Thermal evolution and grain boundary phase transformations in severely deformed nanograined Al–Zn alloys

The structure, phase composition and thermal evolution of binary Al–Zn alloys were studied before and after high-pressure torsion (HPT) in Bridgman anvils. On heating of HPT-deformed samples from room temperature to 300 °C, Zn grains dissolved, and a relatively fine-grained (Al) equilibrium solid so...

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Bibliographic Details
Published in:Acta materialia 2008-12, Vol.56 (20), p.6123-6131
Main Authors: Straumal, B., Valiev, R., Kogtenkova, O., Zieba, P., Czeppe, T., Bielanska, E., Faryna, M.
Format: Article
Language:English
Subjects:
Alloys
Aluminum
Aluminum base alloys
Al–Zn alloys
Grain boundaries
Nanostructure
Severe plastic deformation
Solid solutions
Solidus
Thermal evolution
Wetting phase transition
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Summary:The structure, phase composition and thermal evolution of binary Al–Zn alloys were studied before and after high-pressure torsion (HPT) in Bridgman anvils. On heating of HPT-deformed samples from room temperature to 300 °C, Zn grains dissolved, and a relatively fine-grained (Al) equilibrium solid solution formed. Differential scanning calorimetry curves reveal two-stage melting in the Al–Zn alloys studied, i.e., the melting of the (Al) solid solution starts 10–25 °C below the bulk solidus line. The effect is more pronounced in fine-grained samples. It is explained by the presence of layers of liquid-like phase in the (Al) grain boundaries (GB) between bulk and GB solidus lines. The new metastable GB solidus line appears in the (Al) single-phase region of the Al–Zn phase diagram, it can be compared with the metastable solvus lines for the formation of GP zones and α phases in the (Al)+Zn two-phase area.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2008.08.021