New experimental insight into the mechanisms of nanoplasticity

The evolution of microstructure and texture of a nanocrystalline Pd–10at.% Au alloy (initial grain size 16nm) subjected to severe plastic deformation by high-pressure torsion (HPT) at room temperature is investigated by X-ray line profile analysis and X-ray microdiffraction, respectively. In additio...

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Bibliographic Details
Published in:Acta materialia 2013-11, Vol.61 (19), p.7271-7284
Main Authors: Skrotzki, W., Eschke, A., Jóni, B., Ungár, T., Tóth, L.S., Ivanisenko, Yu, Kurmanaeva, L.
Format: Article
Language:English
Subjects:
Applied sciences
Chemical Sciences
Crystallites
Deformation mechanisms
Dislocations
Engineering Sciences
Exact sciences and technology
High-pressure torsion
Material chemistry
Metals. Metallurgy
Microstructure
Nanoplasticity
Nanostructure
Shear strain
Slip
Surface layer
Texture
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Summary:The evolution of microstructure and texture of a nanocrystalline Pd–10at.% Au alloy (initial grain size 16nm) subjected to severe plastic deformation by high-pressure torsion (HPT) at room temperature is investigated by X-ray line profile analysis and X-ray microdiffraction, respectively. In addition, changes in the microhardness are measured and the texture is modeled. During HPT the microstructure changes: the crystallite size goes over the maximum, the dislocation density goes through a minimum and the density of stacking faults decreases at/up to a shear strain of ∼1, corresponding to a grain size of 20nm. Starting with a random texture, typical brass-type shear components develop at a shear strain above ∼1. The microhardness with decreasing crystallite size goes over a maximum at ∼20nm. The correlated changes in microstructure, texture and strength strongly suggest the transition from a dislocation slip to a grain boundary sliding (GBS)-dominated deformation mechanism. The unexpected brass-type texture and its deviation from the ideal position can be simulated with the Taylor model assuming dominant partial dislocation slip and a certain contribution of GBS, respectively. Taken together, the results of many techniques applied to the same material, in particular those of the texture investigations, provide a more comprehensive and consistent picture of nanoplasticity than reported before for face-centered cubic metals.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2013.08.032