Effect of heat treatment on diffusion, internal friction, microstructure and mechanical properties of ultra-fine-grained nickel severely deformed by equal-channel angular pressing

Divinski, Sergiy V.; Reglitz, Gerrit; Golovin, I.S.; Peterlechner, Martin; Lapovok, Rimma; Estrin, Yuri; Wilde, Gerhard

doi:10.1016/j.actamat.2014.08.064

Cited by 71 publications

(56 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Elongated grain shapes after ECAP-deformation of Ni are well documented in literature, not only after B C 12-processing [23], as applied here, but also after B C 4- [24] and B C 8-processing [25,26]. It is also well documented that the degree of grain refinement for ECAP-deformation is not as high as for HPT-deformation [22].…”

Section: Resultssupporting

confidence: 52%

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

View full text Add to dashboard Cite

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.

show abstract

Section: Resultssupporting

confidence: 52%

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

View full text Add to dashboard Cite

show abstract

“…[123] Further confirmation for the possibility of low temperature GBS in UFG metals comes from diffusion data on pure Ni processed by ECAP which show ultra-fast diffusion at lower temperatures [<400 K (127°C)] with a low activation energy but relaxation of the nonequilibrium grain boundaries at high temperatures [>400 K (127°C)]. [130,131] …”

Section: Observations On the Paradox Of Strength And Ductilitymentioning

confidence: 95%

The Strength–Grain Size Relationship in Ultrafine-Grained Metals

Balasubramanian

Langdon

2016

Metall Mater Trans A

View full text Add to dashboard Cite

Metals processed by severe plastic deformation [SPD] techniques, such as equal-channel angular pressing [ECAP] and high-pressure torsion [HPT], generally have submicrometer grain sizes. Consequently, they exhibit high strength as expected on the basis of the HallPetch [H-P] relationship. Examples of this behavior are discussed using data on Ti, Al-Mg 1 and Ni. These materials typically have grain size above ~50 nm where softening is not expected. An increase in strength is usually accompanied by a decrease in ductility. High strength and ductility can be achieved simultaneously by imposing high strains to give both ultrafine grain sizes and a high fraction of high-angle grain boundaries. An example is presented for a cast Al-7% Si alloy processed by HPT. In some cases, SPD may produce a fine grain size but also lead to a weakening due to microstructural changes as in ECAP of an Al-7034 alloy and HPT of Zn-22% Al. In SPD-processed materials, grain boundary segregation and nanostructural features are present which may lead to higher strengths than those predicted by the H-P relationship in some alloys having nano grain sizes.

show abstract

“…208) The notion of the non-equilibrium grain boundaries was originally proposed by Grabski,10) and was later demonstrated in UFG structure by TEM. [12][13][14][15] The high energy non-equilibrium grain boundaries cause fast diffusion, [16][17][18][19][20][21]210) and resultant room temperature grain boundary sliding in pure aluminum as evidenced by topographical observation by atomic force microscopy. 22,32) Under the high internal stress, atoms at the surface are at a high free energy state with low electron work function of the surface.…”

Section: Effect Of Internal Stressmentioning

confidence: 99%

“…This is evidenced by internal dislocations near the grain boundaries observed by transmission electron microscopy (TEM). [12][13][14][15] Indeed, several unique phenomena were reported, which seems to be attributed to high fraction of non-equilibrium grain boundaries, such as ultra-fast diffusion, [16][17][18][19][20][21] room temperature grain boundary sliding in aluminum. 22) Strength and ductility are primary characteristics dependent on the microstructure of a material, and spectacular achievement of braking the trade-off between two has been reported in SPD-UFG materials.…”

Section: Introductionmentioning

confidence: 99%

Corrosion of Ultrafine Grained Materials by Severe Plastic Deformation, an Overview

Miyamoto

2016

Mater. Trans.

114

View full text Add to dashboard Cite

Corrosion of ultra ne grain (UFG) materials by severe plastic deformation (SPD) is reviewed in light of the existing literature and microstructural change. Fortunately, by holistic survey of the literature, it seems likely that grain re nement by SPD, while enhancing mechanical properties, does not compromise the overall corrosion resistance, and in many case, improve it in comparison with coarse-grained counterparts, although there are some contradictory results within the same materials and same environment. The degree of impact of UFG formation on corrosion is highest in stainless steels followed by aluminum and magnesium alloys whereas it is relatively marginal in pure copper and titanium. The effect of UFG formation by SPD on corrosion is imparted by not only grain re nement, but also other microstructural change occurring commonly in SPD in general and unique to each speci c SPD method. In this review, an attention is paid speci cally to the former case, and this includes shuf ing or redistribution of chemical inhomogeneity into a ner scale, deformation-induced grain boundaries and high internal stress stemming from these grain boundaries. The literature on stress corrosion cracking (SCC) of UFG materials are de nitely insuf cient to nd the general trends, more studies are waited.

show abstract

Effect of heat treatment on diffusion, internal friction, microstructure and mechanical properties of ultra-fine-grained nickel severely deformed by equal-channel angular pressing

Cited by 71 publications

References 50 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

The Strength–Grain Size Relationship in Ultrafine-Grained Metals

Corrosion of Ultrafine Grained Materials by Severe Plastic Deformation, an Overview

Contact Info

Product

Resources

About