Strength enhancement induced by grain boundary solute segregations in ultrafine-grained alloys

A model is proposed explaining enhanced strength of ultrafine-grained alloys that contain grain boundary (GB) solute segregations. In the framework of the proposed model these segregations are treated as homogeneous ellipsoidal inclusions and act as the sources of elastic stresses affecting the emis...

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Bibliographic Details
Published in:International journal of plasticity 2019-12, Vol.123, p.133-144
Main Authors: Bobylev, S.V., Enikeev, N.A., Sheinerman, A.G., Valiev, R.Z.
Format: Article
Language:English
Subjects:
Alloys
Aluminum base alloys
Diameters
Dislocations
Grain boundaries
Grain boundary segregations
Inclusions
Inhomogeneous materials
Segregations
Strengthening mechanisms
Thickness ratio
Ultrafines
Yield strength
Yield stress
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Summary:A model is proposed explaining enhanced strength of ultrafine-grained alloys that contain grain boundary (GB) solute segregations. In the framework of the proposed model these segregations are treated as homogeneous ellipsoidal inclusions and act as the sources of elastic stresses affecting the emission of lattice dislocations from GBs. These segregations pin the ends of lattice dislocation segments at the initial stage of dislocation propagation along GBs, and the unpinning requires a load increase, leading to the enhanced yield strength. We calculate the contribution of GB segregations to the yield strength for the ultrafine-grained 1570 Al alloy. We demonstrate that the maximum yield strength of this alloy is achieved in the case of clustered, nearly spherical Mg segregations with a high Mg concentration and a diameter to thickness ratio of 1.0–1.4, depending on the Mg concentration inside segregations. We also briefly discuss the possible role of GB dislocations in the formation of such concentrated solute segregations as well as the influence of GB segregations on the strengthening of alloys containing nanoscale twins. The results of the calculations agree well with experimental data. •Enhanced strength of alloys containing grain boundary segregations is modeled.•Segregations are the sources of elastic stresses increasing the yield strength.•Small segregations with a high solute concentration provide maximum strengthening.
ISSN:0749-6419
1879-2154
DOI:10.1016/j.ijplas.2019.07.013