Phase strength effects on chemical mixing in extensively deformed alloys

Cordero, Zachary C.; Schuh, Christopher A.

doi:10.1016/j.actamat.2014.09.009

Cited by 49 publications

(15 citation statements)

References 76 publications

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“…The W-Cr system is one that mechanically mixes to a supersaturated solid solution 50 and our as-milled powders had an average grain size of ;13 nm as shown in the TEM micrograph of Fig. 8(a) and were homogeneous after 20 h of milling.…”

Section: Experiments On W-crmentioning

confidence: 99%

Duplex nanocrystalline alloys: Entropic nanostructure stabilization and a case study on W–Cr

2015

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Grain boundary (GB) segregation can markedly improve the stability of nanostructured alloys, where the fraction of GB sites is inherently large. Here, we explore the concept of entropically supported GB segregation in alloys with a tendency to phase-separate and its role in stabilizing nanostructures therein. These duplex nanocrystalline alloys are notably different, both in a structural and thermodynamic sense, from the previously studied "classical" nanocrystalline alloys, which are solid solutions with GB segregation of solute. Experiments are conducted on the W-Cr system, in which nanoduplex structures are expected. Upon heating ball-milled W-15 at.% Cr up to 950°C, a nanoscale Cr-rich phase was found along the GBs. These precipitates mostly dissolved into the W-rich grains leaving behind Cr-enriched GBs upon further heating to 1400°C. The presence of Cr-rich nanoprecipitates and GB segregation of Cr is in line with prediction from our Monte Carlo simulation when GB states are incorporated into the alloy thermodynamics.

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Section: Experiments On W-crmentioning

confidence: 99%

Duplex nanocrystalline alloys: Entropic nanostructure stabilization and a case study on W–Cr

2015

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“…[7,12,40] Besides thermodynamic considerations, it is proposed that large differences in strength of the individual phases of the composites can lead to strong strain localization, thereby, impeding to achieve full supersaturation during deformation. [41] Since dislocations play a key role in the kinetic roughening model and the dislocation shuffling process, which are proposed to be mechanisms for deformation-induced mixing, the crystal structures of the present phases might additionally influence the amount of mixing. [39,42] The aim of this paper is to summarize our results on deformation-induced supersaturation, which is observed during HPT processing at room temperature (RT) of several immiscible binary systems.…”

Section: Introductionmentioning

confidence: 99%

Deformation‐Induced Supersaturation in Immiscible Material Systems during High‐Pressure Torsion

2016

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The review focuses on the supersaturation process of immiscible elements induced by high-pressure torsion deformation. A variety of investigated material systems offers the systematic analysis of the controlling factors for mechanical intermixing, which are mainly determined by the level of the positive heat of mixing and the deformation behavior. The homogeneity of the deformation process strongly influences the degree of supersaturation. Our results show that the fundamental mixing mechanism during deformation is not necessarily the same in all systems, but depends also on the strength differences of the phases and accordingly the deformation behavior.

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“…The composition profile of a Cu/Nb multilayer with a positive heat of mixing after accumulative roll bonding and subsequent high pressure torsion was found to have an oscillation shape between the end members. 55 From the results in the present work and in the above reports, it is seen that the deformation induced intermixing kinetics is dependent not only on the heats of mixing but also on other properties such as deformation behavior of each component 56 …”

Section: A Composition Profile and Diffusion Asymmetrymentioning

confidence: 71%

Intermixing in Cu/Ni multilayers induced by cold rolling

Wang

Perepezko

Larson

et al. 2015

Journal of Applied Physics

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Repeated cold rolling was performed on multilayers of Cu60/Ni40 and Cu40/Ni60 foil arrays to study the details of driven atomic scale interfacial mixing. With increasing deformation, there is a significant layer refinement down to the nm level that leads to the formation of a solid solution phase from the elemental end members. Intriguingly, the composition of the solid solution is revealed by an oscillation in the composition profile across the multilayers, which is different from the smoothly varying profile due to thermally activated diffusion. During the reaction, Cu mixed into Ni preferentially compared to Ni mixing into Cu, which is also in contrast to the thermal diffusion behavior. This is confirmed by observations from X-ray diffraction, electron energy loss spectrum and atom probe tomography. The diffusion coefficient induced by cold rolling is estimated as 1.7 Â 10 À17 m 2 /s, which cannot be attributed to any thermal effect. The effective temperature due to the deformation induced mixing is estimated as 1093 K and an intrinsic diffusivity d b , which quantifies the tendency towards equilibrium in the absence of thermal diffusion, is estimated as 6.38 Â 10 À18 m 2 /s. The fraction of the solid solution phase formed is illustrated by examining the layer thickness distribution and is described by using an error function representation. The evolution of mixing in the solid solution phase is described by a simplified sinusoid model, in which the amplitude decays with increased deformation level. The promoted diffusion coefficient could be related to the effective temperature concept, but the establishment of an oscillation in the composition profile is a characteristic behavior that develops due to deformation. V C 2015 AIP Publishing LLC. [http://dx.

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Phase strength effects on chemical mixing in extensively deformed alloys

Cited by 49 publications

References 76 publications

Duplex nanocrystalline alloys: Entropic nanostructure stabilization and a case study on W–Cr

Duplex nanocrystalline alloys: Entropic nanostructure stabilization and a case study on W–Cr

Deformation‐Induced Supersaturation in Immiscible Material Systems during High‐Pressure Torsion

Intermixing in Cu/Ni multilayers induced by cold rolling

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