Sprengel,

Würschum

2024

Adv Eng Mater

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By dilatometry, the absolute change in the length of a sample is measured. As length, i.e., volume, is a state variable, its change can be monitored for long time ranges. This is the decisive advantage compared to the widely applied calorimetric methods which are based on a rate (change of heat) and where the maximum time range is determined by the resolution limit of the heat flow measurement. In contrast, if the measurement environment is kept at a constant temperature, dilatometric signals can be measured for very long time ranges down to very small changes with resolution in the nm range. The application of high‐stability isothermal dilatometry for studying precipitation phenomena in Al(Mg,Si)‐, Ti(V)‐, and Ti(Cr)‐alloys is summarized in the present review. Al(Mg,Si) turns out as a prime example where the various phases can unambiguously be distinguished by their characteristic length change features. For Ti(V), the influence of the oxygen impurity on the omega phase formation, and for Ti(Cr), the effect of Sn alloying on the omega phase formation can be revealed by dilatometry. The results on Al(Mg, Si) are compared with dilatometry on Al(Cu)‐alloys upon time‐linear heating, for which also the effect of microalloying with Au is studied.

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Magneto‐Optical Control of Ordering Kinetics and Vacancy Behavior in Fe–Al Thin Films Quenched by Laser

Pashenkin,

Tatarskiy,

Churin

et al. 2024

Adv Eng Mater

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One of the issues arising in materials science is the behavior of nonequilibrium point defects in the atomic lattice, which defines the rates of chemical reactions and relaxation processes as well as affects the physical properties of solids. It is previously theoretically predicted that melting and rapid solidification of metals and alloys provide a vacancy concentration in the quenched material, which can be comparable to that quantity at the point of melting. Here, the vacancy behavior is studied experimentally in thin films of the near equiatomic Fe–Al alloy subjected to nanosecond laser annealing with intensities up to film ablation. The effects of laser irradiation are studied by monitoring magneto‐optically the ordering kinetics in the alloy at the very ablation edge, within a narrow (micron‐scale) ring‐shaped region around the ablation zone. Quantitatively, the vacancy supersaturation in the quenched alloy has been estimated by fitting a simulated temporal evolution of the long‐range chemical order to the obtained experimental data. Laser quenching (LQ) of alloys and single‐element materials will be a tool for obtaining novel phase states within a small volume of the crystal.

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Direct measurement of vacancy relaxation by dilatometry

Cited by 19 publications

References 21 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

High‐Precision Dilatometry for the Study of Precipitation Processes and Microalloying Effects in Lightweight Alloys ‐ A Specific Review

Magneto‐Optical Control of Ordering Kinetics and Vacancy Behavior in Fe–Al Thin Films Quenched by Laser

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