Temperature-dependent strain rate sensitivity and activation volume of nanocrystalline Ni

Wang, Y.M.; Hamza, A. V.; Ma, E.

doi:10.1016/j.actamat.2006.02.013

Cited by 431 publications

(235 citation statements)

References 43 publications

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“…[14] does not include a term related to thermal activation. The absence of this term is not consistent with the experimental results obtained on nc materials, [3,5,[16][17][18][19][20][21][22][23][24][25] which clearly show that the deformation behavior of nc material is not athermal and that strain rates measured during the deformation depend on temperature according to the following expression:…”

Section: Composite Model Involving Amorphous Boundary Layercontrasting

confidence: 35%

“…In particular, these investigations focused on nc Ni and nc Cu. As a result of these investigations, there exist several sets of data for these two metals [3,5,[16][17][18][19][20][21][22][23][24][25] that are identified in Table II. All data are characterized in terms of shear stresses s and shear strain rates _ c: To convert tensile data into shear data, the following relations were used:…”

Section: Magnitude Of Deformation Ratesmentioning

confidence: 99%

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Deformation Mechanisms in Nanocrystalline Materials

Mohamed

Yang

2009

Metall Mater Trans A

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As a result of recent investigations on nanocrystalline (nc) materials, extensive experimental data on the deformation behavior of these materials have become available. In this article, an analysis of these data was performed to identify the requirements that a viable deformation mechanism should meet in terms of accounting for the mechanical characteristics and trends that are revealed by the data. The results of the analysis show that a viable deformation mechanism is required to account for the following: (1) an activation volume the value of which is in the range 10 to 40 b 3 ; (2) an activation energy that is close to the activation energy for boundary diffusion but that decreases with increasing applied stress; (3) the magnitudes of deformation rates that cover wide ranges of temperatures, stresses, and grain sizes; (4) inverse Hall-Petch behavior; and (5) limited ductility. The validity of available deformation mechanisms for nc materials is closely examined in the light of these requirements.

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Section: Composite Model Involving Amorphous Boundary Layercontrasting

confidence: 35%

Section: Magnitude Of Deformation Ratesmentioning

confidence: 99%

Deformation Mechanisms in Nanocrystalline Materials

Mohamed

Yang

2009

Metall Mater Trans A

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“…On the other hand, dislocation-mediated plastic deformation entails an activation energy larger than 1 eV, while the activation energy for GB diffusion is smaller than 1 eV (Caillard and Martin, 2003). For example, the activation energy in the ng-Ni is 1.1 eV for dislocation-mediated stress relaxation (Wang et al, 2006) and 0.2-0.7 eV for the GB diffusion (Van Swygenhoven and Caro, 1998). The activation energy for GB diffusion in the ng-Cu ranges from 0.3 eV to 0.72 eV (Cai et al, 2000;Dickenscheid et al, 1991;Horváth et al, 1987).…”

Section: Deformation Parametersmentioning

confidence: 99%

“…The von Mises shear stress conjugated activation volume, called the apparent activation volume (Zhu and Li, 2010;Zhu et al, 2007), is widely adopted (Dao et al, 2007;Lu et al, 2005;Wang et al, 2005Wang et al, , 2006 and also used in the previous work (Yang et al, 2016) for the convenience in comparison. In materials community, resolved shear stress τ r is usually employed and the value of τ r is linked to the uniaxial tensile stress by Taylor factor M, i.e., τ σ = M / r .…”

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confidence: 99%

Time, stress, and temperature-dependent deformation in nanostructured copper: Stress relaxation tests and simulations

Yang

Wang

et al. 2016

Acta Materialia

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a b s t r a c tIn the present work, we performed experiments, atomistic simulations, and high-resolution electron microscopy (HREM) to study the creep behaviors of the nanotwinned (nt) and nanograined (ng) copper at temperatures of 22°C (RT), 40°C, 50°C, 60°C, and 70°C. The experimental data at various temperatures and different sustained stress levels provide sufficient information, which allows one to extract the deformation parameters reliably. The determined activation parameters and microscopic observations indicate transition of creep mechanisms with variation in stress level in the nt-Cu, i.e., from the Coble creep to the twin boundary (TB) migration and eventually to the perfect dislocation nucleation and activities. The experimental and simulation results imply that nanotwinning could be an effective approach to enhance the creep resistance of twin-free ng-Cu. The experimental creep results further verify the newly developed formula (Yang et al., 2016) that describes the time-, stress-, and temperature-dependent plastic deformation in polycrystalline copper.

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“…where _ e f is the failure strain rate [16,26,27]; _ e 0 is a pre-exponential constant or a characteristic strain rate; DU is the activation energy for failure which is a function of the current strain e; k is the Boltzman constant and T is the absolute temperature. A similar postulation used in [16] is introduced: when _ e f equals the imposed strain rate _ e, the atomic system will failure and can no longer support…”

Section: Thermal Activation Explanation To Failure Mode Imentioning

confidence: 99%