Composition and non-equilibrium crystallization in partially devitrified co-rich soft magnetic nanocomposite alloys
✍ Scribed by P.R. Ohodnicki Jr.; Y.L. Qin; D.E. Laughlin; M.E. McHenry; M. Kodzuka; T. Ohkubo; K. Hono; M.A. Willard
- Publisher
- Elsevier Science
- Year
- 2009
- Tongue
- English
- Weight
- 817 KB
- Volume
- 57
- Category
- Article
- ISSN
- 1359-6454
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✦ Synopsis
The body-centered cubic (bcc) phase tends to preferentially nucleate during solidification of highly undercooled liquid droplets of binary alloy systems, including Fe-Co, Fe-Ni and Fe-Cr-Ni. We investigate a similar tendency during the partial devitrification of Co-rich amorphous precursors of composition (Co 1Àx Fe x ) 88 Zr 7 B 4 Cu 1 by identifying the structure and composition of the nanocrystalline grains. The Co:Fe ratio of the bcc nanocrystals varies linearly with the Co:Fe ratio of the amorphous precursor, and can lie well within the single-phase face-centered cubic (fcc) region of the Fe-Co phase diagram at the crystallization temperature. Classical nucleation theory therefore suggests several potential explanations for the preferential nucleation of bcc phase from an amorphous precursor, including: (i) a reduced amorphous/bcc interface energy as compared to the close-packed phases; (ii) a lower strain of precipitation for bcc nuclei as compared to close-packed fcc and hexagonal close-packed nuclei; and (iii) stabilization of the bcc phase by dissolved glassformers such as Zr and B.