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The limits of grain fragmentation in severe plastic deformation

Abstract : Ultra fine grain size materials are good candidates for light weighting because of their high strength thanks to the Hall-Petch relation. One promising way to produce them is severe plastic deformation (SPD) which is a top-bottom technique where grain fragmentation is induced by the extreme large plastic strains. The main mechanism of grain refinement is the grouping of geometrically necessary dislocations (GNDs) into walls of increasing disorientation. It is shown in this lecture that their density is first increasing up to about an equivalent von Mises strain of about 4 than begins to decrease and levels off in a steady state. At the same time, multiscale polycrystal simulations show that the strain heterogeneities are reduced in the polycrystal when the grain size is decreasing. In nano-polycrystalline materials, it is approaching the Taylor homogeneous polycrystal deformation mode. Recent detailed microstructure studies show that the disorientation distributions between neighboring grains can be related to the grain fragmentation process. The difference between the so-called correlated(between neighbors) and the non-correlated (randomly assigned) disorientation distributions have been shown to correlate with the GND density evolution of the polycrystal. These new elements of SPD research help us in the understanding of the grain fragmentation process and the limiting stage during which the smallest possible grain size can be obtained.
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https://hal.univ-lorraine.fr/hal-03181126
Contributor : Jérôme Slowensky <>
Submitted on : Thursday, March 25, 2021 - 2:10:56 PM
Last modification on : Wednesday, April 21, 2021 - 2:50:06 PM

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  • HAL Id : hal-03181126, version 1

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Laszlo Toth. The limits of grain fragmentation in severe plastic deformation. THERMEC 2016. International Conference on PROCESSING & MANUFACTURING OF ADVANCED MATERIALS Processing, Fabrication, Properties, Applications, May 2016, Graz, Austria. ⟨hal-03181126⟩

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