Temperature dependence of activation volume on Cu content of ultra-low carbon steel

Tanaka, Masaki; Izumi, Daichi; Yoshimura, Nobuyuki; Shigesato, Genichi; Hoshino, Manabu; Ushioda, Kohsaku; Higashida, Kenji

doi:10.1080/14786435.2017.1359423

Cited by 19 publications

(6 citation statements)

References 28 publications

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“…It is generally understood that a thermal-activated process for the dislocation motion could be controlled by double-kink nucleation to overcome the Peierls barrier in bcc pure metals. 36) The similar v * of the studied 18Cr ferritic stainless steel to one of pure iron confirms the same mechanism for dislocation motion could work in the α-Fe matrix with Cr in solution as well as pure iron at ambient temperature. In the single-crystal micropillars of the 18Cr ferritic stainless steel, the specimen with a larger diameter (d = 5-6 μm) shows a relatively high v * (approximately 50 b 3 ) as well as the millimeter-sized specimens.…”

Section: Activation Volumesupporting

confidence: 67%

“…9(a)). In a sufficiently large crystal volume (in millimetersized specimens), the nucleation rate of the double-kink is considered reduced at lower temperature, 36) resulting in a reduced v * associated with a thermal-activated process for the dislocation motion in bcc metals. The temperature dependence of v * for pure iron is presented in Fig.…”

Section: Activation Volumementioning

confidence: 99%

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Strain Rate Sensitivity of Flow Stress Measured by Micropillar Compression Test for Single Crystals of 18Cr Ferritic Stainless Steel

Tianqi

Takata

et al. 2020

ISIJ Int.

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We have fabricated cylindrical single-crystal micropillars with different diameter (d) ranges of 2-3 μm and 5-6 μm on a specific grain in the 18Cr ferritic stainless steel with a ferrite single-phase microstructure. The initial strain rate at the onset of plastic deformation was controlled by variable loading rate in the used nanoindenter. The strain rate sensitivity of the stress required for the slip initiation were examined using the fabricated micropillars. The present compression tests addressed the shear stress on an activated single slip system of micron-scale single-crystals. Smaller-sized micropillars (d = 2-3 μm) often exhibit intermittent strain bursts. The stress for slip initiation (after an elastic loading) changes depending on the initial strain rate, resulting in a high strain rate sensitivity (m) of 0.12. Larger-sized micropillars (d = 5-6 μm) show a continuous yielding. A slight change in their yield stress depending on the initial strain rate provides a relatively low m of 0.04. It is similar to one of the millimeter-sized specimens measured by conventional tensile tests. These results provide new insights to optimize the specimen size for the micropillar compression test applied for the 18Cr ferritic stainless steels.

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Section: Activation Volumesupporting

confidence: 67%

Section: Activation Volumementioning

confidence: 99%

Strain Rate Sensitivity of Flow Stress Measured by Micropillar Compression Test for Single Crystals of 18Cr Ferritic Stainless Steel

Tianqi

Takata

et al. 2020

ISIJ Int.

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“…However, these experiments have typically been performed over a much narrower temperature range than was used in the current NEMD simulations. Previous experiments have shown that ΔV* can be temperature-dependent for other processes, such as self-diffusion in zinc metal 55 and dislocation motion in steel 56 . Previous NEMD simulations with ReaxFF have shown that ΔV* can also be pressure-dependent for the decomposition of PFPEs between DLC surfaces 36 .…”

Section: Resultsmentioning

confidence: 99%

Mechanochemistry of phosphate esters confined between sliding iron surfaces

Latorre

Remias²,

Moore

et al. 2021

Commun Chem

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The molecular structure of lubricant additives controls not only their adsorption and dissociation behaviour at the nanoscale, but also their ability to reduce friction and wear at the macroscale. Here, we show using nonequilibrium molecular dynamics simulations with a reactive force field that tri(s-butyl)phosphate dissociates much faster than tri(n-butyl)phosphate when heated and compressed between sliding iron surfaces. For both molecules, dissociative chemisorption proceeds through cleavage of carbon−oxygen bonds. The dissociation rate increases exponentially with temperature and stress. When the rate−temperature−stress data are fitted with the Bell model, both molecules have similar activation energies and activation volumes and the higher reactivity of tri(s-butyl)phosphate is due to a larger pre-exponential factor. These observations are consistent with experiments using the antiwear additive zinc dialkyldithiophosphate. This study represents a crucial step towards the virtual screening of lubricant additives with different substituents to optimise tribological performance.

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“…Previous experiments have shown that ΔV* can be temperature-dependent for other processes, such as diffusion 54 and deformation. 55 Previous NEMD simulations with ReaxFF have shown that ΔV* is pressure-dependent for the decomposition of PFPEs between DLC surfaces. 36 One possible explanation for the increase in ΔV* with increasing temperature observed in the current simulations is that the elastic modulus of the α-Fe(110) surfaces is expected to decrease by around 10 % as the temperature is increased from 300 K to 500 K. 56 This is important since a recent DFT study has shown that ΔV* is inversely proportional to the contact stiffness.…”

Section: Resultsmentioning

confidence: 97%

Mechanochemistry of Phosphate Esters Confined between Sliding Iron Surfaces

Latorre

Remias

Moore

et al. 2021

Preprint

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Small changes to the molecular structure of lubricant additives affect their adsorption and dissociation behaviour at the nanoscale, as well as their friction and wear performance at the macroscale. Here, we show using nonequilibrium molecular dynamics simulations with a reactive force field that secondary trialkylphosphates dissociate much faster than primary trialkylphosphates between sliding iron surfaces. For both molecules, dissociative chemisorption proceeds through cleavage of the carbon − oxygen bond. The rate increases exponentially with temperature and stress, which is indicative of a stress-augmented thermally activated process. Both molecules show similar activation energy and activation volume. The much higher reactivity of secondary trialkylphosphates is driven mostly by the pre-exponential factor, which is almost an order of magnitude larger than for primary trialkylphosphates. These observations and the associated kinetic parameters are consistent with recent macroscale tribometer experiments of the antiwear additive zinc dialkyldithiophosphate. This study represents a crucial step towards the virtual screening of lubricant additives with different substituents for optimal tribological performance.

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Temperature dependence of activation volume on Cu content of ultra-low carbon steel

Cited by 19 publications

References 28 publications

Strain Rate Sensitivity of Flow Stress Measured by Micropillar Compression Test for Single Crystals of 18Cr Ferritic Stainless Steel

Strain Rate Sensitivity of Flow Stress Measured by Micropillar Compression Test for Single Crystals of 18Cr Ferritic Stainless Steel

Mechanochemistry of phosphate esters confined between sliding iron surfaces

Mechanochemistry of Phosphate Esters Confined between Sliding Iron Surfaces

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