Thermal evolution and grain boundary phase transformations in severely deformed nanograined Al–Zn alloys
✍ Scribed by B. Straumal; R. Valiev; O. Kogtenkova; P. Zieba; T. Czeppe; E. Bielanska; M. Faryna
- Publisher
- Elsevier Science
- Year
- 2008
- Tongue
- English
- Weight
- 433 KB
- Volume
- 56
- Category
- Article
- ISSN
- 1359-6454
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✦ Synopsis
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 finegrained 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 a phases in the (Al)+Zn two-phase area.